Beggiatoa: Difference between revisions

Beggiatoa
Scientific classification
Domain:	Bacteria
Phylum:	Pseudomonadota
Class:	Gammaproteobacteria
Order:	Thiotrichales
Family:	Thiotrichaceae
Genus:	Beggiatoa; Trevisan 1842
Species
	Beggiatoa alba; Beggiatoa leptomitoformis

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Beggiatoa is a genus of Gammaproteobacteria belonging to the order Thiotrichales, in the Pseudomonadota phylum. This genus was one of the first bacteria discovered by Ukrainian botanist Sergei Winogradsky. During his research in Anton de Bary's laboratory of botany in 1887, he found that Beggiatoa oxidized hydrogen sulfide (H₂S) as an energy source, forming intracellular sulfur droplets, with oxygen as the terminal electron acceptor and CO₂ used as a carbon source. Winogradsky named it in honor of the Italian doctor and botanist Francesco Secondo Beggiato (1806 - 1883), from Venice.^[3] Winogradsky referred to this form of metabolism as "inorgoxidation" (oxidation of inorganic compounds), today called chemolithotrophy. These organisms live in sulfur-rich environments such as soil, both marine and freshwater, in the deep sea hydrothermal vents, and in polluted marine environments. The finding represented the first discovery of lithotrophy.^[4]^[5]

These colorless and filamentous bacteria, sometimes in association with other sulfur bacteria (for example the genus Thiothrix), can be arranged in biofilm visible to the naked eye formed by a very long white filamentous mat. The white color is due to the stored sulfur. Beggiatoa have cells up to 200 µm in diameter and they are one of the largest prokaryotes on Earth.^[6]

Taxonomy

The genera Beggiatoa is a quite diverse group as it has representatives occupying several habitats and niches, both in fresh and salt water. In the past they have been confused as close relatives of Oscillatoria spp. (Cyanobacteria) for the morphology and motility characters,^[7] but 5S rRNA analysis showed that members of Beggiatoa are phylogenetically distant from Cyanobacteria, being members of the Gammaproteobacteria phylum.^[8]

Despite their diversity, only two species of Beggiatoa have been formally described: the type species Beggiatoa alba and Beggiatoa leptomitoformis, the latter of which was only published in 2017.^[2]^[9]

The capability to oxidize sulfide and store sulfur are the main features which separates Beggiatoa and closely related Thioploca as filamentous colorless sulfur bacteria from other filamentous bacteria (like cyanobacteria and the nonsulfur-oxidizing Cytophaga and Flexibacter).^[10] Another defining feature is the ability to store nitrate inside the vacuoles of the wide marine species’ cells. 16S rRNA sequences base studies inferred that this characteristic is shared between members of a monophyletic clade nested in the Beggiatoa genera; this clade also includes members of Thioploca and Thiomargarita, both presenting only slight differences with Beggiatoas: whereas the former grows sharing a common slime sheath, the latter has not conserved filamentous growth and forms chains of rounded cells. Since the phylogenic history do not reflect the nomenclature, there is a need for a new denomination of genera and species.^[11] The Neo-type strain is the B18LB and it settled the criteria for identification of the freshwater species Beggiatoa alba.^[12]

Genetics

Because of the lack of a pure culture, little is known about the genetics of Beggiatoa. Beggiatoa alba has a GC content between 40 and 42.7 mol%, two or three similar plasmids, and a genome size of about 3 Megabase (Mbp) (strain B18LD).^[6] In a study on Beggiatoa genome sequences obtained from two single filaments of a vacuolated strain, optical mapping showed that the genome size was about 7.4 Mbp; pathways for sulfur oxidation, nitrate and oxygen respiration, and CO₂ fixation were detected, confirming its chemolithoautotrophic physiology. Furthermore, comparative genomics indicated horizontal gene transfer between Beggiatoa and Cyanobacteria of storage, metabolic, and gliding abilities.^[13]

Morphology and motility

Beggiatoa spp. can be divided into three morphological categories^{[citation needed]} (with some exceptions):

Freshwater strains, characterized by narrow filaments with no vacuoles;
Narrow marine strains, without vacuoles (filaments' diameter of about 4.4 µm);
Larger marine strains, with vacuoles for nitrate storing (filaments' diameter vary between 5 and 140 µm)

Narrow filaments are usually composed by cylindrical cells which length is about 1.5 to 8 times their thickness; wider filaments instead are disk-shaped with cell lengths from 0.10 to 0.90 times their cell width. In all of the cultured strains the terminal cells of the filaments appear rounded.^{[citation needed]}

Although they are Gram-negative bacteria, Beggiatoa show unusual cell-wall and membrane organization. A variable number of further membranes that cover the peptidoglycan layer are sometimes present. Their presence may be due to the harsh conditions in which some of these organisms live. Intracellular granules can also be covered by membranes structures. In addition to sulfur granules, Beggiatoa cells often contain granules of polyhydroxybutyrate and polyphosphate. Large marine vacuolated Beggiatoa commonly have cells with a narrow cytoplasm surrounding a large central vacuole used to store nitrate.^[6]^[14]

The filaments move by gliding; this movement is likely connected to string-like structures in the outer membrane and trans-peptidoglycan channels. Filaments can also break, by forming necridia cells in the middle of the filament. The motility of the filament is important for the adaptability of the bacteria, because it allows to move on to more suitable conditions for their cellular metabolism. Beggiatoa filaments typically move away from high oxygen and sulfide levels, and from light exposure.^[14]

Cell growth

Beggiatoa use fragmentation as a reproductive strategy. A colony can develop into a mat through alternating filament elongation and breakage. Breakage can happen in the middle of a stretched filament, at the tip of a filament loop, or where a tip of a loop was once placed. Sacrificial cells interrupt the communication between two parts of one filament; in this way each section can change its gliding direction causing the split.^{[citation needed]}

The average filament length achieved through this process is also result of gene-environment interactions as, for instance, the growth and position of the filament is function of vertical gradients of oxygen and sulfide. Therefore, it is proposed that good environmental conditions will paradoxically cause cell death in order to enhance filament breakage, thus reproduction.^[15]

Metabolism

Beggiatoa group is mainly composed by chemolithotrophic, sulfide-oxidizing bacteria. However, the range of possible metabolic pathways is very diversified, varying from the heterotrophy to the chemolithoautotrophy. Because of this huge variability the diverse bacteria of this genus can differ greatly from each other.^[14]

Carbon metabolism

In Beggiatoa group are present both autotrophic and heterotrophic metabolisms. Autotrophic Beggiatoa carry out the CO₂ fixation through the Calvin cycle and the employment of the RuBisCO enzyme. The latter shows different regulation levels in obligated and facultative autotrophs. For instance, in the obligately autotrophic strain MS-81-1c RuBisCO cannot be repressed, while in the facultatively autotrophic strain MS-81-6 it is tightly regulated to switch from autotrophic to heterotrophic growth and vice versa. Beside the autotrophic strains, most of the freshwater Beggiatoa strains are heterotrophic, requiring organic substrates for growth. Specifically, many of them can be considered mixotrophs, because they grow heterotrophically, oxidizing organic compounds, but they can also use sulfide or other reduced sulfur compounds as electron donors. By this strategy, the organic carbon skeletons are saved for the purpose of increasing biomass and the CO₂ autotrophic fixation is not required. Mixotrophy has been suspected to be the trophic modality for many freshwater strains, but it has only been found in one marine strain of Beggiatoa, MS-81-6.^[14] Also a metabolic pathway of C-1 compounds utilization has been revealed in Beggiatoa leptomitoformis strain D-402, through comprehensive analysis of its genomic, biochemistry, physiology and molecular biology.^[16]

Nitrogen metabolism

Beggiatoa group shows substantial versatility in utilizing nitrogen compounds. Nitrogen can be a source for growth or, in the case of nitrate, it can be an electron acceptor for anaerobic respiration. Heterotrophic freshwater Beggiatoa spp. assimilate nitrogen for growth. Nitrogen sources include nitrate, nitrite, ammonia, amino acids, urea, aspartate, asparagine, alanine and thiourea, depending on the capability of specific strains.

Autotrophic vacuolated Beggiatoa are able to store nitrate in their vacuoles 20.000 times the concentration of the surrounding sea water, and use it as terminal electron acceptor in anoxic conditions. This process, called Dissimilatory Nitrate Reduction to Ammonium (DNRA), reduces nitrate to ammonium. The capability of using nitrate as electron acceptor allows the colonization of anoxic environments, such as microbial mats and sediments. Several species are able to fix nitrogen using nitrogenase enzyme (e.g. Beggiatoa alba).^[6]^[14]

Sulfur metabolism

One of the defining features of the genus Beggiatoa is the production of intracellular inclusions of sulfur resulting from the oxidation of reduced sulfur sources (e.g. hydrogen sulfide). In autotrophic Beggiatoa, sulfide is a source of energy and electrons for carbon fixation and growth. The oxidation of sulfide can be aerobic or anaerobic, in fact it can be coupled with the reduction of oxygen or with the reduction of nitrate. Sulfur produced by the oxidation of sulfide is stored into internal globules and can be used when the concentration of sulfide decreases. Thus, the temporarily storing of elemental sulfur (S⁰) increase the adaptability of an organism and its tolerance to changes in the concentrations of sulfide and oxygen.^[6]^[14]

Sulfide aerobic oxidation: ${\ce {H2S + 1/2O2 -> S^0 + H2O}}$

Sulfide anaerobic oxidation: ${\ce {4H2S + NO3^- + 2H+ -> 4S^0 + NH4^+ + 3H2O}}$

There are some cases of chemoorganotrophy, too. For instance, the strain Beggiatoa sp. 35Flor usually do an aerobic respiration coupled with the oxidation of sulfide, but in anoxic condition a different type of respiration is activated. The energy is gained chemoorganotrophically from oxidation of PHA (polyhydroxyalkanoates), organic compounds previously synthesized through CO₂ fixation during chemolithotrophic growth on oxygen and sulfide. In this case electron acceptor is the sulfur stored into the cell, so the final product is hydrogen sulfide.^[17]

Anaerobic respiration: ${\ce {PHA + S^0 -> CO2 + H2S}}$

Hydrogen metabolism

The strain Beggiatoa sp. 35Flor is able to use hydrogen as alternative electron donor to sulfide. This oxidation process can provide energy for maintenance and assimilatory purposes and is helpful to reduce stored sulfur when it becomes excessive, but it can't provide growth to the strain.^[18]

Hydrogen oxidation: ${\ce {H2 + S^0 -> H2S}}$

Phosphorus metabolism

Beggiatoa’s metabolism include the use of phosphorus in the polyphosphate form. The regulation of this metabolism relies on the environmental conditions. Oxygenated surroundings cause an accumulation of polyphosphate, while anoxia (coupled with an increasing concentration of sulfide) produces a breakdown of polyphosphate and its subsequent release from the cells. The released phosphate can then be deposited as phosphorite minerals in the sediments or stay dissolved in the water.^[14]

Ecology

Filaments have been observed to form dense mats on sediments in a very huge variety of environments. They appear as a whitish layer and since they are present and flourish in marine environments which have been subject to pollution, they can be considered as an indicator species.^[19] Beggiatoa and other related filamentous bacteria can cause settling problems in sewage treatment plants, industrial waste lagoons in canning, paper pulping, brewing, milling, causing the phenomenon called "bulking". Beggiatoa are also able to detoxify hydrogen sulfide in soil and have a role in the immobilization of heavy metals.^[20]^[21]

Beggiatoa live at the oxic/anoxic interface, where they benefits from the presence of both hydrogen sulfide and oxygen. The chemolithoautotrophic strains of Beggiatoa are also considered important primary producers in dark environments.^[6]

Habitat

The incredible number of adaptations and metabolisms of this genus of bacteria are consequences of the extraordinary environmental variability they can live in. Beggiatoa is almost benthic, it can be found in marine (Beggiatoa sp. MS-81-6 and MS-81-1c) or freshwater (Beggiatoa alba) environments and they only need sulfide or thiosulfide as electron donor and an oxidizer. They can usually be found in habitats that have high levels of hydrogen sulfide, these environments include cold seeps, sulfur springs, sewage contaminated water, mud layers of lakes, and near deep hydrothermal vents. Beggiatoa can also be found in the rhizosphere of swamp plants,^[22]^[23] in soil, marine sediments and in the mangrove lagoon too (where they contribute to the lipid pool of the sediments^[24]).^[25] The freshwater species have typical habitats in sulfur springs, ditches, puddles, wetlands, lake sediments and in rice fields, where it can grow associated with the rice plants’ roots. The Beggiatoa that live in marine water can be found in regions where their source of energy (sulfide or thiosulfide) is available. It can be extracted from both inorganic or organic source and usually it is coupled with microoxic condition, therefore very low concentration of oxygen.^[6] This genus of Gammaprotobacteria is also common in localized area of anaerobic decomposition, such as whale carcasses on the deep ocean seafloor.^[6]

A Beggiatoa-like bacterial mat filaments in underwater cave.

Vacuolated Beggiatoa can be very common in coastal upwelling regions (for example Peru and Chile coasts), deep sea hydrothermal vents and cold vents; in these environments the floc mats (hair-like breast) can grow up and cover large areas and reach the height of 30 cm. In deep sea hydrothermal vents and cold-seeps Beggiatoa can grow in filaments that can be up to 200 micrometres in diameter, which makes these ones the largest prokaryotes currently known. Vacuolated Beggiatoa can be found also in hypoxic seafloor, where the filaments can live inside the sediments at the depth of few cm (from 2 to 4 cm); in same cases the Beggiatoa bacterial filaments can be the most abundant part of the microbial biomass in the sediments.^[6]

Beggiatoa is also found in salt marshes, saline, and geothermally active underwater caves. Some studies on these environments have been carried out in the underwater caves of dolomitized limestone in Capo Palinuro, Salerno, (Italy). Here there are hydrothermal sulphidic springs and microbial biofilm is associated with the flow of hydrothermal fluids, whose activity is intermittent and starts during low tide. Mats found in the caves were composed by filaments resembling in most part Beggiatoa, Thiothrix and Flexibacter, and this Beggiatoa-like filaments were morphologically close to those found attached to rocks and the byssus of the mussels from Lucky Strike Hydrothermal vents on the Mid-Atlantic Ridge.^[6]

Interactions with other organisms

Beggiatoa can form complex microbial mats in association with other filamentous bacteria, such as cyanobacteria. The cyanobacteria usually occupy the surface layer of the mat, and produce a great amount of oxygen during the day through photosynthesis. Conversely, Beggiatoa grow beneath the phototrophs, along an oxic/anoxic (oxygen/sulfide) interface, where they produce white patches.^[6] However, during dark acclimation, the mat became anoxic, so the Beggiatoa moved to the mat surface, to avoid the high levels of H₂S and remain at the oxygen/sulfide interface, while cyanobacteria remained in a dense layer below.^[26] Sometimes Beggiatoa mats are enriched by the presence of diatoms and green euglenoids too,^[20] but also protists as ciliates and dinoflagellates have been found associated with the mats at the Guaymas Basin hydrothermal vent ecosystem and they likely consume a large amount of bacterial biomass.^[27]

As the microbial mats can reach 3 cm in width, they can be a food source for many grazers. This trophic connection has been observed in mangrove systems, where Beggiatoa cover part of marine sediments. The bacteria contribute to the diet of meiofauna, in particular rotifers, polychaetes, nematodes and some groups of platyhelminthes, aschelminths and gnathostomulids.^[28] Nematodes seem to encourage development of Beggiatoa mats, by increasing oxygen penetration and nutrient diffusion into the mat.^[29]

Furthermore, many carrion appear covered by mats of Beggiatoa-like filamentous bacteria that overlie anaerobic sulfate-reducing bacteria. They attract many metazoans scavengers, but when they break the mat, it releases hydrogen sulphide that drives away the scavengers. Hence, Beggiatoa can also be considered a carrion defence from the scavengers.^[30]

Role in biogeochemical cycles

Massive mats of some Beggiatoa-like filaments in an underwater cave

Several species of white sulfur bacteria in the family Beggiatoaceae can accumulate and transport NO₃⁻, taken from shallow coastal sediments which is fundamental in metabolism, as well as accumulate it in filaments. The reduction of NO₃⁻ to ammonium implies the oxidation of H₂S (except for geothermal vents, the sulphide derives from the underlying anaerobic sediment in which dissimilatory sulphate reduction occurs^[20]): this reduction leads to the formation of suboxic zones characterized by positive redox potential and only trace concentrations of free H₂S. In marine environment, the presence of these species is important because they have a fundamental role in regulation of the amount of H₂S and NO₃⁻ :

On the one hand, the regulation of free H₂S concentration in marine sediments is fundamental because sulfide-depleted surface sediments are essential for survival of benthic infauna, in fact sulfide is highly toxic to bottom fauna and other organisms living in the sediment;
On the other hand, NO₃⁻ reduction is important for the control of eutrophication in nitrogen-limited coastal waters.^[31]

Beggiatoa can also accumulate phosphorus as polyphosphate, which it subsequently releases as phosphate under anoxic conditions. This might increase the availability of phosphorus to primary producers if the phosphate is released from the sediment to the water column. Studies on phosphorus cycling and phosphorus release Beggiatoa in Baltic Sea have found that the oxidation of sulfide by these bacteria may decrease the rate of iron sulfide formation in the sediments, and thus increase the phosphorus retention capability of the sediment.^[14]

Cultivation

Selective Enrichments

The most successful enrichments for Beggiatoa spp. have been made using a shallow pan or aquarium to which has been added a few centimeters of sand, differing amounts of CaSO₄ and K₂HPO₄, a source of complex organic polymers such as seaweed, several centimeters of sulfide-rich marine mud and seawater. The enrichment must contain the proper sulfide-oxygen interface that can be possible only if air is introduced, for example, by a slow steady flow of freshly aerated seawater. Another type of enrichment associated with Beggiatoa spp. is based on the use of extracted dried grass or hay in a mineral medium because complex polymers such as cellulose residues in the material are a substrate that supports sulfate reduction by other microbes. This also provides the hydrogen sulfide necessary to enrich for Beggiatoa.^[6]

Pure culture isolation

There are three different possible techniques to obtain isolated Beggiatoa strains in pure culture:

Isolation on agar plates
Isolation using liquid media
Isolation and cultivation in gradient media

Isolation on agar plates

Some Beggiatoa-like filaments near a tiny hole

The procedure to isolate a heterotrophic strain requires an agar plate containing dilute organic substrates such as small amount of peptone. Then, tufts of Beggiatoa filaments are collected from the environment, washed with sterile washing solution and placed on the agar plate. In this way, there will be some growing filaments moving away from the central inoculum that can be used as inoculum for a new agar plate.^[6]

For the isolation of marine Beggiatoa strains (that show autotrophic growth), since they are obligate microaerophiles it is essential to provide micro-oxic conditions and to use particular agar plates made with filtered seawater and supplemented with sodium sulfide and sodium acetate. In comparison, for freshwater strains, isolation must be performed under oxic conditions (air atmosphere) using a variety of media containing a low concentration of single organic compound such as acetate, Na₂S or thiosulfate.^[6]

Isolation using liquid media

Liquid media are often used for enrichment, most probable number (MPN) enumeration and bulk cultivation of Beggiatoa. To successfully cultivate heterotrophic or mixotrophic freshwater Beggiatoa, liquid media has to contain little amounts of carbon substrate, either soil extracts or acetate. The type species and strain (Beggiatoa alba str. B18LD) and related strains are generally grown in media that include a salt base, acetate as carbon source, and variable yeast extract and sulfide additions.^[32] Some marine autotrophic Beggiatoa strains are also been cultured on defined liquid mineral medium with thiosulfate, CO₂, and micro-oxic conditions under aeration with 0.25% O₂ (v/v) in the gas phase.^[6]

Isolation and cultivation in gradient media

Autotrophic strains coming from a single filament isolation on agar can easily be maintained and propagated in sulfide gradient tubes in which sulfide-rich agar plugs are overlaid with sulfide-free soft agar. Tubs are loosely closed in order to permit the exchange of headspace gasses with the atmosphere. As result, two opposite layers are formed, one that contains sulfide while the other one oxygen: this allows the growth of a well-defined Beggiatoa layer at the sulfide-oxygen interface. The gradient medium construction requires different amounts of J3 medium (made by agar and NaHCO₃) supplemented with neutralized Na₂S placed in a screw-capped tube. Here, the sulfur source is provided by the flux of sulfide. Another ‘’ layer ‘’ is made by NaHCO₃ without sulfide or thiosulfate:  all of the sulfide will be below the interface between the sulfidic agar plug and the sulfide-free overlay agar while there will be another layer in the top of the tube that represents the oxygen reservoir. It begins to form a gradient shape due to the reaction between sulfide and oxygen: as a result, the filaments rapidly proliferate at the sulfide-oxygen interface, forming a marked layer, or “plate,” of 1 mm but it is also possible to appreciate that these bacteria can track the interface and slowly descend owing to the gradual depletion of the sulfide reservoir.^[6]

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^ Dayton PK, Oliver JS, Thrush SF, Hammerstrom K (February 2019). "Bacteria defend carrion from scavengers". Antarctic Science. 31 (1): 13–15. Bibcode:2019AntSc..31...13D. doi:10.1017/S0954102018000457. ISSN 0954-1020. S2CID 134564783.
^ Sayama M, Risgaard-Petersen N, Nielsen LP, Fossing H, Christensen PB (November 2005). "Impact of bacterial NO3(-) transport on sediment biogeochemistry". Applied and Environmental Microbiology. 71 (11): 7575–7. doi:10.1128/AEM.71.11.7575-7577.2005. PMC 1287653. PMID 16269807.
^ Schmidt TM, Arieli B, Cohen Y, Padan E, Strohl WR (December 1987). "Sulfur metabolism in Beggiatoa alba". Journal of Bacteriology. 169 (12): 5466–72. doi:10.1128/jb.169.12.5466-5472.1987. PMC 213973. PMID 3316186.

External links

"Beggiatoa".
Roxanne L. Nikolaus "Beggiatoa and hydrocarbon seeps - Unique bacteria thriving in a unique environment".

[1] Trevisan V (1842). "Prospetto della Flora Euganea". Coi Tipi Del Seminario. Padova. pp. 1–68.

[Parte_LPSN-2] Parte AC. "Beggiatoa". LPSN.

[3] Burkhardt, Lotte (2022). Eine Enzyklopädie zu eponymischen Pflanzennamen [Encyclopedia of eponymic plant names] (pdf) (in German). Berlin: Botanic Garden and Botanical Museum, Freie Universität Berlin. doi:10.3372/epolist2022. ISBN 978-3-946292-41-8. S2CID 246307410. Retrieved January 27, 2022.

[4] Ljungdahl LG (2003). Biochemistry and physiology of anaerobic bacteria. Springer. p. 17. ISBN 978-0-387-95592-6.

[pmid108947382-5] Mukhopadhyaya PN, Deb C, Lahiri C, Roy P (August 2000). "A soxA gene, encoding a diheme cytochrome c, and a sox locus, essential for sulfur oxidation in a new sulfur lithotrophic bacterium". Journal of Bacteriology. 182 (15): 4278–87. doi:10.1128/JB.182.15.4278-4287.2000. PMC 101942. PMID 10894738.

[Teske_2006-6] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p Teske A, Nelson DC (2006). "The Genera Beggiatoa and Thioploca". In Dworkin M, Falkow S, Rosenberg E, Schleifer KH (eds.). The Prokaryotes. Springer New York. pp. 784–810. doi:10.1007/0-387-30746-x_27. ISBN 978-0-387-25496-8.

[7] Reichenbach H (1981-10-01). "Taxonomy of the gliding bacteria". Annual Review of Microbiology. 35 (1): 339–64. doi:10.1146/annurev.mi.35.100181.002011. PMID 6794424.

[8] Stahl DA, Lane DJ, Olsen GJ, Heller DJ, Schmidt TM, Pace NR (1987). "Phylogenetic Analysis of Certain Sulfide-Oxidizing and Related Morphologically Conspicuous Bacteria by 5S Ribosomal Ribonucleic Acid Sequences". International Journal of Systematic and Evolutionary Microbiology. 37 (2): 116–122. doi:10.1099/00207713-37-2-116. ISSN 1466-5026.

[9] Dubinina G, Savvichev A, Orlova M, Gavrish E, Verbarg S, Grabovich M (February 2017). "Beggiatoa leptomitoformis sp. nov., the first freshwater member of the genus capable of chemolithoautotrophic growth". International Journal of Systematic and Evolutionary Microbiology. 67 (2): 197–204. doi:10.1099/ijsem.0.001584. PMID 27902215.

[10] Teske A, Nelson DC (2006). "The Genera Beggiatoa and Thioploca". In Dworkin M, Falkow S, Rosenberg E, Schleifer KH (eds.). The Prokaryotes. New York, NY: Springer. pp. 784–810. doi:10.1007/0-387-30746-x_27. ISBN 978-0-387-30746-6. {{cite book}}: |work= ignored (help) PDF.

[11] Ahmad A, Kalanetra KM, Nelson DC (June 2006). "Cultivated Beggiatoa spp. define the phylogenetic root of morphologically diverse, noncultured, vacuolate sulfur bacteria". Canadian Journal of Microbiology. 52 (6): 591–8. doi:10.1139/w05-154. PMID 16788728.

[12] Boone DR, Brenner DJ, Castenholz RW, De Vos P, Garrity GM, Krieg NR, Goodfellow N (2001–2012). Bergey's manual of systematic bacteriology (2nd ed.). New York: Springer. ISBN 978-0-387-21609-6. OCLC 619443681.

[13] Mussmann M, Hu FZ, Richter M, de Beer D, Preisler A, Jørgensen BB, et al. (September 2007). Moran NA (ed.). "Insights into the genome of large sulfur bacteria revealed by analysis of single filaments". PLOS Biology. 5 (9): e230. doi:10.1371/journal.pbio.0050230. PMC 1951784. PMID 17760503.

[Ruuskanen_2014-14] ^ ^a ^b ^c ^d ^e ^f ^g ^h Ruuskanen M (2014). "The genus Beggiatoa and its effects on the nutrient cycles of the Baltic Sea". doi:10.13140/RG.2.1.4814.6329. {{cite journal}}: Cite journal requires |journal= (help)

[15] Kamp A, Røy H, Schulz-Vogt HN (October 2008). "Video-supported analysis of Beggiatoa filament growth, breakage, and movement". Microbial Ecology. 56 (3): 484–91. Bibcode:2008MicEc..56..484K. doi:10.1007/s00248-008-9367-x. PMC 2755761. PMID 18335158.

[16] Orlova MV, Tarlachkov SV, Kulinchenko EI, Dubinina GA, Tutukina MN, Grabovich MY (December 2018). "Beggiatoa leptomitoformis D-402". Indian Journal of Microbiology. 58 (4): 415–422. doi:10.1007/s12088-018-0737-x. PMC 6141403. PMID 30262951.

[17] Schwedt A, Kreutzmann AC, Polerecky L, Schulz-Vogt HN (2012). "Sulfur respiration in a marine chemolithoautotrophic beggiatoa strain". Frontiers in Microbiology. 2: 276. doi:10.3389/fmicb.2011.00276. PMC 3253548. PMID 22291687.

[18] Kreutzmann AC, Schulz-Vogt HN (April 2016). Löffler FE (ed.). "Oxidation of Molecular Hydrogen by a Chemolithoautotrophic Beggiatoa Strain". Applied and Environmental Microbiology. 82 (8): 2527–36. Bibcode:2016ApEnM..82.2527K. doi:10.1128/AEM.03818-15. PMC 4959497. PMID 26896131.

[19] Elliott JK, Spear E, Wyllie-Echeverria S (2006). "Mats of Beggiatoa bacteria reveal that organic pollution from lumber mills inhibits growth of Zostera marina". Marine Ecology. 27 (4): 372–380. Bibcode:2006MarEc..27..372E. doi:10.1111/j.1439-0485.2006.00100.x. ISSN 1439-0485.

[Fenchel_1995-20] Fenchel T, Bernard C (1995). "Mats of colourless sulphur bacteria. I. Major microbial processes". Marine Ecology Progress Series. 128: 161–170. Bibcode:1995MEPS..128..161F. doi:10.3354/meps128161. ISSN 0171-8630.

[21] Drewniak L, Krawczyk PS, Mielnicki S, Adamska D, Sobczak A, Lipinski L, et al. (2016-08-10). "Physiological and Metagenomic Analyses of Microbial Mats Involved in Self-Purification of Mine Waters Contaminated with Heavy Metals". Frontiers in Microbiology. 7: 1252. doi:10.3389/fmicb.2016.01252. PMC 4978725. PMID 27559332.

[22] Dudley M. "Beggiatoa". Virginia Tech. Archived from the original on 2009-02-07.

[pmid9872789-23] Ahmad A, Barry JP, Nelson DC (January 1999). "Phylogenetic affinity of a wide, vacuolate, nitrate-accumulating Beggiatoa sp. from Monterey Canyon, California, with Thioploca spp". Applied and Environmental Microbiology. 65 (1): 270–7. Bibcode:1999ApEnM..65..270A. doi:10.1128/AEM.65.1.270-277.1999. PMC 91012. PMID 9872789.

[24] SamKamaleson A, Gonsalves MJ (April 2019). "Role of sulfur-oxidizing bacteria on the ecology in tropical mangrove sediments". Regional Studies in Marine Science. 28: 100574. Bibcode:2019RSMS...2800574S. doi:10.1016/j.rsma.2019.100574. ISSN 2352-4855. S2CID 134524779.

[25] Jean MR, Gonzalez-Rizzo S, Gauffre-Autelin P, Lengger SK, Schouten S, Gros O (2015-02-17). Kellogg CA (ed.). "Two new Beggiatoa species inhabiting marine mangrove sediments in the Caribbean". PLOS ONE. 10 (2): e0117832. Bibcode:2015PLoSO..1017832J. doi:10.1371/journal.pone.0117832. PMC 4331518. PMID 25689402.

[26] Lichtenberg M, Cartaxana P, Kühl M (2020). "Vertical Migration Optimizes Photosynthetic Efficiency of Motile Cyanobacteria in a Coastal Microbial Mat". Frontiers in Marine Science. 7. doi:10.3389/fmars.2020.00359. ISSN 2296-7745. S2CID 218863468.

[27] Pasulka A, Hu SK, Countway PD, Coyne KJ, Cary SC, Heidelberg KB, Caron DA (July 2019). "SSU-rRNA Gene Sequencing Survey of Benthic Microbial Eukaryotes from Guaymas Basin Hydrothermal Vent". The Journal of Eukaryotic Microbiology. 66 (4): 637–653. doi:10.1111/jeu.12711. PMID 30620427. S2CID 58616192.

[28] Pascal PY, Dubois S, Boschker HT, Gros O (2014-12-03). "Trophic role of large benthic sulfur bacteria in mangrove sediment" (PDF). Marine Ecology Progress Series. 516: 127–138. Bibcode:2014MEPS..516..127P. doi:10.3354/meps11035. ISSN 0171-8630.

[29] Salvadó H, Palomo A, Mas M, Puigagut J, Gracia M (May 2004). "Dynamics of nematodes in a high organic loading rotating biological contactors". Water Research. 38 (10): 2571–8. Bibcode:2004WatRe..38.2571S. doi:10.1016/j.watres.2004.03.007. PMID 15159160.

[30] Dayton PK, Oliver JS, Thrush SF, Hammerstrom K (February 2019). "Bacteria defend carrion from scavengers". Antarctic Science. 31 (1): 13–15. Bibcode:2019AntSc..31...13D. doi:10.1017/S0954102018000457. ISSN 0954-1020. S2CID 134564783.

[31] Sayama M, Risgaard-Petersen N, Nielsen LP, Fossing H, Christensen PB (November 2005). "Impact of bacterial NO3(-) transport on sediment biogeochemistry". Applied and Environmental Microbiology. 71 (11): 7575–7. doi:10.1128/AEM.71.11.7575-7577.2005. PMC 1287653. PMID 16269807.

[32] Schmidt TM, Arieli B, Cohen Y, Padan E, Strohl WR (December 1987). "Sulfur metabolism in Beggiatoa alba". Journal of Bacteriology. 169 (12): 5466–72. doi:10.1128/jb.169.12.5466-5472.1987. PMC 213973. PMID 3316186.

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 }}
-'''''Beggiatoa''''' is a [[genus]] of [[Gammaproteobacteria]] belonging to the order [[Thiotrichales]], in the [[Pseudomonadota]] phylum. This genus was one of the first [[bacteria]] discovered by Ukrainian botanist [[Sergei Winogradsky]]. During his research in [[Anton de Bary]]'s laboratory of botany in 1887, he found that ''Beggiatoa'' oxidized [[hydrogen sulfide]] (H<sub>2</sub>S) as an energy source, forming intracellular [[sulfur]] droplets, with [[oxygen]] as the terminal electron acceptor and [[carbon dioxide|CO<sub>2</sub>]] used as a carbon source. Winogradsky named it in honor of the Italian doctor and botanist [[Francesco Secondo Beggiato]] (1806 - 1883), from Venice.<ref>{{cite book | last=Burkhardt | first=Lotte | title=Eine Enzyklopädie zu eponymischen Pflanzennamen |trans-title=Encyclopedia of eponymic plant names | publisher=Botanic Garden and Botanical Museum, Freie Universität Berlin | year=2022 | isbn=978-3-946292-41-8 | url=https://doi.org/10.3372/epolist2022|format=pdf |language=German |location=Berlin | doi=10.3372/epolist2022 | s2cid=246307410 |access-date=January 27, 2022}}</ref> Winogradsky referred to this form of metabolism as "inorgoxidation" (oxidation of inorganic compounds), today called [[chemolithotrophy]]. These organisms live in sulfur-rich environments such as soil, both marine and freshwater, in the deep sea [[hydrothermal vent]]s, and in polluted marine environments. The finding represented the first discovery of [[lithotroph]]y.<ref>{{cite book|author=Ljungdahl LG|url=https://books.google.com/books?id=00wZ1DdZecAC&q=lithotrophy+sulfur&pg=PA17|title=Biochemistry and physiology of anaerobic bacteria|publisher=Springer|year=2003|isbn=978-0-387-95592-6|page=17}}</ref><ref name="pmid108947382">{{cite journal | vauthors = Mukhopadhyaya PN, Deb C, Lahiri C, Roy P | title = A soxA gene, encoding a diheme cytochrome c, and a sox locus, essential for sulfur oxidation in a new sulfur lithotrophic bacterium | journal = Journal of Bacteriology | volume = 182 | issue = 15 | pages = 4278–87 | date = August 2000 | pmid = 10894738 | pmc = 101942 | doi = 10.1128/JB.182.15.4278-4287.2000 }}</ref> Two species of ''Beggiatoa'' have been formally described: the type species ''[[Beggiatoa alba]]'' and ''[[Beggiatoa leptomitoformis]]'', the latter of which was only published in 2017.<ref name = "Parte_LPSN" /><ref>{{cite journal | vauthors = Dubinina G, Savvichev A, Orlova M, Gavrish E, Verbarg S, Grabovich M | title = Beggiatoa leptomitoformis sp. nov., the first freshwater member of the genus capable of chemolithoautotrophic growth | journal = International Journal of Systematic and Evolutionary Microbiology | volume = 67 | issue = 2 | pages = 197–204 | date = February 2017 | pmid = 27902215 | doi = 10.1099/ijsem.0.001584 | doi-access = free }}</ref> This colorless and filamentous bacterium, sometimes in association with other sulfur bacteria (for example the genus ''[[Thiothrix]]''), can be arranged in [[biofilm]] visible to the naked eye formed by a very long white filamentous mat. The white color is due to the stored sulfur. ''Beggiatoa'' have cells up to 200&nbsp;µm in diameter and they are one of the largest [[prokaryote]]s on Earth.<ref name="Teske_2006">{{cite book | vauthors = Teske A, Nelson DC |chapter=The Genera Beggiatoa and Thioploca|date=2006 |title=The Prokaryotes|pages=784–810| veditors = Dworkin M, Falkow S, Rosenberg E, Schleifer KH |publisher=Springer New York|language=en|doi=10.1007/0-387-30746-x_27 |isbn=978-0-387-25496-8 }}</ref>
+'''''Beggiatoa''''' is a [[genus]] of ''[[Gammaproteobacteria]]'' belonging to the order ''[[Thiotrichales]]'', in the ''[[Pseudomonadota]]'' phylum. This genus was one of the first [[bacteria]] discovered by Ukrainian botanist [[Sergei Winogradsky]]. During his research in [[Anton de Bary]]'s laboratory of botany in 1887, he found that ''Beggiatoa'' oxidized [[hydrogen sulfide]] (H<sub>2</sub>S) as an energy source, forming intracellular [[sulfur]] droplets, with [[oxygen]] as the terminal electron acceptor and [[carbon dioxide|CO<sub>2</sub>]] used as a carbon source. Winogradsky named it in honor of the Italian doctor and botanist [[Francesco Secondo Beggiato]] (1806 - 1883), from Venice.<ref>{{cite book | last=Burkhardt | first=Lotte | title=Eine Enzyklopädie zu eponymischen Pflanzennamen |trans-title=Encyclopedia of eponymic plant names | publisher=Botanic Garden and Botanical Museum, Freie Universität Berlin | year=2022 | isbn=978-3-946292-41-8 | url=https://doi.org/10.3372/epolist2022|format=pdf |language=German |location=Berlin | doi=10.3372/epolist2022 | s2cid=246307410 |access-date=January 27, 2022}}</ref> Winogradsky referred to this form of metabolism as "inorgoxidation" (oxidation of inorganic compounds), today called [[chemolithotrophy]]. These organisms live in sulfur-rich environments such as soil, both marine and freshwater, in the deep sea [[hydrothermal vent]]s, and in polluted marine environments. The finding represented the first discovery of [[lithotroph]]y.<ref>{{cite book|author=Ljungdahl LG|url=https://books.google.com/books?id=00wZ1DdZecAC&q=lithotrophy+sulfur&pg=PA17|title=Biochemistry and physiology of anaerobic bacteria|publisher=Springer|year=2003|isbn=978-0-387-95592-6|page=17}}</ref><ref name="pmid108947382">{{cite journal | vauthors = Mukhopadhyaya PN, Deb C, Lahiri C, Roy P | title = A soxA gene, encoding a diheme cytochrome c, and a sox locus, essential for sulfur oxidation in a new sulfur lithotrophic bacterium | journal = Journal of Bacteriology | volume = 182 | issue = 15 | pages = 4278–87 | date = August 2000 | pmid = 10894738 | pmc = 101942 | doi = 10.1128/JB.182.15.4278-4287.2000 }}</ref>
+These colorless and filamentous bacteria, sometimes in association with other sulfur bacteria (for example the genus ''[[Thiothrix]]''), can be arranged in [[biofilm]] visible to the naked eye formed by a very long white filamentous mat. The white color is due to the stored sulfur. ''Beggiatoa'' have cells up to 200&nbsp;µm in diameter and they are one of the largest [[prokaryote]]s on Earth.<ref name="Teske_2006">{{cite book | vauthors = Teske A, Nelson DC |chapter=The Genera Beggiatoa and Thioploca|date=2006 |title=The Prokaryotes|pages=784–810| veditors = Dworkin M, Falkow S, Rosenberg E, Schleifer KH |publisher=Springer New York|language=en|doi=10.1007/0-387-30746-x_27 |isbn=978-0-387-25496-8 }}</ref>
 == Taxonomy ==
 The genera ''Beggiatoa'' is a quite diverse group as it has representatives occupying several habitats and niches, both in fresh and salt water. In the past they have been confused as close relatives of [[Oscillatoria|''Oscillatoria'' spp.]] (''[[Cyanobacteria]]'') for the morphology and motility characters,<ref>{{cite journal | vauthors = Reichenbach H | title = Taxonomy of the gliding bacteria | journal = Annual Review of Microbiology | volume = 35 | issue = 1 | pages = 339–64 | date = 1981-10-01 | pmid = 6794424 | doi = 10.1146/annurev.mi.35.100181.002011 | url = https://www.annualreviews.org/doi/10.1146/annurev.mi.35.100181.002011 }}</ref> but 5S rRNA analysis showed that members of ''Beggiatoa'' are phylogenetically distant from ''Cyanobacteria,'' being members of the ''[[Gammaproteobacteria]]'' phylum.<ref>{{Cite journal| vauthors = Stahl DA, Lane DJ, Olsen GJ, Heller DJ, Schmidt TM, Pace NR |date=1987|title=Phylogenetic Analysis of Certain Sulfide-Oxidizing and Related Morphologically Conspicuous Bacteria by 5S Ribosomal Ribonucleic Acid Sequences|journal=International Journal of Systematic and Evolutionary Microbiology|volume=37|issue=2|pages=116–122|doi=10.1099/00207713-37-2-116|issn=1466-5026|doi-access=free}}</ref>
+Despite their diversity, only two species of ''Beggiatoa'' have been formally described: the type species ''[[Beggiatoa alba]]'' and ''[[Beggiatoa leptomitoformis]]'', the latter of which was only published in 2017.<ref name="Parte_LPSN" /><ref>{{cite journal |vauthors=Dubinina G, Savvichev A, Orlova M, Gavrish E, Verbarg S, Grabovich M |date=February 2017 |title=Beggiatoa leptomitoformis sp. nov., the first freshwater member of the genus capable of chemolithoautotrophic growth |journal=International Journal of Systematic and Evolutionary Microbiology |volume=67 |issue=2 |pages=197–204 |doi=10.1099/ijsem.0.001584 |pmid=27902215 |doi-access=free}}</ref>
-The capability to oxidize [[sulfide]] and store sulfur are the main features which separates ''Beggiatoa'' and closely related ''[[Thioploca]]'' as filamentous colorless sulfur bacteria from other filamentous bacteria (like cyanobacteria and the nonsulfur-oxidizing ''[[Cytophaga]]'' and ''[[Flexibacter]]'')<ref>{{cite book | vauthors = Teske A, Nelson DC |title=The Prokaryotes|chapter=The Genera Beggiatoa and Thioploca|date=2006 |work=The Prokaryotes: Volume 6: Proteobacteria: Gamma Subclass|pages=784–810| veditors = Dworkin M, Falkow S, Rosenberg E, Schleifer KH |place=New York, NY|publisher=Springer|language=en|doi=10.1007/0-387-30746-x_27|isbn=978-0-387-30746-6 }} [https://www.researchgate.net/profile/Andreas-Teske/publication/226700655_The_Genera_Beggiatoaand_Thioploca/links/0f31753887e8286076000000/The-Genera-Beggiatoa-and-Thioploca.pdf?origin=publication_detail PDF].</ref> Another defining feature is the ability to store [[nitrate]] inside the [[vacuole]]s of the wide marine species’ cells. 16S rRNA sequences base studies inferred that this characteristic is shared between members of a monophyletic clade nested in the ''Beggiatoa'' genera; this clade also includes members of ''[[Thioploca]]'' and ''[[Thiomargarita]]'', both presenting only slight differences with Beggiatoas: whereas the former grows sharing a common slime sheath, the latter has not conserved filamentous growth and forms chains of rounded cells. Since the phylogenic history do not reflect the nomenclature, there's a need for a new denomination of [[genera]] and [[species]].<ref>{{cite journal | vauthors = Ahmad A, Kalanetra KM, Nelson DC | title = Cultivated Beggiatoa spp. define the phylogenetic root of morphologically diverse, noncultured, vacuolate sulfur bacteria | journal = Canadian Journal of Microbiology | volume = 52 | issue = 6 | pages = 591–8 | date = June 2006 | pmid = 16788728 | doi = 10.1139/w05-154 | url = http://www.nrcresearchpress.com/doi/10.1139/w05-154 }}</ref> The Neo-type strain is the B18LB and it settled the criteria for identification of the freshwater species ''Beggiatoa alba''.<ref>{{Cite book|url=https://www.worldcat.org/oclc/619443681|title=Bergey's manual of systematic bacteriology|date=2001–2012|publisher=Springer | vauthors = Boone DR, Brenner DJ, Castenholz RW, De Vos P, Garrity GM, Krieg NR, Goodfellow N |isbn=978-0-387-21609-6|edition=2nd|location=New York|oclc=619443681}}</ref>
+The capability to oxidize [[sulfide]] and store sulfur are the main features which separates ''Beggiatoa'' and closely related ''[[Thioploca]]'' as filamentous colorless sulfur bacteria from other filamentous bacteria (like cyanobacteria and the nonsulfur-oxidizing ''[[Cytophaga]]'' and ''[[Flexibacter]]'').<ref>{{cite book | vauthors = Teske A, Nelson DC |title=The Prokaryotes|chapter=The Genera Beggiatoa and Thioploca|date=2006 |work=The Prokaryotes: Volume 6: Proteobacteria: Gamma Subclass|pages=784–810| veditors = Dworkin M, Falkow S, Rosenberg E, Schleifer KH |place=New York, NY|publisher=Springer|language=en|doi=10.1007/0-387-30746-x_27|isbn=978-0-387-30746-6 }} [https://www.researchgate.net/profile/Andreas-Teske/publication/226700655_The_Genera_Beggiatoaand_Thioploca/links/0f31753887e8286076000000/The-Genera-Beggiatoa-and-Thioploca.pdf?origin=publication_detail PDF].</ref> Another defining feature is the ability to store [[nitrate]] inside the [[vacuole]]s of the wide marine species’ cells. 16S rRNA sequences base studies inferred that this characteristic is shared between members of a monophyletic clade nested in the ''Beggiatoa'' genera; this clade also includes members of ''[[Thioploca]]'' and ''[[Thiomargarita]]'', both presenting only slight differences with Beggiatoas: whereas the former grows sharing a common slime sheath, the latter has not conserved filamentous growth and forms chains of rounded cells. Since the phylogenic history do not reflect the nomenclature, there is a need for a new denomination of [[genera]] and [[species]].<ref>{{cite journal | vauthors = Ahmad A, Kalanetra KM, Nelson DC | title = Cultivated Beggiatoa spp. define the phylogenetic root of morphologically diverse, noncultured, vacuolate sulfur bacteria | journal = Canadian Journal of Microbiology | volume = 52 | issue = 6 | pages = 591–8 | date = June 2006 | pmid = 16788728 | doi = 10.1139/w05-154 | url = http://www.nrcresearchpress.com/doi/10.1139/w05-154 }}</ref> The Neo-type strain is the B18LB and it settled the criteria for identification of the freshwater species ''Beggiatoa alba''.<ref>{{Cite book|url=https://www.worldcat.org/oclc/619443681|title=Bergey's manual of systematic bacteriology|date=2001–2012|publisher=Springer | vauthors = Boone DR, Brenner DJ, Castenholz RW, De Vos P, Garrity GM, Krieg NR, Goodfellow N |isbn=978-0-387-21609-6|edition=2nd|location=New York|oclc=619443681}}</ref>
-According to [https://www.ncbi.nlm.nih.gov/taxonomy NCBI] database only two species of ''Beggiatoa'' spp. have been validly published: ''[[Beggiatoa alba]]'', and ''[[Beggiatoa leptomitoformis]].''<ref>{{Cite web |title=Taxonomy browser (Beggiatoa) |url=https://www-ncbi-nlm-nih-gov.ezp3.lib.umn.edu/Taxonomy/Browser/wwwtax.cgi?id=1021 |access-date=February 11, 2024 |website=NCBI}}</ref>
 == Genetics ==
-Because of the lack of a [[pure culture]], little is known about the genetics of ''Beggiatoa''. ''Beggiatoa alba'' exhibits a [[GC-content|GC content]] between 40 and 42.7&nbsp;mol%, and the presence of two or three similar [[plasmid]]s. The [[genome size]] of ''Beggiatoa alba'' strain B18LD is about 3 [[Base pair|Megabase]] (Mb).<ref name="Teske_2006" /> In a study on ''Beggiatoa'' genome sequences obtained from two single filaments of a vacuolated strain, optical mapping showed that the genome size was about 7.4 Mb; pathways for sulfur oxidation, nitrate and oxygen respiration, and CO<sub>2</sub> fixation were detected, confirming its [[chemolithoautotrophic]] physiology. Furthermore, [[comparative genomics]] indicated horizontal gene transfer between ''Beggiatoa'' and ''Cyanobacteria'' of storage, metabolic, and gliding abilities.<ref>{{cite journal | vauthors = Mussmann M, Hu FZ, Richter M, de Beer D, Preisler A, Jørgensen BB, Huntemann M, Glöckner FO, Amann R, Koopman WJ, Lasken RS, Janto B, Hogg J, Stoodley P, Boissy R, Ehrlich GD | display-authors = 6 | title = Insights into the genome of large sulfur bacteria revealed by analysis of single filaments | journal = PLOS Biology | volume = 5 | issue = 9 | pages = e230 | date = September 2007 | pmid = 17760503 | pmc = 1951784 | doi = 10.1371/journal.pbio.0050230 | veditors = Moran NA | doi-access = free }}</ref>
+Because of the lack of a [[pure culture]], little is known about the genetics of ''Beggiatoa''. ''Beggiatoa alba'' has a [[GC-content|GC content]] between 40 and 42.7&nbsp;mol%,  two or three similar [[plasmid]]s, and a [[genome size]] of about 3 [[Base pair|Megabase]] (Mbp) (strain B18LD).<ref name="Teske_2006" /> In a study on ''Beggiatoa'' genome sequences obtained from two single filaments of a vacuolated strain, optical mapping showed that the genome size was about 7.4 Mbp; pathways for sulfur oxidation, nitrate and oxygen respiration, and CO<sub>2</sub> fixation were detected, confirming its [[chemolithoautotrophic]] physiology. Furthermore, [[comparative genomics]] indicated horizontal gene transfer between ''Beggiatoa'' and ''Cyanobacteria'' of storage, metabolic, and gliding abilities.<ref>{{cite journal | vauthors = Mussmann M, Hu FZ, Richter M, de Beer D, Preisler A, Jørgensen BB, Huntemann M, Glöckner FO, Amann R, Koopman WJ, Lasken RS, Janto B, Hogg J, Stoodley P, Boissy R, Ehrlich GD | display-authors = 6 | title = Insights into the genome of large sulfur bacteria revealed by analysis of single filaments | journal = PLOS Biology | volume = 5 | issue = 9 | pages = e230 | date = September 2007 | pmid = 17760503 | pmc = 1951784 | doi = 10.1371/journal.pbio.0050230 | veditors = Moran NA | doi-access = free }}</ref>
 == Morphology and motility ==
 [[File:Beggiatoa-like_filaments.jpg|thumb|348x348px|''Beggiatoa''-like filaments [[Underwater environment|underwater]]]]
-By the observation of their morphological characteristics, ''Beggiatoa'' spp. can be divided into three categories:
+''Beggiatoa'' spp. can be divided into three morphological categories{{Citation needed|date=February 2024}} (with some exceptions):
 # Freshwater strains, characterized by narrow filaments with no [[vacuole]]s;
 # Narrow marine strains, without vacuoles (filaments' [[diameter]] of about 4.4&nbsp;µm);
 # Larger marine strains, with vacuoles for [[nitrate]] storing (filaments' diameter vary between 5 and 140&nbsp;µm)
-Obviously, this classification is purely ideal so some exceptions can exist. Narrow filaments are usually composed by cylindrical cells which length is about 1.5 to 8 times their thickness; wider filaments instead are disk-shaped with cell lengths from 0.10 to 0.90 times their cell width. In all of the cultured strains the terminal cells of the filaments appear rounded. Although they are [[Gram-negative bacteria]], ''Beggiatoa'' show unusual [[Cell wall|cell-wall]] and [[membrane]] organization. Sometimes further membranes are present that cover the [[peptidoglycan layer]], but the number of these additional membranes is variable. Their presence may be due to the harsh conditions in which some of these organisms live. Even the intracellular granules can be covered by extra-membranes structure. Besides the sulfur granules, the cells often show the presence of similarly stored granules of [[polyhydroxybutyrate]] and [[polyphosphate]]. Very common in large marine vacuolated ''Beggiatoa'' are hollow-structured filaments, composed of cells with a narrow [[cytoplasm]] surrounding a large central vacuole used for nitrate storing.<ref name="Teske_2006" /><ref name="Ruuskanen_2014">{{cite journal| vauthors = Ruuskanen M |date=2014|title=The genus Beggiatoa and its effects on the nutrient cycles of the Baltic Sea |language=en|doi=10.13140/RG.2.1.4814.6329}}</ref>
+Narrow filaments are usually composed by cylindrical cells which length is about 1.5 to 8 times their thickness; wider filaments instead are disk-shaped with cell lengths from 0.10 to 0.90 times their cell width. In all of the cultured strains the terminal cells of the filaments appear rounded.{{Cn|date=February 2024}}
+Although they are [[Gram-negative bacteria]], ''Beggiatoa'' show unusual [[Cell wall|cell-wall]] and [[membrane]] organization. A variable number of further membranes that cover the [[peptidoglycan layer]] are sometimes present. Their presence may be due to the harsh conditions in which some of these organisms live. Intracellular granules can also be covered by membranes structures. In addition to sulfur granules, ''Beggiatoa'' cells often contain granules of [[polyhydroxybutyrate]] and [[polyphosphate]]. Large marine vacuolated ''Beggiatoa'' commonly have cells with a narrow [[cytoplasm]] surrounding a large central vacuole used to store nitrate.<ref name="Teske_2006" /><ref name="Ruuskanen_2014">{{cite journal| vauthors = Ruuskanen M |date=2014|title=The genus Beggiatoa and its effects on the nutrient cycles of the Baltic Sea |language=en|doi=10.13140/RG.2.1.4814.6329}}</ref>
-The filaments move by gliding and this movement is likely connected to string-like structures in the outer membrane and trans-[[peptidoglycan]] channels. Sometimes the filaments can also break through the formation of necridia cells in the middle of the filament. The motility of the filament is very important for the adaptability of the bacteria, because it allows to move on more suitable conditions for the [[Metabolism|cellular metabolism]]. The main drivers that guide the movement of ''Beggiatoa'' filaments are high [[oxygen]] and [[sulfide]] levels and light exposure, from which the filaments move away.<ref name="Ruuskanen_2014" />[[File:Beggiatoa_alba.jpg|left|thumb|257x257px|A drawing of ''[[Beggiatoa alba]]:'' A) Particular of intracellular sulfur droplets. B) Kinds of filament arrangement.]]
+The filaments move by gliding; this movement is likely connected to string-like structures in the outer membrane and trans-[[peptidoglycan]] channels. Filaments can also break, by forming necridia cells in the middle of the filament. The motility of the filament is important for the adaptability of the bacteria, because it allows to move on to more suitable conditions for their [[Metabolism|cellular metabolism]]. ''Beggiatoa'' filaments typically move away from high [[oxygen]] and [[sulfide]] levels, and from light exposure.<ref name="Ruuskanen_2014" />[[File:Beggiatoa_alba.jpg|left|thumb|257x257px|A drawing of ''[[Beggiatoa alba]]:'' A) Particular of intracellular sulfur droplets. B) Kinds of filament arrangement.]]
 == Cell growth ==
-''Beggiatoa'' reproducing strategy is [[Fragmentation (reproduction)|fragmentation]]. The growth of a colony leading to mat development is obtained through alternating filament elongation and breakage. Breakage can happen essentially in the middle of a stretched filament, at the tip of a filament loop or where a tip of a loop was once placed. The presence of sacrificial cells is fundamental as they interrupt the communication between two parts of one filament; in this way each section can change its gliding direction causing the split.
+''Beggiatoa'' use [[Fragmentation (reproduction)|fragmentation]] as a reproductive strategy. A colony can develop into a mat through alternating filament elongation and breakage. Breakage can happen in the middle of a stretched filament, at the tip of a filament loop, or where a tip of a loop was once placed. Sacrificial cells interrupt the communication between two parts of one filament; in this way each section can change its gliding direction causing the split.{{Cn|date=February 2024}}
 The average filament length achieved through this process is also result of gene-environment interactions as, for instance, the growth and position of the filament is function of vertical gradients of oxygen and sulfide. Therefore, it is proposed that good environmental conditions will paradoxically cause cell death in order to enhance filament breakage, thus reproduction.<ref>{{cite journal | vauthors = Kamp A, Røy H, Schulz-Vogt HN | title = Video-supported analysis of Beggiatoa filament growth, breakage, and movement | journal = Microbial Ecology | volume = 56 | issue = 3 | pages = 484–91 | date = October 2008 | pmid = 18335158 | pmc = 2755761 | doi = 10.1007/s00248-008-9367-x | bibcode = 2008MicEc..56..484K }}</ref>
@@ Line 79: / Line 83: @@
 === Habitat ===
-The incredible number of adaptations and [[metabolism]]s of this genus of bacteria are consequences of the extraordinary environmental variability they can live in. ''Beggiatoa'' is almost benthic, it can be found in marine (''Beggiatoa'' sp''.'' MS-81-6 and MS-81-1c) or freshwater (''Beggiatoa alba'') environments and they only need sulfide or thiosulfide as electron donor and an oxidizer. They can usually be found in habitats that have high levels of hydrogen sulfide, these environments include [[cold seep]]s, [[sulfur springs]], sewage contaminated water, mud layers of lakes, and near deep [[hydrothermal vent]]s. ''Beggiatoa'' can also be found in the [[rhizosphere]] of swamp plants,<ref>{{cite web | vauthors = Dudley M | url = http://filebox.vt.edu/users/chagedor/biol_4684/Microbes/Beggiatoa.htm | title = Beggiatoa | publisher = Virginia Tech | archive-url = https://web.archive.org/web/20090207052346/http://filebox.vt.edu/users/chagedor/biol_4684/Microbes/Beggiatoa.htm | archive-date = 2009-02-07 }}</ref><ref name="pmid9872789">{{cite journal | vauthors = Ahmad A, Barry JP, Nelson DC | title = Phylogenetic affinity of a wide, vacuolate, nitrate-accumulating Beggiatoa sp. from Monterey Canyon, California, with Thioploca spp | journal = Applied and Environmental Microbiology | volume = 65 | issue = 1 | pages = 270–7 | date = January 1999 | pmid = 9872789 | pmc = 91012 | doi = 10.1128/AEM.65.1.270-277.1999 | bibcode = 1999ApEnM..65..270A }}</ref> in soil, marine sediments and in the [[mangrove]] lagoon too (where they contribute to the lipid pool of the sediments<ref>{{cite journal| vauthors = SamKamaleson A, Gonsalves MJ |date= April 2019 |title=Role of sulfur-oxidizing bacteria on the ecology in tropical mangrove sediments |journal=Regional Studies in Marine Science|language=en|volume=28|pages=100574|doi=10.1016/j.rsma.2019.100574|bibcode= 2019RSMS...2800574S |s2cid= 134524779 |issn=2352-4855}}</ref>).<ref>{{cite journal | vauthors = Jean MR, Gonzalez-Rizzo S, Gauffre-Autelin P, Lengger SK, Schouten S, Gros O | title = Two new Beggiatoa species inhabiting marine mangrove sediments in the Caribbean | journal = PLOS ONE | volume = 10 | issue = 2 | pages = e0117832 | date = 2015-02-17 | pmid = 25689402 | pmc = 4331518 | doi = 10.1371/journal.pone.0117832 | bibcode = 2015PLoSO..1017832J | veditors = Kellogg CA | doi-access = free }}</ref> The freshwater species have typical habitats in sulfur springs, ditches, puddles, wetlands, lake sediments and in rice fields, where it can grow associated with the rice plants’ roots. The ''Beggiatoa'' that live in marine water can be found in regions where their source of energy (sulfide or thiosulfide) is available. It can be extracted from both inorganic or organic source and usually it is coupled with [[microoxic]] condition, therefore very low concentration of oxygen.<ref name="Teske_2006"/> This genus of [[Gammaproteobacteria|Gammaprotobacteria]] is also common in localizated area of anaerobic decomposition as [[whale]] carcass on the deep ocean seafloor.<ref name="Teske_2006" />
+The incredible number of adaptations and [[metabolism]]s of this genus of bacteria are consequences of the extraordinary environmental variability they can live in. ''Beggiatoa'' is almost benthic, it can be found in marine (''Beggiatoa'' sp''.'' MS-81-6 and MS-81-1c) or freshwater (''Beggiatoa alba'') environments and they only need sulfide or thiosulfide as electron donor and an oxidizer. They can usually be found in habitats that have high levels of hydrogen sulfide, these environments include [[cold seep]]s, [[sulfur springs]], sewage contaminated water, mud layers of lakes, and near deep [[hydrothermal vent]]s. ''Beggiatoa'' can also be found in the [[rhizosphere]] of swamp plants,<ref>{{cite web | vauthors = Dudley M | url = http://filebox.vt.edu/users/chagedor/biol_4684/Microbes/Beggiatoa.htm | title = Beggiatoa | publisher = Virginia Tech | archive-url = https://web.archive.org/web/20090207052346/http://filebox.vt.edu/users/chagedor/biol_4684/Microbes/Beggiatoa.htm | archive-date = 2009-02-07 }}</ref><ref name="pmid9872789">{{cite journal | vauthors = Ahmad A, Barry JP, Nelson DC | title = Phylogenetic affinity of a wide, vacuolate, nitrate-accumulating Beggiatoa sp. from Monterey Canyon, California, with Thioploca spp | journal = Applied and Environmental Microbiology | volume = 65 | issue = 1 | pages = 270–7 | date = January 1999 | pmid = 9872789 | pmc = 91012 | doi = 10.1128/AEM.65.1.270-277.1999 | bibcode = 1999ApEnM..65..270A }}</ref> in soil, marine sediments and in the [[mangrove]] lagoon too (where they contribute to the lipid pool of the sediments<ref>{{cite journal| vauthors = SamKamaleson A, Gonsalves MJ |date= April 2019 |title=Role of sulfur-oxidizing bacteria on the ecology in tropical mangrove sediments |journal=Regional Studies in Marine Science|language=en|volume=28|pages=100574|doi=10.1016/j.rsma.2019.100574|bibcode= 2019RSMS...2800574S |s2cid= 134524779 |issn=2352-4855}}</ref>).<ref>{{cite journal | vauthors = Jean MR, Gonzalez-Rizzo S, Gauffre-Autelin P, Lengger SK, Schouten S, Gros O | title = Two new Beggiatoa species inhabiting marine mangrove sediments in the Caribbean | journal = PLOS ONE | volume = 10 | issue = 2 | pages = e0117832 | date = 2015-02-17 | pmid = 25689402 | pmc = 4331518 | doi = 10.1371/journal.pone.0117832 | bibcode = 2015PLoSO..1017832J | veditors = Kellogg CA | doi-access = free }}</ref> The freshwater species have typical habitats in sulfur springs, ditches, puddles, wetlands, lake sediments and in rice fields, where it can grow associated with the rice plants’ roots. The ''Beggiatoa'' that live in marine water can be found in regions where their source of energy (sulfide or thiosulfide) is available. It can be extracted from both inorganic or organic source and usually it is coupled with [[microoxic]] condition, therefore very low concentration of oxygen.<ref name="Teske_2006"/> This genus of [[Gammaproteobacteria|Gammaprotobacteria]] is also common in localized area of anaerobic decomposition, such as [[whale]] carcasses on the deep ocean seafloor.<ref name="Teske_2006" />
 [[File:Beggiatoa.jpg|thumb|357x357px|A Beggiatoa-like bacterial mat filaments in underwater cave.]]
 Vacuolated ''Beggiatoa'' can be very common in coastal [[upwelling]] regions (for example [[Peru]] and [[Chile]] coasts), [[Hydrothermal vent|deep sea hydrothermal vents]] and [[Cold seep|cold vents]]; in these environments the [[Flocculation|floc]] mats (hair-like breast) can grow up and cover large areas and reach the height of 30&nbsp;cm. In deep sea hydrothermal vents and cold-seeps ''Beggiatoa'' can grow in filaments that can be up to 200 micrometres in diameter, which makes these ones the largest [[prokaryote]]s currently known. Vacuolated ''Beggiatoa'' can be found also in hypoxic seafloor, where the filaments can live inside the sediments at the depth of few cm (from 2 to 4&nbsp;cm); in same cases the ''Beggiatoa'' bacterial filaments can be the most abundant part of the microbial biomass in the sediments.<ref name="Teske_2006" />
-''Beggiatoa'' can also be found in [[salt marsh]]es, saline, and geothermally active underwater caves. Some studies on these environments have been carried out in the underwater caves of [[Dolomitization|dolomitized]] limestone in [[Cape Palinuro|Capo Palinuro]], [[Salerno]], ([[Italy]]). Here there are hydrothermal sulphidic springs and [[Biofilm|microbial biofilm]] is associated with the flow of hydrothermal fluids, whose activity is intermittent and starts during low tide. Mats found in the caves were composed by filaments resembling in most part ''Beggiatoa'', ''[[Thiothrix]]''  and ''[[Flexibacter]]'', and this Beggiatoa-like filaments were morphologically close to those found attached to rocks and the [[byssus]] of the [[mussel]]s from Lucky Strike Hydrothermal vents on the [[Mid-Atlantic Ridge]].<ref name="Teske_2006" />
+''Beggiatoa'' is also found in [[salt marsh]]es, saline, and geothermally active underwater caves. Some studies on these environments have been carried out in the underwater caves of [[Dolomitization|dolomitized]] limestone in [[Cape Palinuro|Capo Palinuro]], [[Salerno]], ([[Italy]]). Here there are hydrothermal sulphidic springs and [[Biofilm|microbial biofilm]] is associated with the flow of hydrothermal fluids, whose activity is intermittent and starts during low tide. Mats found in the caves were composed by filaments resembling in most part ''Beggiatoa'', ''[[Thiothrix]]''  and ''[[Flexibacter]]'', and this Beggiatoa-like filaments were morphologically close to those found attached to rocks and the [[byssus]] of the [[mussel]]s from Lucky Strike Hydrothermal vents on the [[Mid-Atlantic Ridge]].<ref name="Teske_2006" />
 === Interactions with other organisms ===
-Frequently, microorganisms of the genus ''Beggiatoa'' can form complex [[microbial mat]]s, where they live in association with many other filamentous bacteria, such as [[cyanobacteria]]. The latter usually occupy the surface layer of the mat and during the day they produce a great amount of oxygen, derived from the photosynthetic activity. Conversely, ''Beggiatoa'' grow along an oxic/anoxic (oxygen/sulfide) interface, beneath the [[phototroph]]s, where they produce white patches.<ref name="Teske_2006" /> However, during dark acclimation, the mat became anoxic, so the ''Beggiatoa'' moved to the mat surface, to avoid the high levels of H<sub>2</sub>S and remain at the oxygen/sulfide interface, while cyanobacteria remained in a dense layer below.<ref>{{cite journal| vauthors = Lichtenberg M, Cartaxana P, Kühl M |date=2020|title=Vertical Migration Optimizes Photosynthetic Efficiency of Motile Cyanobacteria in a Coastal Microbial Mat |journal=Frontiers in Marine Science|language=English|volume=7|doi=10.3389/fmars.2020.00359|s2cid=218863468|issn=2296-7745|doi-access=free}}</ref> Sometimes Beggiatoa mats are enriched by the presence of [[diatom]]s and green [[Euglenid|euglenoids]] too,<ref name="Fenchel_1995" /> but also protists as ciliates and dinoflagellates have been found associated with the mats at the [[Guaymas Basin]] hydrothermal vent ecosystem and they likely consume a large amount of bacterial biomass.<ref>{{cite journal | vauthors = Pasulka A, Hu SK, Countway PD, Coyne KJ, Cary SC, Heidelberg KB, Caron DA | title = SSU-rRNA Gene Sequencing Survey of Benthic Microbial Eukaryotes from Guaymas Basin Hydrothermal Vent | journal = The Journal of Eukaryotic Microbiology | volume = 66 | issue = 4 | pages = 637–653 | date = July 2019 | pmid = 30620427 | doi = 10.1111/jeu.12711 | s2cid = 58616192 }}</ref>
+''Beggiatoa'' can form complex [[microbial mat]]s in association with other filamentous bacteria, such as [[cyanobacteria]]. The cyanobacteria usually occupy the surface layer of the mat, and produce a great amount of oxygen during the day through photosynthesis. Conversely, ''Beggiatoa'' grow beneath the [[Phototroph|phototrophs]], along an oxic/anoxic (oxygen/sulfide) interface, where they produce white patches.<ref name="Teske_2006" /> However, during dark acclimation, the mat became anoxic, so the ''Beggiatoa'' moved to the mat surface, to avoid the high levels of H<sub>2</sub>S and remain at the oxygen/sulfide interface, while cyanobacteria remained in a dense layer below.<ref>{{cite journal| vauthors = Lichtenberg M, Cartaxana P, Kühl M |date=2020|title=Vertical Migration Optimizes Photosynthetic Efficiency of Motile Cyanobacteria in a Coastal Microbial Mat |journal=Frontiers in Marine Science|language=English|volume=7|doi=10.3389/fmars.2020.00359|s2cid=218863468|issn=2296-7745|doi-access=free}}</ref> Sometimes ''Beggiatoa'' mats are enriched by the presence of [[diatom]]s and green [[Euglenid|euglenoids]] too,<ref name="Fenchel_1995" /> but also protists as ciliates and dinoflagellates have been found associated with the mats at the [[Guaymas Basin]] hydrothermal vent ecosystem and they likely consume a large amount of bacterial biomass.<ref>{{cite journal | vauthors = Pasulka A, Hu SK, Countway PD, Coyne KJ, Cary SC, Heidelberg KB, Caron DA | title = SSU-rRNA Gene Sequencing Survey of Benthic Microbial Eukaryotes from Guaymas Basin Hydrothermal Vent | journal = The Journal of Eukaryotic Microbiology | volume = 66 | issue = 4 | pages = 637–653 | date = July 2019 | pmid = 30620427 | doi = 10.1111/jeu.12711 | s2cid = 58616192 }}</ref>
-As the microbial mats can reach 3&nbsp;cm in width, they can represent a source of food for many grazers. This trophic connection has been observed in [[mangrove]] systems, where ''Beggiatoa'' cover part of marine sediments. It has been observed that these bacteria give an important contribution to [[meiofauna]]'s diet, in particular [[rotifer]]s, [[polychaete]]s, [[nematode]]s and some groups of [[platyhelminthes]], [[aschelminth]]s and [[gnathostomulid]]s.<ref>{{cite journal| vauthors = Pascal PY, Dubois S, Boschker HT, Gros O |date=2014-12-03|title=Trophic role of large benthic sulfur bacteria in mangrove sediment |journal=Marine Ecology Progress Series|volume=516|pages=127–138|doi=10.3354/meps11035|bibcode=2014MEPS..516..127P|issn=0171-8630|url=https://archimer.ifremer.fr/doc/00248/35919/34449.pdf}}</ref> A remarkable relationship has been found between nematodes and ''Beggiatoa''. In fact nematodes seem to favor development of Beggiatoa mats, through the increasing of oxygen penetration and nutrient diffusion into the mat.<ref>{{cite journal | vauthors = Salvadó H, Palomo A, Mas M, Puigagut J, Gracia M | title = Dynamics of nematodes in a high organic loading rotating biological contactors | journal = Water Research | volume = 38 | issue = 10 | pages = 2571–8 | date = May 2004 | pmid = 15159160 | doi = 10.1016/j.watres.2004.03.007 | bibcode = 2004WatRe..38.2571S }}</ref>
+As the microbial mats can reach 3&nbsp;cm in width, they can be a food source for many grazers. This trophic connection has been observed in [[mangrove]] systems, where ''Beggiatoa'' cover part of marine sediments. The bacteria contribute to the diet of [[meiofauna]], in particular [[rotifer]]s, [[polychaete]]s, [[nematode]]s and some groups of [[platyhelminthes]], [[aschelminth]]s and [[gnathostomulid]]s.<ref>{{cite journal| vauthors = Pascal PY, Dubois S, Boschker HT, Gros O |date=2014-12-03|title=Trophic role of large benthic sulfur bacteria in mangrove sediment |journal=Marine Ecology Progress Series|volume=516|pages=127–138|doi=10.3354/meps11035|bibcode=2014MEPS..516..127P|issn=0171-8630|url=https://archimer.ifremer.fr/doc/00248/35919/34449.pdf}}</ref> Nematodes seem to encourage development of ''Beggiatoa'' mats, by increasing oxygen penetration and nutrient diffusion into the mat.<ref>{{cite journal | vauthors = Salvadó H, Palomo A, Mas M, Puigagut J, Gracia M | title = Dynamics of nematodes in a high organic loading rotating biological contactors | journal = Water Research | volume = 38 | issue = 10 | pages = 2571–8 | date = May 2004 | pmid = 15159160 | doi = 10.1016/j.watres.2004.03.007 | bibcode = 2004WatRe..38.2571S }}</ref>
-Furthermore, many [[carrion]] appear covered by mats of ''Beggiatoa''-like filamentous bacteria overlying anaerobic [[sulphate-reducing bacteria|sulfate-reducing bacteria]]. They attract many metazoans [[scavenger]]s, but when they break the mat, it releases hydrogen sulphide that drive away the scavengers. Hence, ''Beggiatoa'' can also be considered a carrion defence from the scavengers.<ref>{{cite journal| vauthors = Dayton PK, Oliver JS, Thrush SF, Hammerstrom K |date= February 2019 |title=Bacteria defend carrion from scavengers |journal=Antarctic Science|language=en|volume=31|issue=1|pages=13–15|doi=10.1017/S0954102018000457|bibcode= 2019AntSc..31...13D |s2cid= 134564783 |issn=0954-1020}}</ref>
+Furthermore, many [[carrion]] appear covered by mats of ''Beggiatoa''-like filamentous bacteria that overlie anaerobic [[sulphate-reducing bacteria|sulfate-reducing bacteria]]. They attract many metazoans [[scavenger]]s, but when they break the mat, it releases hydrogen sulphide that drives away the scavengers. Hence, ''Beggiatoa'' can also be considered a carrion defence from the scavengers.<ref>{{cite journal| vauthors = Dayton PK, Oliver JS, Thrush SF, Hammerstrom K |date= February 2019 |title=Bacteria defend carrion from scavengers |journal=Antarctic Science|language=en|volume=31|issue=1|pages=13–15|doi=10.1017/S0954102018000457|bibcode= 2019AntSc..31...13D |s2cid= 134564783 |issn=0954-1020}}</ref>
 === Role in biogeochemical cycles ===
 [[File:Beggiatoa4.jpg|thumb|356x356px|Massive mats of some Beggiatoa-like filaments in an underwater cave]]
-Several species of white sulfur bacteria in the family Beggiatoaceae are able to accumulate and transport [[Nitrate|NO<sub>3</sub><sup>−</sup>]], taken from shallow coastal sediments which is fundamental in metabolism, as well as accumulate it in filaments. The reduction of NO<sub>3</sub><sup>−</sup> to ammonium implies the oxidation of H<sub>2</sub>S (except for geothermal vents, the sulphide derives from the underlying anaerobic sediment in which dissimilatory sulphate reduction occurs<ref name="Fenchel_1995" />): this reduction leads to the formation of suboxic zones characterized by positive [[redox potential]] and only trace concentrations of free H<sub>2</sub>S. In marine environment, the presence of these species is important because they have a fundamental role in regulation of the amount of H<sub>2</sub>S and NO<sub>3</sub><sup>−</sup> :
+Several species of white sulfur bacteria in the family ''Beggiatoaceae'' can accumulate and transport [[Nitrate|NO<sub>3</sub><sup>−</sup>]], taken from shallow coastal sediments which is fundamental in metabolism, as well as accumulate it in filaments. The reduction of NO<sub>3</sub><sup>−</sup> to ammonium implies the oxidation of H<sub>2</sub>S (except for geothermal vents, the sulphide derives from the underlying anaerobic sediment in which dissimilatory sulphate reduction occurs<ref name="Fenchel_1995" />): this reduction leads to the formation of suboxic zones characterized by positive [[redox potential]] and only trace concentrations of free H<sub>2</sub>S. In marine environment, the presence of these species is important because they have a fundamental role in regulation of the amount of H<sub>2</sub>S and NO<sub>3</sub><sup>−</sup> :
 * On the one hand, the regulation of free H<sub>2</sub>S concentration in marine sediments is fundamental because sulfide-depleted surface sediments are essential for survival of [[Benthic zone|benthic]] infauna, in fact sulfide is highly toxic to bottom fauna and other organisms living in the sediment;
 * On the other hand, NO<sub>3</sub><sup>−</sup> reduction is important for the control of [[eutrophication]] in nitrogen-limited coastal waters.<ref>{{cite journal | vauthors = Sayama M, Risgaard-Petersen N, Nielsen LP, Fossing H, Christensen PB | title = Impact of bacterial NO3(-) transport on sediment biogeochemistry | journal = Applied and Environmental Microbiology | volume = 71 | issue = 11 | pages = 7575–7 | date = November 2005 | pmid = 16269807 | pmc = 1287653 | doi = 10.1128/AEM.71.11.7575-7577.2005 }}</ref>
-''Beggiatoa'' can also accumulate phosphorus as polyphosphate and it subsequently releases phosphate in anoxic conditions. This might increase the availability of phosphorus to primary producers if the phosphate is released from the sediment to the water column.  Some studies about the phosphorus cycling and the release of phosphorus linked to ''Beggiatoa'' have been realized in [[Baltic Sea]]. These studies showed that the reduction of sulfide by these bacteria may decrease the rate of iron sulfide formation in the sediments, and thus increase the phosphorus retention capability of the sediment.<ref name="Ruuskanen_2014" />
+''Beggiatoa'' can also accumulate phosphorus as polyphosphate, which it subsequently releases as phosphate under anoxic conditions. This might increase the availability of phosphorus to primary producers if the phosphate is released from the sediment to the water column. Studies on phosphorus cycling and phosphorus release ''Beggiatoa'' in [[Baltic Sea]] have found that the oxidation of sulfide by these bacteria may decrease the rate of iron sulfide formation in the sediments, and thus increase the phosphorus retention capability of the sediment.<ref name="Ruuskanen_2014" />
 == Cultivation ==