Microcystis aeruginosa

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Microcystis aeruginosa
Microcystis aeruginosa.jpeg
Scientific classification
Kingdom: Bacteria
Subkingdom: Eubacteria
Phylum: Cyanobacteria
Class: Cyanophyceae
Order: Chroococcales
Family: Microcystaceae
Genus: Microcystis
Species: M. aeruginosa
Binomial name
Microcystis aeruginosa
Kützing, 1846

Microcystis aeruginosa is a species of freshwater cyanobacteria which can form harmful algal blooms of economic and ecological importance.[1] They are the most common toxic cyanobacterial bloom in eutrophic fresh water.[1] Cyanobacteria produce neurotoxins and peptide hepatotoxins, such as microcystin and cyanopeptolin.[2]

Characteristics[edit]

NOAA MERIS image of large cyanobacterial bloom confirmed as M. aeruginosa[3]

As the etymological derivation implies, Microcystis is characterized by small cells (of only a few micrometers diameter), which lack individual sheaths.[4]

Cells usually are organized into colonies (large colonies of which may be viewed with the naked eye) that begin in a spherical shape, but lose their coherence to become perforated or irregularly shaped over time.[citation needed]

The protoplast is a light blue-green color, appearing dark or brown due to optical effects of gas-filled vesicles; this can be useful as a distinguishing characteristic when using light microscopy. These vesicles provide the buoyancy necessary for M. aeruginosa to stay at a level within the water column at which they can obtain optimum light and carbon dioxide levels for rapid growth.

Ecology[edit]

M. aeruginosa is favored by warm temperatures, but toxicity and maximal growth rates are not totally coupled, as the cyanobacterium has highest laboratory growth rates at 32 °C, while toxicity is highest at 20 °C, lowering in toxicity as a function of increasing temperatures in excess of 28 °C. Growth has been found to be limited below 15 °C.

The aquatic plant Myriophyllum spicatum produces ellagic, gallic, and pyrogallic acids and (+)-catechin, allelopathic polyphenols inhibiting the growth of M. aeruginosa.[5]

Toxins[edit]

See also: Cyanotoxin

M. aeruginosa can produce both neurotoxins (lipopolysaccharides-LPSs)[6] and hepatotoxins (microcystins).

Economic importance[edit]

Because of M. aeruginosa´s microcystin toxin production under the right environmental conditions, it can be a source of drinking water pollution.[7] water quality mitigation measures in the form of water filtration facilities can lead to increased economic costs as well as damage to local tourism caused by lake or other waterway closures.[8]

M. aeruginosa is the subject of research into the natural production of butylated hydroxytoluene (BHT),[9] an antioxidant, food additive, and industrial chemical.

Ecological importance[edit]

In 2009, unprecedented mammal mortality in the southern part of the Kruger National Park led to an investigation which implicated M. aeruginosa. The dead animals included grazers and browsers which preferred drinking from the leeward side of two dams, a natural point of accumulation for drifting Microcystis blooms. Mammals such as elephants and buffalo which usually wade into water before drinking, were unaffected, as were the resident crocodiles. The source of nutrients which supported the Microcystis growth was narrowed down to the dung and urine voided in the water by a large resident hippo population, unaffected by the bloom. The immediate problem was solved by breaching of the dam walls and draining of the water. M. aeruginosa is the most abundant cyanobacterial genus in South Africa, may be a toxic or a harmless strains.[10]

Microcystin has been linked to the death of sea otters in 2010, a threatened species in the US.[11] The poisoning probably resulted from eating contaminated bivalves often consumed by sea otters and humans. The researchers noted that such bivalves in the area exhibited significant biomagnification (to 107 times ambient water levels) of microcystin.[12]

Glyphosate metabolism[edit]

Algal blooms of cyanobacteria thrive in the large phosphorus content of agricultural runoff. Besides consuming phosphorus, M. aeruginosa thrives on glyphosate, although high concentrations may inhibit it.[13] M. aeruginosa has shown glyphosate resistance as result of preselective mutations, and glyphosate serves as a nutrient to this and other microbes that are able to tolerate its effects, while killing those less tolerant.[14]

See also[edit]

References[edit]

  1. ^ a b Oberholster, PJ. "Microcystis aeruginosa: source of toxic microcystins in drinking water". African Journal of Biotechnology March 2004 Volume 3 pp 159-168. Retrieved August 4, 2014. 
  2. ^ "On the Evolution of Nonribosomal Peptide Synthetase Gene Clusters in Cyanobacteria". University of Oslo. 2007. 
  3. ^ "Ecosystem Research and Harmful Algal Blooms". Center of Excellence for Great Lakes and Human Health. NOAA. Retrieved 27 June 2011. 
  4. ^ "Cyanobacteria: Microcystis". The Silica Secchi Disk. Connecticut College: The SilicaSecchi Disk. Retrieved 24 June 2011. 
  5. ^ Myriophyllum spicatum-released allelopathic polyphenols inhibiting growth of blue-greenalgaeMicrocystis aeruginosa. Satoshi Nakai, Yutaka Inoue, Masaaki Hosomi and Akihiko Murakami, Water Research, Volume 34, Issue 11, 1 August 2000, Pages 3026–3032, doi:10.1016/S0043-1354(00)00039-7
  6. ^ Mayer, Alejandro M. S.; Jonathan A. Clifford (May 2011). "Cyanobacterial Microcystis aeruginosa Lipopolysaccharide Elicits Release of Superoxide Anion, Thromboxane B2, Cytokines, Chemokines, and Matrix Metalloproteinase-9 by Rat Microglia". Toxicological Sciences. 121 (1). Retrieved 25 June 2011. 
  7. ^ "Cyanobacterial Toxins: Microcystin-LR in drinking water" (PDF). Background document for development of WHO Guidelines for Drinking Water Quality. World Health Organization (WHO). Retrieved 24 June 2011. 
  8. ^ Somek, Hasim. "A Case Report: Algal Bloom of Microcystis aeruginosa in a Drinking-Water Body, Eğirdir Lake, Turkey" (PDF). A Case Report: Algal Bloom of Microcystis aeruginosa in a Drinking-Water Body, Eğirdir Lake, Turkey. Turkish Journal of Fisheries and Aquatic Sciences. Retrieved 27 June 2011. 
  9. ^ Babu B, Wu JT (December 2008). "Production of Natural Butylated Hydroxytoluene as an Antioxidant by Freshwater Phytoplankton" (PDF). Journal of Phycology. 44 (6): 1447–1454. doi:10.1111/j.1529-8817.2008.00596.x. PMID 27039859. 
  10. ^ Paul J. Oberholster, Jan G. Myburgh, Danny Govender, Roy Bengis, Anna-Maria Botha Identification of toxigenic Microcystis strains after incidents of wild animal mortalities in the Kruger National Park, South Africa. Ecotoxicology and Environmental Safety (2009), Elsevier doi:10.1016/j.ecoenv.2008.12.014
  11. ^ Stephens, Tim (September 10, 2010). "Sea otter deaths linked to toxin from freshwater bacteria". UC Santa Cruz Newscenter. 
  12. ^ Miller, Melissa (2010-09-10). "Evidence for a Novel Marine Harmful Algal Bloom: Cyanotoxin (Microcystin) Transfer from Land to Sea Otters". PLOS ONE. 5: e12576. doi:10.1371/journal.pone.0012576. PMC 2936937Freely accessible. PMID 20844747. 
  13. ^ Qiu, Huimin (2013-03-15). "Physiological and biochemical responses of Microcystis aeruginosa to glyphosate and its Roundup® formulation". Journal of Hazardous Materials. 248–249: 172–176. doi:10.1016/j.jhazmat.2012.12.033. PMID 23357506. 
  14. ^ "Resistance to glyphosate in the cyanobacterium Microcystis aeruginosa as result of pre-selective mutations". Evolutionary Ecology. 21 (4): 535–547. 2007-07-01. doi:10.1007/s10682-006-9134-8.