Bacillus is a genus of gram-positive, rod-shaped bacteria and a member of the phylum Firmicutes. Bacillus species can be obligate aerobes (oxygen reliant), or facultative anaerobes (having the ability to be aerobic or anaerobic). They will test positive for the enzyme catalase when there has been oxygen used or present. Ubiquitous in nature, Bacillus includes both free-living (nonparasitic) and parasitic pathogenic species. Under stressful environmental conditions, the bacteria can produce oval endospores that are not true 'spores', but to which the bacteria can reduce themselves and remain in a dormant state for very long periods. These characteristics originally defined the genus, but not all such species are closely related, and many have been moved to other genera of the Firmicutes.
Many species of Bacillus can produce copious amounts of enzymes which are made use of in different industries. Some species can form intracellular inclusions of polyhydroxyalkanoates under certain adverse environmental conditions, as in a lack of elements such as phosphorus, nitrogen, or oxygen combined with an excessive supply of carbon sources.
Many Bacillus species are able to secrete large quantities of enzymes. Bacillus amyloliquefaciens is the source of a natural antibiotic protein barnase (a ribonuclease), alpha amylase used in starch hydrolysis, the protease subtilisin used with detergents, and the BamH1 restriction enzyme used in DNA research.
Use as model organism
Bacillus subtilis is one of the best understood prokaryotes, in terms of molecular and cellular biology. Its superb genetic amenability and relatively large size have provided the powerful tools required to investigate a bacterium from all possible aspects. Recent improvements in fluorescent microscopy techniques have provided novel insight into the dynamic structure of a single cell organism. Research on B. subtilis has been at the forefront of bacterial molecular biology and cytology, and the organism is a model for differentiation, gene/protein regulation, and cell cycle events in bacteria.
Bacillus species are almost ubiquitous in nature, e.g. in soil, but also occur in extreme environments such as high pH (B. alcalophilus), high temperature (B. thermophilus), or high salt (B. halodurans). B. thuringiensis produces a toxin that can kill insects and thus has been used as insecticide.
Two Bacillus species are considered medically significant: B. anthracis, which causes anthrax, and B. cereus, which causes food poisoning similar to that caused by Staphylococcus. A third species, B. thuringiensis, is an important insect pathogen, and is sometimes used to control insect pests. The type species is B. subtilis, an important model organism. It is also a notable food spoiler, causing ropiness in bread and related food. Some environmental and commercial strains of B. coagulans may play a role in food spoilage of highly acidic, tomato-based products.
An easy way to isolate Bacillus species is by placing nonsterile soil in a test tube with water, shaking, placing in melted mannitol salt agar, and incubating at room temperature for at least a day. Colonies are usually large, spreading, and irregularly shaped. Under the microscope, the Bacillus cells appear as rods, and a substantial portion of the cells usually contain oval endospores at one end, making it bulge.
The cell wall of Bacillus is a structure on the outside of the cell that forms the second barrier between the bacterium and the environment, and at the same time maintains the rod shape and withstands the pressure generated by the cell's turgor. The cell wall is composed of teichoic and teichuronic acids. B. subtilis is the first bacterium for which the role of an actin-like cytoskeleton in cell shape determination and peptidoglycan synthesis was identified, and for which the entire set of peptidoglycan-synthesizing enzymes was localised. The role of the cytoskeleton in shape generation and maintenance is important
The genus Bacillus was named in 1835 by Christian Gottfried Ehrenberg, to contain rod-shaped (bacillus) bacteria. He had seven years earlier named the genus Bacterium. Bacillus was later amended by Ferdinand Cohn to further describe them as spore-forming, Gram-positive, aerobic or facultatively anaerobic bacteria. Like other genera associated with the early history of microbiology, such as Pseudomonas and Vibrio, the 266 species of Bacillus are ubiquitous. The genus has a very large ribosomal 16S diversity and is environmentally diverse.
Several studies have tried to reconstruct the phylogeny of the genus. The Bacillus-specific study with the most diversity covered is by Xu and Cote using 16S and the ITS regions, where they divide the genus into 10 groups, which includes the nested genera Paenibacillus, Brevibacillus, Geobacillus, Marinibacillus and Virgibacillus. However, the tree  constructed by the living tree project, a collaboration between ARB-Silva and LPSN where a 16S (and 23S if available) tree of all validated species was constructed, the genus Bacillus contains a very large number of nested taxa and majorly in both 16S and 23S it is paraphyletic to the Lactobacillales (Lactobacillus, Streptococcus, Staphylococcus, Listeria, etc.), due to Bacillus coahuilensis and others. A gene concatenation study found similar results to Xu and Cote, but with a much more limited number of species in terms of groups, but used Listeria as an outgroup, so in light of the ARB tree, it may be "inside-out".
One clade, formed by B. anthracis, B. cereus, B. mycoides, B. pseudomycoides, B. thuringiensis, and B. weihenstephanensis under current classification standards, should be a single species (within 97% 16S identity), but due to medical reasons, they are considered separate species,:34–35 an issue also present for four species of Shigella and Escherichia coli.
|Phylogeny of the genus Bacillus according to |
- (German) Cohn F.: Untersuchungen über Bakterien. Beitrage zur Biologie der Pflanzen Heft 2, 1872, 1, 127-224.
- Turnbull PCB (1996). Baron S; et al., eds. Bacillus. In: Barron's Medical Microbiology (4th ed.). Univ of Texas Medical Branch. ISBN 978-0-9631172-1-2.
- Madigan M; Martinko J, eds. (2005). Brock Biology of Microorganisms (11th ed.). Prentice Hall. ISBN 0-13-144329-1.
- Graumann P, ed. (2012). Bacillus: Cellular and Molecular Biology (2nd ed.). Caister Academic Press. ISBN 978-1-904455-97-4. .
- Joan L. Slonczewski & John W. Foster (2011), Microbiology: An Evolving Science (2nd Edition), Norton
- Ryan KJ; Ray CG, eds. (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. ISBN 0-8385-8529-9.
- Bacillus entry in LPSN [Euzéby, J.P. (1997). "List of Bacterial Names with Standing in Nomenclature: a folder available on the Internet". Int J Syst Bacteriol. 47 (2): 590–2. doi:10.1099/00207713-47-2-590. ISSN 0020-7713. PMID 9103655.]
- Xu, D.; Cote, J. -C. (2003). "Phylogenetic relationships between Bacillus species and related genera inferred from comparison of 3' end 16S rDNA and 5' end 16S-23S ITS nucleotide sequences". International Journal of Systematic and Evolutionary Microbiology. 53 (3): 695–704. doi:10.1099/Ijs.0.02346-0.
- Yarza, P.; Richter, M.; Peplies, J. R.; Euzeby, J.; Amann, R.; Schleifer, K. H.; Ludwig, W.; Glöckner, F. O.; Rosselló-Móra, R. (2008). "The All-Species Living Tree project: A 16S rRNA-based phylogenetic tree of all sequenced type strains". Systematic and Applied Microbiology. 31 (4): 241–250. doi:10.1016/j.syapm.2008.07.001. PMID 18692976.
- Yarza, P.; Ludwig, W.; Euzéby, J.; Amann, R.; Schleifer, K. H.; Glöckner, F. O.; Rosselló-Móra, R. (2010). "Update of the All-Species Living Tree Project based on 16S and 23S rRNA sequence analyses". Systematic and Applied Microbiology. 33 (6): 291–299. doi:10.1016/j.syapm.2010.08.001. PMID 20817437.
- Alcaraz, L.; Moreno-Hagelsieb, G.; Eguiarte, L. E.; Souza, V.; Herrera-Estrella, L.; Olmedo, G. (2010). "Understanding the evolutionary relationships and major traits of Bacillus through comparative genomics". BMC Genomics. 11: 332. doi:10.1186/1471-2164-11-332. PMC . PMID 20504335. 1471216411332.
- Ole Andreas Økstad and Anne-Brit Kolstø Chapter 2: "Genomics of Bacillus Species" in M. Wiedmann, W. Zhang (eds.), Genomics of Foodborne Bacterial Pathogens, 29 Food Microbiology and Food Safety. Springer Science+Business Media, LLC 2011 DOI 10.1007/978-1-4419-7686-4_2
- Brenner (D.J.): Family I. Enterobacteriaceae Rahn 1937, Nom. fam. cons. Opin. 15, Jud. Com. 1958, 73; Ewing, Farmer, and Brenner 1980, 674; Judicial Commission 1981, 104. In: N.R. Krieg and J.G. Holt (eds), Bergey's Manual of Systematic Bacteriology, first edition, vol. 1, The Williams & Wilkins Co, Baltimore, 1984, pp. 408-420
- Ash, Carol; Priest, Fergus G.; Collins, M. David (1994). "Molecular identification of rRNA group 3 bacilli (Ash, Farrow, Wallbanks and Collins) using a PCR probe test". Antonie van Leeuwenhoek. 64 (3-4): 253–260. doi:10.1007/BF00873085.
- Heyndrickx, M.; Lebbe, L.; Kersters, K.; De Vos, P.; Forsyth, G.; Logan, N. A. (1 January 1998). "Virgibacillus: a new genus to accommodate Bacillus pantothenticus (Proom and Knight 1950). Emended description of Virgibacillus pantothenticus". International Journal of Systematic Bacteriology. 48 (1): 99–106. doi:10.1099/00207713-48-1-99.
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