Bacillus subtilis
A Microbial Biorealm page on the genus Bacillus subtilis
Classification
Domain: Bacteria Division/phylum: Firmicutes Class: Bacilli Order: Bacillales Family: Bacillaceae Genus: Bacillus Species: B. safensis
Genus
Bacillus safensis
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NCBI: Taxonomy |
Description and significance
Bacillus safensis is a Gram-positive, spore-forming, and rod bacterium. It is aerobic and highly resistant to UV and gamma rays and salt. It was first discovered in CAlifornia and Florida on spacecraft and so is believed to have been brought to the USA from Mars. There are numerous strains of this bacterium, everyone belonging to the Firmicutes phylum of Bacteria.
Genome structure
Bacillus safensis is a circular chromosome of 3.68 Mb, with approximately 3928 protein coding sequences and 39 contigs/overlapping DNA fragments greater than 200 base pairs in size. The genome also displays 73 tRNA genes. The strain FO-036b shows a guanine-cytosine content of 41.0-41.4 mol%.
Cell structure and metabolism
Bacillus safensis is an aerobic, mesophilic, gram positive, spore forming chemoheterotroph. Cell shape: rod Cell size: ranges from 0.5-0.7 μm in diameter and 1.0-1.2 μm in length Cell movement: motile, and use polar flagella for locomotion. Colony characteristics: dull white, undulate round, non-luminescent with irregular borders Growth: mesophillic, as they can grow in temperatures ranging between 10-50 °C. Salt tolerance: prefers 0-10% salt, and a pH of 4-8 Resistances: produce spores that are resistant to hydrogen peroxide and UV radiation.
Positive for oxidase and catalase, Vogues-Proskauer Negative for trypsin, mannitol, ed, but H2S, indole, amylase, agarase, lecithinase, DNase, urease, leucine arylamidase, cystine arylamidase, valine arylamidase, trypsin, α-galactosidase, N-acetyl-β-glucosamidase, α-fucosidase, tryptophan deaminase, phenylalanine deaminase, arginine dihydrolase, lysine decarboxylase and ornithine decarboxylase. Cells do not reduce nitrate, but do hydrolyse gelatin, aesculin and RNA. Negative for gas production from D-glucose. Acid is produced from D-glucose, glycerol, L-arabinose, ribose, D-xylose, galactose
Strain VK also contains genes that encode for 1-aminocyclopropane-1-carboxylate deaminase enzyme which enables the plant to tolerate salt, heavy metals, and polyaromatic hydrocarbons. Because it is so tolerant, Bacillus safensis VK is a powerful plant hormone producer.
Ecology
Because Bacillus safensis is resistant to UV rays, gamma rays and is highly salt resistant, it makes for a great plant growth-promoting rhizobacteria.
Several isolates of the genus Bacillus are nearly identical to Bacillus pumilus. The group of isolates related to B. pumilus contains five related species: B. pumilus, B. safensis, B. stratosphericus, B. altitudinis, and B. aerophilus. These species are difficult to distinguish to due to their 99.5% similarity in their 16S rRNA gene sequence. Recently, scientists have discovered an alternate way to differentiate between these closely related species, especially B. pumilus and B. safensis.[10]
DNA gyrase is an important enzyme that introduces a negative supercoil to the DNA and is responsible for the biological processes in DNA replication and transcription.[10] DNA gyrase is made of two subunits, A and B. These subunits are denoted as gyrA and gyrB. The gyrB gene, subunit B protein, is a type II topoisomerase that is essential for DNA replication.[10] This gene is conserved among bacterial species. The rate of evolution at the molecular level deduced from gyrB related gene sequences can be determined at more accelerated rate compared to the 16S rRNA gene sequences.[10] These subunits have provided a way to phylogenetically distinguish between the diversity of species related to B. pumilus, which includes B. safensis. Strain B. safensis DSM19292 shares 90.2% gyrA sequence similarity with B. pumilus strain DSM 27.[10]
In 1952, a strain of B. pumilus was discovered in the DSMZ culture and labeled as strain DSM 354.[10] The strain was identified before B. safensis was discovered. In 2012, a gyrA sequence similarity was tested between the B. pumilus strain DSM 354 B. pumilus strain DSM 27, as well as against B. safensis strain DSM 19292.[10] Strain DSM 354 showed a 90.4% and 98% sequence similarity with B. pumilus strain DSM 27 and B. safensis strain DSM 19292, respectively.[10] These results indicated that DSM 354 may in fact be a B. safensis strain, instead of a B. pumilus strain. These results supported that gyrA sequences could be used to differentiate between closely related bacteria.[10]
Pathology
Bacillus subtilis bacteria are non-pathogenic. They can contaminate food, however, they seldom result in food poisoning. They are used on plants as a fungicide. They are also used on agricultural seeds, such as vegetable and soybean seeds, as a fungicide. The bacteria, colonized on root systems, compete with disease causing fungal organisms. Bacillus subtilis use as a fungicide fortunately does not affect humans (EMBL EBI). Some strains of Bacillus subtilis cause rots in potatoes. It grows in food that is non-acidic, and can cause ropiness in bread that is spoiled (Todar). Some strains related to Bacillus subtilis are capable of producing toxins for insects. Those strains can also be used for protecting crops as well. Bacillus thuringiensis, for example, is another bacterium in the same genus that is used for insect control (EMBL EBI).
Some Bacillus species can cause food poisoning, such as Bacillus cereus and Bacillus licheniformis. Bacillus cereus can result in two different kinds of intoxications. It can either cause nausea, vomiting, and abdominal cramps for 1-6 hours, or diarrhea and abdominal cramps for 8-16 hours. The food poisoning usually occurs from eating rice that is contaminated with Bacillus cereus (EMBL EBI).
Some Bacillus organisms can cause more severe illnesses. Bacillus anthracis, for example, causes Anthrax. It was the first bacterial organism that was known to cause disease in humans. Bacillus anthracis spores can survive for very long periods of time. Anthrax is very rare in humans, however it is more common in animals. The disease often begins with a very high fever and chest pain, and can be fatal if untreated (EMBL EBI).
Application to Biotechnology
Thirteen strains of a novel spore-forming, Gram-positive, mesophilic heterotrophic bacterium were isolated from spacecraft surfaces (Mars Odyssey Orbiter) and assembly-facility surfaces at the Jet Propulsion Laboratory in California and the Kennedy Space Center in Florida. Phylogenetic analysis of 16S rRNA gene sequences has placed these novel isolates within the genus Bacillus, the greatest sequence similarity (99.9 %) being found with Bacillus pumilus. However, these isolates share a mere 91.2 % gyrB sequence similarity with Bacillus pumilus, rendering their 16S rRNA gene-derived relatedness suspect. Furthermore, DNA–DNA hybridization showed only 54–66 % DNA relatedness between the novel isolates and strains of B. pumilus. rep-PCR fingerprinting and previously reported matrix-assisted laser desorption/ionization time-of-flight mass spectrometry protein profiling clearly distinguished these isolates from B. pumilus. Phenotypic analyses also showed some differentiation between the two genotypic groups, although the fatty acid compositions were almost identical. The polyphasic taxonomic studies revealed distinct clustering of the tested strains into two distinct species. On the basis of phenotypic characteristics and the results of phylogenetic analyses of 16S rRNA and gyrB gene sequences, repetitive element primer-PCR fingerprinting and DNA–DNA hybridization, the 13 isolates represent a novel species of the genus Bacillus, for which the name Bacillus safensis sp. nov. is proposed.
Current Research
References
[1] Ara, K., et al. "Bacillus minimum genome factory: effective utilization of microbial genome information." Biotechnol. Appl. Biochem.. 2007 March; 46(Pt 3):169-78.
[2] Bandow, J.E., H. Br�tz, M. Hecker. "Bacillus subtilis Tolerance of Moderate Concentrations of Rifampin Involves the ?B-Dependent General and Multiple Stress Response". Journal of Bacteriology. 2002 January; 184(2): 459�467.
[3]
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[4]
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[5]
Feng, J., et al. "Effect of Fermented Soybean Meal on Intestinal Morphology and Digestive Enzyme Activities in Weaned Piglets". Digestive Diseases and Sciences. 2007 April.
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Graumann, P. 2007. Bacillus: Cellular and Molecular Biology. Caister Academic press. ISBN 978-1-904455-12-7.
[7]
Jamil, B., et al. "Isolation of Bacillus subtilis MH-4 from Soil and its Potential of Polypeptidic Antibiotic Production". Pak J Pharm Sci. 2007 January; 20(1):26-31.
[8]
Kobayashi, K., et al. "Essential Bacillus subtilis genes". Proc Natl Acad Sci U S A. 2003 April 15; 100(8): 4678�4683.
[9]
Kunst, F., et al. "The complete genome sequence of the Gram-positive bacterium Bacillus subtilis". Nature. 1997 November; 390, 249-256.
[10]
Liu, NJ., RJ. Dutton, K. Pogliano. "Evidence that the SpoIIIE DNA Translocase Participates in Membrane Fusion During Cytokinesis and Engulfment". Mol Microbiol 2006 February;59(4):1097-113.
[11]
Marino, M., et al. "Modulation of Anaerobic Energy Metabolism of Bacillus subtilis by arfM (ywiD)". J Bacteriol. 2001 December; 183(23): 6815�6821.
[12]
Morikawa, M. "Beneficial Biofilm Formation by Industrial Bacteria Bacillus subtilis and Related Species". Journal of Bioscience and Bioengineering. 2006; Vol.101, No.1, 1-8.
[13] Nakano, M.M., P. Zuber. "Anaerobic Growth of a 'Strict Aerobe' (Bacillus subtilis)". Annual Review of Microbiology. 1998 October; Vol. 52: 165-190.
[14] Perez, A.R., A. Abanes-De Mello, K. Pogliano. "SpoIIB Localizes to Active Sites of Septal Biogenesis and Spatially Regulates Septal Thinning during Engulfment in Bacillus subtilis". Journal of Bacteriology. 2000 February; 182(4): 1096�1108.
Schaechter, M., J.L. Ingraham, F.C. Neidhardt. Microbe. (ASM Press, Washington, DC, 2006).
[15]
Setlow, P. "Spores of Bacillus subtilis:Their Resistance to and Killing by Radiation, Heat, and Chemicals". Journal of Applied Microbiology. 2006 September; 101(3), 514-525.
[16]
The Institute for Genome Research, Comprehensive Microbial Resource (TIGR CMR).
[17]
Todar, K. "Todar's Online Textbook of Bacteriology".
Edited by Margo Ucar, student of Rachel Larsen and Kit Pogliano
Edited by a student of M Glogowski at Loyola University
