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 some strains of Bacillus safensis are resistant to UV rays, gamma rays and is highly salt resistant, it makes for a great plant growth-promoting rhizobacteria. This is very important in agriculture and crop health.
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
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Edited by Margo Ucar, student of Rachel Larsen and Kit Pogliano
Edited by a student of M Glogowski at Loyola University
