Bacillus subtilis

Bacillus subtilis

Bacillus subtilis (Latin Bacillum / bacillus, chopsticks; subtilis, simple) or hay bacillus is a common gram-positive, rod-shaped, flagellated bacterium. Like all bacteria of the genus Bacillus is B. subtilis aerobically growing Endosporenbildner.

Taxonomy

Taxonomically counting B. subtilis to the Eubacteria (Bacteria), more specifically to the Gram- positive ( Firmicutes ). He is the class of bacilli and clostridia associated with (low GC content ). This class is the bacillus - staphylococcal group is subordinate, which, among other things, the family Bacillaceae with the genus Bacillus ( about 150 species ) including (Claus & Berkeley, 1986). The phylogenetic proximity to pathogens such as Staphylococcus, Listeria, mycobacteria and mycoplasmas makes B. subtilis particularly interesting for molecular biological and medical research.

Historical

B. subtilis was described in 1835 by Christian Gottfried Ehrenberg as Vibrio subtilis ( Curved rods). In 1872 it was renamed by Ferdinand Julius Cohn in Bacillus subtilis (rods ) and associated by Fischer in 1895 a genus of the same name.

Morphology

The rod-like B. subtilis usually has a size of approximately 2 to 3 microns, the thickness is about 0.6 microns. The cells are peritrichous, flagella so many times and distributed throughout the cell and can move it easily. The bacterium is surrounded by a Gram-positive cell wall, the cell can withstand a pressure of 20 atmospheres.

Lifestyle and physiology

B. subtilis is ubiquitous and can be made of soil (especially compost ), water and air are isolated. But his natural habitat, the upper layers of the soil. There is almost constantly exposed to stress and starvation situations due to frequently changing environmental conditions to which it must adapt accordingly.

The name hay bacillus wears it, because it is easy to accumulate in a so-called Heuaufguss. The generation time during optimum nutrient supply, optimal oxygen supply and an optimal growth temperature of 40 ° C about 26 minutes.

B. subtilis feeds chemoorganoheterotroph, that is, he uses produced by other organisms for energy and nutrients endogenous substance to generate. B. subtilis populated both rhizosphere as well as the upper layers of the soil. He has a typical rot bacterium share of the recovery of organic substances in the food cycles. It has a large arsenal of glucan ( polymer- linked sugars) and protein - degrading enzymes that are exported from the cell as needed.

As carbon and energy source ( glucose) is used preferably glucose. With sufficient concentration of glucose prevents the activation of genes whose products infiltrate other carbon sources in the metabolism. In the absence of glucose and other sugars or carbon-containing substrates can be used. ( Catabolite repression )

For energy oxygen serves as the preferred terminal electron acceptor ( cellular respiration ). Again, the use of alternatively suppressed Candidate substrates at oxygen access. Under anaerobic conditions, the cells can produce enough energy for slow growth with glucose and nitrate presence. If no usable as an electron acceptor substrates available, then B. subtilis to survive in a position exclusively by fermentation metabolism in production of lactic acid, ethanol, acetoin and 2,3- butanediol.

Adverse environmental conditions B. subtilis tries to escape by active transport with the help of his scourge. Furthermore, B. subtilis can deal about the so-called general stress response as vegetatively active cell with fluctuations of environmental factors. In the final analysis, B. subtilis, by an atypical cell division program form spores that long periods - but by surrendering ecological niche and leaving evolutionary processes - survive. In the light microscope, spores and prespore in sporulating cells can also be seen without staining as highly refractive, oval structures.

Another feature is the formation of competence. Competence in bacteria means the ability extracellular ( foreign ) DNA accommodate and integrate them in order to expand one's own genome or to use on nutrition.

Relevance to humans

Even today B. subtilis is used in human medicine. In the Red List of available in Germany finished product from 1997 ( Red List, 1997) are encountered, for example, on the preparations Utilin, Utilin N and Bactisubtil, the cells or spores of B. subtilis contain a lyophilized ( freeze-dried suspensions) or suspensions, and for the treatment be applied by chronic dermatoses or diarrhea, fermentation and Fäulnisdyspepsien, enteritis, enterocolitis or intestinal disorders chemo or radiation therapierter cancer patients.

Due to the high heat resistance of B. subtilis spores, these can also be used as an indicator for sterilization processes corresponding in pharmacy, medicine and food industries.

In agriculture, the B. subtilis strain QST 713 is also marketed as "Serenade" and serves as a biological fungicide for seed, for example, cotton, vegetables, peanuts and soybeans. B. subtilis settled during the germination of the root system and prevents competition by fungal infections. Furthermore, the bacteria produce volatile organic compounds ( VOC), which act fungicide. Especially under the presence of glucose production of fungicidal VOC is very high.

Because of its ability to secrete extracellular enzymes B. subtilis is used in particular for the production of detergent enzymes ( eg, subtilisin ), but also for the synthesis of riboflavin (vitamin B2), and the antibiotic bacitracin in the biotechnology industry.

In Japan, the subspecies Bacillus subtilis natto is used for preparing the same specialty natto.

B. subtilis can in rare circumstances also act pathogen, eg can it at eye injuries and penetration of the bacterium to blindness come ( panophthalmia ).

Genetics

B. subtilis is considered the best-studied gram-positive bacterium. Several reasons are responsible for this:

• The discovery of competence by John Spizizen in 1961 allowed the development of methods for mapping of genes by transformation, so that existed before the beginning of the sequencing project already genetic maps.
• Because of its ability to form spores, B. subtilis is investigated as a model system for simple cell differentiation: During sporulation, the regulation of gene expression must be spatially ( in prespore, and the mother-cell ) and in time (it takes about 8 hours to from a vegetative cell one spore produced ) are coordinated.
• B. subtilis, in contrast to other Bacillaceae act very rarely pathogenic ( eg, B. anthracis or B. cereus ) - an ideal prerequisite for laboratory work.
• B. subtilis is of industrial importance.

In the years 1990-1997 its genome has been researched and completely sequenced, with the sequencing strategy based on existing genetic maps. The circular double-stranded DNA comprises 4,214,810 base pairs; the GC content is 43.52 %. Of the total sequence have 86.87 % of the nucleotides encoding function, the remaining nucleotides are in some cases significant regulatory regions between genes. On average, a gene measures 893.41 nucleotides, the longest is 14,793 and the shortest predicted 63 nucleotides long.