Bacillus subtilis
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Bacillus subtilis | |
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nm )
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Scientific classification | |
Domain: | Bacteria |
Phylum: | Bacillota |
Class: | Bacilli |
Order: | Bacillales |
Family: | Bacillaceae |
Genus: | Bacillus |
Species: | B. subtilis
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Binomial name | |
Bacillus subtilis (Ehrenberg 1835)
Cohn 1872 | |
Synonyms | |
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Bacillus subtilis, known also as the hay bacillus or grass bacillus, is a
Description
Bacillus subtilis is a
As with other members of the
B. subtilis has proven highly amenable to
Characteristics
Colony, morphological, physiological, and biochemical characteristics of Bacillus subtilis are shown in the Table below.[4]
Test type | Test | Characteristics |
Colony characters | Size | Medium |
Type | Round | |
Color | Whitish | |
Shape | Convex | |
Morphological characters | Shape | Rod |
Physiological characters | Motility | + |
Growth at 6.5% NaCl | + | |
Biochemical characters | Gram staining | + |
Oxidase | - | |
Catalase | + | |
Oxidative-Fermentative | Fermentative | |
Motility | - | |
Methyl Red | - | |
Voges-Proskauer | + | |
Indole | - | |
H2S Production | + | |
Urease | - | |
Nitrate reductase | + | |
β-Galactosidase | + | |
Hydrolysis of | Gelatin | + |
Aesculin | + | |
Casein | + | |
Tween 40 | + | |
Tween 60 | + | |
Tween 80 | + | |
Acid production from | Glycerol | + |
Galactose | + | |
D-Glucose | + | |
D-Fructose | + | |
D-Mannose | + | |
Mannitol | + | |
N-Acetylglucosamine | + | |
Amygdalin | + | |
Maltose | + | |
D-Melibiose | + | |
D-Trehalose | + | |
Glycogen | + | |
D-Turanose | + |
Note: + = Positive, – =Negative
Habitat
This species is commonly found in the upper layers of the soil and B. subtilis is thought to be a
There is evidence that B. subtilis is saprophytic in nature. Studies have shown that the bacterium exhibits vegetative growth in soil rich in organic matter, and that spores were formed when nutrients were depleted.[15] Additionally, B. subtilis has been shown to form biofilms on plant roots, which might explain why it is commonly found in gut microbiomes.[15] Perhaps animals eating plants with B. subtilis biofilms can foster growth of the bacterium in their gastrointestinal tract. It has been shown that the entire lifecycle of B. subtilis can be completed in the gastrointestinal tract, which provides credence to the idea that the bacterium enters the gut via plant consumption and stays present as a result of its ability to grow in the gut.[15]
Reproduction
Bacillus subtilis can divide symmetrically to make two
Under stressful conditions, such as nutrient deprivation, B. subtilis undergoes the process of sporulation. This process has been very well studied and has served as a model organism for studying sporulation.[16]
Sporulation
Once B. subtilis commits to sporulation, the sigma factor sigma F is secreted.[18] This factor promotes sporulation. A sporulation septum is formed and a chromosome is slowly moved into the forespore. When a third of one chromosome copy is in the forespore and the remaining two thirds is in the mother cell, the chromosome fragment in the forespore contains the locus for sigma F, which begins to be expressed in the forespore.[19] In order to prevent sigma F expression in the mother cell, an anti-sigma factor, which is encoded by spoIIAB,[20] is expressed. Any residual anti-sigma factor in the forespore (which would otherwise interfere with sporulation) is inhibited by an anti-anti-sigma factor, which is encoded by spoIIAA.[20]
Chromosomal replication
Bacillus subtilis is a
Genome
Bacillus subtilis has about 4,100 genes. Of these, only 192 were shown to be indispensable; another 79 were predicted to be essential, as well. A vast majority of essential genes were categorized in relatively few domains of cell metabolism, with about half involved in information processing, one-fifth involved in the synthesis of cell envelope and the determination of cell shape and division, and one-tenth related to cell energetics.[24]
The complete genome sequence of B. subtilis sub-strain QB928 has 4,146,839 DNA base pairs and 4,292 genes. The QB928 strain is widely used in genetic studies due to the presence of various markers [aroI(aroK)906 purE1 dal(alrA)1 trpC2].[25]
Several noncoding RNAs have been characterized in the B. subtilis genome in 2009, including Bsr RNAs.[26] Microarray-based comparative genomic analyses have revealed that B. subtilis members show considerable genomic diversity.[27]
FsrA is a small RNA found in Bacillus subtilis. It is an effector of the iron sparing response, and acts to down-regulate iron-containing proteins in times of poor iron bioavailability.[28][29]
A promising fish probiotic, Bacillus subtilis strain WS1A, that possesses antimicrobial activity against Aeromonas veronii and suppressed motile Aeromonas septicemia in Labeo rohita. The de novo assembly resulted in an estimated chromosome size of 4,148,460 bp, with 4,288 open reading frames.[4][5] B. subtilis strain WS1A genome contains many potential genes, such as those encoding proteins involved in the biosynthesis of riboflavin, vitamin B6, and amino acids (ilvD) and in carbon utilization (pta).[4][5]
Transformation
Natural bacterial transformation involves the transfer of DNA from one bacterium to another through the surrounding medium. In B. subtilis the length of transferred DNA is greater than 1,271 kb (more than 1 million bases).[30] The transferred DNA is likely double-stranded DNA and is often more than a third of the total chromosome length of 4,215 kb.[31] It appears that about 7–9% of the recipient cells take up an entire chromosome.[32]
In order for a recipient bacterium to bind, take up exogenous DNA from another bacterium of the same species and recombine it into its chromosome, it must enter a special physiological state called
While the natural competent state is common within laboratory B. subtilis and field isolates, some industrially relevant strains, e.g. B. subtilis (natto), are reluctant to DNA uptake due to the presence of restriction modification systems that degrade exogenous DNA. B. subtilis (natto) mutants, which are defective in a type I restriction modification system endonuclease, are able to act as recipients of conjugative plasmids in mating experiments, paving the way for further genetic engineering of this particular B. subtilis strain.[38]
By adopting Green Chemistry in the use of less hazardous materials, while saving cost, researchers have been mimicking nature's methods of synthesizing chemicals that can be useful for the food and drug industry, by "piggybacking molecules on shorts strands of DNA" before they are zipped together during their complementary base pairing between the two strands. Each strand will carry a particular molecule of interest that will undergo a specific chemical reaction simultaneously when the two corresponding strands of DNA pairs hold together like a zipper, allowing another molecule of interest, to react with one another in controlled and isolated reaction between those molecules being carried into these DNA complementary attachments. By using this method with certain bacterias that naturally follow a process replication in a multi-step fashion, the researchers can simultaneously carry on the interactions of these added molecules to interact with enzymes and other molecules used for a secondary reaction by treating it like a capsule, which is similar to how the bacteria performs its own DNA replication processes.[39]
Uses
20th century
Cultures of B. subtilis were popular worldwide, before the introduction of
The antibiotic bacitracin was first isolated from a variety of Bacillus licheniformis named "Tracy I"[44] in 1945, then considered part of the B. subtilis species. It is still commercially manufactured by growing the variety in a container of liquid growth medium. Over time, the bacteria synthesizes bacitracin and secretes the antibiotic into the medium. The bacitracin is then extracted from the medium using chemical processes.[45]
Since the 1960s B. subtilis has had a history as a test species in spaceflight experimentation. Its
Wild-type natural isolates of B. subtilis are difficult to work with compared to laboratory strains that have undergone domestication processes of
Bacillus globigii, a closely related but
A strain of B. subtilis formerly known as Bacillus natto is used in the commercial production of the Japanese food nattō, as well as the similar Korean food cheonggukjang.
21st century
- As a model organism, B. subtilis is commonly used in laboratory studies directed at discovering the fundamental properties and characteristics of Gram-positive spore-forming bacteria.[27] In particular, the basic principles and mechanisms underlying formation of the durable endospore have been deduced from studies of spore formation in B. subtilis.
- Its surface-binding properties play a role in safe radionuclide waste [e.g. thorium (IV) and plutonium (IV)] disposal.[citation needed]
- Due to its excellent fermentation properties, with high product yields (20 to 25 gram per litre) it is used to produce various enzymes, such as amylase and proteases.[59]
- B. subtilis is used as a
- It may provide some benefit to saffron growers by speeding corm growth and increasing stigma biomass yield.[63]
- It is used as an "indicator organism" during gas sterilization procedures, to ensure a sterilization cycle has completed successfully. Specifically B. subtilis endospores are used to verify that a cycle has reached spore-destroying conditions.[64][65]
- B. subtilis has been found to act as a useful bioproduct fungicide that prevents the growth of Monilinia vaccinii-corymbosi, a.k.a. the mummy berry fungus, without interfering with pollination or fruit qualities.[66]
- Both metabolically active and non-metabolically active B. subtilis cells have been shown to reduce gold (III) to gold (I) and gold (0) when oxygen is present. This biotic reduction plays a role in gold cycling in geological systems and could potentially be used to recover solid gold from said systems.
Novel and artificial substrains
- Novel strains of B. subtilis that could use 4-fluorotryptophan (4FTrp) but not canonical tryptophan (Trp) for propagation were isolated. As Trp is only coded by a single codon, there is evidence that Trp can be displaced by 4FTrp in the genetic code. The experiments showed that the canonical genetic code can be mutable.[67]
- Recombinant strains pBE2C1 and pBE2C1AB were used in production of polyhydroxyalkanoates (PHA), and malt waste can be used as their carbon source for lower-cost PHA production.[citation needed]
- It is used to produce hyaluronic acid, which is used in the joint-care sector in healthcare[68] and cosmetics.
- Monsanto has isolated a gene from B. subtilis that expresses cold shock protein B and spliced it into their drought-tolerant corn hybrid MON 87460, which was approved for sale in the US in November 2011.[69][70]
- A new strain has been modified to convert nectar into honey by secreting enzymes.[71]
Safety
In other animals
Bacillus subtilis was reviewed by the US FDA Center for Veterinary Medicine and found to present no safety concerns when used in direct-fed microbial products, so the Association of American Feed Control Officials has listed it approved for use as an animal feed ingredient under Section 36.14 "Direct-fed Microorganisms".[citation needed] The Canadian Food Inspection Agency Animal Health and Production Feed Section has classified Bacillus culture dehydrated approved feed ingredients as a silage additive under Schedule IV-Part 2-Class 8.6 and assigned the International Feed Ingredient number IFN 8-19-119.[citation needed] On the other hand, several feed additives containing viable spores of B. subtilis have been positively evaluated by the European Food Safety Authority, regarding their safe use for weight gaining in animal production.
In humans
Bacillus subtilis spores can survive the extreme heat generated during cooking. Some B. subtilis strains are responsible for causing ropiness or rope spoilage – a sticky, stringy consistency caused by bacterial production of long-chain
B. subtilis CU1 (2 × 109 spores per day) was evaluated in a 16-week study (10 days administration of probiotic, followed by 18 days wash-out period per each month; repeated same procedure for total 4 months) to healthy subjects. B. subtilis CU1 was found to be safe and well tolerated in the subjects without any side effects.[74]
Bacillus subtilis and substances derived from it have been evaluated by different authoritative bodies for their safe and beneficial use in food. In the United States, an opinion letter issued in the early 1960s by the
Bacillus subtilis has been granted "Qualified Presumption of Safety" status by the European Food Safety Authority.[77]
See also
- Adenylosuccinate lyase deficiency
- Extremophile
- Guthrie test
- YlbH leader
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External links
- Media related to Bacillus subtilis at Wikimedia Commons
- SubtiWiki "up-to-date information for all genes of Bacillus subtilis"
- Bacillus subtilis Final Risk Assessment on EPA.gov. Archived from the original on 2015-09-09.
- Bacillus subtilis genome browser
- Type strain of Bacillus subtilis at BacDive - the Bacterial Diversity Metadatabase