Streptomyces

Streptomyces, the largest genus of Actinobacteria, is a group of Gram-positive and generally high GC-content bacteria.^[1] Streptomycetes are found predominantly in soil and in decaying vegetation, and most produce spores. Streptomycetes are noted for their distinct "earthy" odor which results from production of a volatile metabolite, geosmin.

Streptomycetes are characterised by a complex secondary metabolism.^[1] They produce over two thirds of the clinically useful antibiotics of natural origin (e.g., neomycin, chloramphenicol)^[2]. The now rarely-used streptomycin takes its name directly from Streptomyces. Streptomycetes are infrequent pathogens, though infections in human such as mycetoma can be caused by S. somaliensis and S. sudanensis and in plants such as scabies can be caused by S. caviscabies and S. scabies.

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Genomics

The complete genome of one of the strain, S. coelicolor A3(2), was published in 2002.^[3] At the time, the S. coelicolor genome was thought to contain the largest number of genes of any bacterium^{[citation needed]}. The first complete genome sequence of S. avermitilis was completed in 2003.^[4] Each of these genomes form a chromosome with a linear structure, unlike most bacterial genomes which exist in the form of circular chromosomes. The genome sequence of S. scabies, a member of the genus with the ability to cause potato scab disease, has been determined at the Wellcome Trust Sanger Institute and is currently in annotation, with publication scheduled for 2007.

Taxonomically, S. coelicolor A3(2) belongs to the species of S. violaceoruber and not a validly described separate species; S. coelicolor A3(2) is not to be mistaken for S. coelicolor (Müller) (ATCC 23899).

Biotechnology

In recent years, biotechnology researchers have begun to use Streptomyces spp. for production of recombinant human proteins. Traditionally, Escherichia coli was the species of choice to host eukaryotic genes since it was well understood and easy to work with.^[5][6] However, E. coli introduces problems such as incorrect (or lack of) glycosylation and incorrect protein folding, resulting in insolubility and loss of bioactivity of the product.^[7] Streptomyces spp. on the other hand have the ability to secrete correctly folded recombinant proteins into the medium after production simplifying the subsequent purification steps. These properties among others make Streptomyces spp. an attractive alternative to other bacteria such as E. coli and Bacillus subtilis^{[citation needed]}.

Medicine

Streptomyces is the largest antibiotic producing genus ([1]), producing both antibacterials and antifungals, and also a wide range of other bioactive compounds such as immunosuppressants

Some of the antifungals produced by Streptomyces spp.

see also polyene antimycotic

• Nystatin (from S. noursei)
• Amphotericin B (from S. nodosus)
• Natamycin (from S. natalensis)

Some of the antibiotics produced by Streptomyces spp.

• Erythromycin (from S. erythreus)
• Neomycin (from S. fradiae)
• Streptomycin (from S. griseus)
• Tetracycline (from S. rimosus)
• Vancomycin (from S. orientalis)
• Rifamycin (from S. mediterranei)
• Chloramphenicol (from S. venezuelae)
• Puromycin (from S. alboniger)

Some of the Alkaloids produced by Streptomyces spp.

• Physostigmine (from S.griseofuscus)

Some of the anti-cancer compounds produced by Streptomyces spp.

• Migrastatin (from S. platensis)

References

Further reading

• Baumberg S (1991). Genetics and Product Formation in Streptomyces. Kluwer Academic. ISBN 978-0306438851. 
• Gunsalus IC (1986). Bacteria: Antibiotic-producing Streptomyces. Academic Press. ISBN 978-0123072092. 
• Hopwood DA (2007). Streptomyces in Nature and Medicine: The Antibiotic Makers. Oxford University Press. ISBN 978-0195150667. 

See also

• Antimycin A - compound produced by this bacteria used in piscicides.