Streptomyces

Streptomyces sp.

  • S. coelicolor
  • S. achromogenes

Streptomyces is a very species-rich genus of Actinobacteria. The species of this genus are Gram- positive, aerobic, mycelial -forming, multicellular form spores and have a high GC content. They appear mainly in soils, where they make perfumes, particularly geosmin, with the characteristic odor of the forest soil. Many Streptomyces species produce antibiotics that are used in human and veterinary medicine.

  • 3.1 antibiotic producers
  • 3.2 Changes in classification
  • 4.1 Literature
  • 4.2 Notes and references

Features

Appearance

The members of the genus Streptomyces are Gram-positive bacteria. As with many members of the order Actinomycetales also forms Streptomyces cells in the form of filaments. These elongated and branched cells form fencing, which are also known as the mycelium. The filaments have a diameter of 0.5-1.0 microns and in the growth phase often no cross- walls.

Similar to fungi, one can distinguish between two types also in the growth of Streptomyces: The substrate mycelium, which propagates in the liquid or solid nutrient medium and in the gas space above into growing aerial mycelium. At the ends of filaments of the aerial mycelium transverse walls are formed in the cell walls in older cultures again, so that a plurality of chains formed by segmentation, usually spheroidal spores. This, to be regarded as bacterial spores exospores thus differ fundamentally from the endospores, which are formed, for example, of the bacterial genera Clostridium and Bacillus.

Chemotaxonomic features

As a representative of the Department of Actinobacteria Actinomycetales in Streptomyces belongs to the bacteria with high GC content, ie a high proportion of the nucleic bases guanine and cytosine in the bacterial DNA. Genetic studies have a GC content of 69-75 mole percent yield.

The complete genome of Streptomyces coelicolor was sequenced and published in 2002. Also the genome of Streptomyces avermitilis has now been sequenced. It contains most of the genes of all previously studied bacteria. Another for prokaryotes is rare feature in that the chromosome is a linear rather than circular. The genome of the previously studied species is exceptionally large for bacteria, the genome size of the bacterial chromosome is Streptomyces coelicolor in 8668 kilobase pairs (kb ), which is almost twice the size of the genome of Escherichia coli ( 4600 kb).

Growth and metabolism

The representatives of the genus Streptomyces are aerobically, ie, require oxygen for their growth. Furthermore, they are characterized by a pronounced secondary metabolism. They produce a large number of antibiotics used in medicine. The now rarely used antibiotic streptomycin is named after the genus Streptomyces.

Occurrence and significance

Streptomyces occurs mainly in soils. Many species produce fragrances, particularly geosmin, with the characteristic odor of the forest soil.

For the human and veterinary medical importance are the many Streptomyces species that produce antibiotics. In addition, producing Streptomyces avidinii, the biotin -binding protein streptavidin. Streptomyces venezuelae similar compounds have been isolated, which are referred to as the streptavidin v1 and v2. Compared with the amino acid sequence of the protein streptavidin or a nine amino acids are changed. As a byproduct of streptomycin from Streptomyces griseus recovery cobalamins can be obtained.

Streptomyces rarely occurs as pathogens in humans are Streptomyces somaliensis and " Streptomyces sudanensis " relevant. In plants Streptomyces Streptomyces scabiei caviscabies and cause ( previously incorrectly referred to as Streptomyces scabies ) the scab. The systematics of some of these species is controversial.

System

The genus Streptomyces is very rich in species. Currently (as of 2013) are more than 600 species and subspecies ( subspecies ) known. In the run for the classification of bacteria as a reference database bacterial species are split across three files. Streptomyces albus is the type species of the genus.

Antibiotic producers

Here are some examples of species that are as antibiotics producers of meaning:

  • Streptomyces achromogenes produced streptozotocin
  • Streptomyces ambofaciens produces spiramycin
  • Streptomyces aureofaciens producing tetracycline and chlortetracycline
  • Streptomyces avermitilis produces avermectins
  • Streptomyces capreolus produces capreomycin
  • Streptomyces carcinostaticus produced neocarzinostatin
  • Streptomyces cervinus produced Cervinomycin
  • Streptomyces clavuligerus produces clavulanic acid
  • Streptomyces coeruleorubidus produces daunorubicin
  • Streptomyces davawensis produced roseoflavin
  • Streptomyces fradiae produces neomycin, tylosin
  • Streptomyces griseus (among others) produces streptomycin
  • Produced Streptomyces hygroscopicus hygromycin B
  • Streptomyces lavendulae produced fosmidomycin, Lavendamycin and mitomycin
  • Streptomyces lincolnensis produced clindamycin
  • Streptomyces natalensis produces natamycin
  • Streptomyces nodosus produces amphotericin B
  • Streptomyces noursei produced nystatin
  • Streptomyces peuceticus produces daunorubicin
  • Streptomyces platensis produced Platensimycin
  • Streptomyces rimosus produces paromomycin
  • Streptomyces spectabilis produces spectinomycin
  • Streptomyces toxytricini produced Lipstatin
  • Streptomyces venezuelae produces chloramphenicol
  • Streptomyces violaceoniger produced Lysolipin
  • Streptomyces violaceoruber produced granaticin

Changed system

The demarcation of many Streptomyces species is controversial another. Thus studies performed from 2005 that involved in the species Streptomyces scab caviscabies Goyer et al. 1996 with the already known species Streptomyces griseus ( Krainsky 1914) Waksman & Henrici must be 1948 matches and consequently renamed. This was in 2008 by studies of Guo et al. refuted. Investigations in 2010 revealed that they instead with the already known species Streptomyces fimicarius ( Duchy 1934) Waksman and Henrici 1948 is identical. This type was in 2012 by Kim et al. identified as a synonym of Streptomyces setonii, so that it is now on the current system Streptomyces setonii ( Millard & Burr 1926) Waksman 1953 emend. Kim et al. 2012 co.

Molecular biological studies, it is checked whether the number of species has on hand, or whether individual species are so closely related to each other that they become a kind - should be combined - possibly with subtypes. The methods used in a study of 2010 consisting of DNA-DNA hybridization, and the multi-locus sequence analysis ( MLSA ). The hybridization technique used to prove the structural relationship of nucleic acids and thus to elucidate the phylogenetic relationship. In the MLSA, the study is restricted to certain genes that are typical for a species or genus. Sequence analysis of 2010 was limited to the detection of five housekeeping genes (english housekeeping gene, non- regulated genes that are expressed regardless of cell type, cell stage and external factors). As a result of the investigation it was proposed to combine the study of the underlying 29 species and 3 subspecies to only 11 species.

The medically important human kind " Streptomyces sudanensis " according to the rules of the International Code of Nomenclature of Bacteria ( ICNB ) is not validly published and is therefore enclosed in quotes. The investigated bacterial strains are closely related to Streptomyces somaliensis.

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