Actinomycetota

Actinobacteria
Scanning electron micrograph of Actinomyces israelii.
Scientific classification
Domain:	Bacteria
Phylum:	Actinobacteria
Class:	Actinobacteria Stackebrandt et al. 1997
Subclasses & Orders
?Candidatus Planktophila Jezbera et al. 2009 ?Cathayosporangium ♠ Runmao et al. 1995 ?Tonsillophilus suis ♠ Azuma and Bak 1980 Acidimicrobidae Stackebrandt et al. 1997 emend. Zhi et al. 2009 Acidimicrobiales Stackebrandt et al. 1997 emend. Zhi et al. 2009 Coriobacteridae Stackebrandt et al. 1997 emend. Zhi et al. 2009 Coriobacteriales Stackebrandt et al. 1997 emend. Zhi et al. 2009 Nitriliruptoridae Kurahashi et al. 2010 Nitriliruptorales Sorokin et al. 2009 Euzebyales Kurahashi et al. 2010 Rubrobacteridae Rainey et al. 1997 emend. Zhi et al. 2009 Gaiellales Albuquerque et al. 2012 Rubrobacterales Rainey et al. 1997 emend. Zhi et al. 2009 Solirubrobacterales Reddy and Garcia-Pichel 2009 Thermoleophilales Reddy and Garcia-Pichel 2009 Actinobacteridae Stackebrandt et al. 1997 emend. Zhi et al. 2009 Bifidobacteriales Stackebrandt et al. 1997 emend. Zhi et al. 2009 Actinomycetales Buchanan 1917 emend. Zhi et al. 2009

Actinobacteria are a group of Gram-positive bacteria with high guanine and cytosine content in their DNA. The G+C content of freshwater Actinobacteria can be as high as 42%, though some may have a low G+C content. They can be terrestrial or aquatic. Although understood primarily as soil bacteria, they might be more abundant in freshwaters. Actinobacteria is one of the dominant bacterial phyla and contains one of the largest of bacterial genera, Streptomyces. Analysis of glutamine synthetase sequence has been suggested for phylogenetic analysis of Actinobacteria.

Although some of the largest and most complex bacterial cells belong to the Actinobacteria, the group of marine Actinomarinales has been described as possessing the smallest free-living prokaryotic cells.

General

Most Actinobacteria of medical or economic significance are in subclass Actinobacteridae, and belong to the order: Actinomycetales. While many of these cause disease in humans, Streptomyces is notable as a source of antibiotics.

Of those Actinobacteria not in Actinomycetales, Gardnerella is one of the most researched. Classification of Gardnerella is controversial, and MeSH catalogues it as both a gram-positive and gram-negative organism.

Actinobacteria, especially Streptomyces sp., are recognized as the producers of many bioactive metabolites that are useful to humans in medicine, such as antibacterials, antifungals, antivirals, antithrombotics, immunomodifiers, anti-tumor drugs and enzyme inhibitors; and in agriculture, including insecticides, herbicides, fungicides and growth promoting substances for plants and animals. Actinobacteria-derived antibiotics that are important in medicine include aminoglycosides, anthracyclines, chloramphenicol, macrolide, tetracyclines etc.

Streptomyces and other actinobacteria are major contributors to biological buffering of soils and have roles in organic matter decomposition conductive to crop production.

Phylogeny

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI) and the phylogeny is based on 16S rRNA-based LTP release 106 by The All-Species Living Tree Project

?Candidatus Planktophila limnetica Jezbera et al. 2009 ?Cathayosporangium alboflavum ♠ Runmao et al. 1995 ?Tonsillophilus suis ♠ Azuma and Bak 1980 Rubrobacter Suzuki et al. 1989   Thermoleophilidae Gaiella occulta Albuquerque et al. 2012 Thermoleophilum Zarilla and Perry 1986 Solirubrobacterales Coriobacteriaceae Acidimicrobiales  Nitriliruptoridae Euzebya tangerina Kurahashi et al. 2010 Nitriliruptor alkaliphilus Sorokin et al. 2009   Actinomycetales ?Boyliae praeputiale ♠ Yates et al. 2002 ?Frankia alni ♪ (Woronin 1866) Von Tubeuf 1895 ?Motilibacter peucedani Lee 2012 Acidothermus cellulolyticus Mohagheghi et al. 1986 Jiangellaceae Micromonosporaceae Propionibacterineae Actinocatenispora Thawai et al. 2006 emend. Seo and Lee 2009 Glycomycetaceae Streptosporangineae Pseudonocardiaceae [incl. Actinopolyspora] Corynebacterineae Catenulisporineae Streptomyces Waksman and Henrici 1943 emend. Witt and Stackebrandt 1991 [incl. Kitasatospora & Streptacidiphilus] Sporichthya Lechevalier et al. 1968 Cryptosporangiaceae Geodermatophilaceae Nakamurellaceae Kineosporiaceae Kineococcus Yokota et al. 1993 Angustibacter luteus Tamura et al. 2010 Micrococcineae [incl. Actinomycetaceae & Bifidobacteriaceae]

Notes:
♪ Prokaryotes where no pure (axenic) cultures are isolated or available, i. e. not cultivated or can not be sustained in culture for more than a few serial passages
♠ Strains found at the National Center for Biotechnology Information (NCBI) but not listed in the List of Prokaryotic names with Standing in Nomenclature (LSPN)

Further reading

• Pandey, B.; Ghimire, P.; Agrawal, V.P. (January 12–15, 2004). Studies on the antibacterial activity of the Actinomycetes isolated from the Khumbu Region of Nepal (PDF). International Conference on the Great Himalayas: Climate, Health, Ecology, Management and Conservation. Kathmandu.
• Baltz, R.H. (2005). "Antibiotic discovery from actinomycetes: Will a renaissance follow the decline and fall?". SIM News. 55: 186–196.
• Baltz, R.H. (2007). "Antimicrobials from Actinomycetes: Back to the Future". Microbe. 2 (3): 125–131.

External links

• Actinomycetes genome database