|Scanning electron micrograph of Actinomyces israelii.|
Stackebrandt et al. 1997
|Subclasses & Orders|
Actinobacteria are a group of Gram-positive bacteria. They were all believed to have high guanine and cytosine content in their DNA. However, recently it has been shown that several freshwater Actinobacteria actually have low G+C content.  The G+C content of freshwater Actinobacteria can be as low as 42%. In view of this, it is recommended that the use of the epithet high G+C Gram positive organisms to refer to Actinobacteria be discontinued. 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.
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 contributes to biological buffering of soils and have roles in organic matter decomposition conductive to crop production.
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 
♪ 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)
- Ventura, M.; Canchaya, C.; Tauch, A.; Chandra, G.; Fitzgerald, G. F.; Chater, K. F.; van Sinderen, D. (5 September 2007). "Genomics of Actinobacteria: Tracing the Evolutionary History of an Ancient Phylum". Microbiology and Molecular Biology Reviews 71 (3): 495–548. doi:10.1128/MMBR.00005-07. PMC 2168647. PMID 17804669.
- "MB451 Actinobacteria lecture". Retrieved 2008-11-21.[dead link]
- Ghai R, McMahon KD, Rodriguez-Valera F (2012). "Breaking a paradigm:cosmopolitan and abundant freshwater actinobacteria are low GC". Environmental Microbiology Reports 4 (1): 29–35. doi:10.1111/j.1758-2229.2011.00274.x. PMID 23757226.
- Servin JA, Herbold CW, Skophammer RG, Lake JA (January 2008). "Evidence excluding the root of the tree of life from the actinobacteria". Mol. Biol. Evol. 25 (1): 1–4. doi:10.1093/molbev/msm249. PMID 18003601.
- Ghai R, Rodriguez-Valera F, McMahon KD, et al. (2011). Lopez-Garcia, Purification, ed. "Metagenomics of the water column in the pristine upper course of the Amazon river". PloS ONE 6 (8): e23785. doi:10.1371/journal.pone.0023785. PMC 3158796. PMID 21915244.
- C.Michael Hogan. 2010. Bacteria. Encyclopedia of Earth. eds. Sidney Draggan and C.J.Cleveland, National Council for Science and the Environment, Washington DC
- Hayward D, van Helden PD, Wiid IJ (2009). "Glutamine synthetase sequence evolution in the mycobacteria and their use as molecular markers for Actinobacteria speciation". BMC Evol. Biol. 9: 48. doi:10.1186/1471-2148-9-48. PMC 2667176. PMID 19245690.
- Ghai R, Mizuno CM, Picazo A, Camacho A, Rodriguez-Valera F (2013). "Metagenomics uncovers a new group of low GC and ultra-small marine Actinobacteria". Scientific Reports 3. doi:10.1038/srep02471. PMID 23959135.
- Gardnerella at the US National Library of Medicine Medical Subject Headings (MeSH)
- Mahajan GB, 2012, Antibacterial agents from actinomycetes - a review. Frontiers in Bioscience (Elite Ed). 4:240-53
- Gupte, M., P. Kulkarni and B.N. Ganguli, 2002. Antifungal Antibiotics. Appl. Microbiol. Biotechnol.,58: 46-57
- Bressan,W, 2003, Biocontrol 48:233-240
- Atta,M.A and M.S.Ahmad, 2009, Austral. J. Basic and Appl. Sci.,3:126-135
- Debananda S. Ningthoujam, SuchitraSanasam, K. Tamreihao and Salam Nimaichand, 2009,Afr. J. Microbiol. Res. 3(11) : 737-742
- J.P. Euzéby. "Actinobacteria". List of Prokaryotic names with Standing in Nomenclature (LPSN) . Retrieved 2011-11-17.
- Sayers et al. "Actinobacteria". National Center for Biotechnology Information (NCBI) taxonomy database . Retrieved 2011-06-05.
- All-Species Living Tree Project."16S rRNA-based LTP release 106: full tree. accessdate=2011-11-17".
- 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". 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.
|Wikispecies has information related to: Actinobacteria|