Actinomycetota

The Actinomycetota (previously known as "Actinobacteria") are a diverse phylum of Gram-positive bacteria with high GC content.<ref>Template:Cite journal</ref> They can be terrestrial or aquatic.<ref name="pmid18003601">Template:Cite journal</ref> They are of great importance to land flora because of their contributions to soil systems. In soil, they help decompose organic matter of dead organisms so the molecules can be taken up anew by plants. While this role is also played by fungi, actinomycetota are much smaller and likely do not occupy the same ecological niche. In this role, the colonies often grow extensive mycelia, as fungi do, and the name of an important order of the phylum, Actinomycetales (the actinomycetes), reflects that they were long believed to be fungi. Some soil actinomycetota (such as Frankia) live symbiotically with the plants whose roots pervade the soil, fixing nitrogen for the plants in exchange for access to some of the plant's saccharides. Other species, such as many members of the genus Mycobacterium, are important pathogens.

Beyond the great interest in Actinomycetota for their soil role, much is yet to be learned about them. Although currently understood primarily as soil bacteria, they might be more abundant in fresh waters.<ref name="amazonMetagenome">Template:Cite journal</ref> Actinomycetota is one of the dominant bacterial phyla and contains one of the largest of bacterial genera: Streptomyces.<ref>Template:Cite book</ref> Streptomyces and other actinomycetota are major contributors to biological buffering of soils.<ref>Template:Cite journal</ref> They are also the source of many antibiotics.<ref>Template:Cite journal</ref><ref name=j.bjid.2012.08.014>Template:Cite journal</ref>

Bacteria of the Actinomycetota genus Bifidobacterium are the most common in the microbiome of human infants.<ref>Template:Cite journal</ref> Although adults have fewer bifidobacteria, intestinal bifidobacteria help maintain the mucosal barrier and reduce lipopolysaccharide in the intestine.<ref name="Pinzone-2012">Template:Cite journal</ref>

Although some of the largest and most complex bacterial cells belong to the Actinomycetota, the group of marine Actinomarinales has been described as possessing the smallest free-living prokaryotic cells.<ref name="Actinomarina">Template:Cite journal</ref>

Some Siberian or Antarctic Actinomycetota are said to be the oldest living organism on Earth, frozen in permafrost at around half a million years ago.<ref>Template:Cite web</ref><ref>Template:Cite web</ref> The symptoms of life were detected by Template:Co2 release from permafrost samples 640 kya or younger.<ref>Template:Cite journal</ref>

General

Most Actinomycetota of medical or economic significance are in class Actinomycetia, and belong to the order Actinomycetales. While many of these cause disease in humans, Streptomyces is notable as a source of antibiotics.<ref name=j.bjid.2012.08.014/>

Of those Actinomycetota not in the 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.<ref>Template:MeshName</ref>

Actinomycetota, especially Streptomyces spp., are recognized as the producers of many bioactive metabolites that are useful to humans in medicine, such as antibacterials,<ref>Template:Cite journal</ref> antifungals,<ref>Template:Cite journal</ref> antivirals, antithrombotics, immunomodifiers, antitumor drugs, and enzyme inhibitors; and in agriculture, including insecticides, herbicides, fungicides, and growth-promoting substances for plants and animals.<ref>Template:Cite journal</ref> Actinomycetota-derived antibiotics that are important in medicine include aminoglycosides, anthracyclines, chloramphenicol, macrolide, tetracyclines, etc.Template:Citation needed

Actinomycetota have high guanine and cytosine content in their DNA.<ref name="pmid17804669">Template:Cite journal</ref> The G+C content of Actinomycetota can be as high as 70%, though some may have a low G+C content.<ref name="lowGCActinoacteria">Template:Cite journal</ref>

Analysis of glutamine synthetase sequence has been suggested for phylogenetic analysis of the Actinomycetota.<ref name="pmid19245690">Template:Cite journal</ref>

Phylogeny

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)<ref name=LPSN>Template:Cite web</ref> and National Center for Biotechnology Information (NCBI).<ref name=NCBI>Template:Cite web</ref>

Whole-genome based phylogeny<ref name="Nouioui">Template:Cite journal</ref>	16S rRNA based LTP_10_2024<ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref>	120 marker proteins based GTDB 09-RS220<ref name="about">Template:Cite web</ref><ref name="tree">Template:Cite web</ref><ref name="taxon_history">Template:Cite web</ref>

See also

• List of bacteria genera
• List of bacterial orders
• List of bacterial vaginosis microbiota
• Amycolatopsis nalaikhensis

Further reading

• Template:Cite journal
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• Template:Cite conference

External links

• Actinomycetes genome database