Actinomycetota | |
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Scanning electron micrograph of Actinomyces israelii . | |
Scientific classification | |
Domain: | Bacteria |
Clade: | Terrabacteria |
Phylum: | Actinomycetota Goodfellow 2021 [1] |
Type genus | |
Actinomyces Harz 1877 (Approved Lists 1980) | |
Classes [2] | |
Synonyms | |
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The Actinomycetota (or Actinobacteria) are a diverse phylum of Gram-positive bacteria with high G+C content. [4] They can be terrestrial or aquatic. [5] They are of great economic importance to humans because agriculture and forests depend on their contributions to soil systems. In soil they help to decompose the 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, like a fungus would, 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. [6] Actinomycetota is one of the dominant bacterial phyla and contains one of the largest of bacterial genera, Streptomyces . [7] Streptomyces and other actinomycetota are major contributors to biological buffering of soils. [8] They are also the source of many antibiotics. [9] [10]
The Actinomycetota genus Bifidobacterium is the most common bacteria in the microbiome of human infants. [11] Although adults have fewer bifidobacteria, intestinal bifidobacteria help maintain the mucosal barrier and reduce lipopolysaccharide in the intestine. [12]
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. [13]
Some Siberian or Antarctic Actinomycetota is said to be the oldest living organism on Earth, frozen in permafrost at around half a million years ago. [14] [15] The symptoms of life were detected by CO2 release from permafrost samples 640 kya or younger. [16]
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. [10]
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. [17]
Actinomycetota, especially Streptomyces spp., are recognized as the producers of many bioactive metabolites that are useful to humans in medicine, such as antibacterials, [18] antifungals, [19] antivirals, antithrombotics, immunomodifiers, antitumor drugs, and enzyme inhibitors; and in agriculture, including insecticides, herbicides, fungicides, and growth-promoting substances for plants and animals. [20] Actinomycetota-derived antibiotics that are important in medicine include aminoglycosides, anthracyclines, chloramphenicol, macrolide, tetracyclines, etc.[ citation needed ]
Actinomycetota have high guanine and cytosine content in their DNA. [21] The G+C content of Actinomycetota can be as high as 70%, though some may have a low G+C content. [22]
Analysis of glutamine synthetase sequence has been suggested for phylogenetic analysis of the Actinomycetota. [23]
Whole-genome based phylogeny [24] | 16S rRNA based LTP_12_2021 [25] [26] [27] | GTDB 08-RS214 [28] [29] [30] | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) [2] and National Center for Biotechnology Information (NCBI). [31]
In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall.
The phylum Bacteroidota is composed of three large classes of Gram-negative, nonsporeforming, anaerobic or aerobic, and rod-shaped bacteria that are widely distributed in the environment, including in soil, sediments, and sea water, as well as in the guts and on the skin of animals.
The Thermomicrobia is a group of thermophilic green non-sulfur bacteria. Based on species Thermomicrobium roseum and Sphaerobacter thermophilus, this bacteria class has the following description:
Streptomyces is the largest genus of Actinomycetota, and the type genus of the family Streptomycetaceae. Over 700 species of Streptomyces bacteria have been described. As with the other Actinomycetota, streptomycetes are gram-positive, and have very large genomes with high GC content. Found predominantly in soil and decaying vegetation, most streptomycetes produce spores, and are noted for their distinct "earthy" odor that results from production of a volatile metabolite, geosmin. Different strains of the same species may colonize very diverse environments.
The Actinomycetales is an order of Actinomycetota. A member of the order is often called an actinomycete. Actinomycetales are generally gram-positive and anaerobic and have mycelia in a filamentous and branching growth pattern. Some actinomycetes can form rod- or coccoid-shaped forms, while others can form spores on aerial hyphae. Actinomycetales bacteria can be infected by bacteriophages, which are called actinophages. Actinomycetales can range from harmless bacteria to pathogens with resistance to antibiotics.
The Actinomycetia are a class of bacteria.
The Bifidobacteriaceae are the only family of bacteria in the order Bifidobacteriales. According to the 16S rRNA-based LTP release 106 published by 'The All-Species Living Tree' Project, the order Bifidobacteriales is a clade nested within the suborder Micrococcineae, also the genus Bifidobacterium is paraphyletic to the other genera within the family, i.e. the other genera are nested within Bifidobacterium.
Streptomycetaceae is a family of Actinomycetota, making up the monotypic order Streptomycetales. It includes the important genus Streptomyces. This was the original source of many antibiotics, namely streptomycin, the first antibiotic against tuberculosis.
The Gemmatimonadota are a phylum of bacteria established in 2003. The phylum contains two classes Gemmatimonadetes and Longimicrobia.
The Actinomycetaceae are a family of bacteria in the order Actinomycetales that contains the medically important genus Actinomyces. These organisms are closely related to the mycobacteria, but were originally classified as fungi because they were thought to be transitional forms between bacteria and fungi.
The Chloroflexota are a phylum of bacteria containing isolates with a diversity of phenotypes, including members that are aerobic thermophiles, which use oxygen and grow well in high temperatures; anoxygenic phototrophs, which use light for photosynthesis ; and anaerobic halorespirers, which uses halogenated organics as electron acceptors.
Streptomyces griseus is a species of bacteria in the genus Streptomyces commonly found in soil. A few strains have been also reported from deep-sea sediments. It is a Gram-positive bacterium with high GC content. Along with most other streptomycetes, S. griseus strains are well known producers of antibiotics and other such commercially significant secondary metabolites. These strains are known to be producers of 32 different structural types of bioactive compounds. Streptomycin, the first antibiotic ever reported from a bacterium, comes from strains of S. griseus. Recently, the whole genome sequence of one of its strains had been completed.
Bacterial phyla constitute the major lineages of the domain Bacteria. While the exact definition of a bacterial phylum is debated, a popular definition is that a bacterial phylum is a monophyletic lineage of bacteria whose 16S rRNA genes share a pairwise sequence identity of ~75% or less with those of the members of other bacterial phyla.
Actinosynnema is a genus in the phylum Actinomycetota (Bacteria).
Adlercreutzia is a genus in the phylum Actinomycetota (Bacteria).
"Tropheryma whipplei" is a bacterium that is the causative organism of Whipple's disease, and rarely, endocarditis.
Streptomyces antibioticus is a gram-positive bacterium discovered in 1941 by Nobel-prize-winner Selman Waksman and H. Boyd Woodruff. Its name is derived from the Greek "strepto-" meaning "twisted", alluding to this genus' chain-like spore production, and "antibioticus", referring to this species' extensive antibiotic production. Upon its first characterization, it was noted that S. antibioticus produces a distinct soil odor.
The Acidimicrobiia are a class of Actinomycetota, in which three families, eight genera, and nine species have been described, Acidimicrobium ferrooxidans is the type species of the order.
The Coriobacteriia are a class of Gram-positive bacteria within the Actinomycetota phylum. Species within this group are nonsporulating, strict or facultative anaerobes that are capable of thriving in a diverse set of ecological niches. Gordonibacter species are the only members capable of motility by means of flagella within the class. Several species within the Coriobacteriia class have been implicated with human diseases that range in severity. Atopobium, Olsenella, and Cryptobacterium species have responsible for human oral infections including periodontitis, halitosis, and other endodontic infections. Eggerthella species have been associated with severe blood bacteraemia and ulcerative colitis.