Thermotogae

The Thermotogae is a class of kingdom Thermotogati and domain Bacteria. It is the sole class in the phylum Thermotogota. The class Thermotogae is composed of Gram-negative staining, anaerobic, and mostly thermophilic and hyperthermophilic bacteria.

Characteristics

The name of this class is derived from the thermophilic nature of many of its species, along with the characteristic sheath structure, or "toga", surrounding the cells of these species. In 2010, some Thermotogae who live in moderate temperatures were identified. Although Thermotogae species exhibit Gram-negative staining, they are bounded by a single-unit lipid membrane, and are thus monoderm bacteria. Because of the ability of some Thermotogae species to thrive at high temperatures, they are considered attractive targets for use in industrial processes. The metabolic ability of Thermotogae to utilize different complex-carbohydrates for production of hydrogen gas led to these species being cited as a possible biotechnological source for production of energy alternative to fossil fuels.

Molecular signatures

Until recently, no biochemical or molecular markers were known that could distinguish the species from the class Thermotogae from all other bacteria. Phylogenetic studies demonstrated that the presence of the same CSI within these two unrelated groups of bacteria is not due to lateral gene transfer, rather the CSI likely developed independently in these two groups of thermophiles due to selective pressure.

! colspan=1 | 120 marker proteins based GTDB 10-RS226

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Taxonomy

This class is presently the sole class in the phylum Thermotogae and consists of four orders (Thermotogales, Kosmotogales, Petrotogales, and Mesoaciditogales) and five families (Thermatogaceae, Fervidobacteriaceae, Kosmotogaceae, Petrotogaceae, and Mesoaciditogaceae). It contains a total of 15 genera and 52 species. In the 16S rRNA trees, the Thermotogae have been observed to branch with the Aquificota (a phylum comprising hyperthermophilic organisms) in close proximity to the archaeal-bacterial branch point. and also by conserved signature indels in several highly conserved universal proteins. The Thermotogae have also been scrutinized for their supposedly profuse Lateral gene transfer with Archaeal organisms. However, recent studies based upon more robust methodologies suggest that incidence of LGT between Thermotogae and other groups including Archaea is not as high as suggested in earlier studies.

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI)

Class Thermotogae Reysenbach 2002
Genus ?Caldotoga Xue et al. 1999
Order Kosmotogales Bhandari & Gupta 2014
Family Kosmotogaceae Bhandari & Gupta 2014
Genus Kosmotoga DiPippo et al. 2009 [Thermococcoides Feng et al. 2010]
Genus Mesotoga Nesbo et al. 2013
Order Mesoaciditogales Itoh et al. 2015
Family Mesoaciditogaceae Itoh et al. 2015
Genus Athalassotoga Itoh et al. 2015
Genus Mesoaciditoga Reysenbach et al. 2013
Order Petrotogales Bhandari & Gupta 2014
Family Petrotogaceae Bhandari & Gupta 2014
Tribe "Marinitogeae" Pelletier 2012
Genus Marinitoga Wery et al. 2001
Tribe "Petrotogeae" Pelletier 2012
Genus Defluviitoga Ben Hania et al. 2012
Genus Geotoga Davey et al. 1993
Genus Oceanotoga Jayasinghearachchi and Lal 2011
Genus Petrotoga Davey et al. 1993
Genus Tepiditoga Mori et al. 2021
Order Thermotogales Reysenbach 2002
Family Fervidobacteriaceae Bhandari & Gupta 2014
Genus Fervidobacterium Patel et al. 1985
Genus Thermosipho Huber et al. 1989 non Kantor et al. 2013
Family "Pseudothermotogaceae" Pallen, Rodriguez-R & Alikhan 2022
Genus Pseudothermotoga Bhandari & Gupta 2014
Family Thermotogaceae Reysenbach 2002
Genus ?Thermopallium Duckworth et al. 1996
Genus Thermotoga Stetter and Huber 1986

Characteristics

Molecular signatures

Taxonomy

See also

References