The Chloroflexota are a
phylum
In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is below Kingdom (biology), kingdom and above Class (biology), class. Traditionally, in botany the term division (taxonomy), division has been used instead ...
of
bacteria
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
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
Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...
(
green non-sulfur bacteria); and
anaerobic halorespirers, which uses halogenated organics (such as the toxic chlorinated
ethenes and
polychlorinated biphenyls) as electron acceptors.
The members of the phylum ''Chloroflexota'' are
monoderms (that is, have one cell membrane with no outer membrane), but they stain mostly gram-negative. Many well-studied phyla of bacteria are
diderms and stain
gram-negative
Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelope consists ...
, whereas well-known monoderms that stain Gram-positive include ''Firmicutes'' (or ''
Bacillota
The Bacillota (synonym Firmicutes) are a phylum of bacteria, most of which have Gram-positive cell wall structure. They have round cells, called cocci (singular coccus), or rod-like forms (bacillus). A few Bacillota, such as '' Megasphaera'', ...
'') (
low G+C gram-positives) and ''
Actinomycetota'' (high-G+C gram-positives).
History
The taxon name was created in the 2001 edition of Volume 1 of
Bergey's Manual of Systematic Bacteriology and is the Latin plural of the name ''
Chloroflexus'', the name of the
type genus of the phylum, a
common practice.
In 1987,
Carl Woese, regarded as one of the forerunner of the molecular phylogeny revolution, divided Eubacteria into 11 divisions based on
16S ribosomal RNA
16S ribosomal RNA (or 16 S rRNA) is the RNA component of the 30S subunit of a prokaryotic ribosome ( SSU rRNA). It binds to the Shine-Dalgarno sequence and provides most of the SSU structure.
The genes coding for it are referred to as 16S ...
(SSU) sequences and grouped the genera ''
Chloroflexus'', ''
Herpetosiphon'' and ''
Thermomicrobium'' into the "green non-sulfur bacteria and relatives",
which was temporarily renamed as "Chloroflexi" in Volume One of Bergey's Manual of Systematic Bacteriology.
Chloroflexota being a deep branching phylum (see
Bacterial phyla), it was considered in Volume One of Bergey's Manual of Systematic Bacteriology to include a single class with the same name.
Since 2001, however, new classes have been created thanks to newly discovered species, and the phylum Chloroflexi is now divided into several classes.
"
Dehalococcoidetes" is a placeholder name given by Hugenholtz & Stackebrandt, 2004, after "''Dehalococcoides ethenogenes''" a species partially described in 1997.
The first species fully described was ''Dehalogenimonas lykanthroporepellens'', by Moe et al. 2009,
but in the description of that species the class was not made official nor were families or orders laid out as the two species share only 90%
16S ribosomal RNA
16S ribosomal RNA (or 16 S rRNA) is the RNA component of the 30S subunit of a prokaryotic ribosome ( SSU rRNA). It binds to the Shine-Dalgarno sequence and provides most of the SSU structure.
The genes coding for it are referred to as 16S ...
identity, meaning that they could fall in different families or even orders.
[
Recent phylogenetic analysis of the Chloroflexota has found very weak support for the grouping together of the different classes currently part of the phylum.][ However, the classes Chloroflexi and Thermomicrobia were found to group together consistently by both the usual phylogenetic means and the identification of shared conserved signature indels in the 50S ribosomal protein L19 and the enzyme UDP-glucose 4-epimerase.][ It has been suggested that the phylum Chloroflexi ''sensu stricto'' should comprise only the classes Chloroflexi and Thermomicrobia, and the other four classes ("Dehalococcoidetes," Anaerolineae, Caldilineae and Ktedonobacteria) may represent one or more independent phyla branching in the neighborhood of the Chloroflexi.][
]
Phylogeny
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature
List of Prokaryotic names with Standing in Nomenclature (LPSN) is an online database that maintains information on the naming and taxonomy of prokaryotes, following the taxonomy requirements and rulings of the International Code of Nomenclatu ...
(LPSN) and National Center for Biotechnology Information
The National Center for Biotechnology Information (NCBI) is part of the National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. The NCBI is lo ...
(NCBI).
Taxonomy
Genus "''Candidatus'' Caldibacter" corrig. Spieck et al. 2020
Genus "''Candidatus'' Chlorotrichoides" corrig. Oren et al. 2020 Chlorothrix" Klappenbach & Pierson 2004 non Dyar 1921 non Berger-Perrot 1982">Chlorothrix_(bacterium).html" ;"title="''Candidatus'' Chlorothrix (bacterium)">Chlorothrix" Klappenbach & Pierson 2004 non Dyar 1921 non Berger-Perrot 1982br />
Genus "''Candidatus'' Nitrocaldera" Spieck et al. 2020
Genus "''Candidatus'' Nitrotheca" Spieck et al. 2020
Class "Bathosphaeria" Mehrshad et al. 2018
*Order "Bathosphaerales" Mehrshad et al. 2018
**Family " Bathosphaeraceae" Mehrshad et al. 2018
***Genus ?"''Candidatus'' Bathosphaera" Mehrshad et al. 2018 (JG30-KF-CM66)
Class " Martimicrobia" Williams et al. 2024
*Order " Martimicrobiales" Williams et al. 2024
**Family " Martimicrobiaceae" Williams et al. 2024
***Genus ?"''Candidatus'' Laranimicrobium" Williams et al. 2024
***Genus ?"''Candidatus'' Martimicrobium" Williams et al. 2024
Class " Poriflexia" Mehrshad et al. 2018
*Genus ?"''Candidatus'' Poriflexus" Kogawa et al. 2022
Class " Spiritibacteria" Williams et al. 2024
*Order " Spiritibacterales" Williams et al. 2024
**Family " Spiritibacteraceae" Williams et al. 2024
***Genus ?"''Candidatus'' Aglaurobacter" Williams et al. 2024
***Genus ?"''Candidatus'' Otrerea" Williams et al. 2024
***Genus ?"''Candidatus'' Spiritibacter" Williams et al. 2024
Class " Tarhunnaeia" Williams et al. 2024
*Order " Tarhunnaeales" Williams et al. 2024
**Family " Tarhunnaeaceae" Williams et al. 2024
***Genus ?"''Candidatus'' Sutekhia" Williams et al. 2024
***Genus ?"''Candidatus'' Tarhunnaea" Williams et al. 2024
Class " Uliximicrobia" Williams et al. 2024
*Order " Uliximicrobiales" Williams et al. 2024
**Family " Uliximicrobiaceae" Williams et al. 2024
***Genus ?"''Candidatus'' Uliximicrobium" Williams et al. 2024
Class " Umbricyclopia" Mehrshad et al. 2018
*Order " Umbricyclopales" Mehrshad et al. 2018
**Family " Umbricyclopaceae" Mehrshad et al. 2018
***Genus ?"''Candidatus'' Umbricyclops" Mehrshad et al. 2018 (TK10)
Class " Limnocylindria" Mehrshad et al. 2018
*Order " Limnocylindrales" Mehrshad et al. 2018
**Family " Limnocylindraceae" Mehrshad et al. 2018 (SL56)
***Genus "''Candidatus'' Aquidulcis" corrig. Rodriguez-R et al. 2020
***Genus "''Candidatus'' Limnocylindrus" Mehrshad et al. 2018
Class Ktedonobacteria Cavaletti et al. 2007 emend. Yabe et al. 2010
*Order Thermogemmatisporales Yabe et al. 2011
**Family Thermogemmatisporaceae Yabe et al. 2011
***Genus '' Thermogemmatispora'' Yabe et al. 2011
Etymology
The name ''Chloroflexi'' is a Neolatin nominative case masculine plural of '' Chloroflexus'', which is the name of the first genus described. The noun is a combination of the Greek adjective ''chloros, -a, on (χλωρός, -ά, -όν)'', meaning "greenish-yellow," and the Latin masculine passive perfect participle ''flexus'' (of ''flecto''), meaning "bent."[ The etymology is unrelated to ]chlorine
Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...
, an element that was discovered in 1810 by Sir Humphry Davy and named after its pale green colour. Another phylum with the same root is '' Chlorobiota'', whereas "''Cyanobacteria
Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...
''" has the root ''cyanos'' (''κύανος''), meaning "blue-green."
See also
* List of Bacteria genera
This article lists the genera of the bacteria
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, ...
* List of bacterial orders
This article lists the orders of the Bacteria. 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 16 ...
References
{{DEFAULTSORT:Chloroflexota
Phototrophic bacteria
Bacteria phyla
Chloroflexota