The members of the phylumChloroflexota aremonoderms (that is, have one cell membrane with no outer membrane), but they stain mostly gram-negative.[2] Many well-studied phyla of bacteria arediderms and staingram-negative, whereas well-known monoderms that stain Gram-positive includeFirmicutes (orBacillota) (low G+C gram-positives) andActinomycetota (high-G+C gram-positives).
In 1987,Carl Woese, regarded as one of the forerunner of the molecular phylogeny revolution, divided Eubacteria into 11 divisions based on16S ribosomal RNA (SSU) sequences and grouped the generaChloroflexus,Herpetosiphon andThermomicrobium into the "green non-sulfur bacteria and relatives",[4][5] which was temporarily renamed as "Chloroflexi" in Volume One of Bergey's Manual of Systematic Bacteriology.[6]
Chloroflexota being a deep branching phylum (seeBacterial phyla), it was considered in Volume One of Bergey's Manual of Systematic Bacteriology to include a single class with the same name.[6] 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,[7] after "Dehalococcoides ethenogenes" a species partially described in 1997.[8] The first species fully described wasDehalogenimonas lykanthroporepellens, by Moe et al. 2009,[9] 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 identity, meaning that they could fall in different families or even orders.[9]
Recent phylogenetic analysis of the Chloroflexota has found very weak support for the grouping together of the different classes currently part of the phylum.[10] The six classes that make up the phylum did not consistently form a well-supported clade in phylogenetic trees based on concatenated sequences for large datasets of proteins, and noconserved signature indels were identified that were uniquely shared by the entire phylum.[10] 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.[10] It has been suggested that the phylum Chloroflexisensu 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.[10]
Genus "CandidatusCaldibacter"corrig. Spieck et al. 2020 Genus "CandidatusChlorotrichoides"corrig. Oren et al. 2020 ["CandidatusChlorothrix"Klappenbach & Pierson 2004 non Dyar 1921 non Berger-Perrot 1982[22]] Genus "CandidatusNitrocaldera"Spieck et al. 2020 Genus "CandidatusNitrotheca"Spieck et al. 2020 Class "Bathosphaeria"Mehrshad et al. 2018
Order "Bathosphaerales"Mehrshad et al. 2018
Family "Bathosphaeraceae"Mehrshad et al. 2018
Genus ?"CandidatusBathosphaera"Mehrshad et al. 2018 (JG30-KF-CM66)
The nameChloroflexi is a Neolatin nominative case masculine plural ofChloroflexus, which is the name of the first genus described. The noun is a combination of the Greek adjectivechloros, -a, on (χλωρός, -ά, -όν),[27] meaning "greenish-yellow," and the Latin masculine passive perfect participleflexus (offlecto),[28] meaning "bent."[6] The etymology is unrelated tochlorine, an element that was discovered in 1810 bySir Humphry Davy and named after its pale green colour. Another phylum with the same root isChlorobiota, whereas "Cyanobacteria" has the rootcyanos (κύανος), meaning "blue-green."[29]
Unlike some other phyla, there is no theme root in the name of genera of Chloroflexota, and in fact many genera beginning with "Chloro-" or ending in"-chloris" are either cyanobacteria or chlorobi.
^Sutcliffe, I. C. (2010). "A phylum level perspective on bacterial cell envelope architecture".Trends in Microbiology.18 (10):464–470.doi:10.1016/j.tim.2010.06.005.PMID20637628.
^Don J. Brenner; Noel R. Krieg; James T. Staley (July 26, 2005) [1984(Williams & Wilkins)]. George M. Garrity (ed.).Introductory Essays. Bergey's Manual of Systematic Bacteriology. Vol. 2A (2nd ed.). New York: Springer. p. 304.ISBN978-0-387-24143-2. British Library no. GBA561951.
^Holland L. (22 May 1990). "Woese,Carl in the forefront of bacterial evolution revolution".Scientist.4 (10).
^abcDon J. Brenner; Noel R. Krieg; James T. Staley (July 26, 2005) [1984(Williams & Wilkins)]. George M. Garrity (ed.).Introductory Essays. Bergey's Manual of Systematic Bacteriology. Vol. 2A (2nd ed.). New York: Springer. p. 304.ISBN978-0-387-24143-2. British Library no. GBA561951.
^Maymo-Gatell, X.; Chien, Y.; Gossett, J. M.; Zinder, S. H. (1997). "Isolation of a Bacterium That Reductively Dechlorinates Tetrachloroethene to Ethene".Science.276 (5318):1568–1571.doi:10.1126/science.276.5318.1568.PMID9171062.
^abcdGupta, R. S.; Chander, P.; George, S. (2012). "Phylogenetic framework and molecular signatures for the class Chloroflexi and its different clades; proposal for division of the class Chloroflexi class. nov. into the suborder Chloroflexineae subord. nov., consisting of the emended family Oscillochloridaceae and the family Chloroflexaceae fam. nov., and the suborder Roseiflexineae subord. nov., containing the family Roseiflexaceae fam. nov".Antonie van Leeuwenhoek.103 (1):99–119.doi:10.1007/s10482-012-9790-3.PMID22903492.S2CID17656551.
^Klappenbach, J. A.; Pierson, B. K. (2004). "Phylogenetic and physiological characterization of a filamentous anoxygenic photoautotrophic bacterium'Candidatus Chlorothrix halophila' Gen. Nov., sp. Nov., recovered from hypersaline microbial mats".Archives of Microbiology.181 (1):17–25.doi:10.1007/s00203-003-0615-7.PMID14655000.S2CID23854988.
^Grégoire, P.; Fardeau, M. L.; Joseph, M.; Guasco, S.; Hamaide, F.; Biasutti, S.; Michotey, V. R.; Bonin, P.; Ollivier, B. (2011). "Isolation and characterization ofThermanaerothrix daxensis gen. nov., sp. nov., a thermophilic anaerobic bacterium pertaining to the phylum "Chloroflexi", isolated from a deep hot aquifer in the Aquitaine Basin".Systematic and Applied Microbiology.34 (7):494–497.doi:10.1016/j.syapm.2011.02.004.PMID21621938.
