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| Chloroflexota | |
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Scientific classification 
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| Domain: | Bacteria |
| Clade: | Terrabacteria |
| Phylum: | Chloroflexota Garrity and Holt 2021[1] |
| Classes | |
| Synonyms | |
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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 (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.[2] Many well-studied phyla of bacteria are diderms and stain gram-negative, whereas well-known monoderms that stain Gram-positive include Firmicutes (or Bacillota) (low G+C gram-positives), Actinomycetota (high-G+C gram-positives) and Deinococcota (gram-positive diderms with thick peptidoglycan).
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.[3]
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 (SSU) sequences and grouped the genera Chloroflexus, Herpetosiphon and Thermomicrobium 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 (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.[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 was Dehalogenimonas 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 no conserved 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 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.[10]
Phylogeny
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[11] and National Center for Biotechnology Information (NCBI).[12]
| 16S rRNA based LTP_08_2023[13][14][15] | 120 marker proteins based GTDB 08-RS214 (28th April 2023).[16][17][18] | |||||||||||||||||||||||||||||||||||||||||||||||||||
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