Chloroflexi (phylum)

The Chloroflexi or Chlorobacteria 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.
Most bacteria, in terms of diversity, are diderms and stain gram-negative, notable exceptions being "Firmicutes" (low G+C gram-positives), "Actinobacteria" (high-G+C gram-positives) and the "Deinococcus–Thermus" group (gram-positive diderms with thick peptidoglycan). In contrast, the members of the phylum Chloroflexi are monoderms, but stain mostly gram-negative.
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 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", which was temporarily renamed as "Chloroflexi" in Volume One of Bergey's Manual of Systematic Bacteriology.
Chloroflexi 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, the class Chloroflexi. Since 2001, however, new classes have been created thanks to newly discovered species, and the phylum Chloroflexi is now divided as follows:
"Dehalococcoidetes" is a placeholder name given by Hugenholtz & Stackebrandt, 2004, after "Dehalococcoides ethenogenes" a species partially described in 1997.<ref name="doi10.1126/science.276.5318.1568"></ref> 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 identity, meaning that they could fall in different families or even orders.
Recent phylogenetic analysis of the Chloroflexi has found very weak support for the grouping together of the different classes currently part of the phylum. 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. 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 (LPSN) and National Center for Biotechnology Information (NCBI). The phylogeny is based on 16S rRNA-based LTP release 132 by The All-Species Living Tree Project
Notes: 
♠ Strains found at the National Center for Biotechnology Information (NCBI) but not listed in the List of Prokaryotic names with Standing in Nomenclature (LSPN).
♪ Prokaryotes where no pure (axenic) cultures are isolated or available; i.e., they are not cultivated or cannot be sustained in culture for more than a few serial passages.
Taxonomy.
Genus ""Candidatus" Chlorothrix" 
Class Thermoflexia 
Class Dehalococcoidia ["Dehalococcoidetes" ]
Class Anaerolineae 
Class Ardenticatenia 
Class Caldilineae 
Class Ktedonobacteria ["Ktedobacteria" (sic) ]
Class Thermomicrobia 
Class Chloroflexia 
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, 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 "Chlorobi", whereas "Cyanobacteria" has the root "cyanos" ("κύανος"), meaning "blue-green."
Unlike some other phyla, there is no theme root in the name of genera of Chloroflexi, and in fact many genera beginning with "Chloro-" or ending in "-chloris" are either cyanobacteria or chlorobi.