Chloroflexi (class)

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Scientific classification
Domain: Bacteria
Phylum: Chloroflexi
Class: Chloroflexi


Chloroflexi is one of six classes of bacteria in the phylum Chloroflexi, known as filamentous green non-sulfur bacteria. They produce energy from light and are named for their green pigment, usually found in photosynthetic bodies called chlorosomes.

Chloroflexi are typically filamentous, and can move about through bacterial gliding. They are facultatively aerobic, but do not produce oxygen in the process of producing energy from light, or phototrophy. Additionally Chloroflexi have a different method of phototrophy (photoheterotrophy) than true photosynthetic bacteria. Phylogenetic analysis indicates that they had a separate origin.[clarification needed]

Whereas most Bacteria, in terms of diversity, are diderms and stain Gram negative with the exception of the Firmicutes (low GC Gram positives), Actinobacteria (high GC gram positives) and the Deinococcus-Thermus group (Gram positive, but diderms with thick peptidoglycan), the members of the phylum Chloroflexi are monoderms and stain mostly Gram negative.[1]


Comparative genomic analysis has recently refined the taxonomy of the class Chloroflexi, dividing the Chloroflexales into the suborder Chloroflexineae consisting of the family Oscillachloridaceae and the family Chloroflexaceae, and the suborder Roseiflexineae containing family Roseiflexaceae.[2] The revised taxonomy was based on the identification of a number of conserved signature indels (CSIs) which serve as highly reliable molecular markers of shared ancestry.[3][4][5] Comparative analyses of Chloroflexi genomes have identified 5 CSIs in different important proteins, such as GroES and Tryptophan synthase, that are uniquely shared by all sequenced species/strains of the Chloroflexi class, but are not found in any other bacteria.[2] Another 9 CSIs have been identified in a number of proteins, including important photosynthesis related proteins such as Magnesium chelatase, that are specific for all or most of the species from the order Chloroflexales.[2] Within the Chloroflexales, 3 CSIs specific for Chloroflexaceae, 4 CSIs specific for Roseiflexaceae, and 7 CSIs specific for the suborder Chloroflexineae, which consists of Chloroflexaceae and Oscillochloridaceae have also been identified in various proteins.[2] Two of the CSIs uniquely found in the Chloroflexaceae family, a 4 aa insert in the protein pyruvate flavodoxin/ferredoxin oxidoreductase (PFOR) and a 2 aa insert in the protein magnesium-protoporphyrin IX monomethyl ester cyclase (ACSF), are located in proteins which play important roles in photosynthesis and are only found in photosynthetic organisms.[2][6]


The currently accepted taxonomy is as follows:[2][7]

Additionally, there are "Kouleothrix aurantiaca" and "Dehalobium chlorocoercia" which have not been fully described.


The name "Chloroflexi" is a Neolatin nominative case masculine plural of "Chloroflexus", which the name of the first genus described. The noun is a combination of the Greek adjective chloros, -a, on (χλωρός, -ά, -όν)[8] meaning "greenish-yellow" and the Latin masculine passive perfect participle flexus (of flecto)[9] meaning "bent" to mean "a green bending".[10] It should be therefore noted that the etymology is not due to chlorine, an element (dephlogisticated muriatic acid air) which was confirmed as such in 1810 by Sir Humphry Davy and named after its pale green colour.

Further reading[edit]

  • Garrity GM, Holt JG (2001). "Phylum BVI. Chloroflexi phy. nov". In D.R. Boone and R.W. Castenholz, eds. Bergey's Manual of Systematic Bacteriology Volume 1: The Archaea and the deeply branching and phototrophic Bacteria (2nd ed.). New York: Springer Verlag. p. 169. ISBN 978-0-387-98771-2. 


  1. ^ 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. PMID 20637628. 
  2. ^ a b c d e f Gupta, 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. PMID 22903492. 
  3. ^ Gupta, R. S. (1998). "Protein phylogenies and signature sequences: A reappraisal of evolutionary relationships among archaebacteria, eubacteria, and eukaryotes". Microbiology and molecular biology reviews : MMBR 62 (4): 1435–1491. PMC 98952. PMID 9841678. 
  4. ^ Rokas, A.; Holland, P. W. (2000). "Rare genomic changes as a tool for phylogenetics". Trends in ecology & evolution 15 (11): 454–459. doi:10.1016/S0169-5347(00)01967-4. PMID 11050348. 
  5. ^ Gupta, R. S.; Griffiths, E. (2002). "Critical issues in bacterial phylogeny". Theoretical population biology 61 (4): 423–434. doi:10.1006/tpbi.2002.1589. PMID 12167362. 
  6. ^ Stolz, F. M.; Hansmann, I. (1990). "An MspI RFLP detected by probe pFMS76 D20S23 isolated from a flow-sorted chromosome 20-specific DNA library". Nucleic acids research 18 (7): 1929. doi:10.1093/nar/18.7.1929. PMC 330654. PMID 1692410. 
  7. ^ Classification of Chloroflexi entry in LPSN [Euzéby, J.P. (1997). "List of Bacterial Names with Standing in Nomenclature: a folder available on the Internet". Int J Syst Bacteriol 47 (2): 590–2. doi:10.1099/00207713-47-2-590. ISSN 0020-7713. PMID 9103655. ]
  8. ^ χλωρός. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project
  9. ^ Lewis, Charlton T. and Charles Short, A Latin Dictionary. Oxford: Clarendon Press, 1879. Online version at Perseus
  10. ^ 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 2A (2nd ed.). New York: Springer. p. 304. ISBN 978-0-387-24143-2. British Library no. GBA561951. 

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