The Chloroflexia are a class of
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...
in the
phylum
In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature ...
Chloroflexota
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 p ...
, known as filamentous green non-sulfur bacteria. They use light for energy and are named for their green pigment, usually found in photosynthetic bodies called
chlorosomes.
Chloroflexia are typically filamentous, and can move about through
bacterial gliding. They are facultatively
aerobic
Aerobic means "requiring air," in which "air" usually means oxygen.
Aerobic may also refer to
* Aerobic exercise, prolonged exercise of moderate intensity
* Aerobics, a form of aerobic exercise
* Aerobic respiration, the aerobic process of cel ...
, but do not produce oxygen in the process of producing energy from light, or
phototrophy. Additionally, Chloroflexia have a different method of phototrophy (
photoheterotrophy) than true
photosynthetic bacteria.
Etymology
The name "Chloroflexi" is a Neolatin plural of "Chloroflexus", which is the name of the first genus described. The noun is a combination of the Greek ''chloros'' (χλωρός) meaning "greenish-yellow" and the Latin ''flexus'' (of ''flecto'') meaning "bent" to mean "a green bending".
The name is not due to chlorine, an element confirmed as such in 1810 by
Sir Humphry Davy and named after its pale green colour.
Taxonomy and molecular signatures
The Chloroflexia class is a group of deep branching
photosynthetic bacteria (with the exception of ''
Herpetosiphon
''Herpetosiphon'' is a genus of bacteria in the family '' Herpetosiphonaceae''.
Phylogeny
References
{{Taxonbar, from=Q16965551
Phototrophic bacteria
Bacteria genera
Chloroflexota ...
'' and ''
Kallotenue'' species) that currently consist of three orders:
Chloroflexales,
Herpetosiphonales
Herpetosiphonales is an order of bacteria in the class Chloroflexia
The Chloroflexia are a class of bacteria in the phylum Chloroflexota, known as filamentous green non-sulfur bacteria. They use light for energy and are named for their green p ...
, and
Kallotenuales.
The Herpetosiphonales and Kallotenuales each consist of a single genus within its own family,
Herpetosiphonaceae
''Herpetosiphonaceae'' is a family of bacteria in the order '' Herpetosiphonales''.
References
External links
Phototrophic bacteria
Chloroflexota
{{bacteria-stub ...
(''
Herpetosiphon
''Herpetosiphon'' is a genus of bacteria in the family '' Herpetosiphonaceae''.
Phylogeny
References
{{Taxonbar, from=Q16965551
Phototrophic bacteria
Bacteria genera
Chloroflexota ...
'') and
Kallotenuaceae (''
Kallotenue''), respectively, whereas the
Chloroflexales are more phylogenetically diverse.
[
]
Microscopic distinguishing characteristics
Members of the phylum Chloroflexota
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 p ...
are monoderms and stain mostly Gram negative, whereas most bacteria species are diderms and stain Gram negative, with the Gram positive exceptions of the Bacillota
The Bacillota (synonym Firmicutes) are a phylum of bacteria, most of which have gram-positive cell wall structure. The renaming of phyla such as Firmicutes in 2021 remains controversial among microbiologists, many of whom continue to use the earl ...
(low GC Gram positives), Actinomycetota
The ''Actinomycetota'' (or ''Actinobacteria'') are a phylum of all gram-positive bacteria. They can be terrestrial or aquatic. They are of great economic importance to humans because agriculture and forests depend on their contributions to s ...
(high GC, Gram positives), and the Deinococcota (Gram positive, diderms with thick peptidoglycan).
Genetic distinguishing characteristics
Comparative genomic analysis has recently refined the taxonomy of the class ''Chloroflexia'', dividing the ''Chloroflexales'' into the suborder '' Chloroflexineae'' consisting of the families '' Oscillachloridaceae'' and '' Chloroflexaceae'', and the suborder Roseiflexineae containing family '' Roseiflexaceae''.[ The revised taxonomy was based on the identification of a number of ]conserved signature indels Conserved signature inserts and deletions (CSIs) in protein sequences provide an important category of molecular markers for understanding phylogenetic relationships. CSIs, brought about by rare genetic changes, provide useful phylogenetic markers ...
(CSIs) which serve as highly reliable molecular markers of shared ancestry.
Physiological distinguishing characteristics
Additional support for the division of the Chloroflexales into two suborders is the observed differences in physiological characteristics where each suborder is characterized by distinct carotenoids
Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, co ...
, quinones
The quinones are a class of organic compounds that are formally "derived from aromatic compounds uch as benzene or naphthalene">benzene.html" ;"title="uch as benzene">uch as benzene or naphthalene] by conversion of an even number of –CH= grou ...
, and fatty acid
In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, f ...
profiles that are consistently absent in the other suborder.
In addition to demarcating taxonomic ranks, CSIs may play a role in the unique characteristics of members within the clade: In particular, a four-amino-acid insert in the protein pyruvate flavodoxin/ferredoxin oxidoreductase, a protein which plays important roles in photosynthetic organisms, has been found exclusively among all members in the genus ''Chloroflexus'', and is thought to play an important functional role.
Additional work has been done using CSIs to demarcate the phylogenetic position of ''Chloroflexia'' relative to neighbouring photosynthetic groups such as the Cyanobacteria.
''Chloroflexota'' species form a distinct lineage with ''Chlorobiota
The green sulfur bacteria are a phylum of obligately anaerobic photoautotrophic bacteria that metabolize sulfur.
Green sulfur bacteria are nonmotile (except ''Chloroherpeton thalassium'', which may glide) and capable of anoxygenic photosynthes ...
'' species, their closest phylogenetic relatives. A CSI has been found to be shared among both ''Chloroflexota'' and ''Chlorobiota'' members, which has been interpreted as the result of a horizontal gene transfer
Horizontal gene transfer (HGT) or lateral gene transfer (LGT) is the movement of genetic material between unicellular and/or multicellular organisms other than by the ("vertical") transmission of DNA from parent to offspring (reproduction). H ...
event between the two relatives.
Phylogeny
Taxonomy
The currently accepted taxonomy is as follows:
Class Chloroflexia Gupta et al. 2013
* Genus "'' Dehalobium''" Wu et al. 2002
* Genus "''Candidatus'' Lithoflexus" Saghai et al. 2020
* Genus "''Candidatus'' Sarcinithrix" Nierychlo et al. 2019
* Order " Thermobaculales"
** Family " Thermobaculaceae"
*** Genus "'' Thermobaculum''" Botero et al. 2004
* Order Kallotenuales Cole et al. 2013
**F amily Kallotenuaceae Cole et al. 2013
*** Genus '' Kallotenue'' Cole et al. 2013
* Order Herpetosiphonales
Herpetosiphonales is an order of bacteria in the class Chloroflexia
The Chloroflexia are a class of bacteria in the phylum Chloroflexota, known as filamentous green non-sulfur bacteria. They use light for energy and are named for their green p ...
Gupta et al. 2013
** Family Herpetosiphonaceae
''Herpetosiphonaceae'' is a family of bacteria in the order '' Herpetosiphonales''.
References
External links
Phototrophic bacteria
Chloroflexota
{{bacteria-stub ...
Gupta et al. 2013
*** Genus "''Candidatus'' Anthektikosiphon" Ward, Fischer & McGlynn 2020
*** Genus ''Herpetosiphon
''Herpetosiphon'' is a genus of bacteria in the family '' Herpetosiphonaceae''.
Phylogeny
References
{{Taxonbar, from=Q16965551
Phototrophic bacteria
Bacteria genera
Chloroflexota ...
'' Holt & Lewin 1968 'Flavilitoribacter''_García-López_et_al._2020.html" ;"title="Flavilitoribacter.html" ;"title="'Flavilitoribacter">'Flavilitoribacter'' García-López et al. 2020">Flavilitoribacter.html" ;"title="'Flavilitoribacter">'Flavilitoribacter'' García-López et al. 2020* Order Chloroflexales Gupta et al. 2013
** Suborder Roseiflexineae Gupta et al. 2013
*** Family Roseiflexaceae Gupta et al. 2013 ["Kouleotrichaceae" Mehrshad et al. 2018]
**** Genus "''Kouleothrix''" Kohno et al. 2002
**** Genus ''Heliothrix'' Pierson et al. 1986
**** Genus ''Roseiflexus'' Hanada et al. 2002
** Suborder Chloroflexineae Gupta et al. 2013
*** Family Chloroflexaceae Gupta et al. 2013
**** Genus ''Candidatus'' Chloranaerofilum Thiel et al. 2016
**** Genus '' Chloroflexus'' Pierson & Castenholz 1974 ''Chlorocrinis''".html" ;"title="Chlorocrinis.html" ;"title="''Chlorocrinis">''Chlorocrinis''"">Chlorocrinis.html" ;"title="''Chlorocrinis">''Chlorocrinis''"*** Family Oscillochloridaceae Gupta et al. 2013
**** Genus ''Candidatus'' Chloroploca Gorlenko et al. 2014
**** Genus ''Chloronema'' ♪ Dubinina & Gorlenko 1975
**** Genus '' Oscillochloris'' Gorlenko & Pivovarova 1989
**** Genus ''Candidatus'' Viridilinea Grouzdev et al. 2018
See also
* List of bacteria genera
* List of bacterial orders
References
Further reading
*
External links
*
External links
{{Taxonbar, from=Q15732012
Bergey's volume 1
Phototrophic bacteria