Chloroflexota
A phylum of bacteria with diverse metabolic and structural traits.
The Chloroflexota are a bacterial phylum often called green non-sulfur bacteria. Its members are monoderms—they have a single cell membrane and lack an outer membrane—yet they can stain either gram-positive or gram-negative. The phylum includes a wide variety of lifestyles: aerobic thermophiles that thrive in high temperatures and use oxygen, anoxygenic phototrophs that harness light for photosynthesis, and anaerobic halorespirers that use toxic halogenated organics, such as chlorinated ethenes and polychlorinated biphenyls, as electron acceptors.
- field
- Bacteriology
- known_for
- Deep branching phylum of bacteria with diverse metabolic phenotypes
- type_phylum
- Chloroflexota
- type_genus
- Chloroflexus
- number_of_classes
- Eight distinct classes
Quick Facts
- Taxon
- Chloroflexota
Facts from the source article.
Lore & Background
The taxon name was originally created as 'Chloroflexi' in the 2001 edition of Volume 1 of Bergey's Manual of Systematic Bacteriology (the name 'Chloroflexota' was adopted later) 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 divided Eubacteria into 10 major groups based on 16S ribosomal RNA sequences and grouped the genera Chloroflexus, Herpetosiphon and Thermomicrobium into the 'green non-sulfur bacteria', which was temporarily renamed as 'Chloroflexi' in Volume One of Bergey's Manual of Systematic Bacteriology. Chloroflexota being a deep branching phylum, it was already divided into multiple classes (e.g., Chloroflexi) in the 2001 edition of Bergey's Manual, with Thermomicrobia included within the phylum as the class Thermomicrobia. Since 2001, however, new classes have been created thanks to newly discovered species, and the phylum is now divided into several classes. 'Dehalococcoidia' (originally proposed as the placeholder 'Dehalococcoidetes' by Hugenholtz & Stackebrandt, 2004, after 'Dehalococcoides mccartyi', formerly 'Dehalococcoides ethenogenes' strain 195) is a class within the phylum. The first fully described species in that lineage was 'Dehalococcoides mccartyi' (described earlier, e.g., by Maymó-Gatell et al. 1997 as 'Dehalococcoides ethenogenes'), not Dehalogenimonas lykanthroporepellens.
Reader's Guide
Recent phylogenetic analysis of the Chloroflexota 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. The phylum's significance lies in its deep branching position among bacteria and its members' diverse metabolic capabilities, including roles in bioremediation through anaerobic halorespiration of toxic compounds.
Did You Know?
- The phylum Chloroflexota are monoderms, having one cell membrane with no outer membrane, but species stain both gram positive and gram negative.
- The taxon name was originally created as 'Chloroflexi' in the 2001 edition of Volume 1 of Bergey's Manual of Systematic Bacteriology; the name 'Chloroflexota' was adopted later.
- The class 'Dehalococcoidia' (originally proposed as the placeholder 'Dehalococcoidetes' by Hugenholtz & Stackebrandt, 2004) is named after 'Dehalococcoides mccartyi' (formerly 'Dehalococcoides ethenogenes' strain 195).
- Recent phylogenetic analysis found very weak support for the grouping together of the different classes currently part of the phylum.
Frequently Asked Questions
What is Chloroflexota?
Chloroflexota is a deeply branching bacterial phylum, often called the green non-sulfur bacteria, that contains eight distinct classes. Its type genus is Chloroflexus, and the phylum is celebrated for packing an extraordinary range of metabolic strategies into a single taxonomic group.
Why is Chloroflexota's cell structure considered paradoxical?
Members of this phylum are monoderms, carrying only a single cell membrane with no outer membrane. Yet they can stain as either gram-positive or gram-negative, which upends the usual assumption that gram-reaction mirrors cell-wall complexity.
What metabolic lifestyles exist within Chloroflexota?
The phylum spans aerobic thermophiles that use oxygen at high temperatures, anoxygenic phototrophs that harvest light for energy, and anaerobic halorespirers that reduce toxic halogenated organics such as chlorinated ethenes and PCBs. This phenotypic breadth makes Chloroflexota one of the most metabolically diverse bacterial phyla known.
How many classes does Chloroflexota contain, and what anchors its taxonomy?
Chloroflexota is subdivided into eight distinct classes, reflecting the wide ecological and metabolic variation among its members. The type genus that anchors the phylum's formal nomenclature is Chloroflexus.
Why is Chloroflexota significant in evolutionary microbiology?
Because it occupies a deep-branching position in the bacterial tree and harbors such varied energy-metabolism pathways, Chloroflexota is a critical reference point for reconstructing early bacterial evolution. Its halorespiring members also carry practical importance for bioremediation of chlorinated industrial pollutants.
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