Chloroflexi

Abstract

The phylum Chloroflexi is a deeply branching phylum of the Bacteria, which harbors extensive intraphylum diversity and is found in a wide range of aquatic and terrestrial environments. Before the name Chloroflexi was first proposed in 2001, members of this phylum were referred to as ‘Green non-sulfur bacteria’. The phylum was named after the genus Chloroflexus, and its type species, Chloroflexus aurantiacus, a filamentous anoxygenic phototrophic bacterium that was first found in hot springs and described by Pierson and Castenholtz in 1974. As a ‘green’ phototrophic bacterium that lived in ‘non-sulphidic’ environments, it represented the group of ‘green non-sulfur bacteria’ (GNSB), which now is termed ‘filamentous anoxygenic phototrophs’ (FAP), a term used specifically for phototrophic members of the Chloroflexi. Members of this phylum have first been described in microbial mats associated with extreme conditions such as thermal and hypersaline environments. Subsequently, Chloroflexi have further been detected in a variety of mesophilic freshwater and marine environments, including wastewater treatment plants and even are part of the human microbiome.