The Gemmatimonadetes are a phylum of bacteria created for the type species Gemmatimonas aurantiaca. This bacterium makes up about 2% of soil bacterial communities and has been identified as one of the top nine phyla found in soils; yet, there are currently only six cultured isolates. Gemmatimonadetes have been found in a variety of arid soils, such as grassland, prairie, and pasture soil, as well as eutrophic lake sediments and alpine soils. This wide range of environments where Gemmatimonadetes have been found suggests an adaptation to low soil moisture. A study conducted showed that the distribution of the Gemmatimonadetes in soil tends to be more dependent on the moisture availability than aggregation, reinforcing the belief that the members of this phylum prefer dryer soils. The phylum Gemmatimonadetes is distinct from the phylum Cyanobacteria and may have diverged in early microbial evolution at least 3 billion years ago.
The first member of this phylum was discovered in 2003 in activated sludge in a sewage treatment system. The bacterium was named Gemmatimonas aurantiaca. This bacterium is identified as strain T-27T, is Gram-negative, and is the only member of this phylum that has been studied in depth. The metabolic pathways and enzymes of this bacterium are unique and it is able to grow by both aerobic and anaerobic respiration.
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LSPN), National Center for Biotechnology Information and the All-Species Living Tree Project.