Gemmatimonadetes


The Gemmatimonadetes are a phylum of bacteria established in 2003. The phylum contains two classes Gemmatimonadetes and Longimicrobia.

Species

The type species Gemmatimonas aurantiaca strain T-27T was isolated from activated sludge in a sewage treatment system in 2003. It is a Gram-negative bacterium able to grow by both aerobic and anaerobic respiration.
The second cultured species was Gemmatirosa kalamazoonensis gen. nov., sp. nov. strain KBS708, which was isolated from organically managed agricultural soil in Michigan USA.

The third cultured species Gemmatimonas phototrophica strain AP64T was isolated from a shallow freshwater desert lake Tiān é hú in North China. A unique feature of this organism is the presence of bacterial photosynthetic reaction centers. It probably acquired genes for anoxygenic photosynthesis via horizontal gene transfer. G. phototrophica is a facultative photoheterotrophic organism. It requires the supply of organic substrate for growth, but it may obtain additional energy for its metabolism from light.
Longimicrobium terrae strain CB-286315T was isolated from a soil sample from a typical Mediterranean forest ecosystem located in Granada, Spain. Due to this large phylogenetic distance from other cultured Gemmatimonades, it established a novel class named Longimicrobia.

Environmental distribution

Data from culture-independent studies indicate that Gemmatimonadetes are widely distributed in many natural habitats. They make 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.. Smaller numbers were also found in various aquatic environments, such as fresh waters and sediments.

Taxonomy

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature, National Center for Biotechnology Information and the All-Species Living Tree Project.