γ-proteobacteria

Gammaproteobacteria is a class of bacteria in the phylum Pseudomonadota (synonym Proteobacteria). It contains about 250 genera, which makes it the most genus-rich taxon of the Prokaryotes. Several medically, ecologically, and scientifically important groups of bacteria belong to this class. All members of this class are Gram-negative. It is the most phylogenetically and physiologically diverse class of the Pseudomonadota.

Members of Gammaproteobacteria live in several terrestrial and marine environments, in which they play various important roles, including in extreme environments such as hydrothermal vents. They can have different shapes, rods, curved rods, cocci, spirilla, and filaments, and include free living bacteria, biofilm formers, commensals and symbionts; some also have the distinctive trait of being bioluminescent. Diverse metabolisms are found in Gammaproteobacteria; there are both aerobic and anaerobic (obligate or facultative) species, chemolithoautotrophics, chemoorganotrophics, photoautotrophs and heterotrophs.