Epsilonproteobacteria

Epsilonproteobacteria is a class of bacteria within the phylum Proteobacteria. Members are Gram-negative, typically small and motile microorganisms that are predominantly microaerophilic or anaerobic. The class is phylogenetically diverse and contains several medically and ecologically important genera, including Helicobacter and Campylobacter, which are well-known human pathogens, as well as Arcobacter and Wolinella.

Most are curved rod-shaped or spiral, with polar flagella enabling motility. They generally grow under low-oxygen conditions and many are chemolithoautotrophs or chemoorganotrophs, capable of oxidizing reduced sulfur compounds or organic substrates.

Epsilonproteobacteria occupy a wide range of environments. A substantial number inhabit the gastrointestinal tracts and mucosal surfaces of animals, including humans. Helicobacter pylori colonizes the stomach and is linked to gastritis and gastric cancer; Campylobacter species cause enteritis. Other members, such as Arcobacter and Wolinella, are found in animals and their environments. Environmentally, some Epsilonproteobacteria such as Sulfurovum and Sulfurimonas exist as sulfur-oxidizing chemolithotrophs in hydrothermal vents and other sulfur-rich habitats.

The class is divided into several orders, including Campylobacterales, which contains the families Helicobacteraceae and Campylobacteraceae. Epsilonproteobacteria are studied for their roles in disease, gut microbiology, and biogeochemical sulfur cycling, as well as for insights into host–microbe interactions and the evolution of the Proteobacteria.