Abstract:Marine hydrothermal systems are high-temperature extreme environments formed under the influence of geothermal activities. According to early studies, γ-Proteobacteria were the main members of sulfur-oxidizing chemolithoautotrophic bacteria in deep-sea hydrothermal vents. At the end of the last century, molecular ecological studies revealed that Campylobacteria (former ε-Proteobacteria) were the dominant bacteria in hydrothermal habitats, such as hydrothermal solution, smoker body, megafauna, and underground sediments, with ecological significance in the life processes including sulfur oxidation and hydrogen oxidation in hydrothermal areas. The article comprehensively reviews the research progress of Campylobacteria in hydrothermal vents from ecological, physiological, and other perspectives. It extensively describes the ecological distribution, diverse metabolic types, strain characteristics, and taxonomic status of Campylobacteria, showcasing the utilization mechanisms of Campylobacteria for elements such as carbon, nitrogen, sulfur, and hydrogen.