Abstract:Nitrate is the main form of nitrogen available to marine microorganisms, and it is also the main limiting factor of nutrients on the production of surface marine organisms. In the ocean, ammonia and nitrite are oxidized to form nitrate. Exploring the niche of nitrite-oxidizing bacteria (NOB) in the marine ecosystem and its response mechanism to marine environmental changes is of great significance to understanding the nitrogen cycle in which microorganisms participate. Here, key bacterial species and their research progress in marine nitrite oxidation are reviewed. The physiological and ecological characteristics of NOB are summarized, and its adaptive strategies in the marine ecosystem are highlighted. Simultaneously, prospective research direction of NOB is elucidated to understand the oxidation process of nitrite in the ocean and the nitrogen cycle in biogeochemistry.