Selenium (Se),belonging to group Ⅵ of the periodic table,is an essential trace element for cell activity as it is required for its incorporation into selenocysteine,selenomethionine and its function in selenoenzymes.Se plays a key role on human immune function,antioxidant defense systems and anticancer.In contrast,insufficient supply of Se is associated with more than 40 diseases.Se exists as four metastable oxidation states in the environment:(-Ⅱ),(0),(+Ⅳ),and (+Ⅵ).Microorganisms take part in all transformation process of those different oxidation states.This review highlights recent advances and summarizes microbial selenium metabolisms in the following aspects: (1)the important function and mechanism of selenium in life; (2)chemistry characteristics and biogeochemical cycle of selenium; (3)diverse population of microorganisms related to oxidation,reduction and methylation of selenium; (4)microbial molecular mechanisms of selenium; and (5)providing a prelude to research spot and application in the future according to our results.In this article,we conclude that microbial metabolisms of selenium plays a fundamental role on biogeochemical cycle,biodiversity,selenium uptake of plant,human health and bioremediation.