Microorganisms involved in the mercury transformations in the ocean

Abstract

Mercury is known as one of the highly toxic heavy metals and presents at low levels in the ocean. Especially methylmercury efficiently accumulates in fish, which leads to human and environmental health risks. Thus, information about the distribution and transformations of mercury and methylmercury in the ocean is important for understanding the accumulation process of mercury in marine biota. In marine environments, microorganisms (bacteria and archaea in this study) are involved in mercury transformations, i.e., methylation, demethylation, and reduction. Genomic and metagenomic studies have revealed the key genes for mercury methylation (hgcAB),demethylation (merB),and reduction (merA).The distributions of these genes in several marine environments have been reported. In this review, we introduce the current understanding of the distribution of total mercury and methylmercury in the ocean, the phylogeny and diversity of the genes involved in the mercury transformations, and highlight the distribution of these genes in the marine environments.