RT Journal Article
SR Electronic
T1 Marine snow as a habitat for microbial mercury methylators in the Baltic Sea
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2020.03.04.975987
DO 10.1101/2020.03.04.975987
A1 Eric Capo
A1 Andrea Garcia Bravo
A1 Anne L. Soerensen
A1 Stefan Bertilsson
A1 Jarone Pinhassi
A1 Caiyan Feng
A1 Anders F. Andersson
A1 Moritz Buck
A1 Erik Björn
YR 2020
UL http://biorxiv.org/content/early/2020/03/05/2020.03.04.975987.abstract
AB Methylmercury (MeHg), a neurotoxic compound biomagnifying in aquatic food webs, can be a threat to human health via fish consumption. However, the composition and distribution of the microbial communities mediating the methylation of mercury (Hg) to MeHg in marine systems remain largely unknown. In order to fill this gap of knowledge, we used the Baltic Sea Reference Metagenome (BARM) dataset to study the distribution of the genes involved in Hg methylation (the hgcAB gene cluster). We determined the relative abundance of the hgcAB genes and their taxonomic identity in 81 brackish metagenomes that cover spatial, seasonal and redox variability in the Baltic Sea water. The hgcAB genes were predominantly detected in anoxic water, but some hgcAB genes were also detected in hypoxic and normoxic waters. Higher relative quantities of hgcAB genes were found in metagenomes from marine snow compared to free-living communities in anoxic water, suggesting that marine snow are hotspot habitats for Hg methylators in oxygen-depleted seawater. Phylogenetic analysis identified well-characterized Hg methylators such as Deltaproteobacteria in oxygen-depleted water, but also uncovered Hg methylators within the Spirochaetes and Lentisphaerae phyla. Altogether, our work unveils the diversity of the microorganisms mediating MeHg production in the Baltic Sea and pinpoint the ecological niches of these microorganisms within the marine water column.