Skip to main content
Research article - Peer-reviewed, 2020

Deltaproteobacteria and Spirochaetes-Like Bacteria Are Abundant Putative Mercury Methylators in Oxygen-Deficient Water and Marine Particles in the Baltic Sea

Capo, Eric; Bravo, Andrea G.; Soerensen, Anne L.; Bertilsson, Stefan; Pinhassi, Jarone; Feng, Caiyan; Andersson, Anders F.; Buck, Moritz; Bjorn, Erik;

Abstract

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 knowledge gap, we used the Baltic Sea Reference Metagenome (BARM) dataset to study the abundance and distribution of the genes involved in Hg methylation (thehgcABgene cluster). We determined the relative abundance of thehgcABgenes and their taxonomic identity in 81 brackish metagenomes that cover spatial, seasonal and redox variability in the Baltic Sea water column. ThehgcABgenes were predominantly detected in anoxic water, but somehgcABgenes were also detected in hypoxic and normoxic waters. Phylogenetic analysis identified putative Hg methylators within Deltaproteobacteria, in oxygen-deficient water layers, but also Spirochaetes-like and Kiritimatiellaeota-like bacteria. Higher relative quantities ofhgcABgenes were found in metagenomes from marine particles compared to free-living communities in anoxic water, suggesting that such particles are hotspot habitats for Hg methylators in oxygen-depleted seawater. Altogether, our work unveils the diversity of the microorganisms with the potential to mediate MeHg production in the Baltic Sea and pinpoint the important ecological niches for these microorganisms within the marine water column.

Keywords

mercury methylation; hgcAB; Baltic Sea; deltaproteobacteria; spirochaetes-like bacteria

Published in

Frontiers in Microbiology

2020, volume: 11, article number: 574080
Publisher: FRONTIERS MEDIA SA

Authors' information

Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Capo, Eric
Umeå University
Bravo, Andrea G.
CSIC - Instituto de Ciencias del Mar (ICM)
Soerensen, Anne L.
Swedish Museum of Natural History
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Pinhassi, Jarone
Linnaeus University
Feng, Caiyan
Umea University
Andersson, Anders F.
Royal Institute of Technology
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Bjorn, Erik
Umea University

UKÄ Subject classification

Microbiology

Publication Identifiers

DOI: https://doi.org/10.3389/fmicb.2020.574080

URI (permanent link to this page)

https://res.slu.se/id/publ/108387