Microorganisms Involved in Methylmercury Demethylation and Mercury Reduction are Widely Distributed and Active in the Bathypelagic Deep Ocean Waters
Sanz-Sáez, Isabel (Institut de Ciències del Mar)
Bravo, Andrea G. (Institut de Ciències del Mar)
Ferri, Marta (Institut de Ciències del Mar)
Carreras, Joan-Martí (Institut de Ciències del Mar)
Sánchez Martínez, M. Olga (Universitat Autònoma de Barcelona. Departament de Genètica i de Microbiologia)
Sebastian, Marta (Institut de Ciències del Mar)
Ruiz González, Clara (Institut de Ciències del Mar)
Capo, Eric (Institut de Ciències del Mar)
Duarte, Carlos M. (King Abdullah University of Science and Technology)
Gasol, Josep M. (Institut de Ciències del Mar)
Sánchez, Pablo (Institut de Ciències del Mar)
Acinas, Silvia G. (Institut de Ciències del Mar)

Data:	2024
Resum:	The ocean's mercury (Hg) content has tripled due to anthropogenic activities, and although the dark ocean (>200 m) has become an important Hg reservoir, concentrations of the toxic and bioaccumulative methylmercury (MeHg) are low and therefore very difficult to measure. As a consequence, the current understanding of the Hg cycle in the deep ocean is severely data-limited, and the factors controlling MeHg, as well as its transformation rates, remain largely unknown. By analyzing 52 globally distributed bathypelagic deep-ocean metagenomes and 26 new metatranscriptomes from the Malaspina Expedition, our study reveals the widespread distribution and expression of bacterial-coding genes merA and merB in the global bathypelagic ocean (∼4000 m depth). These genes, associated with Hg II reduction and MeHg demethylation, respectively, are particularly prevalent within the particle-attached fraction. Moreover, our results indicate that water mass age and the organic matter composition shaped the structure of the communities harboring merA and merB genes living in different particle size fractions, their abundance, and their expression levels. Members of the orders Corynebacteriales, Rhodobacterales, Alteromonadales, Oceanospirillales, Moraxellales, and Flavobacteriales were the main taxonomic players containing merA and merB genes in the deep ocean. These findings, together with our previous results of pure culture isolates of the deep bathypelagic ocean possessing the metabolic capacity to degrade MeHg, indicated that both methylmercury demethylation and Hg II reduction likely occur in the global dark ocean, the largest biome in the biosphere. Methylmercury (MeHg) accumulates in aquatic food webs, posing a human health risk through fish consumption. Despite being present globally, measuring MeHg in oceans remains challenging, hindering understanding of its formation and degradation. Our study proposes the mer operon's role in MeHg demethylation, aiming to analyze key genes (merA and merB) to gain insights into the biogeochemical cycle of Hg in the deep ocean.
Ajuts:	Agencia Estatal de Investigación PID2020-116489RB-I00 Ministerio de Ciencia e Innovación CSD2008-00077 European Commission 749645 Ministerio de Ciencia e Innovación CEX2019-000928-S Ministerio de Ciencia e Innovación RYC2019-026758-I Ministerio de Ciencia e Innovación RYC2019-028400-I
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Mercury ; Methylmercury ; Bathypelagic ; Bacterial demethylation ; Metagenomes ; Metatranscriptomes ; Mer genes
Publicat a:	Environmental Science & Technology, Vol. 58, Num. 31 (July 2024) , p. 13795-13807, ISSN 1520-5851

DOI: 10.1021/acs.est.4c00663
PMID: 39046290

13 p, 14.4 MB

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