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Digital.CSIC. Repositorio Institucional del CSIC

oai:digital.csic.es:10261/352552

Special issue Climate Change, Mercury Pollution, and Global Ecology.-- 10 pages, 6 figures, 1 table, s upplementary data .-- Data availability: Data will be made available on request.-- © 2024 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/bync/4.0/)., Methylmercury (MeHg) is one of the most worrisome pollutants in marine systems. MeHg detoxification is mediated by merB and merA genes, responsible for the demethylation of MeHg and the reduction of inorganic mercury, respectively. Little is known about the biological capacity to detoxify this compound in marine environments, and even less the bacterial transcriptional changes during MeHg detoxification. This study provides the genomic and transcriptomic characterization of the deep ocean bacteria Alteromonas mediterranea ISS312 with capacity for MeHg degradation. Its genome sequence revealed four mer operons containing three merA gene and two merB gene copies, that could be horizontally transferred among distant related genomes by mobile genetic elements. The transcriptomic profiling in the presence of 5 μM MeHg showed that merA and merB genes are within the most expressed genes, although not all mer genes were equally transcribed. Besides, we aimed to identify functional orthologous genes that displayed expression profiles highly similar or identical to those genes within the mer operons, which could indicate they are under the same regulatory controls. We found contrasting expression profiles for each mer operon that were positively correlated with a wide array of functions mostly related to amino acid metabolism, but also to flagellar assembly or two component systems. Also, this study highlights that all merAB genes of the four operons were globally distributed across oceans layers with higher transcriptional activity in the mesopelagic deeper waters. Our study provides new insights about the transcriptional patterns related to the capacity of marine bacteria to detoxify MeHg, with important implications for the understanding of this process in marine ecosystems., This study was supported by grants from the projects Plan Nacional I + D + I MAGGY (grant no. CTM2017-87736-R), Polar ECOGEN (PID2020-116489RB-I00), MICOLOR (PID2021-125469NB-C32), Ramón y Cajal Program (RYC2019-028400) and from the European Commission (project MER-CLUB, 863584-MER_CLUB-EMFF-BlueEconomy-2018). The PhD of C.P.G. was funded by the project MER-CLUB to S.G.A and O.S and by a Marie Curie international Fellowship (H2020-MSCA–IF–2016; project-749645) to A.G.B. This work benefited from the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)., Peer reviewed