Dataset Information

Prevalence of Heterotrophic Methylmercury Detoxifying Bacteria across Oceanic Regions.

ABSTRACT: Microbial reduction of inorganic divalent mercury (Hg²⁺) and methylmercury (MeHg) demethylation is performed by the mer operon, specifically by merA and merB genes, respectively, but little is known about the mercury tolerance capacity of marine microorganisms and its prevalence in the ocean. Here, combining culture-dependent analyses with metagenomic and metatranscriptomic data, we show that marine bacteria that encode mer genes are widespread and active in the global ocean. We explored the distribution of these genes in 290 marine heterotrophic bacteria (Alteromonas and Marinobacter spp.) isolated from different oceanographic regions and depths, and assessed their tolerance to diverse concentrations of Hg²⁺ and MeHg. In particular, the Alteromonas sp. ISS312 strain presented the highest tolerance capacity and a degradation efficiency for MeHg of 98.2% in 24 h. Fragment recruitment analyses of Alteromonas sp. genomes (ISS312 strain and its associated reconstructed metagenome assembled genome MAG-0289) against microbial bathypelagic metagenomes confirm their prevalence in the deep ocean. Moreover, we retrieved 54 merA and 6 merB genes variants related to the Alteromonas sp. ISS312 strain from global metagenomes and metatranscriptomes from Tara Oceans. Our findings highlight the biological reductive MeHg degradation as a relevant pathway of the ocean Hg biogeochemical cycle.

SUBMITTER: Sanz-Saez I

PROVIDER: S-EPMC8928480 | biostudies-literature | 2022 Mar

REPOSITORIES: biostudies-literature

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Publications

Prevalence of Heterotrophic Methylmercury Detoxifying Bacteria across Oceanic Regions.

Sanz-Sáez Isabel I Pereira-García Carla C Bravo Andrea G AG Trujillo Laura L Pla I Ferriol Martí M Capilla Miguel M Sánchez Pablo P Rodríguez Martín-Doimeadios Rosa Carmen RC Acinas Silvia G SG Sánchez Olga O

Environmental science & technology 20220304 6

Microbial reduction of inorganic divalent mercury (Hg2+) and methylmercury (MeHg) demethylation is performed by the mer operon, specifically by merA and merB genes, respectively, but little is known about the mercury tolerance capacity of marine microorganisms and its prevalence in the ocean. Here, combining culture-dependent analyses with metagenomic and metatranscriptomic data, we show that marine bacteria that encode mer genes are widespread and active i ...[more]

PMID: 35245029

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Project description:Many studies have recognized abiotic photochemical degradation as an important sink of methylmercury (CH3Hg) in sunlit surface waters, but the rate-controlling factors remain poorly understood. The overall objective of this study was to improve our understanding of the relative importance of photochemical reactions in the degradation of CH3Hg in surface waters across a variety of marine ecosystems by extending the range of water types studied. Experiments were conducted using surface water collected from coastal sites in Delaware, New Jersey, Connecticut, and Maine, as well as offshore sites on the New England continental shelf break, the equatorial Pacific, and the Arctic Ocean. Filtered water amended with additional CH3Hg at environmentally relevant concentrations was allowed to equilibrate with natural ligands before being exposed to natural sunlight. Water quality parameters - salinity, dissolved organic carbon, and nitrate - were measured, and specific UV absorbance was calculated as a proxy for dissolved aromatic carbon content. Degradation rate constants (0.87-1.67 day-1) varied by a factor of two across all water types tested despite varying characteristics, and did not correlate with initial CH3Hg concentrations or other environmental parameters. The rate constants in terms of cumulative photon flux values were comparable to, but at the high end of, the range of values reported in other studies. Further experiments investigating the controlling parameters of the reaction observed little effect of nitrate and chloride, and potential for bromide involvement. The HydroLight radiative transfer model was used to compute solar irradiance with depth in three representative water bodies - coastal wetland, estuary, and open ocean - allowing for the determination of water column integrated rates. Methylmercury loss per year due to photodegradation was also modeled across a range of latitudes from the Arctic to the Equator in the three model water types, resulting in an estimated global demethylation rate of 25.3 Mmol yr-1. The loss of CH3Hg was greatest in the open ocean due to increased penetration of all wavelengths, especially the UV portion of the spectrum which has a greater ability to degrade CH3Hg. Overall, this study provides additional insights and information to better constrain the importance of photochemical degradation in the cycling of CH3Hg in marine surface waters and its transport from coastal waters to the open ocean.

Dataset Information

Prevalence of Heterotrophic Methylmercury Detoxifying Bacteria across Oceanic Regions.

Publications

Prevalence of Heterotrophic Methylmercury Detoxifying Bacteria across Oceanic Regions.

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