Widespread microbial mercury methylation genes in the global ocean

Methylmercury is a neurotoxin that bioaccumulates from seawater to high concentrations in marine fish, putting human and ecosystem health at risk. High methylmercury levels have been found in the oxic subsurface waters of all oceans, but only anaerobic microorganisms have been shown to efficiently p...

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Bibliographic Details
Published in:Environmental Microbiology Reports
Main Authors: Villar, Emilie, Cabrol, Léa, Heimbürger-Boavida, Lars-Eric
Format: Article in Journal/Newspaper
Language:English
Published: Wiley 2020
Subjects:
Sulfate-reducing bacterium
Nitrospina-like bacteria
Nitrite oxidation
Sp nov
Hgca
Expression
Antarctic
Antarc*
Sea ice
Online Access:https://doi.org/10.1111/1758-2229.12829
https://repositorio.uchile.cl/handle/2250/174719
Description
Summary:Methylmercury is a neurotoxin that bioaccumulates from seawater to high concentrations in marine fish, putting human and ecosystem health at risk. High methylmercury levels have been found in the oxic subsurface waters of all oceans, but only anaerobic microorganisms have been shown to efficiently produce methylmercury in anoxic environments. The microaerophilic nitrite-oxidizing bacteria Nitrospina have previously been suggested as possible mercury methylating bacteria in Antarctic sea ice. However, the microorganisms responsible for processing inorganic mercury into methylmercury in oxic seawater remain unknown. Here, we show metagenomic and metatranscriptomic evidence that the genetic potential for microbial methylmercury production is widespread in oxic seawater. We find high abundance and expression of the key mercury methylating genes hgcAB across all ocean basins, corresponding to the taxonomic relatives of known mercury methylating bacteria from Deltaproteobacteria, Firmicutes and Chloroflexi. Our results identify Nitrospina as the predominant and widespread microorganism carrying and actively expressing hgcAB. The highest hgcAB abundance and expression occurs in the oxic subsurface waters of the global ocean where the highest MeHg concentrations are typically observed. Project IMPEKAB: ANR-15-CE02-0011. AXA Research Fund.

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