Prevalence of Heterotrophic Methylmercury Detoxifying Bacteria across Oceanic Regions

Isabel Sanz-Sáez, Carla Pereira Garcia, Andrea G. Bravo, Laura Trujillo, Marti Pla Ferriol, Capilla Miguel, Pablo Sánchez, Rosa Carmen Rodríguez Martín-Doimeadios, Silvia G. Acinas*, Olga Sanchez Martinez*

*Corresponding author for this work

Research output: Contribution to journalArticleResearchpeer-review

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Abstract

Microbial reduction of inorganic divalent mercury (Hg 2+) 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 Hg 2+ 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.

Original languageEnglish
Pages (from-to)3452-3461
Number of pages10
JournalEnvironmental Science & Technology
Volume56
Issue number6
Early online date4 Mar 2022
DOIs
Publication statusPublished - 15 Mar 2022

Keywords

  • marine bacteria
  • merA
  • merB
  • mercury
  • mercury-resistant bacteria
  • methylmercury
  • minimum inhibitory concentration (MIC)

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