Methylmercury (MeHg) is one of the most worrisome contaminants nowadays; it is neurotoxic for humans, and it can bioaccumulate and biomagnify through the aquatic food webs. The microbial mer operon contains two enzymes, merA, mercuric reductase and merB organomercurial lyase, responsible for the detoxification of MeHg. We sequenced 30 microbial metagenomes from marine sediments collected from 10 different Hg-impacted sites of three marine regions: Bay of Biscay (Nervión and Suances), the Mediterranean (Barcelona) and Baltic Sea (Köpmalhlmen). We built a Hg-detoxification Reference Gene Catalogue (Hg_RGC) with over 16 million non-redundant genes and applied genome-resolved metagenomics to assemble 583 non-redundant metagenome-assembled genomes (MAGs) of medium and high quality named as MERCLUB Microbial MAGs to evaluate the ecology, metabolic potential and activity of MeHg detoxifying bacteria and archaea. From those, we detected 16 MAGs containing the merA gene and 35 MAGs containing the merB gene. Two MAGs contained both merA and merB genes with almost complete genomes related to Actinomycetales (Microbacterium sp.) and Rhodobacterales. We also recovered MAGs containing merA or merB genes from previously overlooked new phyla such as Krumholzibacteriota, Abyssubacteria or Zixibacteria, Finally, a comprehensive phylogenetic analysis for merA and merB was performed integrating merAB genes from our MERCLUB MAGs, Hg_RGC catalogue and isolates from the same sites to infer their genetic diversity and highlight potential new players involved in Hg detoxification processes.

Primary Presenter: Carla Pereira-Garcia, Universidad Autonoma de Barcelona (carla.pereira@uab.cat)

Authors:

Carla Pereira-García,   ()

Pablo Sánchez,   ()

Stefan Bertilsson,   ()

Moritz Buck,   ()

Haiyan Hu,   ()

David Amouroux,   ()

Emmanuel Tessier,   ()

Laura Alonso Sáez,   ()

Anders Lanzen,   ()

Blanca Rincón-Tomás,   ()

Andrea Bravo,   ()

Olga Sánchez,   ()

Silvia Acinas,   ()