Linking microbial activities and low-molecular-weight thiols to hg methylation in biofilms and periphyton from high-altitude tropical lakes in the Bolivian altiplano Bouchet S. auteur aut IRD Goni-Urriza M. auteur aut IRD Monperrus M. auteur aut IRD Guyoneaud R. auteur aut IRD Fernandez P. auteur aut IRD Heredia C. auteur aut IRD Tessier E. auteur aut IRD Gassie C. auteur aut IRD Point David auteur aut IRD Guédron Stéphane auteur aut IRD Acha D. auteur aut IRD Amouroux D. auteur aut IRD text journalArticle eng text/pdf born digital access The sources and factors controlling concentrations of monomethylmercury (MMHg) in aquatic ecosystems need to be better understood. Here, we investigated Hg transformations in sediments, periphyton associated with green algae's or aquatic plants, and benthic biofilms from the Lake Titicaca hydrosystem and compared them to the occurrence of active methylating microorganisms and extracellular Hg ligands. Intense Hg methylation was found in benthic biofilms and green algae's periphyton, while it remained low in sediments and aquatic plants' periphyton. Demethylation varied between compartments but remained overall in the same range. Hg methylation was mainly carried out by sulfate reducers, although methanogens also played a role. Its variability between compartments was first explained by the presence or absence of the hgcAB genes. Next, both benthic biofilm and green algae's periphyton exhibited a great diversity of extracellular low-molecular-weight (LMW) thiols (13 or 14 compounds) present at a range of a few nmol L-1 or mu mol L-1 but clearly dominated by cysteine and 3-mercaptopropionic acid. Hg methylation was overall positively correlated to the total thiol concentrations, albeit to different extents according to the compartment and conditions. This work is the first examining the interplay between active methylating bacterial communities and extracellular ligands in heterotrophic biofilms and supports the involvement of LMW thiols in Hg methylation in real aquatic systems. specialized BOLIVIE ZONE TROPICALE 036 084 Environmental Science and Technology 52 17 9758-9767 2018 0013-936X https://www.documentation.ird.fr/hor/fdi:010074019 10.1021/acs.est.8b01885 0013-936X [F B010074019] https://www.documentation.ird.fr/hor/fdi:010074019 https://www.documentation.ird.fr/intranet/publi/2018/09/010074019.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2018-10-03 2024-12-23 fdi:010074019 fre