{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T21:44:04Z","timestamp":1790199844468,"version":"4.1.0"},"reference-count":39,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2018,9,29]],"date-time":"2018-09-29T00:00:00Z","timestamp":1538179200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","doi-asserted-by":"publisher","award":["PTDC\/MAR\/102748\/2008; UID\/DTP\/04138\/2013; UID\/MULTI\/00612\/2013; SFRH\/BD\/78035\/2011;"],"award-info":[{"award-number":["PTDC\/MAR\/102748\/2008; UID\/DTP\/04138\/2013; UID\/MULTI\/00612\/2013; SFRH\/BD\/78035\/2011;"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJERPH"],"abstract":"<jats:p>Microbial activity is a critical factor controlling methylmercury formation in aquatic environments. Microbial communities were isolated from sediments of two highly mercury-polluted areas of the Tagus Estuary (Barreiro and Cala do Norte) and differentiated according to their dependence on oxygen into three groups: aerobic, anaerobic, and sulphate-reducing microbial communities. Their potential to methylate mercury and demethylate methylmercury was evaluated through incubation with isotope-enriched Hg species (199HgCl and CH3201HgCl). The results showed that the isolated microbial communities are actively involved in methylation and demethylation processes. The production of CH3199Hg was positively correlated with sulphate-reducing microbial communities, methylating up to 0.07% of the added 199Hg within 48 h of incubation. A high rate of CH3201Hg degradation was observed and &gt;20% of CH3201Hg was transformed. Mercury removal of inorganic forms was also observed. The results prove the simultaneous occurrence of microbial methylation and demethylation processes and indicate that microorganisms are mainly responsible for methylmercury formation and accumulation in the polluted Tagus Estuary.<\/jats:p>","DOI":"10.3390\/ijerph15102141","type":"journal-article","created":{"date-parts":[[2018,10,2]],"date-time":"2018-10-02T08:23:50Z","timestamp":1538468630000},"page":"2141","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":30,"title":["Evidence of Mercury Methylation and Demethylation by the Estuarine Microbial Communities Obtained in Stable Hg Isotope Studies"],"prefix":"10.3390","volume":"15","author":[{"given":"Neusa","family":"Figueiredo","sequence":"first","affiliation":[{"name":"Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Maria Lu\u00edsa","family":"Serralheiro","sequence":"additional","affiliation":[{"name":"BioISI\u2014Biosystems &amp; Integrative Sciences Institute, Faculty of Sciences, Universidade de Lisboa, Campo Grande C8, 1749-016 Lisboa, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5190-446X","authenticated-orcid":false,"given":"Jo\u00e3o","family":"Can\u00e1rio","sequence":"additional","affiliation":[{"name":"Centro de Qu\u00edmica Estrutural, Instituto Superior T\u00e9cnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0616-4650","authenticated-orcid":false,"given":"Aida","family":"Duarte","sequence":"additional","affiliation":[{"name":"Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5287-483X","authenticated-orcid":false,"given":"Holger","family":"Hintelmann","sequence":"additional","affiliation":[{"name":"Chemistry Department, Trent University, 1600 West Bank Drive, Peterborough, ON K9J 0G2, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Cristina","family":"Carvalho","sequence":"additional","affiliation":[{"name":"Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2018,9,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"232","DOI":"10.1111\/j.1574-6941.2006.00246.x","article-title":"Mercury (micro) biogeochemistry in polar environments","volume":"59","author":"Barkay","year":"2007","journal-title":"FEMS Microbiol. Ecol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"609","DOI":"10.1080\/10408440600845619","article-title":"The toxicology of mercury and its chemical compounds","volume":"36","author":"Clarkson","year":"2006","journal-title":"Crit. Rev. Toxicol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1731","DOI":"10.1056\/NEJMra022471","article-title":"Toxicology of mercury\u2013Current exposures and clinical manifestations","volume":"349","author":"Clarkson","year":"2003","journal-title":"N. Engl. J. 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