摘要： The contamination of groundwater with mercury (Hg) is an increasing problem worldwide. Yet, little is known about the interactions of Hg with microorganisms and their processes in subsurface environments. We tested the impact of Hg on denitrification in nitrate reducing enrichment cultures derived from subsurface sediments from the Oak Ridge Integrated Field Research Challenge site, where nitrate is a major contaminant and where bioremediation efforts are in progress. We observed an inverse relationship between Hg concentrations and onset and rates of denitrification in nitrate enrichment cultures containing between 53 and 1.1 μM of inorganic Hg; higher Hg concentrations increasingly extended the time to onset of denitrification and inhibited denitrification rates. Microbial community complexity, as indicated by terminal restriction fragment length polymorphism (tRFLP) analysis of the 16S rRNA genes, declined with increasing Hg concentrations; at the 312 nM Hg treatment, a single tRFLP peak was detected representing a culture of Bradyrhizobium sp. that possessed the merA gene indicating a potential for Hg reduction. A culture identified as Bradyrhizobium sp. strain FRC01 with an identical 16S rRNA sequence to that of the enriched peak in the tRFLP patterns, reduced Hg(II) to Hg(0) and carried merA whose amino acid sequence has 97 % identity to merA from the Proteobacteria and Firmicutes . This study demonstrates that in subsurface sediment incubations, Hg may inhibit denitrification and that inhibition may be alleviated when Hg resistant denitrifying Bradyrhizobium spp. detoxify Hg by its reduction to the volatile elemental form. 其他題名： Biodegradation 出版者： Dordrecht: Springer Netherlands 出版日期： 2013-02-01 出處： Biodegradation (Dordrecht), 2013-02, Vol.24 (1), p.33-46 版權： Springer Science+Business Media B.V. 2012 版權： 2014 INIST-CNRS 版權： Springer Science+Business Media Dordrecht 2013 識別號： ISSN: 0923-9820 識別號： ISSN: 1572-9729 識別號： EISSN: 1572-9729 識別號： DOI: 10.1007/s10532-012-9555-8 識別號： PMID: 22678127
