DNA-based Evaluation of Biological Mercury Methylation Potential in Waste Landfill

抄録

Waste landfills are a potential mercury (Hg) sink due to disposal of wastes containing mercury. In addition, anaerobic environments created under the surface in landfills facilitate Hg methylation, which produces methyl Hg (MeHg), the most potent mercury neurotoxin. Although Hg methylation in the environment is primarily mediated by microorganisms, little is known about the occurrence of Hg-methylating microorganisms in landfills. Therefore, this study aimed to assess the potential of biological Hg methylation in waste landfills by applying a DNA-based monitoring tool. First, useful polymerase chain reaction (PCR) primers targeting hgcAB genes that are involved in Hg methylation were selected from previously-developed ones, and PCR detection conditions were optimized. Then, the occurrence of hgcAB genes was investigated in core samples collected from landfills in Japan. Among a total of 20 samples from five landfill sites, hgcAB genes were detected in five samples. In addition, the abundance of hgcAB genes was estimated in three of the five positive samples by most probable number-PCR. The results indicated not ubiquitous but only sporadic occurrence of biological Hg methylation potential in landfill sites even under anaerobic conditions favorable for Hg-methylating microorganisms.