Methylmercury: Bacterial Degradation in Lake Sediments

Abstract

During the first 50 days of a long-term period of incubation of lake sediments with inorganic mercury (Hg²⁺), low concentrations of methylinercury were observed to build up. Upon continued incubation there was a rapid decrease in amount of methylmercury in the system and a concomitant evolution of volatile inorganic mercury (Hg⁰). Transfer of the mixed culture to growth media containing methylmercury resulted in the degradation of methylmercury and the volatilization of Hg⁰. Four bacterial isolates were obtained from the mixed culture which, in pure culture, rapidly degraded methylmercury to methane and Hg⁰. The presence of methane in head space gases was confirmed by flameionization gas chromatography, and the presence of Hg⁰ in head space gases was confirmed by mass spectrometry.