Heavy metal inhibition of methanogenesis by<i>Methanospirillum hungatei</i>GP1

Abstract

Washed whole cells of Methanospirillum hungatei incubated in TES buffer retained methanogenic activity in the absence of any reducing agents. Washed cells grown with 80% H2-20% CO2 and acetate produced methane from H2/CO2 and 50 mM formate at 1.1 to 1.8 and 15 μmol methane · h−1· mg−1 protein, respectively. Cadmium at a concentration of 15 μM and 50 μM mercury, copper or zinc completely inhibited methane production from H2/CO2 by M. hungatei. The chelating agent, EDTA, protected the cells from inhibition by cadmium but acetate and citrate did not. The activity of formate dehydrogenase and hydrogenase remaining in cells after incubation with copper, mercury, zinc or cadmium was reduced with formate dehydrogenase being the more sensitive.