Effect of inorganic sulfide on the growth and metabolism of Methanosarcina barkeri strain DM

Abstract

Minimal growth of M. barkeri strain DM occurred when sulfide was omitted from the growth medium, and addition of either sodium sulfate or coenzyme M to sulfide-depleted media failed to restore growth. Opimal growth occurred in the presence of 1.25 mM added sulfide, giving a molar growth yield (YCH4) of 4.4 mg (dry wt) of cells/mmol of CH4 produced. Increasing sulfide to 12.5 mM led to a decrease in YCH4 (1.9 mg [dry wt]/mmol of CH4), in the specific growth rate and in the intracellular levels of ATP. The specific rate of CH4 production increased. The data suggested that at elevated sulfide levels (12.5 mM) the decrease in YCH4 might be a result of an increase in the relative energy needed for maintenance and of uncoupling of growth from energy production.