Assessment of lead toxicity to Desulfovibrio desulfuricans G20: influence of components of lactate C medium

Abstract

The bioavailability and toxicity of lead (Pb) to Desulfovibrio desulfuricans G20 is greatly influenced by aqueous phase chemical composition. Apparent Pb toxicity is reduced by precipitation and complexation with chemicals found in standard growth media for sulfate-reducing bacteria (SRB). To determine the influence of medium composition on observed Pb toxicity, a new medium was developed to more accurately assess the toxicity of Pb to Desulfovibrio desulfuricans. The new medium, metal toxicity medium (MTM), eliminates abiotic Pb precipitation and minimizes formation of Pb complexes in solution. Significant growth of Desulfovibrio desulfuricans was observed on MTM in the absence of Pb, while no measurable growth was observed at 3 mg/l Pb as PbCl 2. For comparison, in Lactate C medium ( Burlage et al., 1998) abiotic Pb precipitation was apparent, and the specific growth rate at 100 mg/l Pb was only reduced by 8.1% compared to the Pb-free control. Toxicity was measured in terms of longer lag times and slower growth rates (including no growth) as compared to Pb-free controls. This report describes the effects of specific medium components on Pb toxicity to Desulfovibrio desulfuricans and provides a better baseline for comparison of natural and industrial waters for observing heavy metal toxicity on SRB.