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

The bioavailability and toxicity of lead (Pb) to Desulfovibrio desulfurican s G20 is greatly influenced by aqueous phase chemical composition. Apparent Pb toxicity is reduced by precipitation and complexation with chemicals fo und in standard growth media for sulfate-reducing bacteria (SRB). To determ ine the influence of medium composition on observed Pb toxicity, a new medi um was developed to more accurately assess the toxicity of Pb to Desulfovib rio desulfuricans. The new medium, metal toxicity medium (MTM), eliminates abiotic Pb precipitation and minimizes formation of Pb complexes in solutio n. 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 PbCl2. 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 meas ured in terms of longer lag times and slower growth rates (including no gro wth) as compared to Pb-free controls. This report describes the effects of specific medium components on Pb toxicity to Desulfovibrio desulfuricans an d provides a better baseline for comparison of natural and industrial water s for observing heavy metal toxicity on SRB. (C) 2001 Elsevier Science Ltd. All rights reserved.