title: Toxicity of lead in aqueous medium to desulfovibrio desulfuricans G20.
abstract: The toxicity of Pb(II) to sulfate-reducing bacteria (SRB) was studied using Desulfovibrio desulfuricans G20 in a medium specifically designed to assess metal toxicity. The effects of Pb(II) toxicity were observed in terms of longer lag times, lower specific growth rates, and in some cases no measurable growth. With an increase in medium pH from 6 to 8, Pb(II) toxicity decreased. At all pH values, in the presence of Pb(II) concentrations ranging from 3 to 15 microM, specific growth rates decreased and lag times increased. The minimum inhibiting concentration (MIC) of Pb(II) causing a complete inhibition in growth at pH 6 was 10 microM, as compared to 15 microM at pH 7.2 and 8. These MIC values are 40 times lower than previously reported for SRB. Results also show that with increases in initial cell protein concentration (inoculum size), soluble Pb(II) removal rates increased and the degree to which Pb(II) caused increased lag times was reduced. In the presence of Pb(II), in all cases in which D. desulfuricans grew (even after a 312-h lag time), the final cell protein concentration was equivalent to that of the Pb-free control. Live/dead staining, based on membrane integrity, indicated that while Pb(II) inhibited growth, Pb(II) did not cause a loss of D. desulfuricans membrane integrity.
authors.affiliation: Department of Chemical Engineering, Center for Multiphase Environmental Research, Washington State University, Dana Hall, Room 118, Pullman, Washington 99164-2710, USA.
authors.forename: Rajesh K
authors.initials: RK
authors.lastname: Sani
authors.forename: Brent M
authors.initials: BM
authors.lastname: Peyton
authors.forename: Malathi
authors.initials: M
authors.lastname: Jandhyala
mesh_terms: D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000096:biosynthesis; D003470:Culture Media; D003901:Desulfovibrio / Q000187:drug effects* / Q000254:growth & development; D004785:Environmental Pollutants / Q000633:toxicity*; D006863:Hydrogen-Ion Concentration; D007854:Lead / Q000633:toxicity*; D008826:Microbial Sensitivity Tests; D019055:No-Observed-Adverse-Effect Level; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D004785:Environmental Pollutants; D007854:Lead; C029891:lead chloride