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.

Kinetic of biogenic sulfide production for microbial consortia isolated from soils with different bioaccessible concentrations of lead

“…This behavior has been previously observed by Cabrera et al (2006) and Sani et al (2003) using other heavy metals.…”

“…They found that a low concentration of lead (\100 mg L -1 ) favored the growth of Desulfosarcina, a SRB strain. Sani et al (2003) observed that Pb(II) concentrations ranging from 3 to 15 lM enhanced the lag phase of cell growth. In the aforementioned studies, the inhibition toxicities were analyzed as a function of biomass, sulfate consumption, percentage of metals removed, and duration of the lag phase; however, the effect of Pb(II) concentration on BSP has not been evaluated.…”

Horizontal Gene Transfer of P IB -Type ATPases among Bacteria Isolated from Radionuclide- and Metal-Contaminated Subsurface Soils

“…As these populations are expected to function in environments that are affected by mixed wastes, the presence of toxic heavy metals and nitrates that cooccur at sites such as the FRC (13, 47) could potentially limit their activities. For example, Desulfovibrio desulfuricans G20, a model organism for immobilization of metals as metal sulfides, has been shown to be susceptible to micromolar concentrations of heavy metals, including Cu(II), Zn(II), and Pb(II) (52), while mixed cultures of sulfate reducers were inhibited by Cr(VI) (53), Cu(II), and Zn(II) (60). Likewise, some heavy metals, including Cr(VI), have also been shown to negatively affect the growth of Shewanella spp., which have been studied for their role in immobilizing metals and radionuclides by reduction to insoluble forms (62).…”

Final Report - Phase II - Biogeochemistry of Uranium Under Reducing and Re-oxidizing Conditions: An Integrated Laboratory and Field Study

“…In each batch experiment, duplicate treatment profiles were similar in total cell protein, U(VI), sulfate, and sulfide concentrations; however, the length of the lag time was somewhat variable. Similar variability in lag times of D. desulfuricans and Shewanella oneidensis among different experiments has been observed for metals such as Cr, Cu, Ni, Pb, and Zn [14,17,28]. One-way analysis of variance was used to determine any statistically significant differences in G20 lag times among treatments with and without U(VI).…”