Quantification of toxic and inhibitory impact of copper and zinc on mixed cultures of sulfate‐reducing bacteria

Abstract

The adverse effects of copper and zinc on an acetate-utilizing mixed cultures of sulfate-reducing bacteria (SRB) at concentrations below the toxic concentration (minimum metal concentration at which no sulfate reduction is observed) are reported in this paper. Mathematical models were developed to incorporate the toxic and inhibitory effects (defined as the reduction in bacterial population upon exposure to the metal and the decrease in the metabolic rate of sulfate reduction by the SRB, respectively) into the sulfate-reduction biokinetics. The characteristic toxicity and inhibition constants were obtained from the measurements of bacterial populations and dissolved metal concentrations in serum bottle studies conducted at 35 degrees C and pH 6.6. Both copper and zinc had toxic and inhibitory effects on SRB. The toxicity constants for copper and zinc were 10.6 and 2.9 mM(-1), respectively, indicating that exposure to copper resulted in a higher mortality of SRB than did exposure to zinc. The values of the inhibition constants were found to be 17.9 +/- 2.5 and 25.2 +/- 1.0 mM(-1) for copper and zinc, respectively. This implies that dissolved zinc was slightly more inhibitory to SRB than copper. The models presented in the paper can be used to predict the response of a sulfate-reduction bioreactor to heavy metals during acid mine drainage treatment.

Antibacterial properties of F-doped ZnO visible light photocatalyst

“…Furthermore it was noted that among various ZnO powders used in the experiment, powder ZnO:TFA 1:1 was the most effective against E. coli and S. aureus when the visible light was available (log red 2.88 and 4.62, respectively). Based on the studies performed by others [27][28][29][30][31], it is believed that when the light is not available, the primary toxic effect of ZnO on microorganisms can be associated with the release of zinc ions causing disruption of the cell membrane activity and the formation of intercellular reactive oxygen species, mostly H 2 O 2 [32][33][34][35][36][37]. Photocatalysts such as TiO 2 or ZnO activated by UV or/and visible light (Fig.…”

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).…”

The effect of heavy metals and temperature on microbial growth and lag

“…However, higher concentrations result in severe reduction of microbial activity, which is reflected by reduction of the apparent growth rate and increase in lag time. Heavy metal toxicity on microorganisms has been modeled previously by Utgikar et al (2003) who studied the effects of Cu and Zn ions toxicity on sulfate-reducing bacteria. The authors considered constant biomass batch reactors (no net growth), and expressed initial cell death as a decreasing function of the heavy metal concentration.…”

“…The authors considered constant biomass batch reactors (no net growth), and expressed initial cell death as a decreasing function of the heavy metal concentration. However, the authors (Utgikar et al, 2003) did not consider lag in degradation kinetics. Markwiese and Colberg (2000) have proposed a nonlinear regression model relating the lag time for an Iron-Reducing bacteria, but their work is mostly relevant for heavy-metal contaminated anaerobic sedimentary environments.…”