Browsing by Author "Moberly, James G."

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Comparison of single and joint effects of Zn and Cu in continuous flow and batch reactors
(2012-03) Sengor, S. S.; Gikas, P.; Moberly, James G.; Peyton, Brent M.; Ginn, Timothy R.
BACKGROUND: Microbial behavior in batch reactors may be different from that in continuous flow reactors, which is expected to affect microbial response to heavy metal exposure. Four parallel continuous flow reactors and batch growth tests were used to investigate the single and joint toxicity of Zn and Cu to Artrobacter sp. JM018.RESULTS: The results indicated that Cu is more toxic than Zn under all conditions. In the batch reactors, all Zn concentrations showed a stimulatory effect on microbial growth. However in the continuous system, 125 Âµmol Lâˆ’1Â Zn exposure produced inhibition. In the case of mixed Zn and Cu exposures in the batch system, the presence of Zn reduced the severity of Cu inhibition, with a net impact of reduced growth in all cases, whereas in the continuous system microbial growth and substrate utilization rates sharply decreased and ceased.CONCLUSION: The results clearly showed that growth in batch reactors underestimated significantly the heavy metal inhibition, compared with the continuous system. Therefore, the results of batch reactor tests should not be used directly when heavy metal inhibition is to be interpreted for continuous flow systems.
Heavy metal-mineral associations in Coeur d'Alene River sediments: A synchrotron-based analysis
(2009-12) Moberly, James G.; Borch, Thomas; Sani, Rajesh K.; Spycher, Nicolas; Şengör, S. Sevinç; Ginn, Timothy R.; Peyton, Brent M.
Nearly a century of mining activities upstream have contaminated Lake Coeur d’Alene and its tributaries with Pb, Zn, and other heavy metals. Heavy metal concentrations in sediments of the Coeur d’Alene watershed have been shown to be inversely proportional to the sediment size fraction; thus, analysis on a very small scale is essential to determine the mobility and stability of heavy metals in this environment. Micron-scale synchrotron-based methods were used to determine the association of heavy metals with solid phases in sediments of the Coeur d’Alene River. Bulk X-ray diffraction (XRD), extended X-ray absorption fine structure spectroscopy, and synchrotron-based microfocused XRD combined with microfocused X-ray fluorescence mapping indicate the presence of crystalline Pb- and Zn-bearing mineral phases of dundasite [Pb2Al4(CO3)4(OH)8·3H2O], coronadite [PbMn8O16], stolzite [PbWO4], mattheddleite [Pb10(SiO4)3.5(SO4)2Cl2], bindheimite [Pb2Sb2O7], and smithsonite [ZnCO3]. Likely phases for Zn and Pb adsorption were ferrihydrite, diaspore [AlO(OH)], manganite [Mn(III)O(OH)], muscovite [KAl2(Si3Al)O10(OH,F)2], biotite [K(Fe,Mg)3AlSi3O10(F,OH)2], and montmorillonite [Na0.3(Al,Mg)2Si4O10(OH)2·8H2O]. The large predominance of Fe and Mn (hydr)oxides over other sorbent minerals suggests that the metal sorption behavior is dominated by these (hydr)oxide phases.
Influence of pH and inorganic phosphate on toxicity of zinc to Arthrobacter sp. isolated from heavy-metal-contaminated sediments
(2010-10) Moberly, James G.; Staven, A.; Sani, Rajesh K.; Peyton, Brent M.
Because of its high solubility over a wide range of pH conditions, zinc is found in many natural and human-impacted systems. Zinc speciation is critical in assessing zinc toxicity to microorganisms because it varies considerably with pH and is dependent on other aqueous constituents. Combined results of thermodynamic modeling, statistical analysis, and batch culture studies using Arthrobacter sp. JM018 suggest that the toxic species may not be solely limited to the free ion, but also includes ZnHPO40(aq). Cellular uptake of ZnHPO40(aq) through the inorganic phosphate transporter (Pit family), which requires a neutral metal phosphate complex for phosphate transport, may explain the observed toxicity. Based on visual MINTEQ (v3.0) modeling, at 50 Î¼M total zinc, ZnHPO40(aq) constitutes 33, 70, and 76% of the neutral metal phosphate pool at pH 6, 7, and 8, respectively. At 50 Î¼M total zinc, cultures supplied with organic phosphate (glycerol-3-phosphate) show no significant response to pH (p=0.13) while inhibition of inorganic phosphate-supplemented cultures, whose neutral metal phosphates are increasingly dominated by ZnHPO40(aq), show significant pH dependence (p=9.45 x 10-7). Using sodium to decrease the distribution of ZnHPO40(aq) in the neutral metal phosphate pool also decreased the pH dependent toxicity, further supporting this mechanism.These findings show the important role of minor zinc species in organism toxicity and have wider implications because the Pit inorganic phosphate transport system is widely distributed in Bacteria, Archaea, and Eukarya.
Microbial community signature in Lake Coeur d'Alene: Association of environmental variables and toxic heavy metal phases
(2016-03) Moberly, James G.; D'Imperio, Seth; Parker, Albert E.; Peyton, Brent M.
The water and sediments of Lake Coeur d'Alene in northern Idaho (USA) have been impacted by decades of mining operations within the Coeur d'Alene mining district. Using a multivariate statistical approach, correlations were explored between the microbial community (via 16S rDNA microarray) in sediment cores and operationally defined heavy metal phases (via continuous sequential extractions). Candidate phyla NC10, OP8 and LD1PA were only detected in metal contaminated cores and diversity doubled among Natronoanaerobium in metal contaminated cores compared to the uncontaminated control site. This may suggest some increased fitness of these phyla in contaminated sediments. In contrast, diversity within the phyla Aquificae, Coprothermobacteria, and Synergistes was at least double in the uncontaminated control site. In linear models composed of two geochemical variables from the presumed sulfate reducing lineages detected in this study, orders Desulfobacterales, Desulfuromonadales, Desulfotomaculum, and Syntrophobacterales were highly correlated with Pb (positive influence) and Zn (negative influence) in the operationally defined residual fraction, and most taxa within orders from Desulfovibrionales. Bdellovibrionales highly correlated with Pb in the exchangeable/carbonate (negative influence) and oxyhydroxide (positive influence) phases. Diversity within families from metal reducing bacterial lineages Shewanellaceae, Geobacteraceae, and Rhodocyclaceae showed high correlation with Pb in the exchangeable/carbonate (negative influence) and oxyhydroxide (positive influence) phases. To our knowledge, this is the first time these techniques have been used in combination to describe a contaminated system. Resulting correlations suggest the diversity of the microbial community was influenced primarily by partitioning of heavy metals into exchangeable Pb over other Pb phases and, to a lesser extent, residual Pb to residual Zn phase partitioning.
The toxicity of lead to Desulfovibrio desulfuricans G20 in the presence of goethite and quartz
(2010-04) Sani, Rajesh K.; Rastogi, Gurdeep; Moberly, James G.; Dohnalkova, Alice; Ginn, Timothy R.; Spycher, Nicolas; Shende, Rajesh V.; Peyton, Brent M.
An aqueous mixture of goethite, quartz, and lead chloride (PbCl2) was treated with the sulfate reducing bacterium, Desulfovibrio desulfuricans G20 (D. desulfuricans G20), in a medium specifically designed to assess metal toxicity. In the presence of 26 Î¼M of soluble Pb, together with the goethite and quartz, D. desulfuricans G20 grew after a lag time of 5 days compared to 2 days in Pb-, goethite-, and quartz-free treatments. In the absence of goethite and quartz, however, with 26 Î¼M soluble Pb, no measurable growth was observed. Results showed that D. desulfuricans G20 first removed Pb from solutions then growth began resulting in black precipitates of Pb and iron sulfides. Transmission electron microscopic analyses of thin sections of D. desulfuricans G20 treated with 10 Î¼M PbCl2 in goethite- and quartz-free treatment showed the presence of a dense deposit of lead sulfide precipitates both in the periplasm and cytoplasm. However, thin sections of D. desulfuricans G20 treated with goethite, quartz, and PbCl2 (26 Î¼M soluble Pb) showed the presence of a dense deposit of iron sulfide precipitates both in the periplasm and cytoplasm. Energy-dispersive X-ray spectroscopy, selected area electron diffraction patterns, or X-ray diffraction analyses confirmed the structure of precipitated Pb inside the cell as galena (PbS) in goethite- and quartz-free treatments, and iron sulfides in treatments with goethite, quartz, and PbCl2. Overall results suggest that even at the same soluble Pb concentration (26 Î¼M), in the presence of goethite and quartz, apparent Pb toxicity to D. desulfuricans G20 decreased significantly. Further, accumulation of lead/iron sulfides inside D. desulfuricans G20 cells depended on the presence of goethite and quartz.