Effect of hydrogen sulfide on growth of sulfate reducing bacteria

A culture of sulfate reducing bacteria (SRB) growing on lactate and sulfate was incubated at different pH values in the range of 5.8-7.0. The effect of pH on growth rate was determined in this pH range; the highest growth rate was observed at pH 6.7. Hydrogen sulfide produced from sulfate reduction was found to have a direct and reversible toxicity effect on the SRB. A hydrogen sulfide Concentration of 547 mg/L (16.1 mM) completely inhibited the culture growth. Comparison between acetic acid and hydrogen sulfide inhibition is presented and the concomitant inhibition kinetics are mathematically described. (c) 1992 John Wiley & Sons, Inc.     

Effect of Salinity on the Tolerance to Toxic Metals and Oxyanions in Native Moderately Halophilic Spore-forming Bacilli

Summary Ten moderately halophilic spore-forming bacilli were isolated from saline soils in Iran and their intrinsic high-level resistance to chromate, arsenate, tellurite, selenite, selenate and biselenite was identified by an agar dilution method. Minimum inhibitory concentration (MIC) for each oxyanion was determined. All isolates were resistant to higher concentrations of arsenate. The resistance level of the isolates to selenooxyanions was between 10 and 40 mM. Maximum and minimum tolerance against oxyanions was seen in selenite and biselenite, respectively. Although toxic metal resistance in the isolates was not different from non-halophilic bacteria that has been reported, unusual resistance to arsenate (250 mM), sodium chromate (75 mM) and potassium chromate (70 mM) was observed. The results obtained in this study revealed that all isolates were obviously susceptible to silver, nickel, zinc and cobalt, while seven isolates were resistant to lead. Susceptibility to copper and cadmium varied among the isolates. Silver had the maximum toxicity, whereas lead and copper showed minimum toxicity. The impact of salinity on the toxicity of oxyanions was also studied. Our results showed that in general an increase in salinity from 5% (w/v) to 15% (w/v) enhanced tolerance to toxic oxyanions.     

Modeling reduction of uranium U(VI) under variable sulfate concentrations by sulfate-reducing bacteria

The kinetics for the reduction of sulfate alone and for concurrent uranium [U(VI)] and sulfate reduction, by mixed and pure cultures of sulfate-reducing bacteria (SRB) at 21 +/- 3 degrees C were studied. The mixed culture contained the SRB Desulfovibrio vulgaris along with a Clostridium sp. determined via 16S ribosomal DNA analysis. The pure culture was Desulfovibrio desulfuricans (ATCC 7757). A zero-order model best fit the data for the reduction of sulfate from 0.1 to 10 mM. A lag time occurred below cell concentrations of 0.1 mg (dry weight) of cells/ml. For the mixed culture, average values for the maximum specific reaction rate, V(max), ranged from 2.4 +/- 0.2 micromol of sulfate/mg (dry weight) of SRB. h(-1)) at 0.25 mM sulfate to 5.0 +/- 1.1 micromol of sulfate/mg (dry weight) of SRB. h(-1) at 10 mM sulfate (average cell concentration, 0.52 mg [dry weight]/ml). For the pure culture, V(max) was 1.6 +/- 0.2 micromol of sulfate/mg (dry weight) of SRB. h(-1) at 1 mM sulfate (0.29 mg [dry weight] of cells/ml). When both electron acceptors were present, sulfate reduction remained zero order for both cultures, while uranium reduction was first order, with rate constants of 0.071 +/- 0.003 mg (dry weight) of cells/ml. min(-1) for the mixed culture and 0.137 +/- 0.016 mg (dry weight) of cells/ml. min(-1) (U(0) = 1 mM) for the D. desulfuricans culture. Both cultures exhibited a faster rate of uranium reduction in the presence of sulfate and no lag time until the onset of U reduction in contrast to U alone. This kinetics information can be used to design an SRB-dominated biotreatment scheme for the removal of U(VI) from an aqueous source.     

Accumulation,regulation and toxicity of copper,zinc, lead and mercury in Hyalella azteca

Zinc, lead and mercury accumulation in the amphipod Hyalella azteca increases with increasing exposure to metals. During 10 week chronic toxicity tests, metal accumulated at the highest non-toxic/lowest toxic concentration was 126/136 µg Zn g^–1, 7.1/16 µg Pb g^–1 and 56/90 µg Hg g^–1 dry weight. Concentrations of lead and mercyry in control animals were substantially lower (1.3 µg Pb g^–1 and 0.4 µg Hg g^–1), but concentrations of zinc in controls (74 µg g^–1) were about one half those of the lowest toxic concentration. Copper was completely regulated. Accumulated copper concentrations after 10 weeks exposure to all waterborne copper concentrations resulting in less than 100% mortality were not significantly different from controls (79 µg g^–1). Lead and mercury concentrations in wild H. azteca should be useful indicators of potential toxicity. Zinc accumulation may also be a useful indicator of zinc toxicity, but careful comparison with control or reference animals is necessary because of the small differences between toxic and control concentrations. Copper is not accumulated by H. azteca under chronic exposure conditions and body burdens of field animals cannot be used as an indicator of exposure or potential toxic effects. Short term exposures to copper, however, result in elevated copper concentrations in H. azteca, even at concentrations below those causing chronic toxicity. Short term bioaccumulation studies might, therefore, provide a useful indication of potential chronic copper toxicity.     

Effects of cadmium and zinc ions on purified lamb kidney cortex glucose-6-phosphate dehydrogenase activity

Glucose-6-phosphate dehydrogenase (G-6-PD) is the first enzyme in the pentose phosphate pathway. Cadmium is a toxic heavy metal that inhibits several enzymes. Zinc is an essential metal but overdoses of zinc have toxic effects on enzyme activities. In this study G-6-PD from lamb kidney cortex was competitively inhibited by zinc both with respect to glucose-6-phosphate (G-6-P) and NADP⁺ with Ki values of 1.066 ± 0.106 and 0.111 ± 0.007 mM respectively whereas cadmium was a non-competitive inhibitor with respect to both G-6-P and NADP⁺ Ki values of 2.028 ± 0.175 and 2.044 ± 0.289 mM respectively.     

Simulation of constituent processes of anaerobic degradation of organic matter by the 〈methane〉 model

The model of anaerobic digestion described earlier by the authors was used for analysis of the different phases of the process. It was shown that at the glucose conversion a coexistence of hydrogen-producing acidogenic bacteria and hydrogen-utilizing non-methanogenic bacteria causes a hydrogen partial pressure decrease at an increase of solids retention time (i), the intensity of the negative feed-back effect in sulfate-reduction through hydrogen sulfide formation is regulated by the pH level during an oscillation dynamics in acetate/sulfate system (ii), under the toxicity influence the processes of methanogenesis and acetogenesis together with hydrolysis may be rate-limiting steps in the anaerobic system with particulate substrate degradation (iii).Abbreviations B1, B2 two groups of acidogens - DS total dissolved sulfide concentration - HRT hydraulic retention time - MPB methane-producing bacteria - SRB sulfate-reducing bacteria - SRT solids retention time - VFA's volatile fatty acids     

Effects of Copper,Nickel, and Sulfate from the Smelters at Sudbury,Ontario (Canada) on Microbial Communities in Lakes

Analysis of water and sediments from deep and shallow environments in lakes located 6–154 km east or southeast of the smelters at Sudbury, Ontario (Canada) revealed variable, interactive effects of copper, nickel, and sulfate from smelter fallout on lacustrine microfloras. Metal species in sediments were differentiated by sequential extractions, and the nature, abundances, and activities of microbial populations were represented by chlorophyll-a in water and by CO₂ production, fatty acids, phospholipids, dehydrogenase, alkaline phosphatase, and spectral properties of humic matter in sediments. Smelter fallout declined logarithmically with distance from the smelters, and its effects on microfloras depended on the type of microorganism or microbial process and on environmental factors and the abundances of metal species and detoxifying agents. Extractable copper and nickel had toxic effects, which were not attributable solely to the exchangeable fractions, but in certain cases nickel counteracted copper toxicity. Sedimentary sulfide as a whole or sulfide produced by bacterial sulfate reduction, or low oxidation–reduction potential regardless of sulfide concentration, ameliorated metal toxicity by making the metals less bioavailable; and toxicity showed a “quantum jump” when detoxifying agents fell below certain critical concentrations, implying the existence of threshold levels of bioavailable metals above which toxicity increased abruptly. In some cases metal toxicity was lowest in the lakes closest to the smelters (because sulfate concentrations were highest) as well as in the lakes furthest away, and was highest at intermediate distances. The results also suggest that nickel pollution led to ecological succession whereby nickel-tolerant microbial populations replaced nickel-sensitive ones.     

Impact of Clay Minerals on Sulfate-Reducing Activity in Aquifers

Previous studies have shown that sulfate-reduction activity occurs in a heterogeneous manner throughout the terrestrial subsurface. Low-activity regions are often observed in the presence of clay minerals. Here we report that clays inhibit sulfate reduction activity in sediments and in a pure culture of Desulfovibrio vulgaris. Clay minerals including bentonite and kaolinite inhibited sulfate reduction by 70–90% in sediments. Intact clays and clay colloids or soluble components, capable of passing through a 0.2-µm filter, were also inhibitory to sulfate-reducing bacteria. Other adsorbent materials, including anion or cation exchangers and a zeolite, did not inhibit sulfate reduction in sediments, suggesting that the effect of clays was not due to their cation-exchange capacity. We observed a strong correlation between the Al₂O₃ content of clays and their relative ability to inhibit sulfate reduction in sediments (r² = 0.82). This suggested that inhibition might be a direct effect of Al³⁺ (aq) on the bacteria. We then tested pure aluminum oxide (Al₂O₃) and showed it to act in a similar manner to clay. As dissolved aluminum is known to be toxic to a variety of organisms at low concentrations, our results suggest that the effects of clay on sulfate-reducing bacteria may be directly due to aluminum. Thus, our experiments provide an explanation for the lack of sulfate-reduction activity in clay-rich regions and presents a mechanism for the effect.     

Effects of CuDIPS and tween 80 on SJL/J tumorigenesis

Plasma copper and zinc levels were measured in SJL/J mice, an inbred strain characterized by a high, spontaneous incidence of reticulum cell sarcoma (RCS). The changes with age in mean concentrations of these metals were consistent with a physiological response that is required for remission of neoplasia. Treatment of SJL/J mice with a copper complex, Cu(II)(3,4-diisopropylsalicylate)₂ (Cu 3,5-DIPS), dissolved in a 10% Tween 80-saline solution revealed a decrease in survival and decline in the incidence of RCS at 52 wk of age. The toxic effects of Cu 3,5-DIPS therapy appeared to be related to the intraperitoneal route of administration and to extracellular deposition of collagen. The inhibitory effect on tumor development was not related to Cu 3,5-DIPS. Rather, Tween 80 was found to be the factor of importance.     

微生物烟气脱硫中硫酸盐还原阶段的限制性因素及其影响

【目的】利用硫酸盐还原菌(SRB)厌氧活性污泥进行烟气脱硫,探索硫酸盐生物还原的最适条件及重金属离子对硫酸盐生物还原的影响,以提高硫酸盐还原阶段的效率。【方法】对取自污水处理厂的SRB厌氧活性污泥进行高浓度硫酸盐胁迫驯化。分析生物脱硫过程中SRB厌氧污泥还原硫酸盐的限制性因素及影响。【结果】在最适生长条件下(pH 6.5,32°C),经驯化获得的SRB厌氧活性污泥有较强的硫酸盐还原能力。Fe2+的适量添加对硫酸盐还原有一定促进作用。SRB厌氧污泥还原硫酸盐的ThCOD/SO42-最适值为3.00,ThCOD=3.33为最适理论化学需氧量,硫酸盐还原率可达72.15%。SRB厌氧污泥还原硫酸盐反应体系中抑制SRB活性的硫化物浓度为300 mg/L。Pb2+和Ni2+在较低的浓度下(1.0 mg/L和2.0 mg/L)对硫酸盐的还原产生较强的抑制作用,而Cu2+在稍高的浓度下(8.0 mg/L)显示出明显的抑制作用。【结论】经驯化,SRB厌氧活性污泥显示出较强的硫酸盐还原能力,具有应用于工业烟气生物脱硫的潜力。去除重金属离子Pb2+、Ni2+和Cu2+可有效解除对硫酸盐生物还原作用的抑制。     

Effects of cadmium and zinc ions on purified lamb kidney cortex glucose-6-phosphate dehydrogenase activity

Glucose-6-phosphate dehydrogenase (G-6-PD) is the first enzyme in the pentose phosphate pathway. Cadmium is a toxic heavy metal that inhibits several enzymes. Zinc is an essential metal but overdoses of zinc have toxic effects on enzyme activities. In this study G-6-PD from lamb kidney cortex was competitively inhibited by zinc both with respect to glucose-6-phosphate (G-6-P) and NADP+ with Ki values of 1.066 +/- 0.106 and 0.111 +/- 0.007 mM respectively whereas cadmium was a non-competitive inhibitor with respect to both G-6-P and NADP+ Ki values of 2.028 +/- 0.175 and 2.044 +/- 0.289 mM respectively.     

Kinetics and mechanism of tolerance induction on acclimation ofVillorita cyprinoides (Hanley) to copper and zinc

The typical euryhaline clamVillorita cyprinoides (Hanley) was acclimated to copper and zinc at salinity 13 × 10⁻³ and < 1 × 10⁻³ (fresh water). Acclimation enhanced the lethal tolerance, as denoted by dose-survival curves, which was more pronounced after zinc acclimation. In fresh water copper acclimation sensitized the organisms. The copper accumulation trend was significantly changed consequent to metal acclimation, especially after zinc acclimation, indicating some tissue metal regulatory effect. Acclimation to copper equiped the organism to survive for longer periods with increased body burden of copper, while zinc acclimation supressed the uptake of the more toxic ion copper. The earlier report of increased uptake of zinc by this organism during combined exposure with copper is corelated in the present context. The role of metallothionein like protein in providing protection against metal toxicity, the environmental implication of acclimation phenomena are indicated     

Effects of hydraulic retention time and sulfide toxicity on ethanol and acetate oxidation in sulfate-reducing metal-precipitating fluidized-bed reactor

The effects of hydraulic retention time (HRT) and sulfide toxicity on ethanol and acetate utilization were studied in a sulfate-reducing fluidized-bed reactor (FBR) treating acidic metal-containing wastewater. The effects of HRT were determined with continuous flow FBR experiments. The percentage of ethanol oxidation was 99.9% even at a HRT of 6.5 h (loading of 2.6 g ethanol L(-1) d(-1)), while acetate accumulated in the FBR with HRTs below 12 h (loading of 1.4 g ethanol L(-1) d(-1)). Partial acetate utilization was accompanied by decreased concentrations of dissolved sulfide (DS) and alkalinity in the effluent, and eventually resulted in process failure when HRT was decreased to 6.1 h (loading of 2.7 g ethanol L(-1) d(-1)). Zinc and iron precipitation rates increased to over 600 mg L(-1) d(-1) and 300 mg L(-1) d(-1), respectively, with decreasing HRT. At HRT of 6.5 h, percent metal precipitation was over 99.9%, and effluent metal concentrations remained below 0.08 mg L(-1). Under these conditions, the alkalinity produced by substrate utilization increased the wastewater pH from 3 to 7.9-8.0. The percentage of electron flow from ethanol to sulfate reduction averaged 76 +/- 10% and was not affected by the HRT. The lowest HRT did not result in significant biomass washout from the FBR. The effect of sulfide toxicity on the sulfate-reducing culture was studied with batch kinetic experiments in the FBR. Noncompetitive inhibition model described well the sulfide inhibition of the sulfate-reducing culture. (DS) inhibition constants (K(i)) for ethanol and acetate oxidation were 248 mg S L(-1) and 356 mg S L(-1), respectively, and the corresponding K(i) values for H(2)S were 84 mg S L(-1) and 124 mg S L(-1). In conclusion, ethanol oxidation was more inhibited by sulfide toxicity than the acetate oxidation.     

Population Dynamics of a Single-Stage Sulfidogenic Bioreactor Treating Synthetic Zinc-Containing Waste Streams

Waste streams from industrial processes such as metal smelting or mining contain high concentrations of sulfate and metals with low pH. Dissimilatory sulfate reduction carried out by sulfate-reducing bacteria (SRB) at low pH can combine sulfate reduction with metal-sulfide precipitation and thus open possibilities for selective metal recovery. This study investigates the microbial diversity and population changes of a single-stage sulfidogenic gas-lift bioreactor treating synthetic zinc-rich waste water at pH 5.5 by denaturing gradient gel electrophoresis of 16S rRNA gene fragments and quantitative polymerase chain reaction. The results indicate the presence of a diverse range of phylogenetic groups with the predominant microbial populations belonging to the Desulfovibrionaceae from δ-Proteobacteria. Desulfovibrio desulfuricans-like populations were the most abundant among the SRB during the three stable phases of varying sulfide and zinc concentrations and increased from 13% to 54% of the total bacterial populations over time. The second largest group was Desulfovibrio marrakechensis-like SRB that increased from 1% to about 10% with decreasing sulfide concentrations. Desulfovibrio aminophilus-like populations were the only SRB to decrease in numbers with decreasing sulfide concentrations. However, their population was <1% of the total bacterial population in the reactor at all analyzed time points. The number of dissimilatory sulfate reductase (DsrA) gene copies per number of SRB cells decreased from 3.5 to 2 DsrA copies when the sulfide concentration was reduced, suggesting that the cells' sulfate-reducing capacity was also lowered. This study has identified the species present in a single-stage sulfidogenic bioreactor treating zinc-rich wastewater at low pH and provides insights into the microbial ecology of this biotechnological process.     

Toxic effects caused by heavy metals in the yeast Saccharomyces cerevisiae: a comparative study

The decreasing order of toxicity of select heavy metals on the yeast Saccharomyces cerevisiae, in 10 mM MES (2-(N-morpholino)ethanesulfonic acid) pH buffer at pH 6.0, was found to be copper, lead, and nickel. Heavy metal (200 microM) induced a decrease in the number of viable cells by about 50% in the first 5 min for copper and in 4 h for lead, while nickel was not toxic up to a 200 microM concentration over a period of 48 h. Glucose (25 mM) strongly enhanced the toxic effect of 50 microM copper but had little or no effect on the toxicity of 200 microM lead or nickel. Copper, lead, and nickel induced the leakage of UV260-absorbing compounds from cells with different kinetics. The addition of 0.5 mM calcium, before addition of 200 microM copper, showed a protective action against cell death and decreased the release of UV-absorbing compounds, while no effect was observed against lead or nickel toxic effects. Copper complexation capacities of the filtrates of cells exposed for 2 h in 200 microM copper and 24 h in 200 microM lead were 51 and 14 microM, respectively. The implication of the complexation shown by these soluble compounds in the bioavailability of heavy metals is discussed.     

The interactions of water hardness and pH with the acute toxicity of zinc to the brown trout, Salmo trutta L.

Exposure of brown trout, Salmo trutta , to zinc under continuous flow conditions over 96 h showed that both water hardness and pH exert major influences on the toxicity of the metal. 96-h LC50 values for total zinc ranged from <0.14mg 1⁻¹ in alkaline soft water (pH 8; lOmg 1⁻¹ as CaCO₃) to 3.20 mg 1⁻¹ in acidic hard water (pH 5; 204 mg 1⁻¹ as CaCO₃). A variable reduction in zinc toxicity in hard water compared with soft water over the pH range 4–9 was attributed to high external calcium. Zinc toxicity was positively correlated with decreasing acidity over the pH range 5–7, the metal being most toxic at pH 8–9 where metal complexes predominate. Below pH 5 metal toxicity also increased, irrespective of hardness. Water hardness and pH interacted with zinc toxicity in a complex manner, apparently dependent on physical and chemical transformations of the metal, and as changes in uptake. detoxification and excretion by the fish.     

Effects of copper and zinc on growth, feeding and oxygen consumption of Farfantepenaeus paulensis postlarvae (Decapoda: Penaeidae)

The effect of chronic exposure (35 days) to sub-lethal concentrations of copper (17-212 ppb) and zinc (41-525 ppb) on growth of Farfantepenaeus paulensis postlarvae 17 days old (PL(17)) was analysed. The effects of acute exposure of PL(17) to the same metal on food ingestion and oxygen consumption were also evaluated. Studies were performed using copper and zinc singly, and in a mixture of equipotent concentrations (1:2.5). Chronic exposure to copper (85 and 212 ppb) and zinc (106, 212 and 525 ppb) reduced PL(17) growth. Acute exposure to copper (212 ppb) and zinc (525 ppb) reduced the number of Artemia sp. predated during 30 min and the positive feeding response induced by L-isoleucine. Despite of the lower positive feeding response when PL(17) were exposed to zinc, a significant difference from control condition was not seen. Oxygen consumption was reduced by all copper and zinc concentrations tested. The mean reduction was approximately 32%. The copper zinc-mixture did not modify food consumption and feeding response, or the oxygen consumption of the PL(17). The inhibition of food and oxygen consumption induced by copper and zinc could explain, at least in part, the long-term reduction of growth observed in chronically exposed PL(17). Our results also suggest that the inhibition of food consumption induced by copper is possibly due to an effect on chemosensory mechanisms. Finally, an antagonism between copper and zinc was observed, when were employed to analyse feeding behaviour and aerobic metabolism after acute exposure.     

Sulfate Reduction at a Lignite Seam: Microbial Abundance and Activity

In a combined isotope geochemical and microbiological investigation, a setting of multiple aquifers was characterized. Biologically mediated redox processes were observed in the aquifers situated in marine sands of Tertiary age and overlying Quaternary gravel deposits. Intercalated lignite seams define the aquitards, which separate the aquifers. Bacterial oxidation of organic matter is evident from dissolved inorganic carbon characterized by average carbon isotope values between ?18.4 per thousand and ?15.7 per thousand (PDB). Strongly positive sulfur isotope values of up to +50 per thousand (CTD) for residual sulfate indicate sulfate reduction under closed system conditions with respect to sulfate availability. Both, hydrochemical and isotope data are thus consistent with the recent activity of sulfate-reducing bacteria (SRB). Microbiological investigations revealed the presence of an anaerobic food chain in the aquifers. Most-probable-number (MPN) determinations for SRB and fermenting microorganisms reached highest values at the interface between aquifer and lignite seam (1.5 x 103 cells/g sediment dry mass). Five strains of SRB were isolated from highest MPN dilutions. Spore-forming bacteria appeared to dominate the SRB population. Sulfate reduction rates were determined by the 35S-radiotracer method. A detailed assessment indicates an increase in the reduction rate in proximity to the lignite seam, with a maximum turnover of 8.4 mM sulfate/a, suggesting that lignite-drived compounds represent the substrate for sulfate reduction.     

6种重金属对赤子爱胜蚓的急性毒性效应与风险评价

【背景】近年来,土壤重金属污染问题日益凸显,对生态环境、食品安全和人体健康构成了严重威胁,其急性毒性尚未明确。【方法】采用滤纸接触法和人工土壤法测定了铜(Cu2+)、锌(Zn2+)、镍(Ni+)、镉(Cd2+)、铅(Pb2+)和锰(Mn2+)等6种重金属对赤子爱胜蚓的急性毒性效应,并参照欧盟指令91/414/EEC标准评价了其环境风险。【结果】滤纸接触法48h测定结果表明,6种重金属对蚯蚓的LC50为3.17(2.53～3.81)～90.42(69.45～140.47)μg.cm-2,其毒性次序为Cu2+>Zn2+>Ni+>Cd2+>Pb2+>Mn2+。人工土壤法14d测定结果表明,6种重金属对蚯蚓的LC50为1347(1236～1453)～6936(6144～8930)mg.kg-1,其毒性次序为Cu2+>Cd2+>Ni+>Zn2+>Mn2+>Pb2+。风险评价结果显示,Cu2+、Zn2+、Ni+、Cd2+、Pb2+和Mn2+等6种重金属的暴露比(toxicity/exposureratio,TER)分别为3.37、4.46、8.68、1428、13.87和5.85。【结论与意义】6种重金属对土壤动物蚯蚓均具有潜在的毒性效应。Cu2+、Zn2+、Ni+、Mn2+等4种重金属对赤子爱胜蚓存在急性毒性风险,而Cd2+和Pb2+对赤子爱胜蚓的急性毒性风险水平是可接受的。该评价结果可为我国制定基于风险的土壤环境质量标准提供依据。