Sulfidogenic Bacteria Research Articles

Draft genome sequence of the first acid-tolerant sulfate-reducing deltaproteobacterium Desulfovibrio sp. TomC having potential for minewater treatment.

The sulfidogenic bacterium Desulfovibrio sp. TomC was isolated from acidic waste at the abandoned gold ore mining site in the Martaiga gold ore belt, Western Siberia. This bacterium, being the first reported acid-tolerant gram-negative sulfate-reducer of the order Deltaproteobacteria, is able to grow at pH as low as 2.5 and is resistant to high concentrations of metals. The draft 5.3 Mb genome sequence of Desulfovibrio sp. TomC has been established and provides the genetic basis for application of this microorganism in bioreactors and other bioremediation schemes for the treatment of metal-containing wastewater.

The biocidal effect of a novel synthesized gemini surfactant on environmental sulfidogenic bacteria: planktonic cells and biofilms.

A cationic gemini surfactant was synthesized and characterized. The surfactant was successfully applied as a biocide against environmental sulfidogenic bacteria in the bulk phase (planktonic) and on the surface (biofilm). The activity of the synthesized surfactant was discussed based on the redox potential and the sulfide productivity in the bulk phase. The cultivated biofilm structure analysis and corrosion rate were estimated on the metal surface. The lowest metal corrosion rate was recognized at a concentration of 1mM with a metal corrosion inhibition efficiency of 95%. The synthesized gemini surfactant prevented the biofilm formation at a concentration of 0.1mM. The synthesized gemini surfactant displayed a broad spectrum antibacterial activity against Gram-positive and Gram-negative bacteria.

Intestinal and Systemic Inflammatory Responses Are Positively Associated with Sulfidogenic Bacteria Abundance in High-Fat–Fed Male C57BL/6J Mice

Recent studies have highlighted the relation between high-fat (HF) diets, the gut microbiota, and inflammation. However, the role of sulfidogenic bacteria in mediating these effects has been explored only recently. Therefore, we tested the hypothesis that an HF diet rich in saturated fat stimulates sulfidogenic bacteria and that these increases correlate with intestinal and systemic inflammatory responses. Forty C57BL/6J male mice were fed a low-fat (LF; 10% of energy) or an HF lard-based (60% of energy) diet for 6 or 20 wk. Mucosa samples were collected from the ileum, cecum, and colon and used for measuring 16S ribosomal RNA and functional genes of sulfidogenic bacteria. Matching intestinal samples and visceral and subcutaneous white adipose tissue (WAT) depots were used to measure mRNA abundance for inflammatory genes. Mice fed the HF diet had greater (P < 0.05) abundance of 3 types of sulfidogenic bacteria, primarily in colonic mucosa, compared with LF-fed mice at week 20. Although HF feeding did not increase intestinal inflammation at week 6, ileal markers of macrophage infiltration and inflammation were upregulated (P < 0.05) 1- to 6-fold at week 20. HF feeding impaired the localization of the tight junction protein zonula occludens 1 at the apical area of the ileal epithelium at weeks 6 and 20. Mice fed the HF diet had 1- to 100-fold greater (P < 0.05) mRNA levels of markers of macrophage infiltration in visceral and subcutaneous WAT at week 20, but not at week 6, compared with LF-fed mice. These results provide evidence that chronic, but not acute, consumption of an HF lard-based diet may be linked with pathways of microbial metabolism that potentially contribute to chronic intestinal and systemic inflammation. Such linkage provides further support for reducing consumption of saturated fats.

Cationic Gemini Surfactant as a Corrosion Inhibitor and a Biocide for High Salinity Sulfidogenic Bacteria Originating from an Oil‐Field Water Tank

AbstractA novel cationic gemini surfactant (NCGS) was synthesized and characterized. The inhibitory effect of NCGS was evaluated on the basis of protecting a metal surface from the salinity (5.49 % NaCl) and the activity of environmental sulfidogenic bacteria which originated from an oil‐field water tank. Sulfidogenic bacterial activities were determined based on sulfide production, redox potential, changes in biofilm structures and constituents and metal corrosion rate calculations. At high surfactant concentrations, the sulfide production was completely inhibited as well as a considerable drop in the redox potential was observed in the reactor's bulk phase. A minimum inhibitory concentration of the NCGS was achieved at a concentration of 1 mM. The NCGS showed a high ability to inhibit a biofilm over the metal surface at a concentration of 0.1 mM. The lowest metal corrosion rate was detected at a concentration of 5 mM with a metal corrosion inhibition efficiency of 97 %. In addition the NCGS showed a nonspecific biocidal activity against Gram‐positive and Gram‐negative bacterial strains.

Corrosion of carbon steel by bacteria from North Sea offshore seawater injection systems: Laboratory investigation

Influence of sulfidogenic bacteria, from a North Sea seawater injection system, on the corrosion of S235JR carbon steel was studied in a flow bioreactor; operating anaerobically for 100days with either inoculated or filtrated seawater. Deposits formed on steel placed in reactors contained magnesium and calcium minerals plus iron sulfide. The dominant biofilm-forming organism was an anaerobic bacterium, genus Caminicella, known to produce hydrogen sulfide and carbon dioxide. Open Circuit Potentials (OCP) of steel in the reactors was, for nearly the entire test duration, in the range −800<E(OCP)/mV (vs. SCE)<−700. Generally, the overall corrosion rate, expressed as 1/(Rp/Ω), was lower in the inoculated seawater though they varied significantly on both reactors. Initial and final corrosion rates were virtually identical, namely initial 1/(Rp/Ω)=2×10−6±5×10−7 and final 1/(Rp/Ω)=1.1×10−5±2.5×10−6. Measured data, including electrochemical noise transients and statistical parameters (0.05<Localized Index<1; −5<Skewness<−5; Kurtosis>45), suggested pitting on steel samples within the inoculated environment. However, the actual degree of corrosion could neither be directly correlated with the electrochemical data and nor with the steel corrosion in the filtrated seawater environment. Further laboratory tests are thought to clarify the noticed apparent discrepancies.

Corrosion behavior of carbon steel in presence of sulfate-reducing bacteria in seawater environment

• Carbon steel was exposed to sulfidogenic bacteria seeded seawater in a flow loop. • Localized surface attacks followed inoculations with sulfidogenic bacteria. • Bacteria activity does not necessarily lead to significantly elevated corrosion. • Complex corrosion deposits structure. • Antimicrobial treatment temporarily suppressed bacterial activity. The influence of sulfate-reducing bacteria (SRB) on the corrosion behavior of carbon steel was studied in a laboratory test-loop, continuously fed with nutrient supplemented North Sea seawater. The main parts of the test-loop, represented by two separated flow cells, were fitted with steel specimens. The test-loop was operating anoxically for 2200 h and each flow cell was three times inoculated with Desulfovibrio alaskensis or Desulfovibrio desulfuricans species. Additionally, each flow cell was two times perturbed with antimicrobial treatments. Steel specimens exposed in flow cells exhibited comparable appearance and systems responding similarly to inoculations and antimicrobial treatments. The effect of the inoculations in both flow cells on the steel coupons electrochemical behavior was materialized as lower resistance to corrosion and higher surface activity or occurrence of localized pitting events. The localized surface attacks recognized in both flow cells after inoculations continued to progress with the time, although bacterial activity was temporarily suppressed by antimicrobial treatment. Post-exposure sample evaluations might suggest that, some particular steel surface areas have been subjected to a dramatic change in the corrosion mechanism from initial localized attack to general corrosion. The long-term exposure of the carbon steel specimens resulted in identifiable formation of biofilms and corrosion products. Corrosion deposits were characterized by a specific structure built of iron sulfides (FeS), sulfated green rust (GR(SO 4 2− )), magnetite (Fe 3 O 4 ), Fe(III) oxyhydroxides (FeOOH), chukanovite (Fe 2 (OH) 2 CO 3 ), carbonated green rust (GR(CO 3 2− )) and some calcareous deposits. Presented factual evidence reinforced the idea that sulfidogenic species in natural seawater environment may cause localized damage with a specific surface pattern; however, this does not necessarily lead towards significantly elevated corrosion rates.

Acidocella aromatica sp. nov.: an acidophilic heterotrophic alphaproteobacterium with unusual phenotypic traits

Three obligately heterotrophic bacterial isolates were identified as strains of a proposed novel species of extremely acidophilic, mesophilic Alphaproteobacteria, Acidocella aromatica. They utilized a restricted range of organic substrates, which included fructose (but none of the other monosaccharides tested), acetate and several aromatic compounds (benzoate, benzyl alcohol and phenol). No growth was obtained on complex organic substrates, such as yeast extract and tryptone. Tolerance of the proposed type strain of the species (PFBC) to acetic acid was much greater than that typically reported for acidophiles. The bacteria grew aerobically, and catalyzed the dissimilatory reductive dissolution of the ferric iron mineral schwertmannite under both micro-aerobic and anaerobic conditions. Strain PFBC did not grow anaerobically via ferric iron respiration, though it has been reported to grow in co-culture with acid-tolerant sulfidogenic bacteria under strictly anoxic conditions. Tolerance of strains of Acidocella aromatica to nickel were about two orders of magnitude greater than those of other Acidocella spp., though similar levels of tolerance to other metals tested was observed. The use of this novel acidophile in solid media designed to promote the isolation and growth of other (aerobic and anaerobic) acidophilic heterotrophs is discussed.

Microorganisms of the carbonate petroleum reservoir 302 of the Romashkinskoe oilfield and their biotechnological potential

Diversity, geochemical activity, and biotechnological potential of the microorganisms from oil bed 302 of the Romashkinskoe oilfield (Tatarstan, Russia) are reported. The microbial community contained almost no aerobic microorganisms. Sulfatereducing (10 3 -10 6 cells/mL) and fermentative bacteria (10 2 -10 5 cells/mL) pre� dominated in the oilfield. Sulfate reduction was the predominant process in formation water with the rates up to 26.6 µg S 2- L/day. The number of methanogens and methanogenesis rate in formation water did not exceed 10 4 cells/mL and 8.19 µg CH4 L/day, respectively. Analysis of the 16S rRNA gene clone library revealed the sequences of denitrifying bacteria of the genera Sulfurimonas and Thauera. The oil recovery tech� nique combining the stimulation of fermentative bacteria and suppression of sulfate reducers in the oilfield was proposed for development of the bed 302. Fermentative bacteria could be activated by the traditional method, i.e., injection of molasses and nitrogen and phosphorus mineral salts through the injection wells. Introduction of high concentrations of nitrate will activate the growth of denitrifying bacteria, suppress the growth of sulfidogenic bacteria, and result in decreased sulfide concentration in formation water. The pro� posed biotechnology is technologically simple and environmentally friendly.

Biodegradation Potential of Halo(alkali)philic Prokaryotes

Oil and gas exploitation and downstream processing may generate large volumes of contaminated aqueous wastewaters. Without treatment, the discharge of these streams into the environment would lead to considerable environmental problems. A combination of physicochemical and biological treatment processes are applied to treat such polluted streams (e.g., in conventional water purification plants). However, the application of microorganisms in these streams is rather limited streams to salt levels well below those of seawater. The potential of microorganisms to degrade various organic and inorganic pollutants at higher salinities was surveyed in the open literature. The advantage of biological treatment processes that operate at elevated salinities is that no dilution water is needed, which is particularly relevant for arid regions. The available literature is scarce, especially concerning truly halophilic bacteria that thrive at salt concentrations significantly higher than in seawater. The obvious trend of most of the publications indicates a significant inhibition of the biodegradation activity at salt concentrations above 10 wt.%. However, a specialized group of extremophilic microorganisms, called halo(alkali)philes, could replace freshwater or marine organisms in the biodegradation processes at salinities above 1.5 M and pH values above 9. They are present in natural hypersaline habitats and can be activated either directly in situ by addition of micronutrients and aeration, or introduced into engineered water treatment systems. In a number of studies, the possibility of microbial HC degradation up to 5 M NaCl has been mentioned. Relatively little is known about the removal of toxic inorganic compounds, such as H2S, CO, and CN−, at halo(alkaline) conditions. These compounds are clearly associated with the processing of oil, coal, and gas. An exception is the application of sulfur-cycling bacteria, as these organisms have been intensively studied during the last decade. Sulfur-oxidizing and sulfidogenic bacteria can function efficiently at extremely saline and alkaline conditions. The general conclusion from this survey is that many biodegradation routs are, in principal, possible at high salt/pH but more research is needed to make a real progress in the development of engineered processes that can be applied to protect the environment.

Selective removal of transition metals from acidic mine waters by novel consortia of acidophilic sulfidogenic bacteria

SummaryTwo continuous‐flow bench‐scale bioreactor systems populated by mixed communities of acidophilic sulfate‐reducing bacteria were constructed and tested for their abilities to promote the selective precipitation of transition metals (as sulfides) present in synthetic mine waters, using glycerol as electron donor. The objective with the first system (selective precipitation of copper from acidic mine water containing a variety of soluble metals) was achieved by maintaining a bioreactor pH of ∼2.2–2.5. The second system was fed with acidic (pH 2.5) synthetic mine water containing 3 mM of both zinc and ferrous iron, and varying concentrations (0.5–30 mM) of aluminium. Selective precipitation of zinc sulfide was possible by operating the bioreactor at pH 4.0 and supplementing the synthetic mine water with 4 mM glycerol. Analysis of the microbial populations in the bioreactors showed that they changed with varying operational parameters, and novel acidophilic bacteria (including one sulfidogen) were isolated from the bioreactors. The acidophilic sulfidogenic bioreactors provided ‘proof of principle’ that segregation of metals present in mine waters is possible using simple online systems within which controlled pH conditions are maintained. The modular units are versatile and robust, and involve minimum engineering complexity.

Influence of organic loading on the performance and microbial community structure of an anaerobic stage reactor treating pharmaceutical wastewater

An unique up-flow anaerobic stage reactor (UASR) treating pharmaceutical wastewater at various organic loading rate (OLR) was investigated and showed efficient substrate removal at low OLRs (0.43–1.86kg CODm−3d−1) by promoting efficient chemical oxygen demand (COD) reduction (70–75%). However, increasing the OLRs to 3.73kg CODm−3d−1 by reducing the hydraulic retention time (HRT) (4–2d) reduced the COD removal efficiency (45%). Fluorescent in situ hybridisation (FISH) analysis showed that the microbial community of the reactor stages was dominated by methanogenic archaea (56–79% of 4′, 6 diamidino-2-phenylindole (DAPI)-stained cells in all stages) when the reactor was fed at OLR 0.86–2.98kgCODm−3d−1 but decreased in Stage 1 (30% of DAPI-stained cells) when the OLR was at 3.73kgCODm−3d−1. The two methanogenic genera detected were Methanosarcina and Methanosaeta. Generally, Methanosaeta dominated the reactor stages when the OLR was 0.86–1.86kgCODm−3d−1, while Methanosarcina dominated during the period of high OLR (2.98–3.73kgCODm−3d−1). Based on the number of Desulfovibrio cells detected (8–36% of the total eubacteria) in all stages during the entire operation of the reactor, it appears that sulfidogenic bacteria contributed to the overall degradation of organic substances in the pharmaceutical wastewater.

Diversity of culturable sulfidogenic bacteria in two oil–water separation tanks in the north-eastern oil fields of India

Sulfidogenic communities in the production waters of onshore oil fields in north-eastern India were examined using a culturing approach. Production water samples were inoculated into medium selective for Sulfate reducing bacteria (SRB) and Thiosulfate Reducing Bacteria (TRB). The total number of viable sulfidogenic microorganisms in the samples obtained from the two production water tanks was approximately 10 5 MPN ml −1 (most probable number per ml). Most of the isolates were thermo-tolerant and could be grown between 40 and 45 °C. Hydrogen sulfide production by TRB was significantly higher than by SRB. Based on 16S rRNA gene sequencing, the isolates were grouped in nine different phylotypes. Phylogenetic analysis indicated that most of the SRB were affiliated with the phylum Proteobacteria, encompassing Gram-negative bacteria, belonging to the genera Desulfovibrio, Desulfomicrobium, and Desulfobulbus. However, five isolates grouped with the genus Desulfotomaculum were found to be gram-positive SRB. Most of the thiosulfate reducing isolates was affiliated with the phylum Firmicutes, including Clostridium and Fusibacter and also with the phylum Proteobacteria, including the genera Enterobacter and Citrobacter. Phylotypes related to Clostridium (69%) and Desulfovibrio (53%) dominated the community in the production water samples. This study demonstrates the diversity of the TRB and SRB that play a critical role in the souring mediated corrosion of the oil–water separation tanks in the north-eastern India oil fields.

Degradation of Phenol via Phenylphosphate and Carboxylation to 4-Hydroxybenzoate by a Newly Isolated Strain of the Sulfate-Reducing BacteriumDesulfobacterium anilini

A sulfate-reducing phenol-degrading bacterium, strain AK1, was isolated from a 2-bromophenol-utilizing sulfidogenic estuarine sediment enrichment culture. On the basis of phylogenetic analysis of the 16S rRNA gene and DNA homology, strain AK1 is most closely related to Desulfobacterium anilini strain Ani1 (= DSM 4660(T)). In addition to phenol, this organism degrades a variety of other aromatic compounds, including benzoate, 2-hydroxybenzoate, 4-hydroxybenzoate, 4-hydroxyphenylacetate, 2-aminobenzoate, 2-fluorophenol, and 2-fluorobenzoate, but it does not degrade aniline, 3-hydroxybenzoate, 4-cyanophenol, 2,4-dihydroxybenzoate, monohalogenated phenols, or monohalogenated benzoates. Growth with sulfate as an electron acceptor occurred with acetate and pyruvate but not with citrate, propionate, butyrate, lactate, glucose, or succinate. Strain AK1 is able to use sulfate, sulfite, and thiosulfate as electron acceptors. A putative phenylphosphate synthase gene responsible for anaerobic phenol degradation was identified in strain AK1. In phenol-grown cultures inducible expression of the ppsA gene was verified by reverse transcriptase PCR, and 4-hydroxybenzoate was detected as an intermediate. These results suggest that the pathway for anaerobic degradation of phenol in D. anilini strain AK1 proceeds via phosphorylation of phenol to phenylphosphate, followed by carboxylation to 4-hydroxybenzoate. The details concerning such reaction pathways in sulfidogenic bacteria have not been characterized previously.

Control of sulfidogenic bacteria in produced water from the Kathloni oilfield in northeast India

A full-scale study was conducted to evaluate microbiocide efficacy to control the indigenous sulfide-producing bacterial population in produced water at Kathloni, Oil India Limited (OIL), Assam (northeast India). The sulfide-producing culturable bacterial strains present in produced water of Kathloni oilfield were identified as Anaerobaculum mobile, Garciella nitratireducens, Clostridium sporogenes, Thermosediminibacter oceani, Coprothermobacter sp., Thermodesulfovibrio sp., Thermodesulfobacterium sp., Thermodesulfotobacterium sp., and Caldanaerobacter sp. These strains could produce sulfide in the range of 50–200 mg l −1 and volatile fatty acids such as acetic acid, propionic acid, isobutyric acid, butyric acid, and isovaleric acid. Out of 10 microbiocides screened, three (sodium hypochlorite, benzyl trimethyl ammonium chloride, and 2-bromo-2-nitropropane-1,3-diol) were selected to control the growth and sulfide production by the aforementioned mixed bacterial species. A strategy was designed in which these three microbiocides were sequentially applied in an oilfield for 132 days. There was no significant difference in the chemical composition of the produced water after the treatment.

Sulfidogenesis under extremely haloalkaline conditions by Desulfonatronospira thiodismutans gen. nov., sp. nov., and Desulfonatronospira delicata sp. nov. - a novel lineage of Deltaproteobacteria from hypersaline soda lakes

High rates of sulfidogenesis were observed in sediments from hypersaline soda lakes. Anaerobic enrichment cultures at 2 M Na(+) and pH 10 inoculated with sediment samples from these lakes produced sulfide most actively with sulfite and thiosulfate as electron acceptors, and resulted in the isolation of three pure cultures of extremely natronophilic sulfidogenic bacteria. Strain ASO3-1 was isolated using sulfite as a sole substrate, strain AHT 8 with thiosulfate and formate, and strain AHT 6 with thiosulfate and acetate. All strains grew in a mineral soda-based medium by dismutation of either sulfite or thiosulfate, as well as with sulfite, thiosulfate and sulfate as acceptors, and H(2) and simple organic compounds as electron donors. The acetyl-CoA pathway was identified as the pathway for inorganic carbon assimilation by strain ASO3-1. All strains were obligately alkaliphilic, with an optimum at pH 9.5-10, and grew in soda brines containing 1-4 M total Na(+) (optimum at 1.0-2.0 M). The cells accumulated high amounts of the organic osmolyte glycine betaine. They formed a new lineage within the family Desulfohalobiaceae (Deltaproteobacteria), for which the name Desulfonatronospira gen. nov. is proposed. Strains ASO3-1(T) and AHT 8 from Kulunda Steppe formed Desulfonatronospira thiodismutans sp. nov., and strain AHT 6(T) from Wadi al Natrun is suggested as Desulfonatronospira delicata sp. nov.

Microbial communities and geochemical dynamics in an extremely acidic, metal‐rich stream at an abandoned sulfide mine (Huelva, Spain) underpinned by two functional primary production systems

An extremely acidic (pH 2.5-2.75) metal-rich stream draining an abandoned mine in the Iberian Pyrite Belt, Spain, was ramified with stratified macroscopic gelatinous microbial growths ('acid streamers' or 'mats'). Microbial communities of streamer/mat growths sampled at different depths, as well as those present in the stream water itself, were analysed using a combined biomolecular and cultivation-based approach. The oxygen-depleted mine water was dominated by the chemolithotrophic facultative anaerobe Acidithiobacillus ferrooxidans, while the streamer communities were found to be highly heterogeneous and very different to superficially similar growths reported in other extremely acidic environments. Microalgae accounted for a significant proportion of surface streamer biomass, while subsurface layers were dominated by heterotrophic acidophilic bacteria (Acidobacteriacae and Acidiphilium spp.). Sulfidogenic bacteria were isolated from the lowest depth streamer growths, where there was also evidence for selective biomineralization of copper sulfide. Archaeal clones (exclusively Euryarchaeota) were recovered from streamer samples, as well as the mine stream water. Both sunlight and reduced inorganic chemicals (predominantly ferrous iron) served as energy sources for primary producers in this ecosystem, promoting complex microbial interactions involving transfer of electron donors and acceptors and of organic carbon, between microorganisms in the stream water and the gelatinous streamer growths. Microbial transformations were shown to impact the biogeochemical cycling of iron and sulfur in the acidic stream, severely restricting the net oxidation of ferrous iron even when the initially anoxic waters were oxygenated by indigenous acidophilic algae. A model accounting for the biogeochemistry of iron and sulfur in the mine waters is described, and the significance of the acidophilic communities in regulating the geochemistry of acidic, metal-rich waters is described.

Microbial populations associated with treatment of an industrial dye effluent in an anaerobic baffled reactor.

Fluorescent in situ hybridization (FISH) using 16S and 23S rRNA-targeted probes together with construction of an archaeal 16S ribosomal DNA (rDNA) clone library was used to characterize the microbial populations of an anaerobic baffled reactor successfully treating industrial dye waste. Wastewater produced during the manufacture of food dyes containing several different azo and other dye compounds was decolorized and degraded under sulfidogenic and methanogenic conditions. Use of molecular methods to describe microbial populations showed that a diverse group of Bacteria and Archaea was involved in this treatment process. FISH enumeration showed that members of the gamma subclass of the class Proteobacteria and bacteria in the Cytophaga-Flexibacter-Bacteroides phylum, together with sulfate-reducing bacteria, were prominent members of a mixed bacterial population. A combination of FISH probing and analysis of 98 archaeal 16S rDNA clone inserts revealed that together with the bacterial population, a methanogenic population dominated by Methanosaeta species and containing species of Methanobacterium and Methanospirillum and a relatively unstudied methanogen, Methanomethylovorans hollandica, contributed to successful anaerobic treatment of the industrial waste. We suggest that sulfate reducers, or more accurately sulfidogenic bacteria, together with M. hollandica contribute considerably to the treatment process through metabolism of dye-associated sulfonate groups and subsequent conversion of sulfur compounds to carbon dioxide and methane.

Peculiarities of Morphology and Ultrastructure in Bacteria of the GenusDethiosulfovibrio

Cell morphology and fine structure were studied in two strains of rod-shaped, strictly anaerobic, gram-negative sulfidogenic bacteria: strain SRI 2T(DSM 12538) and strain WS100 (DSM 12537) belonging to “Dethiosulfovibriostarorussensis.” Cells of both strains, as well as cells of the type species of the genusDethiosulfovibrio, D. peptidovorans, were found to possess multiple intracellular incomplete cross septa in all growth phases.

2-Bromoethanesulfonate, sulfate, molybdate, and ethanesulfonate inhibit anaerobic dechlorination of polychlorobiphenyls by pasteurized microorganisms

Dechlorination of Aroclor 1242 by pasteurized microorganisms was inhibited by 2-bromoethanesulfonate (BES), sulfate, molybdate, and ethanesulfonate. Consumption of these anions and production of sulfide from BES were detected. The inhibition could not be relieved by hydrogen. Taken together these results suggest that pattern M dechlorination is mediated by spore-forming sulfidogenic bacteria. These results also suggest that BES may inhibit anaerobic dechlorination by nonmethanogens by more than one mechanism.

Competition of methanogenic and sulfidogenic bacteria

The competition of acetotrophic methanogenic bacteria (AMB) and acetotrophic sulfidogenic bacteria (ASRB) was studied by assessing growth rates, activities and acetate and sulfate affinities at different pH levels and sulfide concentrations in batch reactors. Both anaerobic granular sludge and suspended anaerobic sludge were tested. The results indicate that at pH-levels below 6.9 AMB will outcompete ASRB, whereas above a pH of 7.7, ASRB will win the competition. If ASRB and AMB are present in granular sludge growth will be found in a wider pH-range than if they are present as suspended sludge. The affinities for acetate and the sulfide toxicity are dependent on the sludge form as well. In granular sludge the acetate affinities of ASRB and AMB are comparable, whereas in suspended sludge ASRB show a lower affinity than AMB. With respect to sulfide toxicity, the results indicate that above pH 7 sulfide inhibition in granular sludge is caused by the total sulfide concentration, while in suspended sludge the free H2S-concentration determines the toxicity. At high pH-levels growth is stronger inhibited than the activity.