Conversion of dibenzothiophene to biphenyl by sulfate-reducing bacteria isolated from oil field production facilities

Summary Numerous purified and characterized sulfate-reducing bacteria and bacterial communities isolated from oil-field production facilities were shown to convert dibenzothiophene (DBT) into biphenyl (BP). The maximum degree of conversion to biphenyl was 1.14 % and 0.39 % for purified sulfate-reducing bacteria and community bacteria, respectively. The purified sulfate-reducing bacteria and bacterial communities were identified by 16S rRNA ribotyping.     

Sulfate-reducing prokaryotic communities in two deep hypersaline anoxic basins in the Eastern Mediterranean deep sea

In the Eastern Mediterranean Sea, deep hypersaline anoxic basins (DHABs) and deep-sea sediment contain anoxic environments where sulfate reduction is an important microbial metabolic process. The objective of this study was to characterize the sulfate-reducing community in the brine and interface of the DHABs L'Atalante and Urania based on a phylogenetic analysis of the dissimilatory sulfite reductase gene (dsrA). Results demonstrated that the sulfate-reducing community was diverse, except for the sulfidogenic brine of the Urania basin. The similarity of the dsrA sequences between different environments was very low demonstrating that each environment had a unique sulfate-reducing community. Sequences had 67.6-93.3% similarity to dsrA sequences from GenBank database and were mostly related to the delta-proteobacteria. Each environment was dominated by a different family within the delta-proteobacteria except for the Urania interface, which was dominated by sequences related to the Gram-positive Peptococcaceae. We conclude that sulfate-reducing communities inhabiting the L'Atalante and Urania basins are highly diverse with low similarities to each other and contain a sulfate-reducing species composition that is very different from sulfate-reducing species compositions in previously studied ecosystems.     

Influence of redox potential on the anaerobic biotransformation of nitrogen-heterocyclic compounds in anoxic freshwater sediments

The potential for degradation of four nitrogen-heterocyclic compounds was investigated in fresh-water sediment slurries maintained under denitrifying, sulfate-reducing, and methanogenic conditions. Pyridine (10 mg/l) was rapidly transformed within 4 weeks under denitrifying conditions but persisted for up to 3 months under sulfate-reducing and methanogenic conditions. No intermediate biotransformation products of pyridine metabolism were detected under denitrifying conditions. Quinoline (10 mg/l) was completely transformed without a lag phase under methanogenic and sulfate-reducing conditions after incubation for 23 and 45 days, respectively. 2-Hydroxyquinoline was produced concomitantly with quinoline transformation under methanogenic and sulfate-reducing conditions. Under denitrifying conditions, less than 23% of the initial concentration of quinoline was transformed after anaerobic incubation for 83 days. Indole, however, was completely removed from sediment slurries under denitrifying, sulfate-reducing, and methanogenic conditions after anaerobic incubation for 18, 27, and 17 days, respectively. Only low amounts of oxindole (2–4 mg/l) accumulated during indole metabolism under methanogenic and denitrifying conditions, but under sulfate-reducing conditions, oxindole accumulation was stoichiometric with indole transformation. No evidence for biotransformation of carbazole was noted for all anaerobic conditions tested.     

不同pH值条件下硫酸盐还原菌组成及硫酸盐还原机制分析

【目的】从海洋沉积物中富集获得硫酸盐还原菌群,改变pH值进行培养,分析pH值对硫酸盐还原性质的影响,明确菌群组成和进行硫酸盐还原功能基因预测,探究硫酸盐还原机制。【方法】分析硫酸盐还原菌群在不同pH值条件下的硫酸盐还原率,在此基础上,利用高通量测序技术和PICRUSt软件分析硫酸盐还原菌群优势菌组成及硫酸盐还原相关基因相对丰度。【结果】硫酸盐还原菌群在不同pH值培养条件下的生长和硫酸盐还原率出现显著变化(P<0.01),在pH 5.0时达到峰值,分别为0.34±0.01和96.52%±0.44%。高通量测序数据显示,pH 5.0时菌群丰富度和多样性最高,优势菌属为假单胞菌(Pseudomonas)和芽孢杆菌(Bacillus),相对丰度较高的基因为同化性硫酸盐还原相关基因。【结论】硫酸盐还原菌富集生长的最适pH 5.0,在此条件下的高硫酸盐还原率由同化性硫酸盐还原途径主导,为揭示硫酸盐还原机制提供了实验支持,并拓宽了硫酸盐还原菌实践应用方面的种质资源。     

Competition and Coexistence of Sulfate-Reducing and Methanogenic Populations in Anaerobic Biofilms

The microbial population structure and function of natural anaerobic communities maintained in laboratory fixed-bed biofilm reactors were tracked before and after a major perturbation, which involved the addition of sulfate to the influent of a reactor that had previously been fed only glucose (methanogenic), while sulfate was withheld from a reactor that had been fed both glucose and sulfate (sulfidogenic). The population structure, determined by using phylogenetically based oligonucleotide probes for methanogens and sulfate-reducing bacteria, was linked to the functional performance of the biofilm reactors. Before the perturbation, the methanogenic reactor contained up to 25% methanogens as well as 15% sulfate-reducing bacteria, even though sulfate was not present in the influent of this reactor. Methanobacteriales and Desulfovibrio spp. were the most abundant methanogens and sulfate-reducing bacteria, respectively. The presence of sulfate-reducing bacteria (primarily Desulfovibrio spp. and Desulfobacterium spp.) in the absence of sulfate may be explained by their ability to function as proton-reducing acetogens and/or fermenters. Sulfate reduction began immediately following the addition of sulfate consistent with the presence of significant levels of sulfate-reducing bacteria in the methanogenic reactor, and levels of sulfate-reducing bacteria increased to a new steady-state level of 30 to 40%; coincidentally, effluent acetate concentrations decreased. Notably, some sulfate-reducing bacteria (Desulfococcus/Desulfosarcina/Desulfobotulus group) were more competitive without sulfate. Methane production decreased immediately following the addition of sulfate; this was later followed by a decrease in the relative concentration of methanogens, which reached a new steady-state level of approximately 8%. The changeover to sulfate-free medium in the sulfidogenic reactor did not cause a rapid shift to methanogenesis. Methane production and a substantial increase in the levels of methanogens were observed only after approximately 50 days following the perturbation.     

Anaerobic degradation of p-xylene in sediment-free sulfate-reducing enrichment culture

Anaerobic degradation of p-xylene was studied with sulfate-reducing enrichment culture. The enrichment culture was established with sediment-free sulfate-reducing consortium on crude oil. The crude oil-degrading consortium prepared with marine sediment revealed that toluene, and xylenes among the fraction of alkylbenzene in the crude oil were consumed during the incubation. The PCR-denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene for the p-xylene degrading sulfate-reducing enrichment culture showed the presence of the single dominant DGGE band pXy-K-13 coupled with p-xylene consumption and sulfide production. Sequence analysis of the DGGE band revealed a close relationship between DGGE band pXy-K-13 and the previously described marine sulfate-reducing strain oXyS1 (similarity value, 99%), which grow anaerobically with o-xylene. These results suggest that microorganism corresponding to pXy-K-13 is an important sulfate-reducing bacterium to degrade p-xylene in the enrichment culture.     

Diversity and distribution of sulfate-reducing bacteria in permanently frozen Lake Fryxell, McMurdo Dry Valleys, Antarctica

The permanently frozen freshwater Lake Fryxell, located in the Dry Valleys of Antarctica, exhibits an ideal geochemistry for microbial sulfate reduction. To investigate the population of sulfate-reducing bacteria in Lake Fryxell, both 16S rRNA gene and metabolic primer sets targeting the dsrA gene for the dissimilatory sulfite reductase alpha subunit were employed to analyze environmental DNA obtained from the water column and sediments of Lake Fryxell. In addition, enrichment cultures of sulfate-reducing bacteria established at 4 degrees C from Lake Fryxell water were also screened using the dsrA primer set. The sequence information obtained showed that a diverse group of sulfate-reducing prokaryotes of the domain Bacteria inhabit Lake Fryxell. With one exception, the enrichment culture sequences were not represented within the environmental sequences. Sequence data were compared with the geochemical profile of Lake Fryxell to identify possible connections between the diversity of sulfate-reducing bacteria and limnological conditions. Several clone groups were highly localized with respect to lake depth and, therefore, experienced specific physiochemical conditions. However, all sulfate-reducing bacteria inhabiting Lake Fryxell must function under the constantly cold conditions characteristic of this extreme environment.     

Molecular and microscopic identification of sulfate-reducing bacteria in multispecies biofilms.

The population architecture of sulfidogenic biofilms established in anaerobic fixed-bed bioreactors was characterized by selective polymerase chain reaction amplification and fluorescence microscopy. A region of the 16S rRNA common to resident sulfate-reducing bacteria was selectively amplified by the polymerase chain reaction. Sequences of amplification products, with reference to a collection of 16S rRNA sequences representing most characterized sulfate-reducing bacteria, were used to design both general and specific hybridization probes. Fluorescent versions of these probes were used in combination with fluorescence microscopy to visualize specific sulfate-reducing bacterial populations within developing and established biofilms.     

Diversity and Distribution of Sulfate-Reducing Bacteria in Permanently Frozen Lake Fryxell, McMurdo Dry Valleys, Antarctica

The permanently frozen freshwater Lake Fryxell, located in the Dry Valleys of Antarctica, exhibits an ideal geochemistry for microbial sulfate reduction. To investigate the population of sulfate-reducing bacteria in Lake Fryxell, both 16S rRNA gene and metabolic primer sets targeting the dsrA gene for the dissimilatory sulfite reductase alpha subunit were employed to analyze environmental DNA obtained from the water column and sediments of Lake Fryxell. In addition, enrichment cultures of sulfate-reducing bacteria established at 4°C from Lake Fryxell water were also screened using the dsrA primer set. The sequence information obtained showed that a diverse group of sulfate-reducing prokaryotes of the domain Bacteria inhabit Lake Fryxell. With one exception, the enrichment culture sequences were not represented within the environmental sequences. Sequence data were compared with the geochemical profile of Lake Fryxell to identify possible connections between the diversity of sulfate-reducing bacteria and limnological conditions. Several clone groups were highly localized with respect to lake depth and, therefore, experienced specific physiochemical conditions. However, all sulfate-reducing bacteria inhabiting Lake Fryxell must function under the constantly cold conditions characteristic of this extreme environment.     

Molecular and microscopic identification of sulfate-reducing bacteria in multispecies biofilms.

The population architecture of sulfidogenic biofilms established in anaerobic fixed-bed bioreactors was characterized by selective polymerase chain reaction amplification and fluorescence microscopy. A region of the 16S rRNA common to resident sulfate-reducing bacteria was selectively amplified by the polymerase chain reaction. Sequences of amplification products, with reference to a collection of 16S rRNA sequences representing most characterized sulfate-reducing bacteria, were used to design both general and specific hybridization probes. Fluorescent versions of these probes were used in combination with fluorescence microscopy to visualize specific sulfate-reducing bacterial populations within developing and established biofilms.     

Effect of Hydrogenase and Mixed Sulfate-Reducing Bacterial Populations on the Corrosion of Steel

The importance of hydrogenase activity to corrosion of steel was assessed by using mixed populations of sulfate-reducing bacteria isolated from corroded and noncorroded oil pipelines. Biofilms which developed on the steel studs contained detectable numbers of sulfate-reducing bacteria (10⁴ increasing to 10⁷/0.5 cm²). However, the biofilm with active hydrogenase activity (i.e., corrosion pipeline organisms), as measured by a semiquantitative commercial kit, was associated with a significantly higher corrosion rate (7.79 mm/year) relative to noncorrosive biofilm (0.48 mm/year) with 10⁵ sulfate-reducing bacteria per 0.5 cm² but no measurable hydrogenase activity. The importance of hydrogenase and the microbial sulfate-reducing bacterial population making up the biofilm are discussed relative to biocorrosion.     

Interaction between methanogenic and sulfate-reducing microorganisms during dechlorination of a high concentration of tetrachloroethylene

A methanogenic and sulfate-reducing consortium, which was enriched on medium containing tetrachloroethylene (PCE), had the ability to dechlorinate high concentrations of PCE. Dehalogenation was due to the direct activity of methanogens. However, interactions between methanogenic and sulfate-reducing bacteria involved modification of the dechlorination process according to culture conditions. In the absence of sulfate, the relative percentage of electrons used in PCE dehalogenation increased after an addition of lactate in batch conditions. The sulfate reducers would produce further reductant from lactate catabolism. This reductant might be used by methanogenic bacteria in PCE dechlorination. A mutualistic interaction was observed in the absence of sulfate. However in the presence of sulfate, methanogenesis and dechlorination decreased because of interspecific competition, probably between the H(2)-oxydizing methanogenic and sulfate-reducing bacteria in batch conditions. In the semicontinuous fixed-bed reactor, the presence of sulfate did not affect dechlorination and methanogenesis. The sulfate-reducing bacteria may not be competitors of H(2)-consuming methanogens in the reactor because of the existence of microbial biofilm. The presence of the fixed film may be an advantage for bioremediation and industrial treatment of effluent charged in sulfate and PCE. This is the first report on the microbial ecology of a methanogenic and sulfate-reducing PCE-enrichment consortium.     

Is interspecies hydrogen transfer needed for toluene degradation under sulfate-reducing conditions?

Sediments from a hydrocarbon-contaminated aquifer, where periodic shifts between sulfate reduction and methanogenesis occurred, were examined to determine whether the degradation of toluene under sulfate-reducing conditions depended on interspecies hydrogen transfer. Toluene degradation under sulfate-reducing conditions was inhibited by the addition of 5 mM sodium molybdate, but the activity was not restored upon the addition of an actively growing, hydrogen-using methanogen. Toluene degradation was not inhibited in microcosms where hydrogen levels were maintained at a level theoretically sufficient to inhibit toluene degradation if the process proceeded via interspecies hydrogen transfer. Finally, the addition of carbon monoxide, a potent inhibitor of hydrogenase activity, inhibited hydrogen but not toluene consumption in sulfate-reducing microcosms. These results suggest that toluene is degraded directly by sulfate-reducing bacteria without the involvement of interspecies hydrogen transfer. The sequence of experiments used to reach this conclusion could be applied to determine the role of interspecies hydrogen transfer in the degradation of a variety of compounds in different environments or under different terminal electron-accepting conditions.     

Methane production by the sulfate-reducing bacteriumDesulfosarcina variabilis

The sulfate-reducing bacteriumDesulfosarcina variabilis VKM B-1694 was found to produce up to 1.62 Ώmol methane per mg protein when grown on different substrates. The role of methanogenesis and the physicochemical factors determining this process in sulfate-reducing bacteria are discussed.     

Genome sequence of the mercury-methylating and pleomorphic Desulfovibrio africanus Strain Walvis Bay

Desulfovibrio africanus strain Walvis Bay is an anaerobic sulfate-reducing bacterium capable of producing methylmercury (MeHg), a potent human neurotoxin. The mechanism of methylation by this and other organisms is unknown. We present the 4.2-Mb genome sequence to provide further insight into microbial mercury methylation and sulfate-reducing bacteria.     

Evidence for Coexistence of Two Distinct Functional Groups of Sulfate-Reducing Bacteria in Salt Marsh Sediment

Oxidation of acetate in salt marsh sediment was inhibited by the addition of fluoroacetate, and also by the addition of molybdate, an inhibitor of sulfate-reducing bacteria. Molybdate had no effect upon the metabolism of acetate in a freshwater sediment in the absence of sulfate. The inhibitory effect of molybdate on acetate turnover in the marine sediment seemed to be because of its inhibiting sulfate-reducing bacteria which oxidized acetate to carbon dioxide. Sulfide was not recovered from sediment in the presence of molybdate added as an inhibitor of sulfate-reducing bacteria, but sulfide was recovered quantitatively even in the presence of molybdate by the addition of the strong reducing agent titanium chloride before acidification of the sediment. Reduction of sulfate to sulfide by the sulfate-reducing bacteria in the sediment was only partially inhibited by fluoroacetate, but completely inhibited by molybdate addition. This was interpreted as showing the presence of two functional groups of sulfate-reducing bacteria—one group oxidizing acetate, and another group probably oxidizing hydrogen.     

Growth, incidence and activities of dissimilatory sulfate-reducing bacteria in the human oral cavity

Abstract Viable counts and activities of sulfate-reducing bacteria were determined in the oral cavities of 12 healthy volunteers. Of these, 10 harboured viable sulfate-reducing bacteria populations. Six separate sites were sampled: the posterior tongue, anterior tongue, mid buccal mucosa, vestibular mucosa, supragingival plaque and subgingival plaque. Sulfate-reducing bacteria occurred in all areas, with the highest incidence in supragingival plaque. Viable counts and sulfate-reducing activities in each of the regions varied from 0 to 10⁸ cfu (g wet weight)⁻¹ and from 0 to 50 nmol (g wet weight) ⁻¹ h⁻¹, respectively. As sulfate-reducing bacteria can be detected in the oral cavity, they may potentially be involved in terminal oxidative processes carried out by the microflora of the mouth.     

Ethanol utilization by sulfate-reducing bacteria: an experimental and modeling study

A mixed culture of sulfate-reducing bacteria containing the species Desulfovibrio desulfuricans was used to study sulfate-reduction stoichiometry and kinetics using ethanol as the carbon source. Growth yield was lower, and kinetics were slower, for ethanol compared to lactate. Ethanol was converted into acetate and no significant carbon dioxide production was observed. A mathematical model for growth of sulfate-reducing bacteria on ethanol was developed, and simulations of the growth experiments on ethanol were carried out using the model. The pH variation due to sulfate reduction, and hydrogen sulfide production and removal by nitrogen sparging, were examined. The modeling study is distinct from earlier models for systems using sulfate-reducing bacteria in that it considers growth on ethanol, and analyzes pH variations due to the product-formation reactions.     

Carriage, quantification, and predominance of methanogens and sulfate-reducing bacteria in faecal samples

AIMS: To determine carriage rates and densities of methanogens and sulfate-reducing bacteria in adults and children using molecular methods, and to also determine if a reciprocal relationship exists between these organisms. METHODS AND RESULTS: Real-time PCR was used to detect and quantify methanogens and sulfate-reducing bacteria. Real-time PCR was more sensitive than breath methane measurements. Real-time PCR assays were applied to faecal DNA samples collected from 40 children and 12 adults. Methanogens were present in 25% of the children and 42% of the adults studied, and sulfate-reducing bacteria were detected in 15% of the children and 58% of the adults. High levels of sulfate-reducing bacteria were found in two methanogenic adults. CONCLUSIONS: Carriage rates and densities of methanogens and sulfate-reducing bacteria are greater in adults than in children. Competition does not necessarily lead to the predominance of one group in the faecal microflora. SIGNIFICANCE AND IMPACT OF THE STUDY: This study describes sensitive, molecular assays that could be used to monitor these organisms in gastrointestinal disease. Therapeutic exclusion of one group from the bowel would not necessarily lead to the expansion of the other, as there does not appear to be a reciprocal relationship between these groups.     

Effect of the aerenchymatous helophyte Glyceria maxima on the sulfate-reducing communities in two contrasting riparian grassland soils

Aims

The research aimed at studying the effect of flooding with sulfate-rich water on the activity, abundance and diversity of sulfate-reducing micro-organisms present in the root zone of an oxygen-releasing plant growing on two riparian grassland soils with contrasting amounts of iron.

Methods

A series of microcosms was used to investigate the effects. Plants were grown under controlled conditions in microcosms containing a rhizosphere and bulk soil compartment for a period of 12 weeks in the presence of sulfate-rich flood water. Molybdate-treated systems served as non-sulfate-reducing controls.

Results

At harvest, activity and numbers of sulfate-reducing micro-organisms were higher in the absence of molybdate, but a rhizosphere effect and an impact of the presence of high levels of iron were not observed on activity and numbers. Both soils had in common a diverse community of sulfate-reducing micro-organisms covering all major cultured bacterial taxa. The appearance of members of the Desulfovibrionaceae exclusively in the rhizosphere of G. maxima was the only unambiguous indication of a plant effect.

Conclusion

The presence of sulfate-rich flood water stimulated the activity and growth of a part of the sulfate-reducing community leading to a change in community composition. The proximity of aerenchymatous plant roots and the abundance of iron in the soil had a negligible effect on the sulfate-reducing community.