Isolation Of Sulfate-reducing Bacteria Research Articles

Versatile Medium for the Isolation of Sulfur-Reducing Bacteria from Natural Ecotypes

Sulfate-reducing bacteria (SRB) are a diverse group of microorganisms that are commonly isolated from anoxygenic environments (lake depths, soil, or swamps) and are also found in the intestines of humans and animals. They are well known for outcompeting methanogens for common substrates thereby helping in the decrease of methane emissions and also playing a major role in sulfur cycling. Therefore, determining the cultivable methods for their isolation is important. Various media has been used for the cultivation and purification of SRB from natural wetlands. The luxuriant growth of SRB was observed in all the media tested, out of which the best suitable media to recover a maximum of colonies from the natural soil/sediment samples was discovered as a modified postage medium. The enumeration of the isolated SRB was done by the most probable number (MPN) technique. A total of twenty pure isolates of SRB were isolated from different ecotypes.

GROWTH EVALUATION OF SULPHATE-REDUCING BACTERIA (SRB) ASSOCIATED WITH BURIED MILD STEEL RODS

Introduction: Sulphate-reducing bacteria are the major cause of corrosion of underground structure corrosion of underground structures made of mild steel. Objective: This study set out to evaluate the growth pattern of sulphate-reducing bacteria associated with buried mild steel rods in Akure metropolis, Nigeria Methodology: Mild steel rods (12 mm diameter, area 39.97 cm2), were collected from Ondo State Water Corporation (ODSWC), Akure, Nigeria and were buried and monitored for a period of three months. Percentage composition of the mild steel rods was determined. Isolation of sulphate-reducing bacteria was carried out using compounded Postgate C medium. Turbidimetric growth pattern and biochemical characteristics of the isolates were determined using standard protocols. Results: Citrobacter freundii, Citrobacter gilleni, Enterobacter aerogenes, Pseudomonas aeruginosa, Desulfovibrio vulgaris and Bacillus megaterium were the bacterial consortia isolated from the buried mild steel rods. Turbidity was observed to be at low level on the 5th day of sulphate-reducing bacteria (SRB) growth, but increased to optimum on the 10th day of incubation and reduced drastically on the 15th day. The growth outline of sulphate-reducing bacteria (SRB) was confirmed by the swelling turbid periodic growth for all four mediums. Iron (Fe) had the highest percentage mineral composition of 98.7 % whereas lanthanum had the least composition at 0.00031 %. Conclusion: Findings of this study revealed the presence of sulphate-reducing bacteria (SRB) on buried mild steel rods of a water distribution system suggesting induction of corrosion of the underground mild steel pipes.

The antibiofilm and antibacterial effects of medicinal plant extracts on isolated sulfate-reducing bacteria from orthodontic appliances

Sulfate-Reducing Bacteria (SRB) are a heterogeneous group of oral microflorae that cause dental caries, destructive periodontal infections, and biofilms on fixed orthodontic appliances. Plant extracts as a source of antibacterial components may have acceptable activity against SRB strains and their biofilm development. Our study aimed at determining the antibiofilm, antimicrobial efficacy, and cytotoxicity of Iran's endemic plants against pathogenic SRB. Plantago ovata, Terminalia chebula, Eugenia caryophyllata, and Aloe vera extracts were prepared according to standard methods. Patients and orthodontic appliances samples were collected, and SRB strains were isolated using standard tests and 16S rRNA analysis. The extracts' antimicrobial, antibiofilm activity, and cytotoxicity were determined using dilution broth micro, crystal violet staining, and MTT method, respectively. Biofilm involved gene expression of strains determined using Real-time PCR. Three SRB isolates harboring target genes were identified using 16S rDNA that showed a more than 90% of similarity to Desulfomicrobium orale spp. All investigated extracts showed good activity against SRB isolates. T. chebula, E. caryophyllata, and A. vera showed promising antibiofilm activity, and their subMIC concentrations downregulated biofilm-forming related genes in all isolates. T. Chebula had the lowest cytotoxicity, followed by E. caryophyllata and A. vera. T. Chebula also showed the best average selectivity index (SI) of 17.9, followed by E. caryophyllata (12.52). Extracts investigated in the present study had good antibacterial and antibiofilm activity against isolated sulfate-reducing bacteria isolated from patients' orthodontic appliances. Most of these extracts may be potential candidates for the development of antibacterial drugs.

Effects of metals on activity and community of sulfate-reducing bacterial enrichments and the discovery of a new heavy metal-resistant SRB from Santos Port sediment (São Paulo, Brazil).

Sulfate-reducing bacteria (SRB) can be used to remove metals from wastewater, sewage, and contaminated areas. However, metals can be toxic to this group of bacteria. Sediments from port areas present abundance of SRB and also metal contamination. Their microbial community has been exposed to metals and can be a good inoculum for isolation of metal-resistant SRB. The objective of the study was to analyze how metals influence activity and composition of sulfate-reducing bacteria. Enrichment cultures were prepared with a different metal (Zn, Cr, Cu, and Cd) range concentration tracking activity of SRB and 16S rRNA sequencing in order to access the community. The SRB activity decreased when there was an increase in the concentration of the metals tested. The highest concentration of metals precipitated were 0.2 mM of Cd, 5.4 mM of Zn, 4.5 mM of Cu, and 9.6 mM of Cr. The more toxic metals were Cd and Cu and had a greater community similarity with less SRB and more fermenters (e.g., Citrobacter and Clostridium). Meanwhile, the enrichments with less toxic metals (Cr and Zn) had more sequences affiliated to SRB genera (mainly Desulfovibrio). A new Desulfovibrio species was isolated. This type of study can be useful to understand the effects of metals in SRB communities and help to optimize wastewater treatment processes contaminated by metals. The new Desulfovibrio species may be important in future studies on bioremediation of neutral pH effluents contaminated by metals.

Isolation and Potency Test of Sulfate Reducing Bacteria (SRB) as Bioremediation Agent for Ex-Coal Mining Soil

Mining activities can have negative impact on the environment causing water and soil pollution. Chemical physical properties also biological environment to change condition to be low organic matter, low soil pH, low water holding capacity, inadequate nutrient and acid generating material. Coal mining land is acidic cause of sulfur oxidation reaction with rainwater to produce sulfuric acid so that acidic of the soil condition. Biotechnology study is a wise effort to solution environment pollution with Sulfate Reducing Bacteria (SRB) as bioremediation agents. SRB can contaminate sulphate with an indicator pH increase which indicates of a SRB population increase and sulfate content decrease. This study aims to obtain a SRB isolate as potential a bioremediation agent for ex-coal mining soil. This study is experiment research with SRB isolate as treatment, that obtained from ex-coal mining soil at PT. Bukit Asam Tanjung Enim, South Sumatera. The result of this study obtained 10 (ten) SRB isolated a from the bacterial isolation stage. Ten SRB isolates were selected, obtained by five SRB isolates that have black criteria with the number of colonies approaching the same so that it has the potential as a bioremediation agent for ex-coal mining soil. SRB isolates P 10 T 1 R 2 , P 9 T 2 R 2 , P 6 T 1 R 3 , P 5 T 1 R 1 dan P 2 T 1 R 2 were potential tested on ex-coal mining to increase pH and reduce sulfate. The P 5 T 1 R 1 SRB isolate has the potential to reduce sulfate at a concentration of 3561 ppm. Furthermore the result of the 5% LSD test show that this isolates is significantly different that other isolates so that it can be used as bioremediation agent.

Possible synergy effect of hydrogen sulfide and acetate produced by sulfate-reducing bacteria on inflammatory bowel disease development

IntroductionIncreased numbers of sulfate-reducing bacteria (SRB) are often found in the feces of people and animals with inflammatory bowel disease. The final products of their metabolism are hydrogen sulfide and acetate, which are produced during dissimilatory sulfate reduction process. ObjectivesThe aim of the study was to monitor processes concerning sulfate reduction microbial metabolisms, including: the main microbial genera monitoring and their hydrogen sulfide production in the intestines of healthy and not healthy individuals, phylogenetic analysis of SRB isolates, cluster analysis of SRB physiological and biochemical parameters, SRB growth kinetic parameters calculation, same as the application of the two-factor dispersion analysis for finding relationship between SRB biomass accumulation, temperature and pH. Feces samples from healthy people and patients with colitis were used for isolation of sulfate-reducing microbial communities. MethodsMicrobiological, biochemical, biophysical, molecular biology methods, and statistical processing of the results have been used for making an evaluation of gained results. ResultsTwo dominant SRB morphotypes differed in colony size and quantitative ratio in the feces of healthy and colitis patients were observed and identified. In the feces of healthy people, 93% of SRB of morphotype I prevailed (Desulfovibrio) while morphotype II made only 7% (Desulfomicrobium); in the feces of patients with colitis, the ratio of these morphotypes was 99:1, respectively. Hydrogen sulfide concentrations are also higher in the feces of people with colitis and certain synergy effects exist among acetate produced by SRB. ConclusionsThe study results brought important findings concerning colony environments with developed colitis and these findings can lead to the development of possible risk indicators of ulcerative colitis prevalence.

Potential sulfate reducing bacteria for decrease Fe and Mn determination agents on ex-coal mining soil in Samarinda

The aim of this study was to determine the potential of sulfate reducing bacteria (SRB) as reducing agents for decrease Fe and Mn in acid soils of coal mines using five isolates of isolated SRB from post-coal mining sediments in Samarinda. The SRB potential test in reducing Fe and Mn was carried out by growing SRB on liquid Postgate media with varying pH of 3, 4 and 5 with the addition of mine acid soil to each treatment. Each of the pure SRB isolates (1 ml) was inoculated into liquid Postgate media with different pH, namely pH 3, 4 and 5 which had previously been filled with 5 grams of acidic soil after coal mining which had been mashed and sterilized at 121°C for 15 minutes. The culture was incubated in a threaded tube of 10 ml volume to full. The results showed that five isolates of SRB from post-coal mine sediments in Samarinda were Desulfococcus sp., Desulfotomaculum sp., Desulfobacter sp., Desulfobulbus sp. and Desulfobacterium sp. have potential as reducing agents for decrease Fe and Mn in Postgate B liquid media which have been added with coal mine acid soils. The best efficiency of Fe reduction by Desulfobacterium sp. at pH 3 is 6% and the best Mn reduction by bacteria Desulfotomaculum sp. at pH 5 is 4%.

Nitrate reduction in sulfate-reducing bacteria

Sulfate-reducing bacteria (SRBs) gain their energy by coupling the oxidation of organic substrate to the reduction of sulfate to sulfide. Several SRBs are able to use alternative terminal electron acceptors to sulfate such as nitrate. Nitrate-reducing SRBs have been isolated from a diverse range of environments. In order to be able to understand the significance of nitrate reduction in SRBs, we need to examine the ecology and physiology of the nitrate-reducing SRB isolates.

Desulfovibrio desulfuricans isolates from the gut of a single individual: Structural and biological lipid A characterization

The levels of sulfate-reducing bacteria (SRB), including Desulfovibrionaceae, in the gut increase following a fat-enriched diet. Endotoxins from gut microbiota contribute to the inflammation process, leading to metabolic diseases. Thus, we sought to characterize the lipid A structures of Desulfovibrionaceae lipopolysaccharides (LPS) that are associated with the microbiota inflammatory properties. LPS variants were obtained from two SRB isolates from the gut of a single individual. These LPS variants shared similar lipid A moieties with Enterobacterial LPS, but differed from one another with regard to fatty-acid numbers and endotoxic activity. This first complete structural characterization of Desulfovibrio lipid A gives new insights into previously published data on Desulfovibrio lipid A biosynthesis. LPS microdiversity within SRBs illustrates how adaptation can influence pro-inflammatory potential.

Detection of Sulphate-Reducing Bacteria and Others Cultivable Facultative Bacteria in Dental Tissues

To detect for the presence of sulphate-reducing bacteria (SRB) and evaluate the possible association between SRB and cultivable facultative bacterial of oral sites with different periodontal conditions. The study was carried out on 9 samples from different oral sites in 8 patients (two samples were collected from the same patient). Material was collected using modified Postgate E culture medium, indicated for the growth and isolation of SRB. In addition, a reducing solution for anaerobic bacteria was used as a transport solution for facultative bacteria and identified by polymerase chain reaction amplification (PCR) and sequencing of the 16S rRNA gene. SRB was found in 3 patient samples: the first in a root fragment, the second in a root fragment and a healthy tooth with vertical bone loss and a mobility degree of 3; and the third in a healthy tooth extracted for orthodontic treatment. In the final patient, the cultivable facultative species Lactobacillus casei was identified. Other facultative bacterial species were identified in patient 5 (Kurthia Gibsonii) and patient 7 (Pseudomonas aeruginosa). The detection of SRB in different dental tissues with distinct periodontal features demonstrated that new studies need to be developed in order to determine the true role of SRB in the oral microbiota. In addition, it was possible to verify the presence of Lactobacillus casei together with SRB in one sample.

Isolation of Sulfate-Reducing Bacteria from Sediments Above the Deep-Subseafloor Aquifer

On a global scale, crustal fluids fuel a large part of the deep-subseafloor biosphere by providing electron acceptors for microbial respiration. In this study, we examined bacterial cultures from sediments of the Juan de Fuca Ridge, Northeast Pacific (IODP Site U1301). The sediments comprise three distinctive compartments: an upper sulfate-containing zone, formed by bottom-seawater diffusion, a sulfate-depleted zone, and a second (∼140 m thick) sulfate-containing zone influenced by fluid diffusion from the basaltic aquifer. In order to identify and characterize sulfate-reducing bacteria, enrichment cultures from different sediment layers were set up, analyzed by molecular screening, and used for isolating pure cultures. The initial enrichments harbored specific communities of heterotrophic microorganisms. Strains affiliated to Desulfosporosinus lacus, Desulfotomaculum sp., and Desulfovibrio aespoeensis were isolated only from the top layers (1.3–9.1 meters below seafloor, mbsf), while several strains of Desulfovibrio indonesiensis and a relative of Desulfotignum balticum were obtained from near-basement sediments (240–262 mbsf). Physiological tests on three selected strains affiliated to Dv. aespoeensis, Dv. indonesiensis, and Desulfotignum balticum indicated that all reduce sulfate with a limited number of short-chain n-alcohols or fatty acids and were able to ferment either ethanol, pyruvate, or betaine. All three isolates shared the capacity of growing chemolithotrophically with H2 as sole electron donor. Strain P23, affiliating with Dv. indonesiensis, even grew autotrophically in the absence of any organic compounds. Thus, H2 might be an essential electron donor in the deep-subseafloor where the availability of organic substrates is limited. The isolation of non-sporeforming sulfate reducers from fluid-influenced layers indicates that they have survived the long-term burial as active populations even after the separation from the seafloor hundreds of meters above.

Culturable diversity of lithotrophic haloalkaliphilic sulfate-reducing bacteria in soda lakes and the description of Desulfonatronum thioautotrophicum sp. nov., Desulfonatronum thiosulfatophilum sp. nov., Desulfonatronovibrio thiodismutans sp. nov., and Desulfonatronovibrio magnus sp. nov.

Soda lake sediments usually contain high concentrations of sulfide indicating active sulfate reduction. Monitoring of sulfate-reducing bacteria (SRB) in soda lakes demonstrated a dominance of two groups of culturable SRB belonging to the order Desulfovibrionales specialized in utilization of inorganic electron donors, such as formate, H2 and thiosulfate. The most interesting physiological trait of the novel haloalkaliphilic SRB isolates was their ability to grow lithotrophically by dismutation of thiosulfate and sulfite. All isolates were obligately alkaliphilic with a pH optimum at 9.5–10 and moderately salt tolerant. Among the fifteen newly isolated strains, four belonged to the genus Desulfonatronum and the others to the genus Desulfonatronovibrio. None of the isolates were closely related to previously described species of these genera. On the basis of phylogenetic, genotypic and phenotypic characterization of the novel soda lake SRB isolates, two novel species each in the genera Desulfonatronum and Desulfonatronovibrio are proposed.Electronic supplementary materialThe online version of this article (doi:10.1007/s00792-011-0370-7) contains supplementary material, which is available to authorized users.

イオウを利用する素材プロセッシング（ＩＩ）活性汚泥から単離された硫酸還元細菌の特性評価と硫化水素生成

This paper describes hydrogen sulfide generation, isolation and characterization of sulfate-reducing bacteria in the activated sludge obtained from wastewater treatment plant. The sludge, collected from aerobic treatment system, was used as inoculums for hydrogen sulfide generation and for isolation of sulfate-reducing bacteria. Hydrogen sulfide was generated when the sludge was inoculated into a pH controlled medium. Two strains G2 and G3 of sulfate-reducing bacteria were isolated from the sludge. The characteristics and identification of these isolates was based on culture of the experiments and molecular analysis. Reduced sulfate rates in G2 and G3 is 0.39 and 0.41 mmol/dm3 respectively. Two isolates located in the genus Desulfovibrio in the phylogenetic tree based. First one was 16S rRNA gene analysis with the highest homology, 96.6 %, as Desulfovibrio carbinoliphilus (DSM 17524T) . However, the branch of the isolates was separated from the relatives and no strain was recognized in this branch. Also the dsr gene of isolate G3 had the highest homology with Desulfovibrio fructosovorans (DSM 3604T) , 92.7 %. The isolates G2 and G3 belonged to the genus Desulfovibrio as confirmed by the results of these analyses, however, these isolates oxidized organic compounds to carbon dioxide completely although relative strain oxidized it completely. Therefore, these isolates have high possibility that they should be recognized as a new strain.

Isolation of sulfate-reducing bacteria from Tunisian marine sediments and description of Desulfovibrio bizertensis sp. nov.

Several strains of sulfate-reducing bacteria were isolated from marine sediments recovered near Tunis, Korbous and Bizerte, Tunisia. They all showed characteristics consistent with members of the genus Desulfovibrio. One of these strains, designated MB3(T), was characterized further. Cells of strain MB3(T) were slender, curved, vibrio-shaped, motile, Gram-negative, non-spore-forming rods. They were positive for desulfoviridin as bisulfite reductase. Strain MB3(T) grew at temperatures of 15-45 degrees C (optimum 40 degrees C) and at pH 6.0-8.1 (optimum pH 7.0). NaCl was required for growth (optimum 20 g NaCl l(-1)). Strain MB3(T) utilized H(2) in the presence of acetate with sulfate as electron acceptor. It also utilized lactate, ethanol, pyruvate, malate, fumarate, succinate, butanol and propanol as electron donors. Lactate was oxidized incompletely to acetate. Strain MB3(T) fermented pyruvate and fumarate (poorly). Electron acceptors utilized included sulfate, sulfite, thiosulfate, elemental sulfur and fumarate, but not nitrate or nitrite. The G+C content of the genomic DNA was 51 mol%. On the basis of genotypic, phenotypic and phylogenetic characteristics, strain MB3(T) (=DSM 18034(T)=NCIMB 14199(T)) is proposed as the type strain of a novel species, Desulfovibrio bizertensis sp. nov.

Characterization of bacterial community associated to biofilms of corroded oil pipelines from the southeast of Mexico

Microbial communities associated to biofilms promote corrosion of oil pipelines. The community structure of bacteria in the biofilm formed in oil pipelines is the basic knowledge to understand the complexity and mechanisms of metal corrosion. To assess bacterial diversity, biofilm samples were obtained from X52 steel coupons corroded after 40 days of exposure to normal operation and flow conditions. The biofilm samples were directly used to extract metagenomic DNA, which was used as template to amplify 16S ribosomal gene by PCR. The PCR products of 16S ribosomal gene were also employed as template for sulfate-reducing bacteria (SRB) specific nested-PCR and both PCR products were utilized for the construction of gene libraries. The V3 region of the 16S rRNA gene was also amplified to analyse the bacterial diversity by analysis of denaturing gradient gel electrophoresis (DGGE). Ribosomal library and DGGE profiles exhibited limited bacterial diversity, basically including Citrobacter spp., Enterobacter spp. and Halanaerobium spp. while Desulfovibrio alaskensis and a novel clade within the genus Desulfonatronovibrio were detected from the nested PCR library. The biofilm samples were also taken for the isolation of SRB. Desulfovibrio alaskensis and Desulfovibrio capillatus, as well as some strains related to Citrobacter were isolated. SRB consists in a very small proportion of the community and Desulfovibrio spp. were the relatively abundant groups among the SRB. This is the first study directly exploring bacterial diversity in corrosive biofilms associated to steel pipelines subjected to normal operation conditions.

Isolation of Sulfate-Reducing Bacteria from the Terrestrial Deep Subsurface and Description of Desulfovibrio cavernae sp. nov.

Deep subsurface sandstones in the area of Berlin (Germany) located 600 to 1060 m below the surface were examined for the presence of viable microorganisms. The in situ temperatures at the sampling sites ranged from 37 to 45 degrees C. Investigations focussed on sulfate-reducing bacteria able to grow on methanol and triethylene glycol, which are added as chemicals to facilitate the long-term underground storage of natural gas. Seven strains were isolated from porewater brines in the porous sandstone. Three of them were obtained with methanol (strains H1M, H3M, and B1M), three strains with triethylene glycol (strains H1T, B1T, and B2T) and one strain with a mixture of lactate, acetate and butyrate (strain H1-13). Due to phenotypic properties six isolates could be identified as members of the genus Desulfovibrio, and strain B2T as a Desulfotomaculum. The salt tolerance and temperature range for growth indicated that the isolates originated from the indigenous deep subsurface sandstones. They grew in mineral media reflecting the in situ ionic composition of the different brines, which contained 1.5 to 190 g NaCl x l(-1) and high calcium and magnesium concentrations. The Desulfovibrio strains grew at temperatures between 20 and 50 degrees C, while the Desulfotomaculum strain was thermophilic and grew between 30 and 65 degrees C. The strains utilized a broad spectrum of electron donors and acceptors. They grew with carbon compounds like lactate, pyruvate, formate, n-alcohols (C1-C5), glycerol, ethylene glycol, malate, succinate, and fumarate. Some strains even utilized glucose as electron donor and carbon source. All strains were able to use sulfate, sulfite and nitrate as electron acceptors. Additionally, three Desulfovibrio strains reduced manganese oxide, the Desulfotomaculum strain reduced manganese oxide, iron oxide, and elemental sulfur. The 16S rRNA analysis revealed that the isolates belong to three different species. The strains H1T, H3M and B1M could be identified as Desulfovibrio indonesiensis, and strain B2T as Desulfotomaculum geothermicum. The other Desulfovibrio strains (H1M, H1-13, and B1T) showed identical 16S rDNA sequences and similarities as low as 93% to their closest relative, Desulfovibrio aminophilusT. Therefore, these isolates were assigned to a new species, Desulfovibrio cavernae sp. nov., with strain H1M as the type strain.

Isolation of sulfate-reducing bacteria from human thoracoabdominal pus.

To evaluate the prevalence of sulfate-reducing bacteria in septic processes, we searched for these bacteria by culture in 100 consecutive abdominal and pleural pus specimens. Twelve isolates were obtained from abdominal samples and were identified by a multiplex PCR as Desulfovibrio piger (formerly Desulfomonas pigra) (seven strains), Desulfovibrio fairfieldensis (four strains), and Desulfovibrio desulfuricans (one strain).

Isolation of the provisionally named Desulfovibrio fairfieldensis from human periodontal pockets.

Sulfate-reducing bacteria have recently been associated with periodontitis and proposed to play a role in the pathogenesis of this chronic inflammatory process. Eight isolates of sulfate-reducing bacteria belonging to the genus Desulfovibrio were obtained from the periodontal pockets of five out of seven patients presenting with active periodontitis. A multiplex PCR was devised for their identification at the species level. All isolates were identified as Desulfovibrio fairfieldensis, a recently proposed new species. This finding reinforces the suggestion that Desulfovibrio fairfieldensis is a human bacterium that may present a pathogenic potential.

Physiological properties of a sulfate-reducing bacterium isolated from municipal sewage sludge and its possible role as a syntrophic acidogen in the ecosystem.

Three strains of sulfate-reducing bacteria utilizing H2 as the electron donor of sulfate reduction were isolated from anaerobic digester slurry of municipal sewage sludge. The isolates were Gram-negative, non-spore- forming, motile, curved rods with a single polar flagellum. Cytochrome c3 and desulfoviridin were present. The DNA base compositions (mol% Three strains of sulfate-reducing bacteria utilizing H2 as the electron donor of sulfate reduction were isolated from anaerobic digester slurry of municipal sewage sludge. The isolates were Gram-negative, non-spore-forming, motile, curved rods with a single polar flagellum. Cytochrome c3 and desulfoviridin were present. The DNA base compositions (mol%G+C) were 59.6±0.7). The isolates used H2, formate, lactate, pyruvate, fumarate, malate, alcohols and amino acids as the electron donor for sulfate reduction. Alcohols were oxidized to corresponding monocarboxylates, and other organic compounds were to acetate. Sulfate, Three strains of sulfate-reducing bacteria utilizing H2 as the electron donor of sulfate reduction were isolated from anaerobic digester slurry ofmunicipal sewage sludge. The isolates were Gram-negative, non-spore-forming, motile, curved rods with a single polar flagellum. Cytochrome c3 and desulfoviridin were present. The DNA base compositions (mol% G+C) were 59.6±0.7. The isolates used H2, formate, lactate, pyruvate, fumarate, malate, alcohols and amino acids as the electron donor for sulfate reduction. Alcohols were oxidized to corresponding monocarboxylates, and other organic compounds were to acetate. Sulfate, sulfite and thiosulfate, but not nitrate, were used as the electron acceptor and reduced to sulfide. The isolates grew with pyruvate, fumarate, or malate as the energy source in the absence of oxidized sulfur compounds. yruvate was oxidized to acetate with the production of formate and H2. Fumarate and malate were oxidized to acetate, and the oxidation was coupled with the reduction of fumarate or malate to succinate. From the morphological and physiological properties, the isolates were considered to belong to a Desulfovibrio sp. In association with Methanobacterium formicicum as a hydrogen-consuming partner, one of the isolates could also grow in the absence of oxidized sulfur compounds by utilizing organic substrates other than pyruvate, malate and fumarate. In the coculture of the isolate and the methanogen, all the organic compounds other than malate and fumarate, which could serve as the electron donor for sulfate reduction in the pure culture of isolates, were syntrophically oxidized with the production of methane. These results indicate that the isolates of sulfate-reducing bacteria can play a role as a syntrophic degrader of a wide range of organic compounds in the methanogenic sewage sludge devoid of sulfate.

Sulfate-reducing bacteria in the periodontal pocket.

This report is the first to describe the occurrence of sulfate-reducing bacteria in the human mouth. Samples of subgingival dental plaque were examined for the presence of sulfate-reducing bacteria. Using enrichment cultures, sulfate-reducing bacteria were detected in 25 (58%) of 43 individuals, and in 39 (48%) of the 82 samples. Pure isolates of sulfate-reducing bacteria, obtained from a limited number of enrichment cultures, belonged to the genera Desulfobacter and Desulfovibrio. These genera are also the predominant sulfate-reducing bacteria in the human large intestine. The sulfate-reducing bacteria use sulfate as terminal electron acceptor to oxidize low-molecular-weight organic compounds, mainly products of microbial fermentation such as acetate, lactate etc. The numbers of sulfate-reducing bacteria in the mouth are assumed to be limited by sulfate. Potential sources of sulfate in the subgingival area include free sulfate in pocket fluid and glycosaminoglycans from periodontal tissues.