RESUMO
Trichloroethylene (TCE) is known as a toxic organic compound found as a pollutant in water streams around the world. The ultimate goal of the present work was to determine the TCE concentration that would be feasible to biodegrade on a long-term basis by a sulfidogenic sludge while maintaining sulfate reducing activity (SRA). Microcosms were prepared with sulfidogenic sludge obtained from a stabilized sulfidogenic UASB and amended with different TCE concentrations (100-300 µM) and two different proportions of volatile fatty acids (VFA) acetate, propionate and butyrate at COD of 2.5:1:1 and 1:1:1, respectively to evaluate the tolerance of the sludge. The overall results suggested that the continuous exposure of the microorganisms to TCE leads to inhibition of SRA; nonetheless, the SRA can be recovered after adequate supplementation of carbon sources and sulfate. The most suitable TCE concentration to operate on a long-term basis while preserving SRA was 26-35 mg L-1 (200-260 µM). A low level of expression of the mRNA of the sulfite reductase subunit alpha (dsrA) gene was obtained in the presence of the TCE and its intermediate products. This gene was associated to SRB belonging to the genera Desulfovibrio, Desulfosalsimonas, Desulfotomaculum, Desulfococcus, Desulfatiglans and Desulfomonas.
Assuntos
Reatores Biológicos/microbiologia , Esgotos , Bactérias Redutoras de Enxofre/efeitos dos fármacos , Tricloroetileno/toxicidade , Poluentes Químicos da Água/toxicidade , Adaptação Fisiológica , Biodegradação Ambiental , Ácidos Graxos Voláteis/metabolismo , Estudos de Viabilidade , Genes Bacterianos , Esgotos/química , Esgotos/microbiologia , Sulfatos/metabolismo , Bactérias Redutoras de Enxofre/genética , Fatores de Tempo , Tricloroetileno/análise , Poluentes Químicos da Água/análiseRESUMO
Sulfate-reducing bacteria (SRB) play an important role in the sediments of bay areas, estuaries, and lakes. However, information regarding the genetic diversity of SRB in the sediments of drinking water reservoirs is scarce. In this study, we collected sediment samples from different sites in the Zhou Cun drinking water reservoir between April and June 2012. To explore the genetic diversity of SRB, we used the most-probable-number (MPN) method, polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE), and a cloning approach. The average content of acid-volatile sulfide at the deepest sampling site was 205.87 µg/g sediment. This result is often associated with a large abundance of SRB in the associated sediment. The highest MPN estimate (1.15 x 10(5) cells/g sediment) was detected in May at the deepest sampling site. The PCR-DGGE fingerprints of SRB based on the dissimilatory sulfite reductase beta subunit (dsrB) gene varied according to the different sampling sites and dates. The highest abundance of SRB in the sediments was predominantly found at the deepest sampling sites, as expected from the acid-volatile sulfide content. The dominant species were Desulfobulbus sp, Desulfobacterium sp, and uncultured sulfate-reducing bacteria. Redundancy analysis revealed that organic matter and the concentrations of nitrogen and phosphorus in the sediments were significantly correlated with the diversity of SRB communities present. The results of this study provide a better understanding of the sulfate-reducing microbial species in the sediments of the Zhou Cun drinking water reservoir.
Assuntos
Variação Genética , Sulfito de Hidrogênio Redutase/genética , Sulfatos/metabolismo , Bactérias Redutoras de Enxofre/genética , China , Água Potável/química , Água Potável/microbiologia , Sedimentos Geológicos , Filogenia , RNA Ribossômico 16S/genética , Bactérias Redutoras de Enxofre/metabolismoRESUMO
Three strains of sulfate-reducing bacteria (M1(T), D, and E) were isolated from acidic sediments (White river and Tinto river) and characterized phylogenetically and physiologically. All three strains were obligately anaerobic, mesophilic, spore-forming straight rods, stained Gram-negative and displayed variable motility during active growth. The pH range for growth was 3.8-7.0, with an optimum at pH 5.5. The temperature range for growth was 15-40 °C, with an optimum at 30 °C. Strains M1(T), D, and E used a wide range of electron donors and acceptors, with certain variability within the different strains. The nominated type strain (M1(T)) used ferric iron, nitrate, sulfate, elemental sulfur, and thiosulfate (but not arsenate, sulfite, or fumarate) as electron acceptors, and organic acids (formate, lactate, butyrate, fumarate, malate, and pyruvate), alcohols (glycerol, methanol, and ethanol), yeast extract, and sugars (xylose, glucose, and fructose) as electron donors. It also fermented some substrates such as pyruvate and formate. Strain M1(T) tolerated up to 50 mM ferrous iron and 10 mM aluminum, but was inhibited by 1 mM copper. On the basis of phenotypic, phylogenetic, and genetic characteristics, strains M1(T), D, and E represent a novel species within the genus Desulfosporosinus, for which the name Desulfosporosinus acididurans sp. nov. is proposed. The type strain is M1(T) (=DSM 27692(T) = JCM 19471(T)). Strain M1(T) was the first acidophilic SRB isolated, and it is the third described species of acidophilic SRB besides Desulfosporosinus acidiphilus and Thermodesulfobium narugense.
Assuntos
Sedimentos Geológicos/microbiologia , Filogenia , Bactérias Redutoras de Enxofre/classificação , Bactérias Redutoras de Enxofre/fisiologia , Anaerobiose , Técnicas de Tipagem Bacteriana , DNA Bacteriano/genética , Genômica , Bactérias Gram-Negativas/classificação , Bactérias Gram-Negativas/genética , Bactérias Gram-Negativas/fisiologia , Concentração de Íons de Hidrogênio , Microscopia de Contraste de Fase , Oxigênio/química , RNA Ribossômico 16S/genética , Rios , Espanha , Sulfatos/química , Bactérias Redutoras de Enxofre/genética , Temperatura , Índias OcidentaisRESUMO
OBJECTIVE: The aim of the current study was to investigate the presence of sulphate-reducing bacteria (SRB) in human saliva and correlate with oral and systemic conditions. METHODS: Saliva samples were collected from 118 patients and inoculated in 2 ml of modified Postgate's E medium culture. After 28 days of incubation at 30°C the presence of SRB was identified by the production of sulphide. RESULTS: Of 118 saliva samples collected, 35 were positive for the presence of SRB. Three positive samples were randomly chosen to identify the species of SRB by PCR and sequenced. The three selected samples were identified as Desulfovibrio fairfieldensis, Desulfovibrio desulfuricans and Raoultella ornithinolytica. Gastritis (14.4%) was the most prevalent systemic disease, followed by diabetes (3.4%), while periodontitis (11%) and traumatic fibroma (4.2%) were the oral manifestations most frequently found. A bivariate analysis was performed to examine for the presence of SRB and the most prevalent systemic and oral manifestations. Only periodontitis showed a statistically significant association (p = 0.0003). CONCLUSIONS: The results showed SRB can be found in oral microbiota of healthy patients. Regarding the several conditions studied, there was a higher prevalence of SRB in patients with gastritis and patients with periodontal disease, with a possible correlation between the presence of SRB in the oral microbiota and periodontal disease.
Assuntos
Saliva/microbiologia , Bactérias Redutoras de Enxofre/isolamento & purificação , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Sequência de Bases , Criança , Primers do DNA , Humanos , Pessoa de Meia-Idade , Reação em Cadeia da Polimerase , RNA Ribossômico 16S/genética , Especificidade da Espécie , Bactérias Redutoras de Enxofre/classificação , Bactérias Redutoras de Enxofre/genética , Adulto JovemRESUMO
Cultivation and molecular-based approaches were used to study microbial diversity in two Chilean marine sediments contaminated with high (835 ppm) and very high concentrations of copper (1,533 ppm). The diversity of cultivable bacteria resistant to copper was studied at oxic and anoxic conditions, focusing on sulfate-, thiosulfate-, and iron-reducing bacteria. For both sediments, the cultivable bacteria isolated at oxic conditions were mostly affiliated to the genus Bacillus, while at anoxic conditions the majority of the cultivable bacteria found were closely related to members of the genera Desulfovibrio, Sphingomonas, and Virgibacillus. Copper resistance was between 100 and 400 ppm, with the exception of a strain affiliated to members of the genus Desulfuromonas, which was resistant up to 1,000 ppm of copper. In parallel, cloning and sequencing of 16S rRNA was performed to study the total bacterial diversity in the sediments. A weak correlation was observed between the isolated strains and the 16S rRNA operational taxonomic units detected. The presence of copper resistance genes (copA, cusA, and pcoA) was tested for all the strains isolated; only copA was detected in a few isolates, suggesting that other copper resistance mechanisms could be used by the bacteria in those highly copper-contaminated sediments.
Assuntos
Bactérias/isolamento & purificação , Biodiversidade , Cobre/análise , Sedimentos Geológicos/microbiologia , Poluentes da Água/análise , Bactérias/classificação , Bactérias/genética , Chile , Biblioteca Gênica , Genes Bacterianos , Sedimentos Geológicos/química , Filogenia , RNA Ribossômico 16S/genética , Água do Mar/química , Água do Mar/microbiologia , Bactérias Redutoras de Enxofre/classificação , Bactérias Redutoras de Enxofre/genética , Bactérias Redutoras de Enxofre/isolamento & purificação , Microbiologia da ÁguaRESUMO
We studied the abundance and diversity of the sulfate-reducing prokaryotes (SRPs) in two 30-cm marine chilean sediment cores, one with a long-term exposure to copper-mining residues, the other being a non-exposed reference sediment. The abundance of SRPs was quantified by qPCR of the dissimilatory sulfite reductase gene ß-subunit (dsrB) and showed that SRPs are sensitive to high copper concentrations, as the mean number of SRPs all along the contaminated sediment was two orders of magnitude lower than in the reference sediment. SRP diversity was analyzed by using the dsrB-sequences-based PCR-DGGE method and constructing gene libraries for dsrB-sequences. Surprisingly, the diversity was comparable in both sediments, with dsrB sequences belonging to Desulfobacteraceae, Syntrophobacteraceae, and Desulfobulbaceae, SRP families previously described in marine sediments, and to a deep branching dsrAB lineage. The hypothesis of the presence of horizontal transfer of copper resistance genes in the microbial population of the polluted sediment is discussed.
Assuntos
Cobre/toxicidade , Sedimentos Geológicos/microbiologia , Bactérias Redutoras de Enxofre/genética , Poluentes Químicos da Água/toxicidade , Sequência de Bases , Biodiversidade , Chile , Variação Genética , Sedimentos Geológicos/química , Dados de Sequência Molecular , Células Procarióticas/classificação , Células Procarióticas/efeitos dos fármacos , Água do Mar/química , Água do Mar/microbiologia , Bactérias Redutoras de Enxofre/classificação , Bactérias Redutoras de Enxofre/efeitos dos fármacos , Bactérias Redutoras de Enxofre/crescimento & desenvolvimentoRESUMO
Intestinal methanogenesis is one of the major pathways for consumption of hydrogen produced by bacterial fermentation and is considered to affect the efficiency of host energy harvest; however, little information is available regarding the hydrogenotrophic pathways of nonhuman primates in the wild, in general, and of howler monkeys, in particular. Microbial fermentation of plant structural carbohydrates is an important feature in wild howlers owing to the high fiber and low available energy content of leaves, which make up the primary component of their diet. In contrast, captive howlers may consume greater quantities of fruits and vegetables that are higher in water, lower in fiber, and, along with commercial monkey chow commonly added to captive monkey diets, more readily digestible than the natural diet. In this study, we analyzed the composition of methanogens and sulfate-reducing bacteria (SRB) from fecal samples of black howler monkeys (Alouatta pigra) in the wild and in captivity. The hydrogenotrophic microbiota of three groups of monkeys was evaluated by PCR-denaturing gradient gel electrophoresis (DGGE) fingerprinting, small clone library construction, and quantitative real-time PCR. Abundance of methanogens was lower than SRB in all howler monkey groups studied. DGGE banding patterns were highly similar within each wild and captive group but distinct among groups. Desulfovibrionales-enriched DGGE showed reduced microbial diversity in the captive animals compared with their wild counterparts. Taken together, the data demonstrate that environmental or dietary changes of the host imposed by captivity likely influence the composition of intestinal hydrogenotrophs in black howler monkeys.
Assuntos
Alouatta/microbiologia , Fezes/microbiologia , Variação Genética/genética , Metagenoma/genética , Methanobacterium/genética , Bactérias Redutoras de Enxofre/genética , Animais , Animais Selvagens , Animais de Zoológico , DNA Arqueal/química , DNA Arqueal/genética , Eletroforese em Gel de Campo Pulsado/veterinária , Feminino , Masculino , México , Reação em Cadeia da Polimerase/veterinária , Análise de Componente Principal , RNA Ribossômico 16S/química , RNA Ribossômico 16S/genéticaRESUMO
Sulfate reducing bacteria (SRB) are important mercury methylators in sediments, but information on mercury methylators in other compartments is ambiguous. To investigate SRB involvement in methylation in Amazonian periphyton, the relationship between Hg methylation potential and SRB (Desulfobacteraceae, Desulfobulbaceae and Desulfovibrionaceae) abundance in Eichhornia crassipes and Polygonum densiflorum root associated periphyton was examined. Periphyton subsamples of each macrophyte were amended with electron donors (lactate, acetate and propionate) or inhibitors (molybdate) of sulfate reduction to create differences in SRB subgroup abundance, which was measured by quantitative real-time PCR with primers specific for the 16S rRNA gene. Mercury methylation and demethylation potentials were determined by a stable isotope tracer technique using 200HgCl and CH3(202)HgCl, respectively. Relative abundance of Desulfobacteraceae (<0.01-12.5%) and Desulfovibrionaceae (0.01-6.8%) were both highly variable among samples and subsamples, but a significant linear relationship (p<0.05) was found between Desulfobacteraceae abundance and net methylmercury formation among treatments of the same macrophyte periphyton and among all P. densiflorum samples, suggesting that Desulfobacteraceae bacteria are the most important mercury methylators among SRB families. Yet, molybdate only partially inhibited mercury methylation potentials, suggesting the involvement of other microorganisms as well. The response of net methylmercury production to the different electron donors and molybdate was highly variable (3-1104 pg g(-1) in 12 h) among samples, as was the net formation in control samples (17-164 pg g(-1) in 12 h). This demonstrates the importance of community variability and complexity of microbial interactions for the overall methylmercury production in periphyton and their response to external stimulus.
Assuntos
Eichhornia/microbiologia , Compostos de Metilmercúrio/metabolismo , Polygonum/microbiologia , Bactérias Redutoras de Enxofre/metabolismo , Poluentes Químicos da Água/metabolismo , Bolívia , Desulfurococcaceae/genética , Desulfurococcaceae/metabolismo , Eichhornia/metabolismo , Metilação , Raízes de Plantas/metabolismo , Raízes de Plantas/microbiologia , Polygonum/metabolismo , Rizosfera , Bactérias Redutoras de Enxofre/genéticaRESUMO
The deep subseafloor rock in oil reservoirs represents a unique environment in which a high oilcontamination and very low biomass can be observed. Sampling this environment has been a challenge owing to the techniques used for drilling and coring. In this study, the facilities developed by the Brazilian oil company PETROBRAS for accessing deep subsurface oil reservoirs were used to obtain rock samples at 2,822-2,828 m below the ocean floor surface from a virgin field located in the Atlantic Ocean, Rio de Janeiro. To address the bacterial diversity of these rock samples, PCR amplicons were obtained using the DNA from four core sections and universal primers for 16S rRNA and for APS reductase (aps) genes. Clone libraries were generated from these PCR fragments and 87 clones were sequenced. The phylogenetic analyses of the 16S rDNA clone libraries showed a wide distribution of types in the domain bacteria in the four core samples, and the majority of the clones were identified as belonging to Betaproteobacteria. The sulfate-reducing bacteria community could only be amplified by PCR in one sample, and all clones were identified as belonging to Gammaproteobacteria. For the first time, the bacterial community was assessed in such deep subsurface environment.
Assuntos
Ecossistema , Sedimentos Geológicos/microbiologia , Proteobactérias , Água do Mar/microbiologia , Oceano Atlântico , Brasil , Clonagem Molecular , DNA Bacteriano/análise , DNA Bacteriano/isolamento & purificação , Biblioteca Gênica , Oxirredutases atuantes sobre Doadores de Grupo Enxofre/genética , Petróleo , Filogenia , Reação em Cadeia da Polimerase , Proteobactérias/classificação , Proteobactérias/genética , Proteobactérias/isolamento & purificação , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Sulfatos/metabolismo , Bactérias Redutoras de Enxofre/classificação , Bactérias Redutoras de Enxofre/genética , Bactérias Redutoras de Enxofre/isolamento & purificaçãoRESUMO
The anaerobic oxidation of methane (AOM) in the marine subsurface is a significant sink for methane in the environment, yet our understanding of its regulation and dynamics is still incomplete. Relatively few groups of microorganisms consume methane in subsurface environments--namely the anaerobic methanotrophic archaea (ANME clades 1, 2 and 3), which are phylogenetically related to methanogenic archaea. Anaerobic oxidation of methane presumably proceeds via a 'reversed' methanogenic pathway. The ANME are generally associated with sulfate-reducing bacteria (SRB) and sulfate is the only documented final electron acceptor for AOM in marine sediments. Our comparative study explored the coupling of AOM with sulfate reduction (SR) and methane generation (MOG) in microbial communities from Gulf of Mexico cold seep sediments that were naturally enriched with methane and other hydrocarbons. These sediments harbour a variety of ANME clades and SRB. Following enrichment under an atmosphere of methane, AOM fuelled 50-100% of SR, even in sediment slurries containing petroleum-associated hydrocarbons and organic matter. In the presence of methane and sulfate, the investigated microbial communities produce methane at a small fraction ( approximately 10%) of the AOM rate. Anaerobic oxidation of methane, MOG and SR rates decreased significantly with decreasing concentration of methane, and in the presence of the SR inhibitor molybdate, but reacted differently to the MOG inhibitor 2-bromoethanesulfonate (BES). The addition of acetate, a possible breakdown product of petroleum in situ and a potential intermediate in AOM/SR syntrophy, did not suppress AOM activity; rather acetate stimulated microbial activity in oily sediment slurries.