RESUMO

Sulphate reducing bacteria (SRB) offer promise for the treatment of mine waste due to their effectiveness removing toxic heavy metals as highly insoluble metal sulphides and their ability to generate alkalinity. The main objective of this study was to develop a treatment composed of a sulphate-reducing bioreactor with a limestone precolumn for the removal of Cu(II) from a synthetic ARD. The purpose of the limestone column was to increase the pH values and decrease the level of Cu in the effluent to prevent SRB inhibition. The system was fed with a pH-2.7 synthetic ARD containing Cu(II) (10-40 mg/L), sulphate (2000 mg/L) and acetate (2.5 g COD/L) for 150 days. Copper removal efficiencies in the two-stage system were very high (95-99%), with a final concentration of 0.53 mg/L Cu, and almost complete removal occurred in the limestone precolumn. In the same manner, the acidity of the synthetic ARD was effectively reduced in the limestone precolumn to 7.3 and the pH was raised in the bioreactor (7.3-8.0). COD consumption by methanogens was predominant from day 0-118, but SRB dominated at the end of the experiment (day 150) when the average COD removal and sulphide production were 74.8% and 61.7%, respectively. Study of the microbial taxonomic composition in the bioreactor revealed that Methanosarcina and Methanosaeta were the most prevalent methanogens while the genera Desulfotomaculum and Syntrophobacter were the dominant SRB. Among the SRB identified Desulfotomaculum intricatum (99% identity) and Desulfotomaculum acetoxidans (96%) were the most abundant sequences of bacteria capable of using acetate.

Assuntos

RESUMO

Sulphate-reducing bacteria are commonly associated with biological causes of oil well souring. Biosulphetogenesis can directly affect oil quality and storage due to the accumulation of sulphides. In addition, these microorganisms can create bio-incrustation that can clog pipes. Sulphite reductase (SIR) is the enzyme responsible for converting ion sulphite into sulphide and several substances may interfere or control such activity. This interference can hinder growth of the sulphate-reducing bacteria and, consequently, it reduces sulphide accumulation in situ. This work focuses on molecular modelling techniques along with in vitro experiments in order to investigate the potential of two essential oils and one vegetable oil as main inhibitors of sulphite reductase activity. Docking simulation identified several substances present in Rosmarinus officinalis, Tea tree and Neem extractable oils as potential inhibitors of SIR. Substances present in Neem vegetable oil are the most potent inhibitors, followed by Rosmarinus officinalis and Tea tree essential oils. The Neem oil mixture showed a superior effectiveness in intracellular SIR inhibitory effects.

Assuntos

RESUMO

RESUMO O controle do crescimento microbiano é um desafio crescente na produção de petróleo e gás, uma vez que a presença de determinadas bactérias traz impactos econômica e ambientalmente negativos. As bactérias redutoras de sulfato (BRS) são particularmente problemáticas, uma vez que são responsáveis pela corrosão biológica ligada à produção de sulfeto de hidrogênio, efeito conhecido como souring. A principal forma de controle das BRS atualmente é a injeção de biocidas, no entanto essa estratégia, além de requerer aplicação contínua, tem se revelado pouco efetiva na eliminação de biofilmes e é associada a um alto risco de contaminação das águas. Portanto, é necessário que se busquem abordagens mais eficientes e específicas em relação ao controle microbiológico. O uso de vírus bacteriófagos vem ao encontro dessas necessidades, pois eles, após se multiplicarem, geralmente provocam a lise celular, liberando novas partículas virais e evitando que a bactéria se prolifere. Diante disso, este estudo propõe estabelecer um método para a concentração e a determinação da eficiência de recuperação de bacteriófagos de BRS presentes em água de reator oriunda de poços de petróleo. As amostras foram coletadas de dois reatores operados em batelada alimentada e que simulam um poço de petróleo. As amostras de água de reator foram primeiramente clarificadas, os vírus eluídos desse sedimento e, em seguida, concentrados por ultracentrifugação. O concentrado viral foi então purificado com Vertrel XF. Ensaios de semeadura experimental de miofago P1 nas amostras de água do reator revelaram taxa de recuperação viral de 27,7%, contra ao 16% obtidos com outros protocolos.

ABSTRACT The control of microbial growth is an increasing challenge in the production of oil and gas, since the presence of certain bacteria has economic and environmental negative impacts. Sulphate reducing bacteria are particularly problematic, since they are responsible for the biological corrosion associated with the production of hydrogen sulfide, an effect known as souring. The main form of control is the use of biocides; however, this strategy, in addition to requiring continuous application, has proven to be ineffective in the elimination of biofilms and is associated with a high risk of water contamination. Therefore, it is necessary to seek more efficient and specific approaches to microbiological control. The use of bacteriophage viruses meets these needs, because after they multiply, they usually cause cell lysis, releasing new viral particles and preventing the bacteria from proliferating. In view of this, this study proposes to establish a method for the concentration and detection of bacteriophages of Sulphate Reducing Bacteria present in reactor water from oil wells. The samples were collected from two reactors, operated in a batch fed to simulate an oil well. The reactor water samples were first clarified, viruses adsorbed to sediment were eluted and then concentrated by ultracentrifugation. The viral concentrate was then purified with Vertrel-XF. Experimental seeding of P1 myophage in water samples from the reactor revealed a viral recovery rate of 27.7%, compared to the 16% obtained by use of other protocols.

RESUMO

Combination of the treatment of effluents with high organic loads and the production of electricity is the driving forces stimulating the development of microbial fuel cells (MFC). The increase in electricity production in MFCs requires not only the optimization of the operational parameters but also the inhibition of the metabolic pathways, which compete with electricity production, such as methanogenesis. The presence of both sulphate and sulphide ions in conventional anaerobic reactors hampers the growth of methanogenic archaea and justifies the use of sulphate and therefore sulphate-reducing bacteria (SRB) in the anodic half-cell of MFC. Most importantly, the literature on the subject reveals that SRB are able to directly transfer electrons to solid electrodes, enabling the production of electrical energy. This technology is versatile because it associates the removal of both sulphate and the chemical oxygen demand (COD) with the production of electricity. Therefore, the current work revises the main aspects related to the inoculation of MFC with SRB focusing on (i) the microbial interactions in the anodic chamber, (ii) the electron transfer pathways to the solid anode, and also (iii) the sulphate and COD removal yields along with the electricity production efficiencies.

Assuntos

RESUMO

Desulfovibrio alaskensis is a Gram-negative bacterial species that belongs to the group of Sulphate Reducing Bacteria (SRB) and presents prophages in genomes, a common characteristic of the genus Desulfovibrio. Genetic material can be transported by outer membrane vesicles, however, no data regarding the production of these vesicles has been reported for D. alaskensis. To verify the expression of D. alaskensis prophages and their involvement with outer membrane vesicles, the DSM16109 strain was used. The DSM16109 strain had three prophages and presented reduced growth after mitomycin C addition when compared to the control culture. This reduction was accompanied by the presence of virus-like particles (VLPs), indicating mitomycin C dependent prophage induction. The increase in the number of cap gene copies and transcriptions of the three prophages was verified in the control sample, however, without the formation of VLPs. Prophage genes were identified in outer membrane vesicles from cultures treated and not treated with mitomycin C. DSM16109 prophages are expressed spontaneously but only in the presence of mitomycin C was it possible to observe VLP formation. Due to the genetic material detection from the prophages within outer membrane vesicles, this property may be related to the horizontal transfer of viral genes.

Assuntos

RESUMO

AIM: Although feed medicated with antibiotics is widely used in animal production to prevent and treat bacterial infections, the effect of these drugs on nontarget anaerobic bacteria is unknown. We aimed to clarify whether a single exposure of sulphate-reducing bacteria (SRB) from a tilapia pond to oxytetracycline (OTC) concentrations relevant to aquaculture impacts their function, abundance and community structure. METHODS AND RESULTS: To demonstrate changes in SO4(2-) content, SRB abundance, dsrB copy number and SRB diversity, sediment mesocosms were spiked with 5, 25, 50 and 75 mg OTC kg(-1) and examined for 30 days by means of ion chromatography, qPCR, cultivation and fluorescent in situ hybridization (FISH). On day 3, we measured higher SO4(2-) concentrations (ca. two-fold) and a reduction in dsrB copy numbers of approximately 50% in the treatments compared to the controls. After 30 days, a subtle yet measurable enrichment of bacteria from the order Desulfovibrionales occurred in mesocosms receiving ≥ 50 mg OTC kg(-1), notwithstanding that SRB counts decreased two orders of magnitude. OTC was dynamically and reversibly converted into 4-epioxytetracycline and other related compounds in a dose-dependent manner during the experiment. CONCLUSIONS: A single exposure to rather high OTC concentrations triggered functional and structural changes in a SRB community that manifested quickly and persisted for a month. SIGNIFICANCE AND IMPACT OF THE STUDY: This study improves our limited knowledge on the ecotoxicology of antibiotics in anaerobic environments.

Assuntos

RESUMO

AIM: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.

RESUMO

As bactérias redutoras de sulfato do gênero Desulfovibrio sp. podem ser encontradas normalmente formando parte da biota intestinal e oral de seres humanos saudáveis, participando, direta ou indiretamente, com seus produtos metabólicos, de diversas afecções como: periodontites, câncer colorretal, infecções e sepsemias. Propõe-se com esta revisão avaliar os aspectos normais e as possíveis alterações patológicas correlacionadas com as bactérias redutoras de sulfato no organismo humano. As conclusões levam a crer que o desequilíbrio na biota oral e intestinal pode levar a aumento no número de bactérias redutoras de sulfato e na produção de sulfeto, como produto metabólico final, podendo representar um fator adicional no desenvolvimento daquelas afecções. Além disso, por haver forte propensão para formar associações bacterianas, aumentando seu potencial patológico, pode ser difícil a identificação do seu verdadeiro papel nas morbidades em que estão envolvidas assim como o seu potencial virulento.

Sulfate-reducing bacteria of the genus Desulfovibrio spp. can be routinely detected as member of the normal intestinal and oral microbiota in health individuals. This bacterial group produces metabolic byproducts, which participate, direct or indirect, in several diseases, such as periodontitis, colorectal cancer, infections and sepsis. The purpose of the present study was to assess the association between sulfate-reducing bacteria and normal conditions and pathology alterations in human. In conclusion, it is possible that alteration of the oral and intestinal flora can result in increase of sulfate-reducing bacteria levels and products of sulfide as final metabolic. Therefore, these conditions can represent an important fact associated with those diseases. In addition, this bacterial group presents a great tendency in to associate with other microorganisms. Like that, it can increase the pathologic potential and can difficult the identification of the true involvement with several diseases as well as its virulent potential.

Assuntos