Groups Of Sulfate-reducing Bacteria Research Articles

Microeukaryotes have unexpected importance in cold seep food webs through predation and parasitism

Cold seeps are inhabited by a high abundance of chemosynthetic prokaryotes and invertebrates. However, a complete food web between invertebrates and prokaryotes cannot be established without the important link of microeukaryotes. Yet, question such as which microeukaryotes are at work in cold seeps is still mostly open. We, therefore, compared the biological communities in cold seeps and adjacent areas of the South China Sea by the metabarcoding and quantitative PCR (qPCR) of nuclear 18S and 16S rRNA genes, and estimated the potentially ecological roles of microeukaryotes by cross-domain microbial network analysis. The anaerobic methane oxidizing archaea (ANME), sulfate-reducing bacteria (SRB) and Radiolaria accounted for most variations between microbial communities from the cold seeps and adjacent areas. A significant correlation was detected between the copy numbers of 18S rRNA gene and communities of the ANME and SRB in cold seeps, indicating close links between microeukaryotes and chemosynthetic prokaryotes. After adding microeukaryotic nodes microbial network became more complex, and the negative correlation proportion and average path length increased, suggesting increased predation and parasitism. The ANME and SRB groups were mainly negatively correlated with and potentially preyed by Acantharea and Cercozoa, which were then negatively correlated with annelids and mollusks. Parasitic microeukaryotes of Syndiniales widely existed in cold seeps and had close relationships with Polycystinea. Parasitism might cause the death of Polycystinea and the release of Syndiniales spores, which may be an important carbon source for the cold seep biota. Using Mantel analyses, we also demonstrated that trophic relationships are closer in cold seeps than in the adjacently deep-sea sediments, and that microeukaryote-metazoans linkages in cold seeps are closer than those between prokaryotes and metazoans. Overall, our study outlines the main components of food webs in cold seeps and highlights that microeukaryotes have an unexpected importance in the carbon cycle.

Study on the evolution process of corrosion behavior under the sulfate reducing bacteria biofilm in shale gas gathering pipelines

Pipeline corrosion induced by sulfate-reducing bacteria (SRB) is particularly severe during the hydraulic fracturing technology in shale gas exploitation. To investigate the evolution of corrosion beneath the SRB biofilms, 49-day corrosion experiments were performed with and without SRB. The weight loss experiment demonstrated that the corrosion in the Blank group was mitigated by the corrosion product film. In contrast, the SRB group exhibited an initial inhibitory phase followed by an exacerbation. Scanning electron microscopy (SEM) revealed stratification in the Blank group, whereas SRB initially formed colonies and extracellular polymeric substances (EPS), eventually the biofilm evolved into a mixed layer with the corrosion product. 3D microscopy showed a relatively flat surface in the Blank group. Conversely, corrosion pits beneath SRB biofilm were circular and could reach a depth of 29.77 μm, significantly greater than in the Blank group. Over time, SRB-induced pits deepened from the edges to the center and widened to approximately 740 μm, accompanied by an increase in quantity. Energy Dispersive Spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS) analyses detected the presence of elements P, S, and FeS in the SRB group, serving as important indicators of SRB corrosion. Electrochemical experiments revealed significantly higher corrosion currents in the SRB group. The evolution of SRB corrosion consisted of three phases: initial, intermediate, and starvation phases. During the starvation phase, localized corrosion proved to be the most severe, with a corrosion rate of 1.28 mm/a. Therefore, the study of SRB-induced corrosion should be prioritized to study the localization phenomena.

Desulfovibrio mangrovi sp. nov., a sulfate-reducing bacterium isolated from mangrove sediments: a member of the proposed genus "Psychrodesulfovibrio".

"Psychrodesulfovibrio", a proposed genus within the family Desulfovibrionaceae, is a group of sulfate-reducing bacteria with biogeochemical significance but restricted child taxa availability. In this study, a strictly anaerobic bacterium, designed strain FT415T, was isolated from mangrove sediments in Futian Mangrove Nature Reserve in Shenzhen, China. The strain was Gram-stain-negative, motile, and vibrio-shaped with a single polar flagellum, which grew at the temperature range of 15-42°C (optimum 37°C), pH range of 6.0-7.5 (optimum 6.8), and in the presence of 0-36gl-1 NaCl (optimum 6gl-1 NaCl). In the presence of sulfate, electron donors including lactate, ethanol, pyruvate, malate, fumarate, succinate, cysteine, and glycerol were incompletely oxidized to acetate, and H2 and formate were used as electron donors with acetate as the carbon source by strain FT415T. Sulfate, thiosulfate, sulfide, and anthraquinone-2,6-disulfonate were reduced in the presence of lactate. Fe(III) oxide was reduced without cell growth. Fermentative growth was observed with pyruvate and cysteine. Vitamins were not required for growth. The major cellular fatty acids (> 10%) were C16:0, summed feature 10 (C18:1 c11/t9/t6 and/or unknown ECL 17.834), C16:1 cis 9, and C18:0. The major polar lipids were phosphatidylethanolamine, phospholipids, and aminolipids. The predominant menaquinone was MK-6(H2). The genomic DNA G+C content was 56.7%. Phylogenetic analysis showed that strain FT415T shared a 98.1% similarity in 16S rRNA gene sequence, an average nucleotide identity value of 84.0%, an average amino-acid identity value of 85.4%, and a digital DNA-DNA hybridization value of 25.7% with its closest relative Desulfovibrio subterraneus HN2T, which has been proposed to be transferred to the genus "Psychrodesulfovibrio". Based on phenotypic, phylogenetic, and genotypic evidence, a new species of the family Desulfovibrionaceae, Desulfovibrio mangrovi sp. nov. was proposed with the type strain FT415T (=GDMCC 1.3410T=KCTC 25525T).

Improving Methane Production from Waste Activated Sludge Assisted by Fe(II)-Activated Peroxydisulfate Pretreatment via Anaerobic Digestion: Role of Interspecific Syntrophism Mediated by Sulfate-Reducing Bacteria

Sulfate radical generated via peroxydisulfate (PDS) activation has been extensively applied to energy recovery from waste activated sludge (WAS) during anaerobic digestion (AD), while the residual sulfate is still a limitation for its further application. In this study, a novel coupling strategy of Fe(II)-activated PDS pretreatment [Fe(II)_PDS] with sulfate-reducing bacteria (SRB) mediated was explored to enhance methane yield from WAS during AD. Results showed that the similar methane yield was obtained in Fe(II)_PDS + SRB (16.6 mL/g VSS) and zero-valent iron (ZVI)_PDS + SRB (16.9 mL/g VSS), which enhanced by 19.9–56.5% than other groups, while the hydrolysis rate constant (0.0065 h–1) in Fe(II)_PDS + SRB was much higher than that observed in ZVI_PDS + SRB (0.0046 h–1). Meanwhile, the concentration of short-chain fatty acids (SCFAs) peaked at 360.9 mg COD/g VSS (5 d) in the Fe(II)_PDS + SRB group, with the acetic acid (HAc) and propionic acid (HPr) accumulative proportion of 73.5%, and the total concentration promoted by 28.5% than that of the ZVI_PDS + SRB group, which provided a more ideal substrate for methanogens. The ultimate utilization efficiency of SCFAs reached 62.4% in the Fe(II)_PDS + SRB group. Moreover, MiSeq sequencing, canonical correspondence analysis, and molecular ecological network analysis revealed the intrinsic interaction of the functional microbial consortia, that is, anaerobic fermentation bacteria, SRB, nitrate-reducing bacterium, and acetotrophic methanogen, with the abundances of 9.52, 2.4, 4.93, and 77.7% in the Fe(II)_PDS + SRB group. Considering the treatment performance and the difficulty of the subsequent disposal, Fe(II) may be the superior activator than ZVI for free radicals (i.e., SO4•– and HO•) generation from PDS and further played the important role for interspecific syntrophism coupling with SRB during AD. Results of this study may provide a promising way for energy recovery from WAS.

Using heat-activated persulfate to accelerate short-chain fatty acids production from waste activated sludge fermentation triggered by sulfate-reducing microbial consortium

Persulfate has been applied extensively for waste activated sludge (WAS) decomposition due to the strong oxidizing sulfate radical generated as a product. However, the efficiency is not improved without activation to produce free radicals. In this study, a novel coupling strategy of heat-activated persulfate (Heat_PS) pretreatment and sulfate-reducing bacteria (SRB) triggering was explored to enhance short-chain fatty acids (SCFAs) produced by WAS fermentation. The remaining sulfate acts as an essential acceptor of electrons for the metabolism of synergistic SRB, thereby boosting WAS acidification by energetic cooperation with anaerobic fermenters. The results showed that SCFAs yield in the Heat_PS + SRB group peaked at 431.89 mg COD/gVSS, with the proportion of acetate reaching 57.8 %. This was 6.33 and 1.75 times higher than that in raw and single Heat_PS treated WAS, respectively. Carbon balance revealed a conversion rate of 26.1 % of carbon content in WAS to SCFAs, with 4.5 % lower CO2 equivalents emitted than that in raw WAS fermentation by the assessments of environmental impacts. This was partially attributed to the strong decomposition of WAS by SO4•− and •OH oxidation from heat-activated PS and the SRB trigger. In addition, the synergistic relationship among acidogenic/fermentative bacteria and SRB consortia was further verified by the positive correlation among Desulfovibrio, the hydrolytic Escherichia-Shigella, Morganella and the fermetative Macellibacteroides and Bacteroides, as revealed by molecular ecological networks (MENs) analysis. The results of this study may highlight the cooperation of the synergistic micribial consortia as an additional perspective for the recovery of value-added biological metabolites from complex biotransformation.

Spartina alterniflora invasion and mangrove restoration alter diversity and composition of sediment diazotrophic community

Ecological restoration using native mangrove species (i.e., Kandelia obovata) is a practical approach for controlling Spartina alterniflora invasion in the coastal wetlands. Diazotrophs play a critical role in enhancing productivity of both S. alterniflora and mangrove plant, via providing new nitrogen to the coastal wetlands ecosystems. However, response of the diazotrophic community to S. alterniflora invasion and subsequent mangrove restoration remains unclear. The present study monitored sediment physicochemical properties and diazotrophic communities across a chronosequence of restored mangrove wetland (bare mudflat, invasive S. alterniflora stands, 3-year and 10-year K. obovata restoration areas, and mature K. obovata forests over 30 years). The results showed an orderly succession in the sediment properties and diazotrophic community composition after S. alterniflora invasion and along mangrove restoration chronosequences. Almost all sediment nutrient contents (e.g., TC, TN, and C/N) were significantly (P < 0.05) increased by S. alterniflora invasion, then they decreased sharply in the newly restored mangrove and increased gradually with restoration ages, with the highest values in the mature mangrove. The diazotrophs demonstrated distinct community structure in different seasons. Diazotrophic alpha diversity increased with S. alterniflora invasion and mangrove restoration age in winter. Sulfate-reducing bacteria (SRB) was the dominant diazotrophic group, especially Desulfuromonadales. Moreover, network analyses revealed that SRB groups were the major keystone taxa. The relative abundance of Desulfuromonadales decreased, while the abundance of Chromatiales increased gradually with the S. alterniflora invasion and mangrove restoration age. Redundancy analysis revealed that TC, TN, and TS were the significant (P < 0.05) environmental factors in altering sediment diazotrophic communities in both seasons. These findings expand the current understanding of succession patterns of diazotrophic communities in mangrove restoration and provide new perspectives on the sustainable management of mangrove ecosystems.

Microbial Diversity of Bacteria Involved in Biomineralization Processes in Mine-Impacted Freshwaters.

In order to increase the knowledge about geo-bio interactions in extreme metal-polluted mine waters, we combined microbiological, mineralogical, and geochemical analyses to study the indigenous sulfate-reducing bacteria (SRB) involved in the heavy metal (HM) biomineralization processes occurring in Iglesiente and Arburese districts (SW Sardinia, Italy). Anaerobic cultures from sediments of two different mining-affected streams of this regional framework were enriched and analyzed by 16S rRNA next-generation sequencing (NGS) technique, showing sequences closely related to SRB classified in taxa typical of environments with high concentrations of metals (Desulfovibrionaceae, Desulfosporosinus). Nevertheless, the most abundant genera found in our samples did not belong to the traditional SRB groups (i.e., Rahnella, Acinetobacter). The bio-precipitation process mediated by these selected cultures was assessed by anaerobic batch tests performed with polluted river water showing a dramatic (more than 97%) Zn decrease. Scanning electron microscopy (SEM) analysis revealed the occurrence of Zn sulfide with tubular morphology, suggesting a bacteria-mediated bio-precipitation. The inocula represent two distinct communities of microorganisms, each adapted to peculiar environmental conditions. However, both the communities were able to use pollutants in their metabolism and tolerating HMs by detoxification mechanisms. The Zn precipitation mediated by the different enriched cultures suggests that SRB inocula selected in this study have great potentialities for the development of biotechnological techniques to reduce contaminant dispersion and for metal recovery.

Biased samples to study reservoir souring processes: A numerical analysis

Production water samples are commonly used to study reservoir souring process. The aim of this study is to examine the reliability of these samples by using a state of the art coupled Thermo-Hydro-bioChemical numerical model. The transport and growth of five different representative sulfate-reducing strains (SRSs) in a model subsurface environment are simulated numerically by considering various biofilm formation characteristics and injection flow rates. After one pore volume (PV) injection, and assuming no biofilm formation, for three injection flow rates corresponding to pore velocities of 5.58 × 10−8, 83.7 × 10−8 and 167.4 × 10−8 m/s, souring within the reservoir is partially or completely derived by two SRSs that have an optimal growth temperature of 28 and 39 °C. However, the produced water taken after one PV is dominated by a SRS that has an optimal temperature of 82 °C. For a higher pore velocity of 558 × 10−8 m/s, without considering any biofilm formation, produced water sample contains the same SRSs as the reservoir. However, if half of the produced biomass by various SRSs participates in biofilm formation, even for the high pore velocity of 558 × 10−8 m/s, the produced water sample cannot reveal the SRSs that derive souring in the reservoir. Therefore, utilizing produced water samples may be misleading in reservoir souring studies. The results presented in this work suggest that more accurate prediction of reservoir souring requires characterization of the major groups of sulfate reducing bacteria in the injection water and undisturbed formation brine, and understanding their biofilm formation behavior.

Biofilters are potential hotspots for H2S production in brackish and marine water RAS

The production of hydrogen sulphide (H2S) is a major concern and challenge in marine land-based recirculating aquaculture systems (RAS). In order to gain a thorough understanding on H2S production dynamics in RAS, an anaerobic batch reactors experiment was performed, evaluating the production potential of total dissolved sulphide (TDS) and H2S and characterizing the microbial communities in different RAS environments (solid waste, biomedia+RAS-water, biomedia+seawater [SW], and RAS-water) during 33 days. The highest H2S concentrations were achieved in the reactors with biomedia+RAS-water, where biofilms growing on biomedia hosted a high abundance of sulphate reducing bacteria (SRB), which activated once anoxic conditions and carbon sources were introduced. The biofilms in the biomedia+SW reactors produced lower amounts of H2S than the biomedia+RAS-water reactors, due to the lower abundance of SRB. The solid waste produced H2S at low rate, the production being limited by the substrate competition between SRB and other microbial groups. No production of H2S was observed in the reactors with only RAS-water, due to the absence of SRB and suitable carbon sources. Based on measurements of production of H2S in this study, a moving bed biofilter submerged in brackish water (17 ppt) can potentially produce 139 g of H2S per biofilter m3, when the biomedia is not adequately mixed and oxygenated. Altogether, the results demonstrate that although SRB are found both in biofilters and solid waste, these two environments exhibit different H2S production dynamics. Biofilters produce large quantities of H2S under anoxic conditions, while solid waste deposited to the rearing tanks exhibits a lower but constant production of H2S. However, both of these H2S sources can be suppressed through fast removal of solids from rearing tanks and optimal operational conditions for biofilters.

Feasibility of Co-Treating Olive Mill Wastewater and Acid Mine Drainage

Previous tests using a growth medium and olive mill wastewater (OMWW) have shown that it supplies carbon and electron donors suitable for sulphate reducing bacteria (SRB). We assessed the co-treatment of acid mine drainage (AMD) and OMWW using SRB-enriched bioreactors and identified the most abundant bacterial populations present under optimized conditions. The process requires a neutralizing agent to create optimal pH conditions for successful removal of the AMD’s main contaminants. Concentrations of SO42−, Al, Fe, Cu, Zn, and Mn decreased to below Portugal’s maximum admissible values for irrigation waters, and all but Mn were reduced to less than Portugal’s emission limit values (ELVs) for wastewater discharges. Phenol concentrations—the main pollutants in OMWW—dropped to values between 1/10 and 1/5 their initial concentrations in batch tests using mixtures of AMD and OMWW, and to 1/2 their initial concentrations in flow-through tests. The final total phenol concentrations were still above the ELV for wastewater discharges, but phenols are not regulated in irrigation waters, and OMWW is used by some producers to irrigate soils. Six main SRB groups were identified as likely having a fundamental role in the bioremediation process: the genera Desulfovibrio, Sulfurospirillum, and Acetobacter and the families Sphingomonadaceae, Prevotellaceae, and Deferribacteraceae.

Modeling the anaerobic treatment of sulfate-rich urban wastewater: Application to AnMBR technology

Although anaerobic membrane bioreactors (AnMBR) are a core technology in the transition of urban wastewater (UWW) treatment towards a circular economy, the transition is being held back by a number of bottlenecks. The dissolved methane released from the effluent, the need to remove nutrients (ideally by recovery), or the energy lost by the competition between methanogenic and sulfate-reducing bacteria (SRB) for the biodegradable COD have been identified as the main issues to be addressed before AnMBR becomes widespread. Mathematical modeling of this technology can be used to obtain further insights into these bottlenecks plus other valuable information for design, simulation and control purposes. This paper therefore proposes an AnMBR anaerobic digestion model to simulate the crucial SRB-related process since these bacteria degrade more than 40% of the organic matter. The proposed model, which is included in the BNRM2 collection model, has a reduced but all-inclusive structure, including hydrolysis, acidogenesis, acetogenesis, methanogenesis and other SRB-related processes. It was calibrated and validated using data from an AnMBR pilot plant treating sulfate-rich UWW, including parameter values obtained in off-line experiments and optimization methods. Despite the complex operating dynamics and influent composition, it was able to reproduce the process performance. In fact, it was able to simulate the AD of sulfate-rich UWW considering only two groups of SRB: heterotrophic SRB growing on both VFA (propionate) and acetate, and autotrophic SRB growing on hydrogen. Besides the above-mentioned constraints, the model reproduced the dynamics of the mixed liquor solids concentration, which helped to integrate biochemical and filtration models. It also reproduced the alkalinity and pH dynamics in the mixed liquor required for assessing the effect of chemical precipitation on membrane scaling.

Total Microbial Activity and Sulfur Cycling Microbe Changes in Response to the Development of Hypoxia in a Shallow Estuary

—We examined the effects of changing from oxic to anoxic conditions on microbial communities using both biogeochemical and molecular approaches in a semi-enclosed estuary (Jinhae Bay, Republic of Korea). Total microbial activity, represented by oxygen demand in the water column (WOD) or sediment (SOD), revealed that the respective microbial communities in the water and sediment responded differently to low dissolved-oxygen (DO) conditions. In the sediment, SOD and the total microbial abundance, as assessed by quantitative polymerase chain reaction (qPCR) analysis, decreased under low DO conditions, indicating that the microbial adaptation to anaerobic metabolism was not well established during hypoxia development. In the water column, however, neither the total abundance of microbes nor the WOD were affected by hypoxic conditions. Regardless of DO concentration, WOD showed a positive correlation with water temperature, implying that the aerobic metabolism was sustained even under hypoxic conditions, through the intermittent supply of oxygen. In addition to the spatially different responses of microorganisms, unique responses of specific groups were noted in sulfur (S) cycling microbes. Sulfide-oxidizing prokaryotes (SOP) dominated in the water column, and no significant changes were evident in their abundance or diversity with hypoxia. However, in sediment, distinctive sulfate-reducing bacteria (SRB) were present at each sampling period during hypoxia development (a “SRB succession”), implying that each SRB group has varying sensitivity to DO and other electron acceptors. Vertical profiles of dissolved inorganic nitrogen, including ammonium (NH4+) and nitrate (NO3-), and changes in archaeal abundance suggest that NH4+-oxidizing archaea (AOA) might vary spatially and temporally, depending on NH4+ and oxygen availability in the water column, under mature hypoxic conditions, which is similar to the nitrogen (N) dynamics in the permanent oxygen minimum zone (OMZ).

Paint particles are a distinct and variable substrate for marine bacteria

While paint particles are an important part of the microplastic sphere, they have, as yet, received much less research coverage, particularly regarding microplastic-microbiological interactions. This study investigated the biofilm communities of a variety of paint particles from brackish sediment using 16S rRNA gene sequencing. Paint particle biofilm communities appear to be distinct from natural (water and sediment), non-synthetic particle (cellulose) and common microplastic biofilm communities. Notably, there appears to be 1 group of sulphate-reducing bacteria from the Desulfobacteraceae family, Desulfatitalea tepidiphilia, that dominate certain paint biofilms. Of the 8 investigated paint-associated communities, four paints displayed this high Desulfobacteraceae presence. However, it is currently unclear from the chemical analysis performed of the paint surface chemistry (ATR FT-IR spectroscopy, Raman spectroscopy, SEM-EDX) what the drivers behind this might be. As such, this study provides important insights as the first to analyse microplastic-paint biofilm communities and paves the way for future research.

Desulfovibrio alaskensis prophages and their possible involvement in the horizontal transfer of genes by outer membrane vesicles

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.

Depth-related change of sulfate-reducing bacteria community in mangrove sediments: The influence of heavy metal contamination

This study provides new insight towards the effects of heavy metal contamination on sulfate-reducing bacteria (SRB) in mangrove ecosystem. We investigated SRB communities in mangrove sediments (0–30 cm depth) from Futian, Xixiang and Shajing mangrove wetlands in Shenzhen, China, with different heavy metal contamination levels. The results showed that SRB community abundance (1.71 × 107–3.04 × 108 dsrB gene copies g−1 wet weight sediment) was depth-related and significantly correlated with Cd and Ni concentrations. The α-diversity indices of SRB community (Chao1 = 21.25–84.50, Shannon = 2.31–2.96) were significantly correlated with Cd level in mangrove sediments. Desulfobacteraceae, Desulfobulbaceae and Syntrophobacteraceae acted as major SRB groups in mangrove sediments, and Syntrophobacteraceae was most sensitive to metal contamination. UniFrace clustering analysis revealed that SRB community structure was influenced by the heavy metal concentrations. Moreover, redundancy analysis indicated that Cd and total phosphorus were the major environmental factors affecting the SRB structure in mangrove sediments.

Analysis of cultivable aerobic bacterial community composition and screening for facultative sulfate-reducing bacteria in marine corrosive steel

Anaerobic, aerobic, and facultative bacteria are all present in corrosive environments. However, as previous studies to address corrosion in the marine environment have largely focused on anaerobic bacteria, limited attention has been paid to the composition and function of aerobic and facultative bacteria in this process. For analysis in this study, ten samples were collected from rust layers on steel plates that had been immersed in seawater for different periods (i.e., six months and eight years) at Sanya and Xiamen, China. The cultivable aerobic bacterial community structure as well as the number of sulfate-reducing bacteria (SRB) were analyzed in both cases, while the proportion of facultative SRB among the isolated aerobic bacteria in each sample was also evaluated using a novel approach. Bacterial abundance results show that the proportions are related to sea location and immersion time; abundances of culturable aerobic bacteria (CAB) and SRB from Sanya were greater in most corrosion samples than those from Xiamen, and abundances of both bacterial groups were greater in samples immersed for six months than for eight years. A total of 213 isolates were obtained from all samples in terms of CAB community composition, and a phylogenetic analysis revealed that the taxa comprised four phyla and 31 genera. Bacterial species composition is related to marine location; the results show that Firmicutes and Proteobacteria were the dominant phyla, accounting for 98.13% of the total, while Bacillus and Vibrio were the dominant genera, accounting for 53.06% of the total. An additional six facultative SRB strains were also screened from the isolates obtained and were found to encompass the genus Vibrio (four strains), Staphylococcus (one strain), and Photobacterium (one strain). It is noteworthy that mentions of Photobacterium species have so far been absent from the literature, both in terms of its membership of the SRB group and its relationship to corrosion.

Screening and characterization of prophages in Desulfovibrio genomes

Bacteria of the genus Desulfovibrio belong to the group of Sulphate Reducing Bacteria (SRB). SRB generate significant liabilities in the petroleum industry, mainly due to their ability to microbiologically induce corrosion, biofilm formation and H2S production. Bacteriophages are an alternative control method for SRB, whose information for this group of bacteria however, is scarce. The present study developed a workflow for the identification of complete prophages in Desulfovibrio. Poly-lysogenesis was shown to be common in Desulfovibrio. In the 47 genomes analyzed 53 complete prophages were identified. These were classified within the order Caudovirales, with 69.82% belonging to the Myoviridade family. More than half the prophages identified have genes coding for lysozyme or holin. Four of the analyzed bacterial genomes present prophages with identity above 50% in the same strain, whose comparative analysis demonstrated the existence of colinearity between the sequences. Of the 17 closed bacterial genomes analyzed, 6 have the CRISPR-Cas system classified as inactive. The identification of bacterial poly-lysogeny, the proximity between the complete prophages and the possible inactivity of the CRISPR-Cas in closed bacterial genomes analyzed allowed the choice of poly-lysogenic strains with prophages belonging to the Myoviridae family for the isolation of prophages and testing of related strains for subsequent studies.

English

Sulfate reducing bacteria (SRB) was successfully isolated from Estuary Dam in Suwung Denpasar, Indonesia. This estuary catches highly polluted water from Badung River which runs across and hence carries pollution due to waste disposal from Denpasar City. SRB was studied in detail for their ability to reduce sulfate to sulfide with organic material as an oxidizing agent. SRB exploration of the estuary ecosystem of the contaminated dam was accomplished through isolation, selection and characterization of the isolates obtained. The result of this study found superior SRB named DPS 1711, DPS 1705 and DPS 1703. The bacteria have the ability to grow at pH 3, room temperature and uses compost as organic substrate. This ability is an important factor for the application of isolates in the treatment of acid mine waste. Isolates have optimum optical density under the pH range of 4 to 7 and the best at pH 5 have a growth rate profile at a temperature range of 25 to 40&deg;C. The isolates observed were Gram-negative stem, motile bacteria which only grow in anaerobic condition. Physiological-biochemical characterization showed the three isolates, namely DPS 1703, DPS 1705 and DPS 1711 were SRB groups identified as Desulfotomaculum orientis. Key words: Sulfate reducing bacteria, polluted waters, estuary dam ecosystem. &nbsp

Anaerobic oxidation of methane coupled to thiosulfate reduction in a biotrickling filter

Microorganisms from an anaerobic methane oxidizing sediment were enriched with methane gas as the substrate in a biotrickling filter (BTF) using thiosulfate as electron acceptor for 213days. Thiosulfate disproportionation to sulfate and sulfide were the dominating sulfur conversion process in the BTF and the sulfide production rate was 0.5mmoll−1day−1. A specific group of sulfate reducing bacteria (SRB), belonging to the Desulforsarcina/Desulfococcus group, was enriched in the BTF. The BTF biomass showed maximum sulfate reduction rate (0.38mmoll−1day−1) with methane as sole electron donor, measured in the absence of thiosulfate in the BTF. Therefore, a BTF fed with thiosulfate as electron acceptor can be used to enrich SRB of the DSS group and activate the inoculum for anaerobic oxidation of methane coupled to sulfate reduction.

Sulfate-reducing bacteria slow intestinal transit in a bismuth-reversible fashion in mice.

Hydrogen sulfide (H2 S) serves as a mammalian cell-derived gaseous neurotransmitter. The intestines are exposed to a second source of this gas by sulfate-reducing bacteria (SRB). Bismuth subsalicylate binds H2 S rendering it insoluble. The aim of this study was to test the hypothesis that SRB may slow intestinal transit in a bismuth-reversible fashion. Eighty mice were randomized to five groups consisting of Live SRB, Killed SRB, SRB+Bismuth, Bismuth, and Saline. Desulfovibrio vulgaris, a common strain of SRB, was administered by gavage at the dose of 1.0×109 cells along with rhodamine, a fluorescent dye. Intestinal transit was measured 50minutes after gavage by euthanizing the animals, removing the small intestine between the pyloric sphincter and the ileocecal valve and visualizing the distribution of rhodamine across the intestine using an imaging system (IVIS, Perkin-Elmer). Intestinal transit (n=50) was compared using geometric center (1=minimal movement, 100=maximal movement). H2 S concentration (n=30) was also measured when small intestinal luminal content was allowed to generate this gas. The Live SRB group had slower intestinal transit as represented by a geometric center score of 40.2±5.7 when compared to Saline: 73.6±5.7, Killed SRB: 77.9±6.9, SRB+Bismuth: 81.0±2.0, and Bismuth: 73.3±4.2 (P<.0001). Correspondingly, the Live SRB group had the highest luminal H2 S concentration of 4181.0±968.0ppb compared to 0±0ppb for the SRB+Bismuth group (P<.0001). Live SRB slow intestinal transit in a bismuth-reversible fashion in mice. Our results demonstrate that intestinal transit is slowed by SRB and this effect could be abolished by H2 S-binding bismuth.