[Show abstract][Hide abstract] ABSTRACT: Libraries of 16S rRNA genes cloned from methanogenic oil degrading microcosms amended with North Sea crude oil and inoculated with estuarine sediment indicated that bacteria from the genera Smithella (Deltaproteobacteria, Syntrophaceace) and Marinobacter sp. (Gammaproteobacteria) were enriched during degradation. Growth yields and doubling times (36 days for both Smithella and Marinobacter) were determined using qPCR and quantitative data on alkanes, which were the predominant hydrocarbons degraded. The growth yield of the Smithella sp. [0.020 g(cell-C)/g(alkane-C)], assuming it utilized all alkanes removed was consistent with yields of bacteria that degrade hydrocarbons and other organic compounds in methanogenic consortia. Over 450 days of incubation predominance and exponential growth of Smithella was coincident with alkane removal and exponential accumulation of methane. This growth is consistent with Smithella's occurrence in near surface anoxic hydrocarbon degrading systems and their complete oxidation of crude oil alkanes to acetate and/or hydrogen in syntrophic partnership with methanogens in such systems. The calculated growth yield of the Marinobacter sp., assuming it grew on alkanes, was [0.0005 g(cell-C)/g(alkane-C)] suggesting that it played a minor role in alkane degradation. The dominant methanogens were hydrogenotrophs (Methanocalculus spp. from the Methanomicrobiales). Enrichment of hydrogen-oxidizing methanogens relative to acetoclastic methanogens was consistent with syntrophic acetate oxidation measured in methanogenic crude oil degrading enrichment cultures. qPCR of the Methanomicrobiales indicated growth characteristics consistent with measured rates of methane production and growth in partnership with Smithella.
[Show abstract][Hide abstract] ABSTRACT: The subsurface microbiology of an Athabasca oil sands reservoir in western Canada containing severely biodegraded oil was investigated by combining 16S rRNA gene- and polar lipid-based analyses of reservoir formation water with geochemical analyses of the crude oil and formation water. Biomass was filtered from formation water, DNA was extracted using two different methods, and 16S rRNA gene fragments were amplified with several different primer pairs prior to cloning and sequencing or community fingerprinting by denaturing gradient gel electrophoresis (DGGE). Similar results were obtained irrespective of the DNA extraction method or primers used. Archaeal libraries were dominated by Methanomicrobiales (410 of 414 total sequences formed a dominant phylotype affiliated with a Methanoregula sp.), consistent with the proposed dominant role of CO(2) -reducing methanogens in crude oil biodegradation. In two bacterial 16S rRNA clone libraries generated with different primer pairs, > 99% and 100% of the sequences were affiliated with Epsilonproteobacteria (n = 382 and 72 total clones respectively). This massive dominance of Epsilonproteobacteria sequences was again obtained in a third library (99% of sequences; n = 96 clones) using a third universal bacterial primer pair (inosine-341f and 1492r). Sequencing of bands from DGGE profiles and intact polar lipid analyses were in accordance with the bacterial clone library results. Epsilonproteobacterial OTUs were affiliated with Sulfuricurvum, Arcobacter and Sulfurospirillum spp. detected in other oil field habitats. The dominant organism revealed by the bacterial libraries (87% of all sequences) is a close relative of Sulfuricurvum kujiense - an organism capable of oxidizing reduced sulfur compounds in crude oil. Geochemical analysis of organic extracts from bitumen at different reservoir depths down to the oil water transition zone of these oil sands indicated active biodegradation of dibenzothiophenes, and stable sulfur isotope ratios for elemental sulfur and sulfate in formation waters were indicative of anaerobic oxidation of sulfur compounds. Microbial desulfurization of crude oil may be an important metabolism for Epsilonproteobacteria indigenous to oil reservoirs with elevated sulfur content and may explain their prevalence in formation waters from highly biodegraded petroleum systems.
[Show abstract][Hide abstract] ABSTRACT: Libraries of 16S rRNA genes cloned from methanogenic oil degrading microcosms amended with North Sea crude oil and inoculated with estuarine sediment indicated that bacteria from the genera Smithella (Deltaproteobacteria, Syntrophaceace) and Marinobacter sp. (Gammaproteobacteria) were enriched during degradation. Growth yields and doubling times (36 days for both Smithella and Marinobacter) were determined using qPCR and quantitative data on alkanes, which were the predominant hydrocarbons degraded. The growth yield of the Smithella sp. [0.020 g(cell‐C)/g(alkane‐C)], assuming it utilized all alkanes removed was consistent with yields of bacteria that degrade hydrocarbons and other organic compounds in methanogenic consortia. Over 450 days of incubation predominance and exponential growth of Smithella was coincident with alkane removal and exponential accumulation of methane. This growth is consistent with Smithella's occurrence in near surface anoxic hydrocarbon degrading systems and their complete oxidation of crude oil alkanes to acetate and/or hydrogen in syntrophic partnership with methanogens in such systems. The calculated growth yield of the Marinobacter sp., assuming it grew on alkanes, was [0.0005 g(cell‐C)/g(alkane‐C)] suggesting that it played a minor role in alkane degradation. The dominant methanogens were hydrogenotrophs (Methanocalculus spp. from the Methanomicrobiales). Enrichment of hydrogen‐oxidizing methanogens relative to acetoclastic methanogens was consistent with syntrophic acetate oxidation measured in methanogenic crude oil degrading enrichment cultures. qPCR of the Methanomicrobiales indicated growth characteristics consistent with measured rates of methane production and growth in partnership with Smithella.
[Show abstract][Hide abstract] ABSTRACT: In-reservoir petroleum biodegradation has resulted in vast deposits of heavy oil around the globe. Extraction of heavy oil
is more costly and less efficient than conventional oil production and consequently oil biodegradation on geological timescales
has significant economic and environmental impacts. The processes that have led to the biodegradation of oil in situ have
only recently begun to be elucidated and we have at best a qualitative understanding of the factors that promote oil biodegradation
in petroleum reservoirs. A synthesis of current thinking on the mechanisms of, and controls on, in-reservoir oil biodegradation
is presented. This is placed in the context of oil-field microbiology and used to identify potentially fruitful avenues of
research required to fill some of the gaps in our knowledge.
[Show abstract][Hide abstract] ABSTRACT: Most of the world's remaining petroleum resource has been altered by in-reservoir biodegradation which adversely impacts oil quality and production, ultimately making heavy oil. Analysis of the microorganisms in produced reservoir fluid samples is a route to characterization of subsurface biomes and a better understanding of the resident and living microorganisms in petroleum reservoirs. The major challenges of sample contamination with surface biota, low abundances of microorganisms in subsurface samples, and viscous emulsions produced from biodegraded heavy oil reservoirs are addressed here in a new analytical method for intact polar lipids (IPL) as taxonomic indicators in petroleum reservoirs. We have evaluated the extent to which microbial cells are removed from the free water phase during reservoir fluid phase separation by analysis of model reservoir fluids spiked with microbial cells and have used the resultant methodologies to analyze natural well-head fluids from the Western Canada Sedimentary Basin (WCSB). Analysis of intact polar membrane lipids of microorganisms using liquid chromatography-mass spectrometry (LC-MS) techniques revealed that more than half of the total number of microorganisms can be recovered from oil-water mixtures. A newly developed oil/water separator allowed for filtering of large volumes of water quickly while in the field, which reduced the chances of contamination and alterations to the composition of the subsurface microbial community after sample collection. This method makes the analysis of IPLs (or indirectly microorganisms) from well-head fluids collected in remote field settings possible and reliable. To the best of our knowledge this is the first time that IPLs have been detected in well-head oil-water mixtures.
[Show abstract][Hide abstract] ABSTRACT: Biodegradation of crude oil in subsurface petroleum reservoirs has adversely affected the majority of the world's oil, making recovery and refining of that oil more costly. The prevalent occurrence of biodegradation in shallow subsurface petroleum reservoirs has been attributed to aerobic bacterial hydrocarbon degradation stimulated by surface recharge of oxygen-bearing meteoric waters. This hypothesis is empirically supported by the likelihood of encountering biodegraded oils at higher levels of degradation in reservoirs near the surface. More recent findings, however, suggest that anaerobic degradation processes dominate subsurface sedimentary environments, despite slow reaction kinetics and uncertainty as to the actual degradation pathways occurring in oil reservoirs. Here we use laboratory experiments in microcosms monitoring the hydrocarbon composition of degraded oils and generated gases, together with the carbon isotopic compositions of gas and oil samples taken at wellheads and a Rayleigh isotope fractionation box model, to elucidate the probable mechanisms of hydrocarbon degradation in reservoirs. We find that crude-oil hydrocarbon degradation under methanogenic conditions in the laboratory mimics the characteristic sequential removal of compound classes seen in reservoir-degraded petroleum. The initial preferential removal of n-alkanes generates close to stoichiometric amounts of methane, principally by hydrogenotrophic methanogenesis. Our data imply a common methanogenic biodegradation mechanism in subsurface degraded oil reservoirs, resulting in consistent patterns of hydrocarbon alteration, and the common association of dry gas with severely degraded oils observed worldwide. Energy recovery from oilfields in the form of methane, based on accelerating natural methanogenic biodegradation, may offer a route to economic production of difficult-to-recover energy from oilfields.
[Show abstract][Hide abstract] ABSTRACT: The role of environmental selection in governing the structure of communities of freshwater sulfur bacteria (Achromatium spp) was experimentally tested by mixing sediments from two geographically separated lakes (Rydal Water (RY) and Hell Kettles (HK)) that harboured Achromatium spp. Community profiles of Achromatium spp in sediment microcosms at day 0 and after 60 days were compared to determine whether initial Achromatium community composition or subsequent selection by the sediment environment had greater influence in dictating the final Achromatium community structure. It was found that Achromatium spp from the HK community became established in mixed sediments at the expense of members of the RY community. This selection for the HK Achromatium community was more pronounced when sediment composition was manipulated to resemble HK sediments. Our findings definitively demonstrate that environmental selection is the primary determinant of Achromatium community structure in these sediments.
The ISME Journal 12/2007; 1(7):596-605. · 9.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Developed for tertiary nitrification, this biofilter also removed carbonaceous BOD (cBOD) and (SS). Because the biofilter is expanded, it cannot clog, and therefore does not require backflushing; yet, it removed a significant proportion of the influent SS. This unanticipated capability was due to the activities of heterotrophic bacteria, protozoa, and metazoa (nematode and oligochaete worms). The expanded bed is an intensified process, which is based on natural immobilization of microbes to small support particles. Using glassy coke as the support material, an attached layer of microbes develops, forming particulate biofilms having a superficial surface area of 1 800 m2 m(-3)(expandedbed). Autotrophic nitritifiers (Nitrosomonas spp.) were detected in the biofilm using rRNA-based molecular methods and were likely responsible, at least in part, for reducing the ammonia concentration by up to 99% (to 0.1 mg L(-1)), while the other organisms reduced cBOD and SS by up to 56% and 62%, respectively. Furthermore, the influent concentrations of Escherichia coli, coliform and heterotrophic bacteria were reduced by over 80%. It thereby provides a single process solution for combined tertiary nitrification and solids removal. Operating the process to consistently achieve < 0.5mg NH3N L(-1) and at the same time removing a significant fraction of cBOD and SS, it can replace processes such as SAFs or NTFs followed by a sandfilter.
Water Science & Technology 02/2006; 54(8):37-46. · 1.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A sandwich hybridization assay for high-throughput, rapid, simple, and inexpensive quantification of specific microbial populations was evaluated. The assay is based on the hybridization of a target rRNA with differentially labeled capture and detector probes. Betaproteobacterial ammonia-oxidizing bacteria (AOB) were selected as the target group for the study, since they represent a phylogenetically coherent group of organisms that perform a well-defined geochemical function in natural and engineered environments. Reagent concentrations, probe combinations, and washing, blocking, and hybridization conditions were optimized to improve signal and reduce background. The detection limits for the optimized RNA assay were equivalent to approximately 10(3) to 10(4) and 10(4) to 10(5) bacterial cells, respectively, for E. coli rRNA and RNA extracted from activated sludge, by using probes targeting the majority of bacteria. Furthermore, the RNA assay had good specificity, permitted discrimination of rRNA sequences that differed by a 2-bp mismatch in the probe target region, and could distinguish the sizes of AOB populations in nitrifying and nonnitrifying wastewater treatment plants.
Applied and Environmental Microbiology 01/2006; 71(12):8481-90. · 3.95 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Autotrophic ammonia-oxidising bacteria (AOB) are a crucial component of the microbial communities of nitrifying wastewater treatment systems. Nitrification is known to occur in reactors of different configuration, but whether AOB communities are different in reactors of different design is unknown. We compared the diversity and community structure of the betaproteobacterial AOB in two full-scale treatment reactors - a biological aerated filter (BAF) and a trickling filter - receiving the same wastewater. Polymerase chain reaction (PCR) of 16S ribosomal RNA (rRNA) gene fragments with AOB-selective primers was combined with denaturing gradient gel electrophoresis (DGGE) to allow comparative analysis of the dominant AOB populations. The phylogenetic affiliation of the dominant AOB was determined by cloning and sequencing PCR-amplified 16S rRNA gene fragments. DGGE profiles were compared using a probability-based similarity index (Raup and Crick). The use of a probability-based index of similarity allowed us to evaluate if the differences and similarities observed in AOB community structure in different samples were statistically significant or could be accounted for by chance matching of bands in DGGE profiles, which would suggest random colonisation of the reactors by different AOB. The community structure of AOB was different in different sections of each of the reactors and differences were also noted between the reactors. All AOB-like sequences identified, grouped within the genus Nitrosomonas. A greater diversity of AOB was detected in the trickling filters than in the BAF though all samples analysed appeared to be dominated by AOB most closely related to Nitrosococcus mobilis. Numerical analysis of DGGE profiles indicated that the AOB communities in depth profiles from the filter beds were selected in a non-random manner.
[Show abstract][Hide abstract] ABSTRACT: The diversity and community structure of the beta-proteobacterial ammonia oxidising bacteria (AOB) in a range of different lab-scale industrial wastewater treatment reactors were compared. Three of the reactors treat waste from mixed domestic and industrial sources whereas the other reactor treats waste solely of industrial origin. PCR with AOB selective primers was combined with denaturing gradient ge electrophoresis to allow comparative analysis of the dominant AOB populations and the phylogenetic affiliation of the dominant AOB was determined by cloning and sequencing or direct sequencing of bands excised from DGGE gels. Different AOB were found within and between different reactors. All AOB sequences identified were grouped within the genus Nitrosomonas. Within the lab-scale reactors there appeared to be selection for a low diversity of AOB and predominance of a single AOB population. Furthermore, the industrial input in both effluents apparently selected for salt tolerant AOB, most closely related to Nitrosococcus mobilis and Nitrosomonas halophila.
Water Science & Technology 02/2003; 48(3):17-24. · 1.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Lab-scale reactors are commonly used to simulate full-scale plants as they permit the effects of defined experimental perturbations to be evaluated. Ideally, lab- and full-scale reactors should possess similar microbial populations. To determine this we compared the diversity of the beta-proteobacterial autotrophic ammonia-oxidising bacteria (AOB) in a full-scale and lab-scale biological aerated filter (BAF) using PCR with AOB selective primers combined with denaturing gradient gel electrophoresis (DGGE). PCR amplified 16S rRNA gene fragments from the nitrification unit of the lab-and full-scale BAF were subjected to cloning and sequencing to determine the phylogenetic affiliation of the AOB. A high degree of comparability between the lab-and full-scale BAF was observed with respect to AOB populations. However minor differences were apparent. The importance of these minor constituents in the overall performance of the reactor is unknown. Nonetheless the lab-scale reactor in this study did appear to reflect the dominant AOB community within the full-scale equivalent.
Water Science & Technology 02/2002; 46(1-2):319-22. · 1.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The diversity and ecology of natural communities of the uncultivated bacterium Achromatium oxaliferum were studied by use of culture-independent approaches. 16S rRNA gene sequences were PCR amplified from DNA extracted from highly purified preparations of cells that were morphologically identified as A. oxaliferum present in freshwater sediments from three locations in northern England (Rydal Water, Jenny Dam, Hell Kettles). Cloning and sequence analysis of the PCR-amplified 16S rRNA genes revealed that multiple related but divergent sequences were routinely obtained from the A. oxaliferum communities present in all the sediments examined. Whole-cell in situ hybridization with combinations of fluorescence-labelled oligonucleotide probes revealed that the divergent sequences recovered from purified A. oxaliferum cells corresponded to genetically distinct Achromatium subpopulations. Analysis of the cell size distribution of the genetically distinct subpopulations demonstrated that each was also morphologically distinct. Furthermore, there was a high degree of endemism in the Achromatium sequences recovered from different sediments; identical sequences were never recovered from different sampling locations. In addition to ecological differences that were apparent between Achromatium communities from different freshwater sediments, the distribution of different subpopulations of Achromatium in relation to sediment redox profiles indicated that the genetically and morphologically distinct organisms that coexisted in a single sediment were also ecologically distinct and were adapted to different redox conditions. This result suggests that Achromatium populations have undergone adaptive radiation and that the divergent Achromatium species occupy different niches in the sediments which they inhabit.
Applied and Environmental Microbiology 12/1999; 65(11):5089-99. · 3.95 Impact Factor