The sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough possesses four periplasmic hydrogenases to facilitate the oxidation of molecular hydrogen. These include an [Fe] hydrogenase, an [NiFeSe] hydrogenase, and two [NiFe] hydrogenases encoded by the hyd, hys, hyn1, and hyn2 genes, respectively. In order to understand their cellular functions, we have compared the growth rates of existing (hyd and hyn1) and newly constructed (hys and hyn-1 hyd) mutants to those of the wild type in defined media in which lactate or hydrogen at either 5 or 50% (vol/vol) was used as the sole electron donor for sulfate reduction. Only strains missing the [Fe] hydrogenase were significantly affected during growth with lactate or with 50% (vol/vol) hydrogen as the sole electron donor. When the cells were grown at low (5% [vol/vol]) hydrogen concentrations, those missing the [NiFeSe] hydrogenase suffered the greatest impairment. The growth rate data correlated strongly with gene expression results obtained from microarray hybridizations and real-time PCR using mRNA extracted from cells grown under the three conditions. Expression of the hys genes followed the order 5% hydrogen > 50% hydrogen > lactate, whereas expression of the hyd genes followed the reverse order. These results suggest that growth with lactate and 50% hydrogen is associated with high intracellular hydrogen concentrations, which are best captured by the higher activity, lower affinity [Fe] hydrogenase. In contrast, growth with 5% hydrogen is associated with a low intracellular hydrogen concentration, requiring the lower activity, higher affinity [NiFeSe] hydrogenase.Hydrogen is intimately involved in the metabolism of sulfate-reducing bacteria (SRB) of the genus Desulfovibrio (17). In addition to utilizing molecular hydrogen directly as an electron donor for sulfate reduction, hydrogen may play a central role as an intermediate in the generation of a chemiosmotic gradient from the oxidation of organic molecules. This process has become known as hydrogen cycling (18). The current emphasis on developing more efficient energy production strategies has made understanding SRB metabolism a critical endeavor, especially with respect to the SRB connection with hydrogen and the impact of SRB on the petroleum industry through oil reservoir souring and pipeline corrosion.Hydrogenases catalyze the heterolytic cleavage of molecular hydrogen into protons and electrons (H 2 7 2H ϩ ϩ 2e) (9). These enzymes are present ubiquitously in both Archaea and Bacteria, including many SRB. The fully sequenced Desulfovibrio vulgaris Hildenborough has a total of six hydrogenases (14). Four of them are periplasmic and therefore presumably are involved in hydrogen oxidation, including a soluble iron-only [Fe] hydrogenase (Hyd) (16), two membrane-associated nickel-iron [NiFe] hydrogenase isozymes (Hyn1 and Hyn2) (14, 23), and a membrane-associated nickel-iron-selenium [NiFeSe] hydrogenase (Hys) (31). The [NiFe] hydrogenases are widely distributed in SRB (35), but many Desulfovibri...
Community analysis of a mesothermic oil field, subjected to continuous field-wide injection of nitrate to remove sulfide, with denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA genes indicated the presence of heterotrophic and sulfide-oxidizing, nitrate-reducing bacteria (hNRB and soNRB). These reduce nitrate by dissimilatory nitrate reduction to ammonium (e.g., Sulfurospirillum and Denitrovibrio) or by denitrification (e.g., Sulfurimonas, Arcobacter, and Thauera). Monitoring of ammonium concentrations in producing wells (PWs) indicated that denitrification was the main pathway for nitrate reduction in the field: breakthrough of nitrate and nitrite in two PWs was not associated with an increase in the ammonium concentration, and no increase in the ammonium concentration was seen in any of 11 producing wells during periods of increased nitrate injection. Instead, ammonium concentrations in produced waters decreased on average from 0.3 to 0.2 mM during 2 years of nitrate injection. Physiological studies with produced waterderived hNRB microcosms indicated increased biomass formation associated with denitrification as a possible cause for decreasing ammonium concentrations. Use of anammox-specific primers and cloning of the resulting PCR product gave clones affiliated with the known anammox genera "Candidatus Brocadia" and "Candidatus Kuenenia," indicating that the anammox reaction may also contribute to declining ammonium concentrations. Overall, the results indicate the following: (i) that nitrate injected into an oil field to oxidize sulfide is primarily reduced by denitrifying bacteria, of which many genera have been identified by DGGE, and (ii) that perhaps counterintuitively, nitrate injection leads to decreasing ammonium concentrations in produced waters.
The purpose of this research is to identify the significance of climate factors related to the significance of change of dry matter yield (DMY) of whole crop maize (WCM) by year through the exploratory data analysis. The data (124 varieties; n=993 in 7 provinces) was prepared after deletion and modification of the insufficient and repetitive data from the results (124 varieties; n=1027 in 7 provinces) of import adaptation experiment done by National Agricultural Cooperation Federation. WCM was classified into early-maturity (25 varieties, n=200), mid-maturity (40 varieties, n=409), late-maturity (27 varieties, n=234) and others (32 varieties, n=150) based on relative maturity and days to silking. For determining climate factors, 6 weather variables were generated using weather data. For detecting DMY and climate factors, SPSS21.0 was used for operating descriptive statistics and Shapiro-Wilk test. Mean DMY by year was classified into upper and lower groups, and a statistically significant difference in DMY was found between two groups (p<0.05). To find the reasons of significant difference between two groups, after statistics analysis of the climate variables, it was found that Seeding-Harvesting Accumulated Growing Degree Days (SHAGDD), Seeding-Harvesting Precipitation (SHP) and Seeding-Harvesting Hour of sunshine (SHH) were significantly different between two groups (p<0.05), whereas Seeding-Harvesting number of Days with Precipitation (SHDP) had no significant effects on DMY (p>0.05). These results indicate that the SHAGDD, SHP and SHH are related to DMY of WCM, but the comparison of R 2 among three variables (SHAGDD, SHP and SHH) couldn't be obtained which is needed to be done by regression analysis as well as the prediction model of DMY in the future study.
A compact ultra-wideband (UWB) quasi-Yagi antenna with microstrip-to-coplanar stripline transition balun is presented in this paper. A planar balun with very short length (5.1 mm) has a 3dB back-to-back insertion loss bandwidth from 4.3 GHz to 10.8 GH. The proposed antenna has end-fire pattern and a good front-to-back ratio of 11.7 dB at 8.5 GHz. The cross polarization levels are -22 dBi and -25 dBi in the H-plane and Eplane, respectively.Index Terms -Balun, broadband antenna, end-fire antenna, IR-UWB, microstrip-to-coplanar stripline, quasi-Yagi.
Nitrate can control souring in fields with high bottom hole temperature (BHT) and where sulfide is produced in the near-injection-wellbore-region (NIWR). The objective of the treatment is to lower the sulfide concentration in produced water and oil, reducing corrosion risk in producing wells and above-ground infrastructure. Achieving this objective can be problematic for fields with low BHT or for fields in which the reservoir contributes sulfate to the produced water, as is demonstrated by analysing three PWRI case studies. Nitrate was found to effectively oxidize sulfide in produced waters, even when excess oil organics were present. An alternative strategy that should be considered is, therefore, to inject nitrate in the produced waters in a dose corresponding to the sulfide concentration.
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