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Use of Stable-Isotope Probing, Full-Cycle rRNA Analysis, and Fluorescence In Situ Hybridization-Microautoradiography To Study a Methanol-Fed Denitrifying Microbial Community 总被引:10,自引:3,他引:7 下载免费PDF全文
Maneesha P. Ginige Philip Hugenholtz Holger Daims Michael Wagner Jürg Keller Linda L. Blackall 《Applied microbiology》2004,70(1):588-596
A denitrifying microbial consortium was enriched in an anoxically operated, methanol-fed sequencing batch reactor (SBR) fed with a mineral salts medium containing methanol as the sole carbon source and nitrate as the electron acceptor. The SBR was inoculated with sludge from a biological nutrient removal activated sludge plant exhibiting good denitrification. The SBR denitrification rate improved from less than 0.02 mg of NO3−-N mg of mixed-liquor volatile suspended solids (MLVSS)−1 h−1 to a steady-state value of 0.06 mg of NO3−-N mg of MLVSS−1 h−1 over a 7-month operational period. At this time, the enriched microbial community was subjected to stable-isotope probing (SIP) with [13C]methanol to biomark the DNA of the denitrifiers. The extracted [13C]DNA and [12C]DNA from the SIP experiment were separately subjected to full-cycle rRNA analysis. The dominant 16S rRNA gene phylotype (group A clones) in the [13C]DNA clone library was closely related to those of the obligate methylotrophs Methylobacillus and Methylophilus in the order Methylophilales of the Betaproteobacteria (96 to 97% sequence identities), while the most abundant clone groups in the [12C]DNA clone library mostly belonged to the family Saprospiraceae in the Bacteroidetes phylum. Oligonucleotide probes for use in fluorescence in situ hybridization (FISH) were designed to specifically target the group A clones and Methylophilales (probes DEN67 and MET1216, respectively) and the Saprospiraceae clones (probe SAP553). Application of these probes to the SBR biomass over the enrichment period demonstrated a strong correlation between the level of SBR denitrification and relative abundance of DEN67-targeted bacteria in the SBR community. By contrast, there was no correlation between the denitrification rate and the relative abundances of the well-known denitrifying genera Hyphomicrobium and Paracoccus or the Saprospiraceae clones visualized by FISH in the SBR biomass. FISH combined with microautoradiography independently confirmed that the DEN67-targeted cells were the dominant bacterial group capable of anoxic [14C]methanol uptake in the enriched biomass. The well-known denitrification lag period in the methanol-fed SBR was shown to coincide with a lag phase in growth of the DEN67-targeted denitrifying population. We conclude that Methylophilales bacteria are the dominant denitrifiers in our SBR system and likely are important denitrifiers in full-scale methanol-fed denitrifying sludges. 相似文献
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Microzonation of Denitrification Activity in Stream Sediments as Studied with a Combined Oxygen and Nitrous Oxide Microsensor 总被引:14,自引:6,他引:8 下载免费PDF全文
Peter Bondo Christensen Lars Peter Nielsen Niels Peter Revsbech Jan Srensen 《Applied microbiology》1989,55(5):1234-1241
Microzonation of denitrification was studied in stream sediments by a combined O2 and N2O microsensor technique. O2 and N2O concentration profiles were recorded simultaneously in intact sediment cores in which C2H2 was added to inhibit N2O reduction in denitrification. The N2O profiles were used to obtain high-resolution profiles of denitrification activity and NO3− distribution in the sediments. O2 penetrated about 1 mm into the dark-incubated sediments, and denitrification was largely restricted to a thin anoxic layer immediately below that. With 115 μM NO3− in the water phase, denitrification was limited to a narrow zone from 0.7 to 1.4 mm in depth, and total activity was 34 nmol of N cm−2 h−1. With 1,250 μM NO3− in the water, the denitrification zone was extended to a layer from 0.9 to 4.8 mm in depth, and total activity increased to 124 nmol of N cm−2 h−1. Within most of the activity zone, denitrification was not dependent on the NO3− concentration and the apparent Km for NO3− was less than 10 μM. Denitrification was the only NO3−-consuming process in the dark-incubated stream sediment. Even in the presence of C2H2, a significant N2O reduction (up to 30% of the total N2O production) occurred in the reduced, NO3−-free layers below the denitrification zone. This effect must be corrected for during use of the conventional C2H2 inhibition technique. 相似文献
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Degradation and Fate of Carbon Tetrachloride in Unadapted Methanogenic Granular Sludge 总被引:2,自引:0,他引:2 下载免费PDF全文
Miriam H. A. Van Eekert Thomas J. Schrder Alfons J. M. Stams Gosse Schraa Jim A. Field 《Applied microbiology》1998,64(7):2350-2356
The potential of granular sludge from upflow anaerobic sludge blanket (UASB) reactors for bioremediation of chlorinated pollutants was evaluated by using carbon tetrachloride (CT) as a model compound. Granular sludges cultivated in UASB reactors on methanol, a volatile fatty acid mixture, or sucrose readily degraded CT supplied at a concentration of 1,500 nmol/batch (approximately 10 μM) without any prior exposure to organohalogens. The maximum degradation rate was 1.9 μmol of CT g of volatile suspended solids−1 day−1. The main end products of CT degradation were CO2 and Cl−, and the yields of these end products were 44 and 68%, respectively, of the initial amounts of [14C]CT and CT-Cl. Lower chlorinated methanes accumulated in minor amounts temporarily. Autoclaved (dead) sludges were capable of degrading CT at rates two- to threefold lower than those for living sludges, indicating that abiotic processes (mediated by cofactors or other sludge components) played an important role in the degradation observed. Reduced components in the autoclaved sludge were vital for CT degradation. A major part (51%) of the CT was converted abiotically to CS2. The amount of CO2 produced (23%) was lower and the amount of Cl− produced (86%) was slightly higher with autoclaved sludge than with living sludge. Both living and autoclaved sludges could degrade chloroform. However, only living sludge degraded dichloromethane and methylchloride. These results indicate that reductive dehalogenation, which was mediated better by living sludge than by autoclaved sludge, is only a minor pathway for CT degradation. The main pathway involves substitutive and oxidative dechlorination reactions that lead to the formation of CO2. Granular sludge, therefore, has outstanding potential for gratuitous dechlorination of CT to safe end products. 相似文献
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Annual Pattern of Denitrification and Nitrate Ammonification in Estuarine Sediment 总被引:11,自引:2,他引:9 下载免费PDF全文
Kirsten Schannong Jrgensen 《Applied microbiology》1989,55(7):1841-1847
The seasonal variation and depth distribution of the capacity for denitrification and dissimilatory NO3− reduction to NH4+ (NO3− ammonification) were studied in the upper 4 cm of the sediment of Norsminde Fjord estuary, Denmark. A combination of C2H2 inhibition and 15N isotope techniques was used in intact sediment cores in short-term incubations (maximum, 4 h). The denitrification capacity exhibited two maxima, one in the spring and one in the fall, whereas the capacity for NO3− ammonification was maximal in the late summer, when sediments were progressively reduced. The denitrification capacity was always highest in the uppermost 1 cm of the sediment and declined with depth. The NO3− ammonification was usually higher with depth, but the maximum activity in late summer was observed within the upper 1 cm. The capacity for NO3− incorporation into organic material was investigated on two occasions in intact sediment cores and accounted for less than 5% of the total NO3− reduction. Denitrification accounted for between 13 and 51% of the total NO3− reduction, and NH4+ production accounted for between 4 and 21%, depending on initial rates during the time courses. Changes of the rates during the incubation were observed in the late summer, which reflected synthesis of denitrifying enzymes. This time lag was eliminated in experiments with mixed sediment because of preincubation with NO3− and alterations of the near-environmental conditions. The initial rates obtained in intact sediment cores therefore reflect the preexisting enzyme content of the sediment. 相似文献
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Anaerobic Ammonium Oxidation Measured in Sediments along the Thames Estuary, United Kingdom 总被引:7,自引:3,他引:4 下载免费PDF全文
Until recently, denitrification was thought to be the only significant pathway for N2 formation and, in turn, the removal of nitrogen in aquatic sediments. The discovery of anaerobic ammonium oxidation in the laboratory suggested that alternative metabolisms might be present in the environment. By using a combination of 15N-labeled NH4+, NO3−, and NO2− (and 14N analogues), production of 29N2 and 30N2 was measured in anaerobic sediment slurries from six sites along the Thames estuary. The production of 29N2 in the presence of 15NH4+ and either 14NO3− or 14NO2− confirmed the presence of anaerobic ammonium oxidation, with the stoichiometry of the reaction indicating that the oxidation was coupled to the reduction of NO2−. Anaerobic ammonium oxidation proceeded at equal rates via either the direct reduction of NO2− or indirect reduction, following the initial reduction of NO3−. Whether NO2− was directly present at 800 μM or it accumulated at 3 to 20 μM (from the reduction of NO3−), the rate of 29N2 formation was not affected, which suggested that anaerobic ammonium oxidation was saturated at low concentrations of NO2−. We observed a shift in the significance of anaerobic ammonium oxidation to N2 formation relative to denitrification, from 8% near the head of the estuary to less than 1% at the coast. The relative importance of anaerobic ammonium oxidation was positively correlated (P < 0.05) with sediment organic content. This report of anaerobic ammonium oxidation in organically enriched estuarine sediments, though in contrast to a recent report on continental shelf sediments, confirms the presence of this novel metabolism in another aquatic sediment system. 相似文献
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Microelectrode Measurements of Nitrate Gradients in the Littoral and Profundal Sediments of a Meso-Eutrophic Lake (Lake Vechten, The Netherlands) 总被引:3,自引:2,他引:1 下载免费PDF全文
NO3− concentration profiles were measured in the sediments of a meso-eutrophic lake with a newly developed microelectrode. The depth of penetration of NO3− varied from only 1.3 mm in organic-rich profundal silty sediments to 5 mm in organic-poor littoral sandy sediments. The thickness of the zone of denitrification in the organic-rich sediments was <500 μm. Oxygen profiles measured simultaneously revealed that the zone of denitrification was directly adjacent to the aerobic zone. The results demonstrate high denitrification rates (0.26 to 1.31 mmol m−2 day−1) at in situ nitrate concentrations in the overlying water (0.030 mmol liter−1) and limitation of denitrification by nitrate availability. 相似文献
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Capacity for Denitrification and Reduction of Nitrate to Ammonia in a Coastal Marine Sediment 总被引:37,自引:23,他引:14 下载免费PDF全文
Jan Srensen 《Applied microbiology》1978,35(2):301-305
The capacity for dissimilatory reduction of NO3− to N2 (N2O) and NH4+ was measured in 15NO3−-amended marine sediment. Incubation with acetylene (7 × 10−3 atmospheres [normal]) caused accumulation of N2O in the sediment. The rate of N2O production equaled the rate of N2 production in samples without acetylene. Complete inhibition of the reduction of N2O to N2 suggests that the “acetylene blockage technique” is applicable to assays for denitrification in marine sediments. The capacity for reduction of NO3− by denitrification decreased rapidly with depth in the sediment, whereas the capacity for reduction of NO3− to NH4+ was significant also in deeper layers. The data suggested that the latter process may be equally as significant as denitrification in the turnover of NO3− in marine sediments. 相似文献
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Production and Loss of Nitric Oxide from Denitrification in Anaerobic Brookston Clay 总被引:4,自引:3,他引:1 下载免费PDF全文
D. J. McKenney K. F. Shuttleworth J. R. Vriesacker W. I. Findlay 《Applied microbiology》1982,43(3):534-541
Nitric oxide, nitrous oxide, and nitrite ion production was measured in a Brookston clay column undergoing anaerobic denitrification. A flow system method was used whereby argon carrier gas continuously stripped soil gases from the column, allowing steady-state rates to be obtained. Over several days the temporal change in rates of these gases and NO2− followed a pattern of increase and decay which may be expected of a reaction proceeding by several consecutive steps. The method permits observation of the relatively large net production rate of NO, which is normally not observed in static systems based on head space analysis of gaseous denitrification products. In the first several hours after the onset of anoxic conditions, the net rate of NO production, fNO, increased sharply to a maximum (~1 × 10−10 mol of N/g of soil per min), paralleling the rapid increase in NO2− level, and then followed a more gradual decline extending over approximately 45 h. A similar but less pronounced pattern was observed for N2O, with net rates of production being considerably less than for NO. The ratio [NO-N]/[N2O-N] decreased with time from ~2.5 at 6 h to ~2.0 at 45 h. Estimated rates of N2 production appeared to be initially high, decreased rapidly within a few hours, and then gradually increased with time after the establishment of anaerobic conditions. 相似文献
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Simultaneous Measurement of Denitrification and Nitrogen Fixation Using Isotope Pairing with Membrane Inlet Mass Spectrometry Analysis 总被引:4,自引:1,他引:3 下载免费PDF全文
A method for estimating denitrification and nitrogen fixation simultaneously in coastal sediments was developed. An isotope-pairing technique was applied to dissolved gas measurements with a membrane inlet mass spectrometer (MIMS). The relative fluxes of three N2 gas species (28N2, 29N2, and 30N2) were monitored during incubation experiments after the addition of 15NO3−. Formulas were developed to estimate the production (denitrification) and consumption (N2 fixation) of N2 gas from the fluxes of the different isotopic forms of N2. Proportions of the three isotopic forms produced from 15NO3− and 14NO3− agreed with expectations in a sediment slurry incubation experiment designed to optimize conditions for denitrification. Nitrogen fixation rates from an algal mat measured with intact sediment cores ranged from 32 to 390 μg-atoms of N m−2 h−1. They were enhanced by light and organic matter enrichment. In this environment of high nitrogen fixation, low N2 production rates due to denitrification could be separated from high N2 consumption rates due to nitrogen fixation. Denitrification and nitrogen fixation rates were estimated in April 2000 on sediments from a Texas sea grass bed (Laguna Madre). Denitrification rates (average, 20 μg-atoms of N m−2 h−1) were lower than nitrogen fixation rates (average, 60 μg-atoms of N m−2 h−1). The developed method benefits from simple and accurate dissolved-gas measurement by the MIMS system. By adding the N2 isotope capability, it was possible to do isotope-pairing experiments with the MIMS system. 相似文献
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Nitrate Reduction in a Groundwater Microcosm Determined by 15N Gas Chromatography-Mass Spectrometry 总被引:1,自引:0,他引:1 下载免费PDF全文
Aerobic and anaerobic groundwater continuous-flow microcosms were designed to study nitrate reduction by the indigenous bacteria in intact saturated soil cores from a sandy aquifer with a concentration of 3.8 mg of NO3−-N liter−1. Traces of 15NO3− were added to filter-sterilized groundwater by using a Darcy flux of 4 cm day−1. Both assimilatory and dissimilatory reduction rates were estimated from analyses of 15N2, 15N2O, 15NH4+, and 15N-labeled protein amino acids by capillary gas chromatography-mass spectrometry. N2 and N2O were separated on a megabore fused-silica column and quantified by electron impact-selected ion monitoring. NO3− and NH4+ were analyzed as pentafluorobenzoyl amides by multiple-ion monitoring and protein amino acids as their N-heptafluorobutyryl isobutyl ester derivatives by negative ion-chemical ionization. The numbers of bacteria and their [methyl-3H]thymidine incorporation rates were simultaneously measured. Nitrate was completely reduced in the microcosms at a rate of about 250 ng g−1 day−1. Of this nitrate, 80 to 90% was converted by aerobic denitrification to N2, whereas only 35% was denitrified in the anaerobic microcosm, where more than 50% of NO3− was reduced to NH4+. Assimilatory reduction was recorded only in the aerobic microcosm, where N appeared in alanine in the cells. The nitrate reduction rates estimated for the aquifer material were low in comparison with rates in eutrophic lakes and coastal sediments but sufficiently high to remove nitrate from an uncontaminated aquifer of the kind examined in less than 1 month. 相似文献
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Mikio Sayama Nils Risgaard-Petersen Lars Peter Nielsen Henrik Fossing Peter Bondo Christensen 《Applied microbiology》2005,71(11):7575-7577
Experiments demonstrated that Beggiatoa could induce a H2S-depleted suboxic zone of more than 10 mm in marine sediments and cause a divergence in sediment NO3− reduction from denitrification to dissimilatory NO3− reduction to ammonium. pH, O2, and H2S profiles indicated that the bacteria oxidized H2S with NO3− and transported S0 to the sediment surface for aerobic oxidation. 相似文献
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Selenate Reduction to Elemental Selenium by Anaerobic Bacteria in Sediments and Culture: Biogeochemical Significance of a Novel, Sulfate-Independent Respiration 总被引:19,自引:12,他引:7 下载免费PDF全文
Ronald S. Oremland James T. Hollibaugh Ann S. Maest Theresa S. Presser Laurence G. Miller Charles W. Culbertson 《Applied microbiology》1989,55(9):2333-2343
Interstitial water profiles of SeO42−, SeO32−, SO42−, and Cl− in anoxic sediments indicated removal of the seleno-oxyanions by a near-surface process unrelated to sulfate reduction. In sediment slurry experiments, a complete reductive removal of SeO42− occurred under anaerobic conditions, was more rapid with H2 or acetate, and was inhibited by O2, NO3−, MnO2, or autoclaving but not by SO42− or FeOOH. Oxidation of acetate in sediments could be coupled to selenate but not to molybdate. Reduction of selenate to elemental selenium was determined to be the mechanism for loss from solution. Selenate reduction was inhibited by tungstate and chromate but not by molybdate. A small quantity of the elemental selenium precipitated into sediments from solution could be resolublized by oxidation with either nitrate or FeOOH, but not with MnO2. A bacterium isolated from estuarine sediments demonstrated selenate-dependent growth on acetate, forming elemental selenium and carbon dioxide as respiratory end products. These results indicate that dissimilatory selenate reduction to elemental selenium is the major sink for selenium oxyanions in anoxic sediments. In addition, they suggest application as a treatment process for removing selenium oxyanions from wastewaters and also offer an explanation for the presence of selenite in oxic waters. 相似文献
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Effects of Carbon Substrates on Nitrite Accumulation in Freshwater Sediments 总被引:4,自引:3,他引:1 下载免费PDF全文
The contribution of the biochemical pathways nitrification, denitrification, and dissimilatory NO3− reduction to NH4+ (DNRA) to the accumulation of NO2− in freshwaters is governed by the species compositions of the bacterial populations resident in the sediments, available carbon (C) and nitrogen (N) substrates, and environmental conditions. Recent studies of major rivers in Northern Ireland have shown that high NO2− concentrations found in summer, under warm, slow-flowing conditions, arise from anaerobic NO3− reduction. Locally, agricultural pollutants entering rivers are important C and N sources, providing ideal substrates for the aquatic bacteria involved in cycling of N. In this study a range of organic C compounds commonly found in agricultural pollutants were provided as energy sources in 48-h incubation experiments to investigate if the chemical compositions of the pollutants affected which NO3− reduction pathway was followed and influenced subsequent NO2− accumulation. Carbon stored within the sediments was sufficient to support DNRA and denitrifier populations, and the resulting NO2− peak (80 μg of N liter−1 [approximate]) observed at 24 h was indicative of the simultaneous activities of both bacterial groups. The value of glycine as an energy source for denitrification or DNRA appeared to be limited, but glycine was an important source of additional N. Glucose was an efficient substrate for both the denitrification and DNRA pathways, with a NO2− peak of 160 μg of N liter−1 noted at 24 h. Addition of formate and acetate stimulated continuous NO2− production throughout the 48-h period, caused by partial inhibition of the denitrification pathway. The formate treatment resulted in a high NO2− accumulation (1,300 μg of N liter−1 [approximate]), and acetate treatment resulted in a low NO2− concentration (<100 μg of N liter−1). 相似文献
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Natural denitrification rates and activities of denitrifying enzymes were measured in an agricultural soil which had a 20-year past history of low pH (pH ca. 4) due to fertilization with acid-generating ammonium salts. The soil adjacent to this site had been limed and had a pH of ca. 6.0. Natural denitrification rates of these areas were of similar magnitude: 158 ng of N g−1 of soil day−1 for the acid soil and 390 ng of N g−1 of soil day−1 at the neutral site. Estimates of in situ denitrifying enzyme activity were higher in the neutral soil, but substantial enzyme activity was also detected in the acid soil. Rates of nitrous oxide reduction were very low, even when NO3− and NO2− were undetectable, and were ca. 400 times lower than the rates of N2O production from NO3−. Denitrification rates measured in slurries of the acid and neutral soil showed distinctly different pH optima (pH 3.9 and pH 6.3) which were near the pH values of the two soils. This suggests that an acid-tolerant denitrifying population had been selected during the 20-year period of low pH. 相似文献
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Environmental Parameters Regulating Gaseous Nitrogen Losses from Two Forested Ecosystems via Nitrification and Denitrification 总被引:10,自引:3,他引:10 下载免费PDF全文
Gaseous N losses from disturbed and reference forested watersheds at the Coweeta Hydrologic Laboratory in western North Carolina were studied by in situ N2O diffusion measurements and laboratory incubations throughout a 10-month period. Soil temperature, percent base saturation, and water-filled pore space accounted for 43% of the variation in in situ N2O diffusion measurements. Laboratory incubations distinguished the gaseous N products of nitrification and denitrification. Nitrifying activity, ambient NO3−, and nitrification N2O were positively correlated with percent base saturation. However, differences between watersheds in soil N substrate caused by presence of leguminous black locust in the disturbed watershed were confounded with differences in soil acidity. Denitrification was most strongly affected by soil moisture, which in turn was determined by precipitation events and slope position. Gaseous N losses from well-drained midslope and toeslope landscape positions appeared to be minor relative to other N transformations. Favorable conditions for denitrification occurred at a poorly drained site near the stream of the disturbed watershed. Laboratory incubations revealed high rates of NO3− reduction in these soils. We speculate that the riparian zone is a major site of depletion of NO3− from the soil solution via denitrification. 相似文献
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Anaerobic Growth and Denitrification among Different Serogroups of Soybean Rhizobia 总被引:1,自引:1,他引:0 下载免费PDF全文
We screened soybean rhizobia originating from three germplasm collections for the ability to grow anaerobically in the presence of NO3− and for differences in final product formation from anaerobic NO3− metabolism. Denitrification abilities of selected strains as free-living bacteria and as bacteroids were compared. Anaerobic growth in the presence of NO3− was observed in 270 of 321 strains of soybean rhizobia. All strains belonging to the 135 serogroup did not grow anaerobically in the presence of NO3−. An investigation with several strains indicated that bacteria not growing anaerobically in the presence of NO3− also did not utilize NO3− as the sole N source aerobically. An exception was strain USDA 33, which grew on NO3− but failed to denitrify. Dissimilation of NO3− by the free-living cultures proceeded without the significant release of intermediate products. Nitrous oxide reductase was inhibited by C2H2, but preceding steps of denitrification were not affected. Final products of denitrification were NO2−, N2O, or N2; serogroups 31, 46, 76, and 94 predominantly liberated NO2−, whereas evolution of N2 was prevalent in serogroups 110 and 122, and all three were formed as final products by strains belonging to serogroups 6 and 123. Anaerobic metabolism of NO3− by bacteroid preparations of Bradyrhizobium japonicum proceeded without delay and was evident by NO2− accumulation irrespective of which final product was formed by the strain as free-living bacteria. Anaerobic C2H2 reduction in the presence of NO3− was observed in bacteroid preparations capable of NO3− respiration but was absent in bacteria that were determined to be deficient in dissimilatory nitrate reductase. 相似文献
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Members of the Family Comamonadaceae as Primary Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate)-Degrading Denitrifiers in Activated Sludge as Revealed by a Polyphasic Approach 下载免费PDF全文
Shams Tabrez Khan Yoko Horiba Masamitsu Yamamoto Akira Hiraishi 《Applied microbiology》2002,68(7):3206-3214
The distribution and phylogenetic affiliations of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)-degrading denitrifying bacteria in activated sludge were studied by a polyphasic approach including culture-independent biomarker and molecular analyses as well as cultivation methods. A total of 23 strains of PHBV-degrading denitrifiers were isolated from activated sludges from different sewage treatment plants. 16S ribosomal DNA (rDNA) sequence comparisons showed that 20 of the isolates were identified as members of the family Comamonadaceae, a major group of β-Proteobacteria. When the sludges from different plants were acclimated with PHBV under denitrifying conditions in laboratory scale reactors, the nitrate removal rate increased linearly during the first 4 weeks and reached 20 mg NO3−-N h−1 g of dry sludge−1 at the steady state. The bacterial-community change in the laboratory scale sludges during the acclimation was monitored by rRNA-targeted fluorescence in situ hybridization and quinone profiling. Both approaches showed that the population of β-Proteobacteria in the laboratory sludges increased sharply during acclimation regardless of their origins. 16S rDNA clone libraries were constructed from two different acclimated sludges, and a total of 37 clones from the libraries were phylogenetically analyzed. Most of the 16S rDNA clones were grouped with members of the family Comamonadaceae. The results of our polyphasic approach indicate that β-Proteobacteria, especially members of the family Comamonadaceae, are primary PHBV-degrading denitrifiers in activated sludge. Our data provide useful information for the development of a new nitrogen removal system with solid biopolymer as an electron donor. 相似文献