共查询到20条相似文献,搜索用时 203 毫秒
1.
Competition for ammonium between plant roots and nitrifying and heterotrophic bacteria and the effects of protozoan grazing 总被引:10,自引:2,他引:8
The competition for limiting amounts of ammonium between the chemolithotrophic ammonium-oxidizing species Nitrosomonas europaea, the heterotrophic species Arthrobacter globiformis and roots of Plantago lanceolata (Ribwort plantain) was studied in a series of model systems of increasing complexity, i.e. energy-limited continuous cultures,
non-water-saturated continuously percolated soil columns and pots with γ-sterilized soil planted with axetic P. lanceolata seedlings. The effects of bacterial grazing by the flagellate species Adriamonas peritocrescens on the competition for ammonium were also investigated in the three model systems.
It was found that N. europaea was a weaker competitor for ammonium than either A. globiformis or plant roots of P. lanceolata. It is assumed that the heterotrophic bacteria have a higher affinity for ammonium than the nitrifying bacteria, whereas
growing plant roots have a greater capacity to exploit the soil for ammonium than the immobile nitrifying bacteria. It is
not very likely that allelochemicals were involved in suppressing the nitrification process. Four reasons are given for this
assumption.
Presence of the flagellates strongly stimulated the potential nitrification rate in all model systems. It is assumed that
there is a more even distribution over the soil of either nitrifying bacteria or their substrate ammonium in the presence
of flagellates. In addition to the distribution effect, there is a stimulation of the potential ammonium oxidation rate. The
results are discussed in the light of the function of nitrate as nitrogen sink in the biogeochemical nitrogen cycle. 相似文献
2.
Summary The production of nitrate in an old established dune grassland soil and its uptake by plants was studied by comparing amounts of mineral nitrogen and numbers of nitrifying bacteria in the rhizosphere on the one hand, and on the other accumulated nitrate and levels of nitrate reductase (NaR) of individual plants of three Plantago species,i. e., P. major, P. lanceolata andP. coronopus. For these three Plantago species andP. media basal levels of NaR in the absence of nitrate were determined in plants grown in culture solutions. The basal NaR levels ofP. major andP. media (species occurring on nutrient-rich soils) were significantly higher than those ofP. lanceolata andP. coronopus (species found on nutrient-poor soils). NaR activity increased in the presence of nitrate and was suppressed by ammonium.From the numbers of nitrifying bacteria in the rhizosphere and NaR activity in the leaves it was concluded that nitrate was produced in the root environments of the three Plantago species and that the compound was taken up by the plants. NaR activities and numbers of nitrifying bacteria were higher for individuals ofP. major than for those ofP. lanceolata andP. coronopus. No correlation was found between the ammonium levels and the numbers of nitrifying bacteria in the soil, and no indications of inhibition of nitrifying bacteria in the rhizosphere were obtained. For individuals ofP. lanceolata a correlation was found between the numbers of nitrifying bacteria in the soil and NaR activity in the leaves. The results are discussed in relation to the ecological habitats of the three species.Grassland Species Research Group Publication No.38. 相似文献
3.
Okkyoung Choi Atreyee Das Chang‐Ping Yu Zhiqiang Hu 《Biotechnology and bioengineering》2010,107(6):1004-1011
Nitrifying bacteria, cyanobacteria, and algae are important microorganisms in open pond wastewater treatment systems. Nitrification involving the sequential oxidation of ammonia to nitrite and nitrate, mainly due to autotrophic nitrifying bacteria, is essential to biological nitrogen removal in wastewater and global nitrogen cycling. A continuous flow autotrophic bioreactor was initially designed for nitrifying bacterial growth only. In the presence of cyanobacteria and algae, we monitored both the microbial activity by measuring specific oxygen production rate (SOPR) for microalgae and cyanobacteria and specific oxygen uptake rate (SOUR) for nitrifying bacteria. The growth of cyanobacteria and algae inhibited the maximum nitrification rate by a factor of 4 although the ammonium nitrogen fed to the reactor was almost completely removed. Terminal restriction fragment length polymorphism (T‐RFLP) analysis indicated that the community structures of nitrifying bacteria remained unchanged, containing the dominant Nitrosospira, Nitrospira, and Nitrobacter species. PCR amplification coupled with cloning and sequencing analysis resulted in identifying Chlorella emersonii and an uncultured cyanobacterium as the dominant species in the autotrophic bioreactor. Notwithstanding their fast growth rate and their toxicity to nitrifiers, microalgae and cyanobacteria were more easily lost in effluent than nitrifying bacteria because of their poor settling characteristics. The microorganisms were able to grow together in the bioreactor with constant individual biomass fractions because of the uncoupled solids retention times for algae/cyanobacteria and nitrifiers. The results indicate that compared to conventional wastewater treatment systems, longer solids retention times (e.g., by a factor of 4) should be considered in phototrophic bioreactors for complete nitrification and nitrogen removal. Biotechnol. Bioeng. 2010;107: 1004–1011. © 2010 Wiley Periodicals, Inc. 相似文献
4.
S. V. Kalyuzhnyi N. M. Shestakova T. P. Tourova A. B. Poltaraus M. A. Gladchenko A. I. Trukhina T. N. Nazina 《Microbiology》2010,79(2):237-246
The phylogenetic diversity of a microbial community involved in anaerobic oxidation of ammonium nitrogen in the DEAMOX process
was studied. Analysis of clone libraries containing 16S rRNA gene inserts of Bacteria, (including Planctomycetes) and Archaea revealed the presence of nucleotide sequences of the microorganisms involved in the main reactions of the carbon, nitrogen,
and sulfur cycles, including nitrifying, denitrifying, and ANAMMOX bacteria. In the bacterial clone library, 16S rRNA gene
sequences of representatives of the phyla Proteobacteria, Bacteroidetes, Chloroflexi, Firmicutes, Verrucomicrobia, Lentisphaerae, Spirochaetales, and Planctomycetes, as well as of some new groups, were detected. In the archaeal clone library, nucleotide sequences of methanogens belonging
to the orders Methanomicrobiales, Methanobacteriales, and Methanosarcinales were found. It is possible that both ANAMMOX bacteria and bacteria of the genus Nitrosomonas are involved in anaerobic ammonium oxidation in the DEAMOX reactor. Many sequences were similar to those from the clone libraries
obtained previously from the ANAMMOX community of marine sediments. It is also probable that the DEAMOX reactions occur in
natural ecosystems (in marine and freshwater sediments and the oceanic water column), thereby providing for the coupling of
the nitrogen and sulfur cycles. 相似文献
5.
黄土丘陵区不同植被土壤氮素转化微生物生理群特征及差异 总被引:5,自引:0,他引:5
采用最大或然计数法(most probable number, MPN)对黄土高原洞子沟流域不同植被恢复阶段土壤氮素微生物生理群(氨化细菌、亚硝化细菌、反硝化细菌)数量分布特征进行了测定,结果表明:1)土壤氨化细菌、亚硝化细菌和反硝化细菌数量随植被恢复而增加,三者最大值分别为最小值的74、4和31倍,其中氨化细菌和反硝化细菌的数量在铁杆蒿群落最低,辽东栎群落最高,亚硝化细菌数量在丁香群落最低,辽东栎群落最高;2)植被恢复对各氮素生理群影响不同,对氨化细菌影响最大,其次分别为反硝化细菌和亚硝化细菌;3)各氮素生理群数量差异较大,氨化细菌>反硝化细菌>亚硝化细菌。研究区氨化细菌占总数的75%-80%,反硝化细菌占20%-25%时,生态系统最为稳定;4)土壤理化性质与各功能菌关系紧密,其中,土壤容重和硝态氮含量与微生物数量相关性最大,全钾、矿化氮和微生物量氮也表现出很大的相关性。 相似文献
6.
Competition and coexistence of aerobic ammonium- and nitrite-oxidizing bacteria at low oxygen concentrations 总被引:5,自引:0,他引:5
Sliekers AO Haaijer SC Stafsnes MH Kuenen JG Jetten MS 《Applied microbiology and biotechnology》2005,68(6):808-817
In natural and man-made ecosystems nitrifying bacteria experience frequent exposure to oxygen-limited conditions and thus
have to compete for oxygen. In several reactor systems (retentostat, chemostat and sequencing batch reactors) it was possible
to establish co-cultures of aerobic ammonium- and nitrite-oxidizing bacteria at very low oxygen concentrations (2–8 μM) provided
that ammonium was the limiting N compound. When ammonia was in excess of oxygen, the nitrite-oxidizing bacteria were washed
out of the reactors, and ammonium was converted to mainly nitrite, nitric oxide and nitrous oxide by Nitrosomonas-related bacteria. The situation could be rapidly reversed by adjusting the oxygen to ammonium ratio in the reactor. In batch
and continuous tests, no inhibitory effect of ammonium, nitric oxide or nitrous oxide on nitrite-oxidizing bacteria could
be detected in our studies. The recently developed oxygen microsensors may be helpful to determine the kinetic parameters
of the nitrifying bacteria, which are needed to make predictive kinetic models of their competition. 相似文献
7.
Immobilization of nitrifying bacteria in porous pellets of urethane gel for removal of ammonium nitrogen from waste-water 总被引:1,自引:0,他引:1
T. Sumino H. Nakamura N. Mori Y. Kawaguchi M. Tada 《Applied microbiology and biotechnology》1992,36(4):556-560
Summary The effects of immobilizing materials on the activity of nitrifying bacteria and removal of ammonium nitrogen (NH4-N) from waste-water by immobilized nitrifying bacteria were investigated using six urethane prepolymers. With a urethane prepolymer containing 2.27% free isocyanate, a high activity yield of nitrifying bacteria was obtained. There was a drastic improvement over the conventional method of immobilization by acrylamide in the activity yield. Inorganic synthetic waste-water was treated at a high loading rate of 0.24 kg N·m–3·day–1. The NH4-N concentration of the effluent could be reduced to 2 mg·1–1 or less and the removal was 90%. The life of the pellets in terms of activity was at least 120 days.
Offprint requests to: T. Sumino 相似文献
8.
Effects of Grazing by Flagellates on Competition for Ammonium between Nitrifying and Heterotrophic Bacteria in Chemostats 总被引:9,自引:3,他引:6
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The enhanced mineralization of organic nitrogen by bacteriophagous protozoa is thought to favor the nitrification process in soils, in which nitrifying bacteria have to compete with heterotrophic bacteria for the available ammonium. To obtain more insight into this process, the influence of grazing by the bacteriovorous flagellate Adriamonas peritocrescens on the competition for limiting amounts of ammonium between the ammonium-oxidizing species Nitrosomonas europaea and the heterotrophic species Arthrobacter globiformis was studied in the presence of Nitrobacter winogradskyi in continuous cultures at dilution rates of 0.004 and 0.01 h-1. The ammonium concentration in the reservoir was maintained at 2 mM, whereas the glucose concentration was increased stepwise from 0 to 7 mM. A. globiformis won the competition for limiting amounts of ammonium when the glucose concentration in the reservoirs increased, in agreement with previously described experiments in which the flagellates were not included. The numbers of nitrifying bacteria decreased as the numbers of heterotrophic bacteria rose with increasing glucose concentrations. Critical C/N ratios, i.e., ratios between glucose and ammonium in the reservoirs at which no nitrate was found in the culture vessels, of 12.5 and 10.5 were determined at dilution rates of 0.004 and 0.01 h-1, respectively. Below these critical values, coexistence of the competing species was found. The numbers of nitrifying bacteria decreased more in the presence of flagellates than in their absence, presumably by selective predation on the nitrifying bacteria, either in the liquid culture or on the glass wall of the culture vessels. Despite this, the rate of nitrate production did not decrease more in the presence of flagellates than in their absence. This demonstrates that no correlation has to be expected between numbers of nitrifying bacteria and their activity and that a constant nitrification rate per cell cannot be assumed for nitrifying bacteria. Above the critical C/N ratios, low numbers of nitrifying bacteria were still found in the culture vessels, probably because of attachment of the nitrifying bacteria to the glass wall of the culture vessels. Like the numbers of heterotrophic bacteria, the numbers of flagellates increased when the glucose concentrations in the reservoirs increased. Numbers of 2 × 105 and 12 × 105 flagellates ml-1 were found at 7 mM glucose at dilution rates of 0.004 and 0.01 h-1, respectively. It was concluded that the critical C/N ratios were practically unaffected by the presence of protozoa. Although nitrate production rates were equal in the presence and absence of flagellates, the numbers of nitrifying bacteria decreased more strongly in their presence. This indicates a higher activity per nitrifying cell in the presence of flagellates. 相似文献
9.
Activity of nitrifiers in relation to nitrogen nutrition of plants in natural ecosystems 总被引:4,自引:1,他引:3
Three aspects of the nitrate production in natural ecosystems are discussed,i.e. the population biology of nitrifying bacteria, the nitrate-producing activity of these organisms and the uptake of nitrate by higher plants. It is concluded that the three methods used in enumerating the nitrifying bacteria,i.e. the Most Probable Number method, the Fluorescent Antibody technique and the Potential Nitrification Rate, all have serious drawbacks and count different segments of the nitrifying populations.From the number of nitrifying bacteria no reliable estimate of the rate production can be obtained and also estimates that are made using field-incubation and15N–NH
4
+
techniques do not yield reliable data. Possibly the best results can be obtained using Schimel's method to estimate the actual nitrification rate using15N–NO
3
–
, but this method has still not been tested under different sets of soil conditions.From the nitrate reductase activity and the chemical composition of the plant a picture can be obtained of the quantities of nitrate and ammonium that have been taken up. However, it is shown that nitrate and ammonium are taken up in different proportions that they are produced. It is concluded that the various parameters have to be studied simultaneously, preferably in defined systems with plants, in which the participating organisms are known. 相似文献
10.
11.
Elke Neubacher Mario Prast Ernst-Josef Cleven Ulrike-Gabriele Berninger 《Hydrobiologia》2008,596(1):241-250
Ciliated protists are important predators of bacteria in many aquatic habitats, including sediments. Since, many biochemical
transformations within the nitrogen cycle are performed by bacteria, ciliates could have an indirect impact on the nitrogen
cycle through selective grazing on nitrogen-transforming bacteria. As a case study, we examined ciliate grazing on nitrifying
bacteria of the genera Nitrosomonas and Nitrospira. All experiments were designed as in vitro-experiments with cultures of different bacteria and ciliate species. The nitrifying
bacteria used in our experiments were Nitrosomonas europaea [Winogradsky 1892] and Nitrospira moscoviensis [Ehrich 2001]. The ciliates comprised of four species that are known as efficient bacterivores and common members of the
protist community in aquatic systems: Paramecium aurelia [Müller 1773], Euplotes
octocarinatus [Carter 1972], Tetrahymena pyriformis [Ehrenberg 1830] and Cyclidium glaucoma [Müller 1786]. Our experimental approach, using a combination of DAPI and FISH staining, was successful in allowing the observation
of ingestion of specific bacteria and their detection within ciliate food vacuoles. However, the ciliates in this study showed
no significant selective grazing. No food preferences for a any bacterial taxon or any size class or morphotype were detected.
Correlation with time between ciliate abundance and bacterial abundance or biovolume, using log transformed growth rates of
ciliates and bacteria, showed no significant results. On the bacterial side, neither an active defence mechanism of the nitrifying
bacteria against ciliate grazing, such as changes in morphology, nor competition for resources were observed. These results
suggest that in our in vitro-experiments grazing by ciliates has no influence on abundance and growth of nitrifying bacteria
and nitrification. 相似文献
12.
Abstract
Nitrification in freshwater, a key process in the nitrogen cycle, is now well known to take place predominantly on suspended
particles and in sediment. Nitrobacter is the most commonly isolated nitrite oxidizing bacteria from water environments. Three methods for counting nitrite oxidizing
communities (especially Nitrobacter) in sediment were investigated: MPN-Griess, fluorescent antibodies (immunofluorescence), and a more recent molecular method
coupling specific DNA amplification by PCR and statistical MPN quantification. After preliminary adjustments of the MPN-PCR
technique, the detection level and the yield of each method were determined by inoculating a sediment with a pure Nitrobacter culture. The best recovery yield was obtained with the immunofluorescence technique (21.3%) and the lowest detection level
was reached with the MPN-Griess method (103
Nitrobacter/g dry weight sediment). The MPN-PCR method resulted in the lowest recovery yields and needs further adaptation to become
a reliable and precise tool for investigations of nitrifying bacteria in sediment.
Received: 6 July 1998; Accepted: 17 December 1998 相似文献
13.
Immunofluorescent Assay for the Marine Ammonium-Oxidizing Bacterium Nitrosococcus oceanus 总被引:12,自引:10,他引:2
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Nitrification is one of the important microbiological transformations of nitrogen in the ocean. Traditional enrichment-culture methods for enumerating the autotrophic bacteria which oxidize ammonium to nitrite are very time consuming (months) and are believed to seriously underestimate natural abundances. A fluorescent-antibody assay for a marine ammonium-oxidizing bacterium was developed to provide a rapid and direct means of identifying these microorganisms. Antibodies to Nitrosococcus oceanus were prepared and tested against pure cultures of marine, freshwater, and soil ammonium oxidizers and against bacteria from natural seawater samples. Cell counts of culture samples determined by the fluorescent-antibody assay agreed with hemacytometer and acridine orange counts. Our results demonstrated that the immunofluorescent assay is a powerful tool for the detection of Nitrosococcus in the marine environment. 相似文献
14.
Franco-Rivera A Paniagua-Michel J Zamora-Castro J 《Journal of industrial microbiology & biotechnology》2007,34(4):279-287
Constructed ammonium oxidizing biofilms (CAOB) and constructed nitrite oxidizing biofilms (CNOB) were characterized during
the bioremediation of a wastewater effluent. The maximum ammonium removal rate and removal efficiency in CAOB was 322 mg N-NH4+ m−3 d−1 and 96%, respectively, while in CNOB a maximum removal rate of 255 mg N-NH4+ m−3 d−1 and a removal efficiency of 76% was achieved. Both constructed biofilms on low-density polyester Dacron support achieved
removal efficiencies higher than that of the concentrations normally present in reactors without constructed biofilms (P < 0.05). Nitrifying bacteria from the constructed biofilms cultures were typed by sequencing 16S rRNA genes that had been
amplified by PCR from genomic DNA. Analysis of enrichment biofilms has therefore provided evidence of high removal of ammonium
and the presence of Nitrosomonas eutropha, N. halophila and N. europaea in CAOB, while in CNOB Nitrobacter hamburgensis, N. winogradskyi and N. alkalicus were identified according to 16S rRNA gene sequences comparison. The biofilm reactors were nitrifying over the whole experimental
period (15 days), showing a definite advantage of constructed biofilms for enhancing a high biomass concentration as evidenced
by environmental electron microscopic analysis (ESEM). Our research demonstrates that low-density polyester Dacron can be
effectively used for the construction of nitrifying biofilms obtaining high removal efficiencies of nitrogen in a relatively
short time from municipal effluents from wastewater treatment plants. CAOB and CNOB are potentially promissory for the treatment
of industrial wastewaters that otherwise requires very large and expensive reactors for efficient bioremediation of effluents. 相似文献
15.
Comammox Nitrospira are abundant ammonia oxidizers in diverse groundwater‐fed rapid sand filter communities
下载免费PDF全文
![点击此处可从《Environmental microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Susan Jane Fowler Alejandro Palomo Arnaud Dechesne Paul D. Mines Barth F. Smets 《Environmental microbiology》2018,20(3):1002-1015
The recent discovery of completely nitrifying Nitrospira demands a re‐examination of nitrifying environments to evaluate their contribution to nitrogen cycling. To approach this challenge, tools are needed to detect and quantify comammox Nitrospira. We present primers for the simultaneous quantification and diversity assessement of both comammox Nitrospira clades. The primers cover a wide range of comammox diversity, spanning all available high quality sequences. We applied these primers to 12 groundwater‐fed rapid sand filters, and found comammox Nitrospira to be abundant in all filters. Clade B comammox comprise the majority (~75%) of comammox abundance in all filters. Nitrosomonadaceae were present in all filters, although at low abundance (mean = 1.8%). Ordination suggests that temperature impacts the structure of nitrifying communities, and in particular that increasing temperature favours Nitrospira. The nitrogen content of the filter material, sulfate concentration and surface ammonium loading rates shape the structure of the comammox guild in the filters. This work provides an assay for simultaneous detection and diversity assessment of clades A and B comammox Nitrospira, expands our current knowledge of comammox Nitrospira diversity and demonstrates a key role for comammox Nitrospira in nitrification in groundwater‐fed biofilters. 相似文献
16.
Ion exchange resins and glass microscope slides were used to investigate factors affecting attachment of nitrifying bacteria to solid surfaces and the effect of attachment on inhibition ofNitrobacter by potassium ethyl xanthate. The ammonium oxidizerNitrosomonas attached preferentially to cation exchange resins while the nitrite oxidizerNitrobacter colonized anion exchange resins more extensively. Colonization was always associated with growth, and the site of substrate (NH4
+ or NO2
–) adsorption was the major factor in attachment and colonization. The specific growth rate of cells colonizing either ion exchange resin beads or glass surfaces was greater than that of freely suspended cells, butNitrobacter populations colonizing glass surfaces were more sensitive to the inhibitor potassium ethyl xanthate. The findings indicate that surface growth alone does not protect soil nitrifying bacteria from inhibition by potassium ethyl xanthate and explain different patterns of inhibition for ammonium and nitrite oxidizers in the soil. 相似文献
17.
Development of a simultaneous partial nitrification and anaerobic ammonia oxidation process in a single reactor 总被引:9,自引:0,他引:9
Up-flow oxygen-controlled biofilm reactors equipped with a non-woven fabric support were used as a single reactor system for autotrophic nitrogen removal based on a combined partial nitrification and anaerobic ammonium oxidation (anammox) reaction. The up-flow biofilm reactors were initiated as either a partial nitrifying reactor or an anammox reactor, respectively, and simultaneous partial nitrification and anammox was established by careful control of the aeration rate. The combined partial nitrification and anammox reaction was successfully developed in both biofilm reactors without additional biomass inoculation. The reactor initiated as the anammox reactor gave a slightly higher and more stable mean nitrogen removal rate of 0.35 (± 0.19) kg-N m−3 d−1 than the reactor initiated as the partial nitrifying reactor (0.23 (± 0.16) kg-N m−3 d−1). FISH analysis revealed that the biofilm in the reactor started as the anammox reactor were composed of anammox bacteria located in inner anoxic layers that were surrounded by surface aerobic AOB layers, whereas AOB and anammox bacteria were mixed without a distinguishable niche in the biofilm in the reactor started as the partial nitrifying reactor. However, it was difficult to efficiently maintain the stable partial nitrification owing to inefficient aeration in the reactor, which is a key to development of the combined partial nitrification and anammox reaction in a single biofilm reactor. 相似文献
18.
Competition for Ammonium between Nitrifying and Heterotrophic Bacteria in Continuously Percolated Soil Columns 总被引:5,自引:1,他引:4
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Frank J. M. Verhagen Hendrik Duyts Hendrikus J. Laanbroek 《Applied microbiology》1992,58(10):3303-3311
Although the absence of nitrate formation in grassland soils rich in organic matter has often been reported, low numbers of nitrifying bacteria are still found in these soils. To obtain more insight into these observations, we studied the competition for limiting amounts of ammonium between the chemolithotrophic ammonium-oxidizing species Nitrosomonas europaea and the heterotrophic species Arthrobacter globiformis in the presence of Nitrobacter winogradskyi with soil columns containing calcareous sandy soil. The soil columns were percolated continuously at a dilution rate of 0.007 h-1, based on liquid volumes, with medium containing 5 mM ammonium and different amounts of glucose ranging from 0 to 12 mM.A. globiformis was the most competitive organism for limiting amounts of ammonium. The numbers of N. europaea and N. winogradskyi cells were lower at higher glucose concentrations, and the potential ammonium-oxidizing activities in the uppermost 3 cm of the soil columns were nonexistent when at least 10 mM glucose was present in the reservoir, although 107 nitrifying cells per g of dry soil were still present. This result demonstrated that there was no correlation between the numbers of nitrifying bacteria and their activities. The numbers and activities of N. winogradskyi cells decreased less than those of N. europaea cells in all layers of the soil columns, probably because of heterotrophic growth of the nitrite-oxidizing bacteria on organic substrates excreted by the heterotrophic bacteria or because of nitrate reduction at reduced oxygen concentrations by the nitrite-oxidizing bacteria. Our conclusion was that the nitrifying bacteria were less competitive than the heterotrophic bacteria for ammonium in soil columns but that they survived as viable inactive cells. Inactive nitrifying bacteria may also be found in the rhizosphere of grassland plants, which is rich in organic carbon. They are possibly reactivated during periods of net mineralization. 相似文献
19.
《Bioscience, biotechnology, and biochemistry》2013,77(9):1574-1578
Factors affecting heterotrophic nitrification by Alcaligenes faecalis OKK17, which was isolated from sewage sludge, were examined. Specific nitrifying activity increased as the pH increased up to 8.5. Most of the nitrogenous compounds (88%) in the culture supernatant were converted to hydroxylamine or nitrite at pH 9 but 87% of them remained as ammonium at pH 7. These results imply that the substrate for heterotrophic nitrification is ammonium and that the organism oxidizes ammonium to lower its toxic effect. Although the addition of acetate to a defined medium increased growth of the bacterium up to C/N = ca. 6, the accumulation of nitrification products almost paralleled the growth and the specific nitrifying activity decreased. Pyruvate and oxaloacetate increased the specific nitrifying activity six- to eightfold compared with the other organic acids examined, but the key enzyme activities in the glyoxylate cycle were not increased. Acetate, glyoxylate, and malonate did not increase the specific nitrifying activity, but they increased the enzyme activities. These results imply that the involvement of acetate metabolism in the heterotrophic nitrification is unlikely. 相似文献
20.
Microscale Distribution of Populations and Activities of Nitrosospira and Nitrospira spp. along a Macroscale Gradient in a Nitrifying Bioreactor: Quantification by In Situ Hybridization and the Use of Microsensors 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Andreas Schramm Dirk de Beer Johan C. van den Heuvel Simon Ottengraf Rudolf Amann 《Applied microbiology》1999,65(8):3690-3696
The change of activity and abundance of Nitrosospira and Nitrospira spp. along a bulk water gradient in a nitrifying fluidized bed reactor was analyzed by a combination of microsensor measurements and fluorescence in situ hybridization. Nitrifying bacteria were immobilized in bacterial aggregates that remained in fixed positions within the reactor column due to the flow regimen. Nitrification occurred in a narrow zone of 100 to 150 μm on the surface of these aggregates, the same layer that contained an extremely dense community of nitrifying bacteria. The central part of the aggregates was inactive, and significantly fewer nitrifiers were found there. Under conditions prevailing in the reactor, i.e., when ammonium was limiting, ammonium was completely oxidized to nitrate within the active layer of the aggregates, the rates decreasing with increasing reactor height. To analyze the nitrification potential, profiles were also recorded in aggregates subjected to a short-term incubation under elevated substrate concentrations. This led to a shift in activity from ammonium to nitrite oxidation along the reactor and correlated well with the distribution of the nitrifying population. Along the whole reactor, the numbers of ammonia-oxidizing bacteria decreased, while the numbers of nitrite-oxidizing bacteria increased. Finally, volumetric reaction rates were calculated from microprofiles and related to cell numbers of nitrifying bacteria in the active shell. Therefore, it was possible for the first time to estimate the cell-specific activity of Nitrosospira spp. and hitherto-uncultured Nitrospira-like bacteria in situ. 相似文献