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1.
Nitrification and denitrification by Thiosphaera pantotropha in aerobic chemostat cultures 总被引:4,自引:0,他引:4
Abstract: Thiosphaera pantotropha has been reported to denitrify aerobically and nitrify heterotrophically. However, recent evidence has indicated that these properties (particularly aerobic denitrification) have been lost. The occurrence and levels of aerobic denitrification and heterotrophic nitrification by T. pantotropha in chemostat cultures have therefore been re-evaluated. Only low nitrate reduction rates were observed: the apparent nitrogen loss was of the same order of magnitude as the combined error in the calculated nitrogen consumption. However, 15 N mass spectrometry revealed low aerobic denitrification rates (about 10% of the rates originally published by this group). Heterotrophic nitrification rates were about a third of previous observations. N2 and N2 O were both produced from NH4 + , NO3 − and NO2 − . Periplasmic nitrate reductase was present in aerobically grown cells. 相似文献
2.
Lesley A. Robertson Tage Dalsgaard Niels-Peter Revsbech J.Gijs Kuenen 《FEMS microbiology ecology》1995,18(2):113-120
Abstract: Because of a revival in the controversy surrounding 'aerobic denitrification', especially in relation to Thiosphaera pantotropha , activity in aerobic batch cultures was evaluated using gas chromatography and mass spectrometry after the addition of 15 N-labelled NH4 + and NO2 − . Aerobic denitrifying activity in T. pantotropha was present, but only at about 10% of the originally-reported levels. The activity of ' Pseudomonas denitrificans ' was similar to previously-reported values. Alcaligenes faecalis showed significant aerobic denitrifying activity, producing almost equivalent amounts of N2 and N2 O. An unidentified pseudomonad, isolate G4, presumably requires anoxia for enzyme activity as it did not denitrify aerobically, even though it has a constitutive denitrifying pathway. 相似文献
3.
Aims: Statistical optimization of medium components for improved chitinase production by Paenibacillus sp. D1.
Methods and Results: Urea, K2 HPO4 , chitin and yeast extract were identified as significant components influencing chitinase production by Paenibacillus sp. D1 using Plackett–Burman method. Response surface methodology (central composite design) was applied for further optimization. The concentrations of medium components for improved chitinase production were as follows (g l−1 ): urea, 0·33; K2 HPO4 , 1·17; MgSO4 , 0·3; yeast extract, 0·65 and chitin, 3·75. This statistical optimization approach led to the production of 93·2 ± 0·58 U ml−1 of chitinase.
Conclusions: The important factors controlling the production of chitinase by Paenibacillus sp. D1 were identified as urea, K2 HPO4 , chitin and yeast extract. Statistical approach was found to be very effective in optimizing the medium components in manageable number of experimental runs with overall 2·56-fold increase in chitinase production.
Significance and Impact of the Study: The present investigation provides a report on statistical optimization of medium components for improved chitinase production by Paenibacillus sp. D1. Paenibacillus species are gram-positive, spore-forming bacteria with several PGPR and biocontrol potentials. However, only few reports concerning mycolytic enzyme production especially chitinases are available. Chitinase produced by Paenibacillus sp. D1 represents new source for biotechnological and agricultural use. 相似文献
Methods and Results: Urea, K
Conclusions: The important factors controlling the production of chitinase by Paenibacillus sp. D1 were identified as urea, K
Significance and Impact of the Study: The present investigation provides a report on statistical optimization of medium components for improved chitinase production by Paenibacillus sp. D1. Paenibacillus species are gram-positive, spore-forming bacteria with several PGPR and biocontrol potentials. However, only few reports concerning mycolytic enzyme production especially chitinases are available. Chitinase produced by Paenibacillus sp. D1 represents new source for biotechnological and agricultural use. 相似文献
4.
Jens Kirk Thomsen J.J. Lønsmann Iversen Raymond P. Cox 《FEMS microbiology letters》1993,110(3):319-323
Abstract The effects of oxygen on the use of nitrate as an electron acceptor by the denitrifying bacterium Thiosphaera pantotropha were investigated during growth on acetate. In batch cultures under aerobic conditions nitrate was not utilised and the growth rate constant was 0.55 h−1 . The corresponding value for growth on nitrate under anoxic conditions was 0.37 h−1 . In acetate-limited continuous cultures with feedback control of the dissolved oxygen concentration, nitrate utilisation was totally inhibited by the lowest concentration of oxygen tested (22 μM). Carbon conversion efficiencies with acetate increased from 0.28 with nitrate to 0.44 with oxygen. The rates of nitrification calculated from nitrogen balance studies were not greater than 1.5% of the rate of anoxic denitrification. 相似文献
5.
Abstract The competitive advantages provided by a capacity for aerobic denitrification have been tested by comparing Thiosphaera pantotropha (which denitrifies aerobically and anaerobically), with a strain of Paracoccus denitrificans (which only denitrifies under anaerobic conditions) in acetate-limited chemostats. A comparison of μ -Cs curves based on K s and μ max measurements indicated that Pa. denitrificans could be expected to dominate mixtures of the two species at high growth rates when the dissolved oxygen was above 80% of air saturation and NH3 was the sole source of nitrogen. The comparison also suggested t that at lower growth rates, lower dissolved oxygen tensions, and/or in the presence of nitrate, Tsa. pantotropha should have the competitive advantage. Chemostat experiments with mixtures of the two species showed that Tsa. pantotropha did, indeed, dominate the population when expected. However, when Pa. denitrificans was expected to dominate, only a small increase in the Pa. denitrificans numbers was possible before Tsa. pantotropha formed a biofilm on the walls of the chemostat instead of washing out, and was again able to out-compete Pa. denitrificans for acetate. Experiments with axenic chemostat cultures subjected to aerobic/anaerobic switches showed that Tsa. pantotropha , with its constitutive denitrifying system, was able to adjust smoothly to the changing environmental conditions and thus continued to grow. Pa. denitrificans does not have constitutive denitrifying enzymes, and could consequently not adjust its metabolism to the lack of oxygen rapidly enough. It therefore washed out at a rate equivalent to the dilution rate. 相似文献
6.
Production of clover broomrape seed germination stimulants by red clover root requires nitrate but is inhibited by phosphate and ammonium 总被引:4,自引:0,他引:4
The effect of nutrients (nitrate, ammonium, urea, phosphate and potassium) on the production and/or exudation of germination stimulants for clover broomrape ( Orobanche minor Sm.), a root holoparasite, by its host red clover ( Trifolium pratense L.) was examined using hydroponically grown material. Potassium (K2 SO4 ) concentrations up to 100 mg l–1 (based on K) did not affect the production of germination stimulants by red clover while, in contrast, phosphate (NaH2 PO4 ) was highly inhibitory even at concentrations as low as 1 mg l–1 (based on P). Nitrate (NaNO3 ) markedly promoted stimulant production in a dose-dependent manner from 2 to 50 mg l–1 (based on N). Ammonium [(NH4 )2 SO4 ] had no effect at 2 mg l–1 (based on N) but was inhibitory at higher concentrations. Ammonium is known to be a seed germination inhibitor of root parasites, indicating that ammonium has a dual inhibitory action. Urea had no effect at 2 mg l–1 (based on N) but was promotive at higher concentrations. These results provide a basis for the inhibitory effects of nitrogen fertilizer on infection by root parasitic weeds, broomrapes and witchweeds, and explain why these parasites prevail in areas where there is lower phosphorus availability in soils. 相似文献
7.
A new method using lysozyme for the production of axenic cultures of Anabaena flos-aquae De Brebisson and Aphanothece nidulans P. Richter was developed. Cyanobacterial growth was not inhibited at concentrations up to 1.2 g·L−1 of lysozyme, whereas the growth of heterotrophic bacteria was suppressed. At concentrations up to 0.8 g·L−1 of lysozyme, ampicillin caused a reduction of heterotrophic bacteria. The axenic cultures of these strains were acquired through a simple treatment using 1.0 g·L−1 of lysozyme without ampicillin. These cyanobacteria resisted digestion by lysozyme at our experimental concentrations, whereas bacteria were digested selectively. This method of purification seems to be especially useful with cyanobacterial species that are sensitive to antibiotics or other germicidal agents. 相似文献
8.
Abstract Freshly isolated soil bacteria were screened for different characteristics of the H2 metabolism without prior selection for growth on H2 . The bacteria were isolated from different grain size fractions of a neutral meadow cambisol and an acidic forest cambisol, and then tested (1) for the ability to oxidize H2 , (2) for chemolithoautotrophic growth on H2 as sole electron donor and energy source, (3) for DNA-DNA-hybridization with two hydrogenase gene fragments from Alcaligenes eutrophus and Rhizobium leguminosarum , and (4) for reduction of 2,3,5-triphenyl-2H-tetrazoliumchloride (TTC) in the presence of H2 . Many (65–90%) of the isolates were able to reduce TTC, but only 30–65% were actually able to oxidize H2 indicating that the TTC test was not a specific characteristic for H2 oxidation ability. The TTC test was only reliable in pure cultures of known bacteria with optimized test conditions, here shown for Alcaligenes eutrophus, Bradyrhizobium japonicum and Nocardia opaca , but not in mixed cultures of unknown bacteria. Still less (< 30%) of the isolates were able to grow chemolithoautotrophically indicating that culturable aerobic bacteria with the ability for H2 oxidation are more abundant than bacteria with the ability for chemolithoautotrophic growth. The DNA-DNA-hybridization test failed to detect many of the bacteria with H2 oxidation activity, probably since the hydrogenase genes present in the isolates were too diverse to be all detected by the DNA probes applied. 相似文献
9.
Algal growth enhancement by bacteria: Is consumption of photosynthetic oxygen involved? 总被引:9,自引:0,他引:9
Jean-Luc Mouget Azzeddine Dakhama Marc C. Lavoie Joël de la Noüe 《FEMS microbiology ecology》1995,18(1):3-5
Abstract: Pseudomonas diminuta and P. vesicularis , two obligate aerobes isolated from laboratory algal cultures, stimulated the growth of the green microalgae Scenedesmus bicellularis and Chlorella sp., without releasing any growth promoting substance. An intimate contact between both microorganisms was necessary for significant algal growth enhancement. The possibility of algal growth stimulation by bacterial attenuation of photosynthetic oxygen tension was indirectly examined by simulating the effect of bacteria through a physical removal of oxygen (air suction). Vacuum-treated cultures showed an increase in growth rate and photosynthetic activity as compared to the control, a result which cannot be explained by differences in CO2 /HCO3 − pump activity. In the presence of P. diminuta , the photosynthetic activity of S. bicellularis was more strongly stimulated under a limited concentration of inorganic carbon. It is suggested that, apart from a CO2 supply, aerobic bacteria can promote algal growth by reducing the photosynthetic oxygen tension within the microenvironment of the algal cells, thereby creating more favorable conditions for optimal photosynthetic algal growth. 相似文献
10.
Eva Marie Muehe Simone Gerhardt Bernhard Schink & Andreas Kappler 《FEMS microbiology ecology》2009,70(3):3-11
In order to assess the importance of nitrate-dependent Fe(II) oxidation and its impact on the growth physiology of dominant Fe oxidizers, we counted these bacteria in freshwater lake sediments and studied their growth physiology. Most probable number counts of nitrate-reducing Fe(II)-oxidizing bacteria in the sediment of Lake Constance, a freshwater lake in Southern Germany, yielded about 105 cells mL−1 of the total heterotrophic nitrate-reducing bacteria, with about 1% (103 cells mL−1 ) of nitrate-reducing Fe(II) oxidizers. We investigated the growth physiology of Acidovorax sp. strain BoFeN1, a dominant nitrate-reducing mixotrophic Fe(II) oxidizer isolated from this sediment. Strain BoFeN1 uses several organic compounds (but no sugars) as substrates for nitrate reduction. It also reduces nitrite, dinitrogen monoxide, and O2 , but cannot reduce Fe(III). Growth experiments with cultures amended either with acetate plus Fe(II) or with acetate alone demonstrated that the simultaneous oxidation of Fe(II) and acetate enhanced growth yields with acetate alone (12.5 g dry mass mol−1 acetate) by about 1.4 g dry mass mol−1 Fe(II). Also, pure cultures of Pseudomonas stutzeri and Paracoccus denitrificans strains can oxidize Fe(II) with nitrate, whereas Pseudomonas fluorescens and Thiobacillus denitrificans strains did not. Our study demonstrates that nitrate-dependent Fe(II) oxidation contributes to the energy metabolism of these bacteria, and that nitrate-dependent Fe(II) oxidation can essentially contribute to anaerobic iron cycling. 相似文献
11.
Helicobacter pylori utilises urea for amino acid synthesis 总被引:2,自引:0,他引:2
C.L. Williams T. Preston M. Hossack C. Slater K.E.L. McColl 《FEMS immunology and medical microbiology》1996,13(1):87-94
Abstract Helicobacter pylori has one of the highest urease activities of all known bacteria. Its enzymatic production of ammonia protects the organism from acid damage by gastric juice. The possibility that the urease activity allows the bacterium to utilise urea as a nitrogen source for the synthesis of amino acids was investigated. H. pylori (NCTC 11638) was incubated with 50 mM urea, enriched to 5 atom% excess 15 N, that is the excess enrichment of 15 N above the normal background, in the presence of either NaCl pH 6.0, or 0.2M citrate pH 6.0. E. coli (NCTC 9001) was used as a urease-negative control. 15 N enrichment was detected by isotope ratio mass spectrometry. H. pylori showed intracellular incorporation of 15 N in the presence of citrate buffer pH 6.0 but there was no significant incorporation of 15 N in unbuffered saline or by E. coli in either pH 6.0 citrate buffer or unbuffered saline. The intracellular fate of the urea-nitrogen was determined by means of gas chromatography/mass spectrometry following incubation with 15 N enriched 5 mM urea in the presence of either 0.2 M citrate buffer pH 6.0 or 0.2 M acetate buffer pH 6.0. After 5 min incubation in either buffer the 15 n label appeared in glutamate, glutamine, phenylalanine, aspartate and alanine. It appears, therefore, that at pH and urea concentrations typical of the gastric mucosal surface, H. pylori utilises exogenous urea as a nitrogen source for amino acid synthesis. The ammonia produced by H. pylori urease activity thus facilitates the organism's nitrogen metabolism at neutral pH as well as protecting it from acid damage at low pH. 相似文献
12.
Exopolysaccharide and storage polymer production in Enterobacter aerogenes type 8 strains 总被引:1,自引:1,他引:0
Many exopolysaccharide (EPS)-producing bacterial strains also synthesize storage polymers. The production of slime EPS and of the storage polymer glycogen was compared in batch cultures of EPS+ and EPS- isogenic strains of Enterobacter aerogenes type 8. Conditions of nutrient imbalance with high C: N ratios favoured both EPS and storage polymer synthesis and resulted in little subsequent degradation of glycogen. In the EPS+ strain, glycogen synthesis was consistently lower than in the EPS- strain, indicating that substrate was preferentially used for EPS production. Reduced levels of carbon substrate in the growth medium resulted in lower storage polymer synthesis and in the degradation of the glycogen formed in EPS-producing bacteria. Considerable differences in the synthesis and breakdown of intracellular carbohydrate were observed between bacteria grown in synthetic media with ammonium salts and the same bacteria grown in medium with casein hydrolysate as the nitrogen source. Growth in media depleted in magnesium was slower than in complete media but high yields of glycogen were obtained in both the EPS+ and EPS- strains. 相似文献
13.
The effects of tridemorph and vinclozolin were studied on different types of microorganisms, urea hydrolysis and nitrification
in soil and in culture. The fungicides adversely affected the population of bacteria, fungi and actinomycetes as a function
of time of incubation. Urea hydrolysis both in culture and soil were also inhibited by the fungicides, and tridemorph was
more detrimental. In soil, 45μg/g of tridemorph inhibited 50 % of ammonification of urea, ID50 for nitrite production was 750μg/g. In urea-hydrolyzing cultures, 80, 75 and 77 mg/L of tridemorph were the ID50 values for urea hydrolysis byMicrococcus sp.,Proteus sp. andP. vulgaris respectively. 相似文献
14.
Interspecies hydrogen transfer in co-cultures of methanol-utilizing acidogens and sulfate-reducing or methanogenic bacteria 总被引:2,自引:0,他引:2
Abstract The metabolism of methanol by acidogenic bacteria ( Butyribacterium methylotrophicum, Sporomusa ovata and Acetobacterium woodii ) was studied in pure culture and in defined mixed cultures with sulfate-reducing bacteria ( Desulfovibrio vulgaris ) or methanogenic bacteria ( Methanobrevibacter arboriphilus strain AZ). In the mixed cultures, less acids (acetate and/or butyrate) were formed per unit methanol converted than in pure cultures. In these mixed cultures, a significant production of sulfide or methane was observed despite the inability of the sulfate reducer and the methanogen to use methanol as an energy substrate. These results are explained in terms of interspecies hydrogen transfer between the acidogens (converting part of the methanol to 1 CO2 and 3 H2 ) and the Desulfovibrio or Methanobrevibacter species. The bioenergetic aspects of this process and its ecological implications are discussed. 相似文献
15.
Comparison of quantitative and qualitative methods of detecting hydrogen peroxide produced by human vaginal strains of lactobacilli 总被引:1,自引:0,他引:1
A quantitative method was developed for the measurement of micromolar quantities of H2 O2 produced in Rogosa broth and peptonized milk broth by vaginal strains of lactobacilli isolated from women. The production of substantial amounts reproducibly was dependent on the growth of the organisms in acid media (pH ≤6.0) under anaerobic or micro-aerophilic conditions with continuous agitation. The addition to the media of the enzyme inhibitor, 3-amino-l,2,4-triazole, with or without catalase sometimes induced the production of H2 O2 especially in non-agitated cultures. However, other agents such as concanavalin and o -dianisidine had no enhancing effect, and catalase or peroxidase alone completely inhibited H2 O2 production.
The H2 O2 produced in the acid media was stable for more than a month at 5°C but not in media at pH ≥ 7.0. Of five strains of lactobacilli tested by the quantitative method and by a chromogenic qualitative method (Rogosa-catalase or -peroxidase agar), three consistently produced H2 O2 measurable by the former method, but none did so after growth of the organisms on Rogosa-catalase/peroxidase agar which suggested that the qualitative method was unreliable. The fact that H2 O2 was produced in substantial quantities by some strains and not at all by others enabled H2 O2 -producers and non-producers to be distinguished easily. 相似文献
The H
16.
Guy P.M.A. Hardy M. Joost Teixeira de Mattos Oense M. Neijssel 《FEMS microbiology letters》1993,107(1):107-110
Abstract When grown in carbon source-limited chemostat cultures with lactate or glucose as the carbon and energy source and xylose as an additional source of reducing equivalents, Pseudomonas putida NCTC 10936 oxidized xylose to xylonolactone and xylonate. No other products were formed from this pentose, nor was it incorporated into biomass. The presence of xylose in these cultures resulted in higher Yglucose and Ylactate values as compared to cultures without xylose indicating that biologically useful energy was conserved during the periplasmic oxidation of xylose. As the Y0 values for growth on glucose or on lactate alone were equal to the Y0 values with xylose as co-substrate, it is concluded that for flucose- or lactate-limited growth energy conservation by PQQH2 oxidation is as efficient as by NADH2 oxidation. 相似文献
17.
Enhanced degradation of petrol (Slovene diesel) in an aqueous system by immobilized Pseudomonas fluorescens 总被引:1,自引:1,他引:0
The rate of degradation of n -alkanes C12 -C18 , in petrol (Slovene diesel) in an aqueous system, by free and immobilized Pseudomonas fluorescens in shaking flasks was investigated. Cells were immobilized to a biosupport, Biofix, and a biosorbant, Drizit. Analysis of cellular growth of the free and immobilized bacteria over 8 d of incubation with diesel as the sole carbon source, showed a reduction in the lag phase in the immobilized cultures in comparison to the free system. The free system degraded 52·3% of C12 and 11·6% of C13 , but C14 -C18 were not degraded. In comparison to the free system and diesel which had not been exposed to experimental conditions (unexposed), the immobilized systems degraded significantly more of C13 -C18 . Biofix-immobilized cells degraded 14·8% of C12 and an average of 53·5% of C13 -C18 . Drizit-immobilized cells degraded 24·5% of C12 , 52·4% of C13 and an average of 91·2% of C14 -C18 . This study shows the successful use of immobilized bacteria technology to enhance the degradation of diesel in an aqueous system. 相似文献
18.
The metabolism of sugar and malic acid by Leuconostoc oenos: effect of malic acid, pH and aeration conditions 总被引:1,自引:1,他引:0
M. Paula Firme M. Cristina Leitão M. Vitória San Romão 《Journal of applied microbiology》1994,76(2):173-181
The co-metabolism of sugars by Leuconostoc oenos was studied under different environmental conditions. Under aerobic conditions, growth and sugar metabolism were poorer than under CO2 or N2 atmosphere and acetic acid accumulated to a larger extent. Glycerol was found in the aerobic cultures while erythritol was detected under N2 or CO2 . When medium conditions make growth difficult (low pH, aerobic conditions, low nutrients), sugars were only slightly metabolized and growth was very slow while malic acid was rapidly and completely degraded, leading to an increase in the y ATP . Aeration effects on the malic acid degradation rate depended on the nutrients and carbon source in the medium. Malic acid clearly stimulated bacterial growth, allowing an increase in the molar growth yields and ATP production. The results suggest that under adverse conditions cells are not able to grow and malic degradation supplies additional energy production. 相似文献
19.
R J Chróst J Owczarek K Matusiak 《Acta microbiologica Polonica. Series B: Microbiologia applicata》1975,7(4):231-236
Studies were conducted to determine the role of bacteria and algae in the degradation of urea in industrial waste waters. The microflora accompanying algae in continuous cultures on waste waters from the nitrogen fertilizers industry was found to include bacteria capable of intensive degradation of urea. Urea hydrolyzing bacteria are with time eliminated from the algal culture. This elimination can be attributed to algal metabolites which inhibit the development of sensitive bacteria. The Chlorella vulgaris strain used in the treatment of wast waters from the nitrogen fertilizers industry did not hydrolyse urea. 相似文献