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1.
A. Sellstedt 《Planta》1986,167(3):382-386
Acetylene reduction, 15N2 reduction and H2 evolution were measured in root systems of intact plants of grey alder (Alnus incana (L.) Moench) in symbiosis with Frankia. The ratios of C2H2: 15N2 were compared with C2H2:N2 ratios calculated from C2H2 reduction and H2 evolution, and with C2H2:N2 ratios calculated from accumulated C2H4 production and nitrogen content. It was possible to calculate C2H2:N2 ratios from C2H2 reduction and H2 evolution because this source of Frankia did not show any hydrogenase activity. The ratios obtained using the different methods ranged from 2.72 to 4.42, but these values were not significantly different. It was also shown that enriched 15N could be detected in the shoot after a 1-h incubation of the root-system. It is concluded that the measurement of H2 evolution in combination with C2H2 reduction represents a nondestructive assay for nitrogen fixation in a Frankia symbiosis which shows no detectable hydrogenase activity. 相似文献
2.
Molecular weight and quaternary structure of ribulose bisphosphate carboxylase from the cyanobacterium,Synechococcus sp. 总被引:3,自引:0,他引:3
T. John Andrews Kay M. Abel Diedrik Menzel Murray R. Badger 《Archives of microbiology》1981,129(5):344-348
Inhibition of photosynthetic growth of Rhodopseudomonas capsulata by metronidazole was dependent on the nitrogen supply in culture solutions. Cultures fixing dinitrogen were more susceptible to inhibition by low concentrations than those supplied with NH
4
+
. Light-dependent C2H2 reduction and H2 production by washed cells were inhibited by 80% and 60% respectively by 1 mM metronidazole. When this compound was first reduced with H2-palladised asbestos prior to assay, it only partially restricted C2H2 reduction in washed cells (33%) compared with unreduced inhibitor (68%). Metronidazole was without effect on other metabolic functions. Thus, even at 40 mM it did not inhibit either (a) dark or light respiration in cells grown under photo- and chemo-heterotrophic conditions; (b) H2-dependent photoreduction of 14CO2; (c) -glutamyltransferase activity of glutamine synthetase in cell-free extracts (25 mM inhibitor).Metronidazole (1 mM) completely inhibited C2H2 reduction by washed cells of Azotobacter vinelandii. The dithionite-dependent C2H2 reduction of a partially purified nitrogenase was only partially inhibited (30%) by 1 mM metronidazole. 相似文献
3.
Several blue-green algae were surveyed for the occurrence of the hydrogenase which was assayed by the oxyhydrogen or Knallgas reaction in the intact organisms. In aerobically grown cultures, the reaction was detectable in Anabaena cylindrica, Nostoc muscorum and in two Anabaena variabilis species, whereas virtually no activity was observed in Anacystis nidulans and Cyanophora paradoxa. In these latter two algae, the reaction was, however, found after growth under molecular hydrogen for several days, which drastically increased the activity levels with all the algae tested. In the nitrogen fixing species, the activity of the Knallgas reaction was enhanced when all combined nitrogen was omitted from the media. H2 and hydrogenase could not significantly support the CO2-fixation in photoreduction experiments with all blue-green algae investigated here. Hydrogenase was assayed by the dithionite and methyl viologen dependent evolution of hydrogen and was found to be present with essentially the same specific activity levels in preparations of both heterocysts and vegetative cells from Anabaena cylindrica. Na2S2O4 as well as H2 supported the C2H2-reduction of the isolated heterocysts. The H2-dependent C2H2-reduction did not require the presence of oxygen but was strictly light-dependent where H2 served as an electron donor to photosystem I of these cells. It is concluded that hydrogen can be utilized by two different pathways in blue-green algae.Abbreviations Chl
chlrophyll
- CP
creatine phosphate
- CP kinase
creatine phosphokinase
- DCMU
N-(3,4-dichlorophenyl)N,N-dimethylurea 相似文献
4.
The production of biomass, polysaccharide storage material and H2 from malate was studied in the wild-type and mutants RdcI, RdcII and RdcI/cII of Rhodobacter capsulatus. The mutants are defective in either copy I, copy II or both copies of the nitrogenase genes nifA and nifB. Stationary phase levels of biomass, polysaccharide and H2 were determined in phototrophic batch cultures grown with 30 mM of d,l-malate and either 2, 5, or 8 mM of ammonium or 7 mM of glutamate. Calculation of the amounts of malate converted into the
three products revealed that, at 8 mM of ammonium and 7 mM of glutamate, malate consumption and product formation were balanced.
But with decreasing ammonium concentrations malate not converted into biomass was utilized with decreasing efficiency in polysaccharide
and H2 formation. This suggests formation of unknown products at the lower ammonium concentrations. Under conditions of optimal
N supply, 80% of the malate not used for biomass production was converted by the wild-type and strain RdcII to H2 and CO2. Mutant RdcI exhibited slightly decreased H2 production. The double mutant did not evolve H2 but accumulated increased amounts of polysaccharide. However, the amounts of polysaccharide were lower than should be expected
if all of the spare malate, not utilized by the double mutant for H2 production, was converted into storage material. This and incomplete conversion of malate into known products at low ammonium
supplies suggests that polysaccharide accumulation does not compete with the process of H2 formation for malate. 相似文献
5.
W. De Boer P. J. A. Klein Gunnewiek R. A. Kester A. Tietema H. J. Laanbroek 《Plant and Soil》1993,149(2):292-296
The effectiveness of acetylene (C2H2) as inhibitor of nitrification was studied in relation to the decomposition of C2H2. This was done by examining the effects of single and multiple additions of different C2H2 concentrations (10, 100, 1000 Pa) on mineral N and NO3
–-N production in samples of the organic (FH) and upper mineral (Ah) layer of an acid oak-beech forest soil. The decomposition of C2H2 was much faster in Ah samples than in FH samples. A single addition of 10 Pa C2H2 was not sufficient for complete inhibition of nitrification in the Ah samples. Nitrification was blocked completely by all other C2H2 treatments in both FH and Ah samples. Addition of C2H2 decreased net mineral N production in Ah samples but not in FH samples. Addition of carboxymethyl-cellulose and chitin to Ah soil had no affect on the rate of decomposition of C2H2. Chitin had a negative effect on net NO3
–-N production. 相似文献
6.
Nelli Mnatsakanyan Karine Bagramyan Armen Trchounian 《Cell biochemistry and biophysics》2004,41(3):357-365
Fermenting Escherichia coli is able to produce formate and molecular hydrogen (H2) when grown on glucose. H2 formation is possessed by two hydrogenases, 3 (Hyd-3) and 4 (Hyd-4), those, in conjunction with formate dehydrogenase H (Fdh-H),
constitute distinct membrane-associated formate hydrogenylases. At slightly alkaline pH (pH 7.5), the production of H2 was found to be dependent on Hyd-4 and the F0F1-adenosine triphosphate (ATPase), whereas external formate increased the activity of Hyd-3. In this study with cells grown
without and with external formate H2 production dependent on pH was investigated. In both types of cells, H2 production was increased after lowering of pH. At acidic pH (pH 5.5), this production became insensitive either to N,N′-dicyclohexylcarbodiimide or to osmotic shock and it became largely dependent on Fdh-H and Hyd-3 but not Hyd-4 and the F0F1-ATPase. The results indicate that Hyd-3 has a major role in H2 production at acidic pH independently on the F0F1-ATPase. 相似文献
7.
GABOR J. BETHLENFALVAY SALAH S. ABU-SHAKRA KATHLEEN FISHBECK DONALD A. PHILLIPS 《Physiologia plantarum》1978,43(1):31-34
The effect on nitrogen fixation of excising leaves or pods in pea (Pisum sativum L. cv. Alaska) was determined over a 60-day period. Flower buds or their subtending leaves were removed, and C2H2 reduction, H2 evolution and N accumulation were measured at weekly intervals. Highest percentage nitrogen content in all treatments coincided with time of maximal C2H2-reduction rates. Nitrogen fixation, calculated from C2H2 reduction and H2- evolution data, was significantly lower in the partially defoliated and generally higher in the depodded plants than in the controls. Total N accumulation was greatest in the depodded plants and least in the defoliated ones. Percentage nitrogen content and N2-fixation rates in the depodded plants were maximized approximately 10 days later than in the defoliated or control plants. The absolute rates of C2H2 reduction and H2 evolution were significantly altered by plant organ removal, but the relative rates were proportional. As a result the ratios of H2/C2H4 production and the related relative efficiency of N2 fixation in the treatments were not significantly different from the controls. 相似文献
8.
Filimonova MN Gubskaya VP Nuretdinov IA Benedik MJ Cherepanova NA Leshchinskaya IB 《Biochemistry. Biokhimii?a》2001,66(3):323-327
The mechanism of action of p-chloromercuribenzoate (PCMB) on Serratia marcescens nuclease was investigated. The analysis showed that PCMB forms complexes with DNA. Binding of C7H5O2Hg+ to DNA changes the secondary structure of the DNA. These changes alter the enzymatic activity of S. marcescens nuclease, which was previously found to be sensitive to the secondary structure of the substrates. The nuclease activity was either suppressed or stimulated in the presence of PCMB depending on the C7H5O2Hg+ to nucleotide equivalent ratio. Binding of C7H5O2Hg+ to DNA did not form an abortive enzyme–substrate complex. Binding of Mg2+ to the C7H5O2Hg–DNA complex caused appropriate changes in secondary structure of the substrate. Since Mg2+ and C7H5O2Hg+, though differing in the type of metal cation, are similar in their mechanisms of influence on enzymatic activity of S. marcescens nuclease, the identity of other metal-containing effectors in their mechanism of action on Serratia marcescens nuclease is assumed. 相似文献
9.
Summary From acetylene reduction assays over a 10-month period starting in April 1979, nodule activities averaged 18.78 (se 4.67) moles C2H4 g nodule dw–1 h–1 forAlnus rubra and 59.95 (se 12.14) moles C2H4 g nodule dw–1 h–1 forCytisus scorparius. Plant rates were 1.91 (se. 47) moles C2H4 plant–1 h–1 forA. rubra and 0.55 (se. 17) moles C2H4 plant–1 h–1 forC. Scoparius. Plant activity and total leaf N were strongly correlated with the dw of other plant parts, but nodule activity and percent leaf N were not. Plant and nodule activities were not associated with temperature, moisture stress, precipitation events or percent light for either species over the growing season nor for 54A. rubra sampled in mid-season 1979 on one replication. After 5 to 6 growing seasons, 14A. rubra on the same site ranged from 30 to 332 cm in height and showed strong correlation between nodule dw, leaf dw, plant size and total leaf N. Results from this study and others indicate logistic equations may be modified to predict the effect of adding a N2 fixing plant to a population of non N2 fixing trees. 相似文献
10.
Various electron donors were found to stimulate C2H2 reduction (N2 fixation) by isolated heterocysts from Anabaena variabilis and Anabaena cylindrica. Intermediates of glycolysis and the tricarboxylic acid cycle as well as unphosphorylated sugars like glucose, fructose and erythrose were among these electron donors. The transfer of electrons from donors like H2, NADH, glyoxylate and glycollate was strictly light-dependent, whereas others like NADPH or pyruvate plus coenzyme A supported C2H2 reduction also in the dark. In all cases, the overall activity was enhanced by light. The stimulation by light was more distinct with heterocysts from A. variabilis than with heterocysts from A. cylindrica.The present communication establishes that pyruvate supports C2H2 reduction by heterocysts from either A. variabilis or A. cylindrica with rates comparable to those with other electron donors. Pyruvate could, however, support C2H2 reduction only in the presence of coenzyme A, and the concentrations of both coenzyme A and pyruvate were crucial. A pyruvate-dependent reduction of ferredoxin by extracts from heterocysts was recorded spectrophotometrically. Glyoxylate, which is an inhibitor of thiamine pyrophosphate-dependent decarboxylations, inhibited pyruvate-dependent C2H2 reduction. This result supports the conclusion that pyruvate is metabolised by pyruvate: ferredoxin oxidoreductase in heterocysts. High concentrations of pyruvate and other electron donors inhibited C2H2 reduction which suggests that nitrogenase activity in heterocysts may be controlled by the availability of electron donors.Dedicated to Professor Norbert Pfennig, Konstanz, on the occasion of his 60th birthday 相似文献
11.
Summary Carbon dioxide concentrations were elevated in three estuarine communities for an entire growing season. Open top chambers were used to raise CO2 concentrations ca. 336 ppm above ambient in monospecific communities of Scirpus olneyi (C3) and Spartina patens (C4), and a mixed community of S. olneyi, S. patens and Distichlis spicata (C4). Nitrogen and carbon concentration (% wt) of aboveground tissue was followed throughout growth and senescence. Green shoot %N was reduced and %C was unchanged under elevated CO2 in S. olneyi. This resulted in a 20%–40% increase in tissue C/N ratio. There was no effect of CO2 on either C4 species. Maximum aboveground N (g/m2) was unchanged in S. olneyi, indicating that increased productivity under elevated CO2 was dependent on reallocation of stored N. There was no change in the N recovery efficiency of S. olneyi in pure stand and a decrease in the mixed community. Litter C/N ratio was not affected by elevated CO2 suggesting that decomposition and N mineralization rates will also remain unchanged. Continued growth responses to elevated CO2 could, however, be limited by the ability of S. olneyi to increase the total aboveground N pool. 相似文献
12.
The blue-green alga Anabaena cylindrica is found to consume molecular hydrogen in a hydrogenase dependent reaction. This hydrogen uptake proceeds in the dark and is strictly dependent on oxygen, thus representing a Knallgas reactions. Its rate is almost as high as that of the endogenous respiration in Anabaena. Studies with inhibitors reveal that hydrogen is utilized via the complete respiratory chain providing additional energy for the alga. CO plus C2H2 completely block the Knallgas reaction which explains the previously reported considerable increase in the total H2 formation representing the difference between the nitrogenase-dependent H2-evolution and the reutilization of the gas catalysed by the hydrogenase in intact Anabaena.H2 is able to support the C2H2-reduction in the dark in a reaction again strictly dependent on oxygen. Moreover, H2 is also consumed in experiments carried out under far red light and in the presence of dichlorophenyl-dimenthyl-urea (DCMU) where the energy for nitrogen fixation is no longer provided by respiration but by cyclic photophosphorylation. Under these conditions, H2 is found to supply electrons for the formation of C2H4 from C2H2 in a reaction no longer dependent on the presence of oxygen. Moreover, in these experiments, the presence of H2 stabilizes the C2H2-reduction activity against the deleterious effect of oxygen.Thus, this communication provides evidence for a triplicate function of the H2-uptake catalysed by hydrogenase in intact Anabaena which is (a) to provide energy by the Knallgas reaction, (b) to supply reducing equivalents for nitrogenase, (c) to protect nitrogenase from damage by oxygen.Abbreviations DCMU
N-(3,4-dichlorophenyl)N,N-dimethylurea
- DNP
2-4-dinitrophenol
- FCCP
carbonylcyanid-p-trifluormethoxyphenyl-hydrazone(=p-CF3-CCP)
- Chl
chlorophyll 相似文献
13.
The sporangiophore of the fungus Phycomyces blakesleeanus has the property of growing away from a barrier which is few mm from the growing zone of the sporangiophore (avoidance or autochemotropic response). A model has been published (Cohen, R.J., Jan, N.Y., Matricon, J., Delbrück, M.: J. Gen. Physiol. 66, 67–95 (1975)). To explain the avoidance response which postulates that the sporangiophore emits and readsorbs a volatile growth-promoting effector (gas X) and that the barrier modifies the effector distribution by acting as an aerodynamic obstacle, causing a higher concentration of gas X on the side of the sporangiophore closer to the barrier. From this model we deduced three properties of the gas X. Of the several gases tested (N2, CO2, CH4, C2H2, C2H4, C2H6) only ethylene (C2H4) had all these three properties, a finding which suggests that it has a role in the avoidance response (autochemotropism).Abbreviation Spph
Sporangiophore 相似文献
14.
Nitrogen fixation was measured in four subarctic streams substantially modified by beaver (Castor canadensis) in Quebec. Acetylene-ethylene (C2H2 C2H4) reduction techniques were used during the 1982 ice-free period (May–October) to estimate nitrogen fixation by microorganisms colonizing wood and sediment. Mean seasonal fixation rates were low and patchy, ranging from zero to 2.3 × 10–3 µmol C2H4 · cm–2 · h–1 for wood, and from zero to 7.0 × 10–3 µmol C2H4 · g AFDM–1 · h–1 for sediment; 77% of all wood and 63% of all sediment measurements showed no C2H2 reduction. Nonparametric statistical tests were unable to show a significant difference (p > 0.05) in C2H2 reduction rates between or within sites for wood species or by sediment depth.Nitrogen contributed by microorganisms colonizing wood in riffles of beaver influenced watersheds was small (e.g., 0.207 g N · m–2 · y–1) but greater than that for wood in beaver ponds (e.g., 0.008 g N · m–2 · y–1) or for streams without beaver (e.g., 0.003 g N · m–2 · y–1). Although mass specific nitrogen fixation rates did not change significantly as beaver transform riffles into ponds, the nitrogen fixed by organisms colonizing sediment in pond areas (e.g., 5.1 g N · m–2 · y–1) was greater than that in riffles (e.g., 0.42 g N · m–2 · y–1). The annual nitrogen contribution is proportional to the amount of sediment available for microbial colonization. We estimate that total nitrogen accumulation in sediment, per unit area, is enhanced 9 to 44 fold by beaver damming a section of stream. 相似文献
15.
Isolated cotyledons of Phaseolus vulgaris L. cv. Canadian Wonder accumulated 14C2H4 (0.7–1 l l-1) from air to give partition coefficients of 1 to 4, which greatly exceeded the value obtained with steam killed cotyledons (0.05) and with water (0.11). After 14C2H4 treatment, 98% of the 14C in the tissue remained as 14C2H4. The labelled ethylene accumulated by cotyledons was released only slowly (1–10% h-1) either in an air stream or into toluene. Heating to 60°C for 2 h, but not freezing and thawing, caused the immediate release of 14C2H4 from the tissue. Propylene and vinyl chloride competitively inhibited the accumulation of 14C2H4.Cotyledons emanated endogenous ethylene at a very low rate but after heating (although not freezing and thawing) 13 nl of ethylene per g fresh mass were released within minutes. It was concluded that french bean cotyledons hold ethylene in a compartmented form in sufficient amount to account for at least 200 h of emanation.Abbreviation PPO
diphenyloxazole 相似文献
16.
A mixed beech and spruce forest soil was incubated under potential denitrification assay (PDA) condition with 10% acetylene (C2H2) in the headspace of soil slurry bottles. Nitrous oxide (N2O) concentration in the headspace, as well as nitrate, nitrite and ammonium concentrations in the soil slurries were monitored during the incubation. Results show that nitrate disappearance rate was higher than N2O production rate with C2H2 blockage during the incubation. Sum of nitrate, nitrite, and N2O with C2H2 blockage could not recover the original soil nitrate content, showing an N imbalance in such a closed incubation system. Changes in nitrite and ammonium concentration during the incubation could not account for the observed faster nitrate disappearance rate and the N imbalance. Non-determined nitric oxide (NO) and N2 production could be the major cause, and the associated mechanisms could vary for different treatments. Commonly applied PDA measurement likely underestimates the nitrate removal capacity of a system. Incubation time and organic matter/nitrate ratio are the most critical factors to consider using C2H2 inhibition technique to quantify denitrification. By comparing the treatments with and without an antibiotic, the results suggest that microbial N uptake probably played a minor role in N balance, and other denitrifying enzymes but nitrate reductase could be substantially synthesized during the incubation. 相似文献
17.
A model system is described where Azospirillum and germinated wheat seeds were grown in association for a week and then assayed for nitrogen fixation (C2H2-reduction) and denitrification (N2O-formation) activities. The association performed C2H2-reduction and N2O-formation under microaerobic conditions. Both activities were measurable after already 3–5 h of incubation with substantial rates and were strictly dependent on the presence of both plants and bacteria. During the week of the growth of the association, the bacteria had lived exclusively from the carbon compounds supplied by the roots of the plants. C2H2-reduction activity by the association was more or less the same with all the Azospirillum brasilense strains, but lower with A. lipoferum and with the A. amazonense strains tested. Two nitrogenase negative mutants of Azospirillum brasilense showed virtually no activity in the association. C2H2-reduction activity was strongly dependent on the growth temperature of the association. Denitrification (N2O-formation) was high also at higher temperatures and at pH-values in the medium around 7.8 but not at neutrality and was strictly dependent on nitrate. The Azospirillum strain used strongly determined the rate of the N2O-formation in the association. It is suggested that Azospirillum may be beneficial to crops particularly under tropical conditions.Dedicated to Professor Dr. Gerhart Drews, Freiburg, on the occasion of his 60th birthday 相似文献
18.
Methylobacterium dichloromethanicum was found to be able to utilize dichloromethane (DCM) as the source of carbon and energy with the production of biomass, CO2, and HCl. A comparative analysis of the abundances of the major DCM isotopomers 35Cl2
12C1H2, 35Cl37Cl12C1H2, and 37Cl2
12CH21H2 made it possible to estimate the fractionation of chlorine isotopes during the bacterial metabolism of DCM. The kinetic chlorine isotope effects for 35Cl37Cl12C1H2 (m/z 86) and 37Cl2
12C1H2 (m/z 88) relative to 35Cl2
12C1H2 (m/z 84) were characterized by 86/84 = 1.006 ± 0.002 and 88/84 = 1.023 ± 0.003, respectively. The inference is made that the growth of M. dichloromethanicum on DCM is accompanied by the mass-independent fractionation of the DCM isotopomers. 相似文献
19.
Combined gasification and fermentation technologies can potentially produce biofuels from renewable biomass. Gasification
generates synthesis gas consisting primarily of CO, CO2, H2, N2, with smaller amounts of CH4, NOx, O2, C2 compounds, ash and tars. Several anaerobic bacteria species can ferment bottled mixtures of pure synthesis gas constituents.
However, there are challenges to maintaining culture viability of synthesis gas exposed cells. This study was designed to
enhance culture stability and improve ethanol-to-acetate ratios using resting (non-growing) cells in synthesis gas fermentation.
Resting cell states were induced in autotrophic Clostridium ljungdahlii cultures with minimal ethanol and acetate production due to low metabolic activity compared to growing cell production levels
of 5.2 and 40.1 mM of ethanol and acetate. Clostridium autoethanogenum cultures were not induced into true resting states but did show improvement in total ethanol production (from 5.1 mM in growing
cultures to 9.4 in one nitrogen-limited medium) as well as increased shifts in ethanol-to-acetate production ratios. 相似文献
20.
A comparative study has been made on the pigment composition and nitrogenase activity of whole filaments and isolated beterocysts from a mutant strain of Anabaena CA. The whole cell absorption spectra of intact filaments and isolated heterocysts showed close resemblance especially between 550–700 nm region. On a quantitative basis the chlorophyll a content was found almost equal between the vegetative cell and heterocyst but the c-phycocyanin content in the heterocyst was about 1/2 that of the vegetative cell. The purification of the phycobiliprotein on DEAE-cellulose showed the presence of c-phycocyanin (max 615 nm) and allophycocyanin (max 645 nm, shoulder 620 nm). Isolated heterocysts under H2 showed acetylene reduction rates of 57 nmol C2H4/mg dry wt·min (342 mol C2H4/mg chl a·h), whereas intact filaments reduced at the rate of 18 nmol C2H4/mg dry wt·min (108 mol C2H4/mg chl a·h). This rate accounts for 30% recovery of nitrogenase activity in isolated heterocysts compared to whole filaments. The activity was strictly light dependent and was linear under H2 for more than 3 h. Addition of as little as 5% H2 under argon stimulated the C2H2 reductionseveral fold. The acetylene reduction (nitrogenase activity) also showed tolerance to 5% added O2 either under H2 or argon. The results suggest that the heterocyst of Anabaena CA-V is different in some characteristics (viz., higher endogenous C2H2 reduction rate, prolonged activity and higher levels of phycobiliproteins) than those reported in other Anabaena species. 相似文献