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1.
Hydrogen-supported nitrogenase activity was demonstrated in Anabaena cylindrica cultures limited for reductant. Nitrogen-fixing Anabaena cylindrica cultures sparged in the light with anaerobic gases in the presence of the photosynthesis inhibitor DCMU slowly lost their ability to reduce acetylene in the light under argon but exhibited near normal activities in the presence of 11% H2 (balance argon). The hydrogen-supported nitrogenase activity was half-saturated between 2 and 3% H2 and was strongly inhibited by oxygen (50% inhibition at about 5–6% O2). Batch cultures of Anabaena cylindrica approaching stationary growth phase (“old” cultures) lost nitrogenase-dependent hydrogen evolution almost completely. In these old cultures hydrogen relieved the inhibitory effects of DCMU and O2 on acetylene reduction. Our results suggest that heterocysts contain an uptake hydrogenase which supplies an electron transport chain to nitrogenase but which couples only poorly with the respiratory chain in heterocysts and does not function in CO2 fixation by vegetative cells. 相似文献
2.
Summary The effects of oxygen, light and photosynthesis inhibitors on nitrogenase activities in Anabaena cylindrica batch cultures were followed as a function of time after inoculation. During the early rapid growth period the nitrogenase activities of cultures grown under air/CO2 or N2/CO2 were relatively resistant to oxygen and DCMU inhibition. These cultures also exhibited oxygen-dependent nitrogenase activity in the dark of up to 50% of that measured in the light. After active growth ceased the cultures continued to slowly grow for a prolonged period of time. The nitrogenase activities of these old cultures were very sensitive to oxygen and DCMU inhibition. These cultures also had little or no dark nitrogenase activities. The photosynthesis inhibitor DBMIB was not a specific inhibitor of light-driven electron transport since it inhibited both light and dark nitrogenase activities. Nitrogenase activities induced under oxygen-free/CO2 gas mixtures initially were significantly more sensitive to oxygen inhibition than those induced under air/CO2. We discuss these results in relation to heterocyst function. 相似文献
3.
The site of nitrogen fixation in the blue-green alga Anabaenacylindrica Lemra (Fogg strain) was investigated. Less than 4%of the total nitrogen fixed during a relatively short period(5-15 min) was recovered in heterocysts. When estimated on thecellular nitrogen basis, vegetative cells can fix molecularnitrogen at the same rate as do heterocysts. There was no positivecorrelation between nitrogen fixation and heterocyst formation.Results do not support the hypothesis that the heterocyst isthe main site for nitrogen fixation in blue-green algae.
1 This work was supported by grant (No. 38814) from the Ministryof Education. (Received July 23, 1971; ) 相似文献
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Photostimulation of nitrogen fixation in Anabaena cylindrica 总被引:5,自引:0,他引:5
P Fay 《Biochimica et biophysica acta》1970,216(2):353-356
6.
Ammonia at a concentration of 1 ? 103M completely inhibitednitrogenase activity, as measured by acetylene reduction, inthe blue-green alga Anabaena cylindrica. Free ammonia was undetectablein cells grown either on N2 or ammonia within the limits ofprecision of the method used. Glutamic acid formed a major aminoacid pool in N2-grown cells, and basic amino acids, i.e. lysine,histidine and arginine were abundant in ammonia-grown cells.A 10-fold increase in the amounts of labile amino compound(s)was observed when N2-grown cells were exposed to ammonia. When cells were incubated under anaerobic conditions, the acetylene-reducingactivity increased 2-fold or more; ammonia had no effect. Oxygenwas required for ammonia to inhibit acetylene reduction. Modes of inhibition by ammonia on acetylene reduction were comparedwith those by chloramphenicol, puromycin, cycloheximide, DCMUand CCCP. On the basis of these comparisons we concluded thatammonia not only acts as a suppressor of nitrogenase synthesisbut also inhibits acetylene-reducing activity by lowering thesupply of reductant and/or of energy for the nitrogenase system.
1This work was supported by grant No. 38814 from the Ministryof Education. (Received July 30, 1973; ) 相似文献
7.
We have studied the evolution of hydrogen by photobleached filaments of the heterocystous bluegreen alga Anabaena cylindrica. The photobleached cells became orange-yellow due to the heavy accumulation of carotenoids. We found that the yellow filaments produced much larger amounts of hydrogen than the normal, green ones, while the nitrogenase activity responsible for hydrogen evolution increased to a lesser extent. We suggest that a reversible hydrogenase activity induced in photobleached filaments is responsible for the excess amount of hydrogen. 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU) inhibits the hydrogen evolution of the yellow filaments which produce much more oxygen and fix less CO2 than the green filaments. Therefore we consider the water to be a possible electron source for this hydrogenase. The low efficiency of light energy conversion (0.3%) in nitrogenase-catalyzed H2 evolution (Laczkó, 1980 Z. Pflanzenphysiol. 100, 241–245) is increased to 1.5–2% by the appearance of the reversible hydrogenase activity.Abbreviations Chl
chlorophyll
- Car
carotenoids
- Phy
phycocyanin
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethyl-urea
- PSI
photosystem I
- PSII
photosystem II 相似文献
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9.
A study was made of the effects of cadmium on the Cyanobacterium(blue-green alga) Anabaena cylindrica Lemm. as part of the paddy-fieldecosystem. A simple culture vessel has been designed, which allows periodicalmeasurement of growth (optical density) and nitrogenase activity(C2H2-C2H4 method). The influence of medium renewal was checked:the renewal of the medium maintained a higher growth rate andhigher nitrogen fixation ability. The cadmium effects were studied using six concentration levelsranging from 0 (control) to 2 parts 106 with renewedmedia (10% every day). No significant differences could be seen up to 1 part 106for nitrogenase activity and relative percentage of heterocysts(decreasing as a function of time from ±4% to ±1.5%). Inhibition of growth (OD and dry weight) was weak at 1 part106 but important at 2 parts 106; at this concentrationcadmium induced morphological and physiological effects: chlorosis,cellular malformations and destruction, and increase in heterocystfrequency (up to 7.72% ±0.19). The cadmium concentration factors were much lower than thosereported for other plants like Chlorella and water pests 相似文献
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The role of the oxyhydrogen reaction in the nitrogen metabolism of Anabaena cylin-drica, particularly under conditions of dinitrogen starvation, was investigated. It was shown that although this reaction supports nitrogenase activity in the dark, when the cells are deprived of nitrogen the rate of hydrogen uptake is little changed. Measurements of ammonia excretion into the medium in the presence of methionine sulfoximine under such conditions indicated that hydrogen uptake supported the turnover of cell protein as an alternative source of nitrogen. In the absence of H2 and O2 in the dark, nitrogenase activity was negligible but protein turnover continued. In their presence nitrogenase activity was greatly stimulated; turnover was also stimulated but to a greater extent in the absence of nitrogenase substrates. The oxyhydrogen reaction also stimulated uptake of ammonium ions by intact filaments in argon in the dark. Only at very low hydrogen tensions can net hydrogen formation be obtained in argon/CO2 in the light, casting considerable doubt on the suitability of hydrogenase-containing organisms for biophotolytic hydrogen formation. Addition of exogenous ammonia to the cultures incubated in argon resulted in a pronounced stimulation of H2 uptake; nitrate and its derivatives had no such effect, nor did various amino acid derivatives of ammonia. 相似文献
12.
Both nitrogen fixation and acetylene reduction by intact cellsof Anabaena cylindrica were inhibited by oxygen, but nitrogenfixation was invariably less sensitive than acetylene reduction.The C2H2/N2 ratio ranged from 6 to 8 in the absence of oxygen,and it decreased with increase in partial pressure of oxygento 2 at a pO2 of 0.3 atm. (Received June 5, 1979; ) 相似文献
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Summary Crude cell-free extracts of Anabaena cylindrica synthesized adenosine-5-phosphosulphate (AP35S) and 3-phosphoadenosine-5-phosphosulphate (PAP35S) from 35SO4
2- in the presence of Mg2+, ATP and inorganic pyrophosphatase. Maximum AP35S and PAP35S were produced at pH 7.15 and 8.05, respectively. APS kinase was detected in the supernatant of crude cell-free extracts by a spectrophotometric procedure. ATP-Sulphurylase had an absolute requirement for Mg2+ and less than 30% AP35S was formed when Mg2+ was replaced by either Mn2+ or Co2+. Nucleotide triphosphates other than ATP and 2-deoxyATP were ineffective in this reaction. Maximum enzyme activity was observed at equimolar concentrations of Mg2+ and ATP and excess of either of these was inhibitory. Other nucleotide triphosphates, like GTP, UTP, CTP, TTP, ITP, or 2-deoxyATP also inhibited the enzyme activity. Inhibition by GTP was competitive with respect to ATP. ATP-sulphurylase activity was not affected by cysteine, methionine or glutathione.Abbreviations APS
adenosine-5-phosphosulphate
- PAPS
3-phosphoadenosine-5-phosphosulphate 相似文献
15.
Nitrogen-starved cultures of the alga Anabaena cylindrica 629 produced hydrogen and oxygen continuously for 7 to 19 days. Hydrogen production attained a maximum level after 1 to 2 days of starvation and was followed by a slow decline. The maximum rates were 30 ml of H2 evolved per liter of culture per h or 32 mul of H2 per mg of dry weight per h. In 5 to 7 days the rate of H2 evolution by the more productive cultures fell to one-half its maximum value. The addition of 10(-4) to 5 X 10(-4) M ammonium increased the rate of oxygen evolution and the total hydrogen production of the cultures. H2-O2 ratios were 4:1 under conditions of complete nitrogen starvation and about 1.7:1 after the addition of ammonium. Thus, oxygen evolution was affected by the extent of the nitrogen starvation. Thermodynamic efficiencies of converting incident light energy to free energy of hydrogen via algal photosynthesis were 0.4%. Possible factors limiting hydrogen production were decline of reductant supply and filament breakage. Hydrogen production by filamentous, heterocystous blue-green algae could be used for development of a biophotolysis system. 相似文献
16.
Nitrogen-starved cultures of the alga Anabaena cylindrica 629 produced hydrogen and oxygen continuously for 7 to 19 days. Hydrogen production attained a maximum level after 1 to 2 days of starvation and was followed by a slow decline. The maximum rates were 30 ml of H2 evolved per liter of culture per h or 32 mul of H2 per mg of dry weight per h. In 5 to 7 days the rate of H2 evolution by the more productive cultures fell to one-half its maximum value. The addition of 10(-4) to 5 X 10(-4) M ammonium increased the rate of oxygen evolution and the total hydrogen production of the cultures. H2-O2 ratios were 4:1 under conditions of complete nitrogen starvation and about 1.7:1 after the addition of ammonium. Thus, oxygen evolution was affected by the extent of the nitrogen starvation. Thermodynamic efficiencies of converting incident light energy to free energy of hydrogen via algal photosynthesis were 0.4%. Possible factors limiting hydrogen production were decline of reductant supply and filament breakage. Hydrogen production by filamentous, heterocystous blue-green algae could be used for development of a biophotolysis system. 相似文献
17.
Glyoxylate Induced Changes in the Carbon and Nitrogen Metabolism of the Cyanobacterium Anabaena cylindrica
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Bergman B 《Plant physiology》1986,80(3):698-701
Addition of millimolar concentrations of glyoxylate to nitrogen-fixing cultures of Anabaena cylindrica, grown aerobically in the light, caused the following effects: an increase in the number of glycogen granules and in the excretion of carbohydrates; a decreased phycocyanin concentration, but an increase in the chlorophyll a to phycocyanin ratio. Also, an enhancement in the carbon to nitrogen ratio was noted, but this was restored if NH4+ was added simultaneously. The most pronounced effect of glyoxylate addition was a 20-fold increase in the glycine pool. The effect of glyoxylate on N2 fixation (acetylene reduction) was enhanced at high light intensities, but it did not affect the in vitro ribulose-1,5-bisphosphate carboxylase activity. However, addition of millimolar concentrations of glycolate did not cause changes in nitrogenase activity, CO2 fixation, and NH3 release comparable to those caused by glyoxylate. The primary mechanism of action of glyoxylate appears to be within the glycolate pathway of the vegetative cells and metabolically downstream from glycolate. 相似文献
18.
Hona Laczkó 《Physiologia plantarum》1985,63(2):221-224
The role of O2 photoreduction was studied in intact cells of normal and photobleached Anabaena cylindrica Lemm. strain PCC 7122. We found that O2 photoreduction represents a protective mechanism against over-reduction of the photosyn-thetic electron transport chain only in normal Anabaena cells. This protective mechanism was not functioning in photobleached cells in spite of the increased rate of photosynthetic electron flow. A new electron acceptor, the induced reversible hydrogenase, is suggested to be operating in photobleached Anabaena cylindrica . 相似文献
19.
Intermittent illumination increased H2 and C2H4 yields per unit of light from growing cells and from nitrogren-starved cells by 1.7- and 1.35-fold, respectively, as compared with continuous illumination. 相似文献
20.
Duration of Hydrogen Formation by Anabaena cylindrica B629 in Atmospheres of Argon, Air, and Nitrogen
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The time course of hydrogen formation by Anabaena cylindrica was followed beneath an argon atmosphere alone and also beneath atmospheres of argon, nitrogen, and air in the presence of carbon monoxide (0.2%) and acetylene (5%). Hydrogen production beneath argon alone was comparable in rate and duration (7 to 12 days) to that which occurred beneath air in the presence of carbon monoxide (0.2%) and acetylene (5%). However, much greater longevity (16 to 26 days) and improved rates of hydrogen formation were obtained when algae were incubated beneath argon and particularly nitrogen, each supplemented with carbon monoxide and acetylene. The total hydrogen produced by these cultures was up to three times as much as that released by cultures incubated beneath argon alone. Hydrogen-oxygen ratios for argon cultures either with or without carbon monoxide and acetylene were initially 1:5 but approximated 1:2 when measured over the entire incubation period. In each case oxygen production and nitrogenase activity (acetylene reduction) continued at reduced rates after hydrogen evolution had ceased. The effects of methionine sulfoximine (2 μM), ammonium ions (0.5 mM), or both on oxygen production were generally negligible, while effects on hydrogen production were variable depending on the atmosphere used; in most cases, eventual destabilization of the system occurred. A brief comparison was made of the time courses of anaerobic and aerobic hydrogen formation by the marine cyanobacterium Calothrix membranacea. It was found that shaking of cultures was beneficial for hydrogen production but not strictly necessary. It is concluded that hydrogen production by A. cylindrica in air and particularly nitrogen in the presence of carbon monoxide and acetylene offers the best potential of the atmospheres considered on the basis of four criteria: rates and longevity of hydrogen formation, practicality of the atmosphere used, and tolerance of hydrogen evolution to slight changes in composition of the atmosphere. 相似文献