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1.
Short-term effect of ammonia on nitrogenase activity of Anabaena variabilis (ATCC29413) 总被引:1,自引:0,他引:1
Abstract Intact filaments of the cyanobacterium Anabaena variabilis switch off nitrogenase activity very rapidly upon addition of NH4 Cl when incubated in an alkaline environment (pH 10.0) permitting a fast NH3 -influx into the cells. When assayed in cell-free extracts (prepared from ammonia-treated filaments), nitrogenase remains inhibited in the presence of an ATP-regenerating system. Furthermore, l -methionine- d,l -sulfoximine, an inhibitor of glutamine synthetase, added to the filaments, prevents inactivation of nitrogenase by ammonia, showing that ammonia is not the compound directly responsible for nitrogenase switch-off. 相似文献
2.
Characterization of genes for an alternative nitrogenase in the cyanobacterium Anabaena variabilis. 总被引:14,自引:6,他引:8
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T Thiel 《Journal of bacteriology》1993,175(19):6276-6286
Anabaena variabilis ATCC 29413 is a heterotrophic, nitrogen-fixing cyanobacterium that has been reported to fix nitrogen and reduce acetylene to ethane in the absence of molybdenum. DNA from this strain hybridized well at low stringency to the nitrogenase 2 (vnfDGK) genes of Azotobacter vinelandii. The hybridizing region was cloned from a lambda EMBL3 genomic library of A. variabilis, mapped, and sequenced. The deduced amino acid sequences of the vnfD and vnfK genes of A. variabilis showed only about 56% similarity to the nifDK genes of Anabaena sp. strain PCC 7120 but were 76 to 86% similar to the anfDK or vnfDK genes of A. vinelandii. The organization of the vnf gene cluster in A. variabilis was similar to that of A. vinelandii. However, in A. variabilis, the vnfG gene was fused to vnfD; hence, this gene is designated vnfDG. A vnfH gene was not contiguous with the vnfDG gene and has not yet been identified. A mutant strain, in which a neomycin resistance cassette was inserted into the vnf cluster, grew well in a medium lacking a source of fixed nitrogen in the presence of molybdenum but grew poorly when vanadium replaced molybdenum. In contrast, the parent strain grew equally well in media containing either molybdenum or vanadium. The vnf genes were transcribed in the absence of molybdenum, with or without vanadium. The vnf gene cluster did not hybridize to chromosomal DNA from Anabaena sp. strain PCC 7120 or from the heterotrophic strains, Nostoc sp. strain Mac and Nostoc sp. strain ATCC 29150. A hybridizing ClaI fragment very similar in size to the A. variabilis ClaI fragment was present in DNA isolated from several independent, cultured isolates of Anabaena sp. from the Azolla symbiosis. 相似文献
3.
Abstract Azospirillum brasilense strain Cd, but not A. lipoferum , could grow and reduce acetylene to ethylene when grown on Mo-free Nfb medium with Fe. Purified Nfb medium lacking both Mo and Fe did not support growth of A. brasilense Cd. Supplementation of − Mo + Fe Nfb medium with vanadium or several other metal salts did not stimulate growth or acetylene reduction. In Mo-free Nfb semisolid medium containing Fe and W, the organism showed good pellicle growth and reduced acetylene to ethylene and ethane. Moreover, a significantly higher amount of H2 was produced in Mo-free medium than in Nfb containing Mo. The data suggest the presence of an alternate nitrogenase system 3 (Fe-nitrogenase) in A. brasilense Cd besides the normal Mo-nitrogenase. 相似文献
4.
Mutants ofAnabaena variabilis Kütz. that have a decreased ability to grow photoautotrophically have been isolated by a modification of the techniques used to isolate auxotrophic mutants of that filamentous cyanobacterium, and have been stably propagated. Three mutants have a reduced content of phycocyanin and, as determined by in situ assays of partial reaction sequences of photosynthesis, an impairment in photosystem II. Three other strains, all of which appear to have a normal complement of carotenoids when grown heterotrophically, are sensitive to light.Abbreviations Used TES
N-tris(hydroxymethyl)-methyl-2-aminoethanesulfonic acid, sodium salt
- HEPES
N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid, sodium salt
- MV
methylviologen
- DBMIB
2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone
- DAB
3,3-diaminobenzidine
- P-BQ
p-benzoquinone
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- Fecy
K-ferricyanide
- NTG
N-methyl-N-nitro-N-nitrosoguanidine 相似文献
5.
Characterization of genes for a second Mo-dependent nitrogenase in the cyanobacterium Anabaena variabilis.
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Anabaena variabilis ATCC 29413 is a filamentous heterocystous cyanobacterium that fixes nitrogen under a variety of environmental conditions. Under aerobic growth conditions, nitrogen fixation depends upon differentiation of heterocysts and expression of either a Mo-dependent nitrogenase or a V-dependent nitrogenase in those specialized cells. Under anaerobic conditions, a second Mo-dependent nitrogenase gene cluster, nifII, was expressed in vegetative cells long before heterocysts formed. A strain carrying a mutant gene in the nifII cluster did not fix nitrogen under anaerobic conditions until after heterocysts differentiated. The nifII cluster was similar in organization to the nifI cluster that is expressed in heterocysts and that includes nifBSUHDKENXW as well as three open reading frames that are conserved in both cyanobacterial nif clusters. 相似文献
6.
Distribution pattern and levels of nitrogenase (EC 1.7.99.2) and glutamine synthetase (GS, EC 6.3.1.2) were studied in N2-, NO3? and NH4+ grown Anabaena cylindrica (CCAP 1403/2a) using immunogold electron microscopy. In N2- and NO3? grown cultures, heterocysts were formed and nitrogenase activity was present. The nitrogenase antigen appeared within the heterocysts only and showed an even distribution. The level of nitrogenase protein in the heterocysts was identical with both nitrogen sources. In NO3? grown cells the 30% reduction in the nitrogenase activity was due to a corresponding decrease in the heterocyst frequency and not to a repressed nitrogenase synthesis. In NH4? grown cells, the nitrogenase activity was almost zero and new heterocysts were formed to a very low extent. The heterocysts found showed practically no nitrogenase protein throughout the cytoplasm, although some label occurred at the periphery of the heterocyst. This demonstrates that heterocyst differentiation and nitrogenase expression are not necessarily correlated and that while NH4+ caused repression of both heterocyst and nitrogenase synthesis, NO3? caused inhibition of heterocyst differentiation only. The glutamine synthetase protein label was found throughout the vegetative cells and the heterocysts of all three cultures. The relative level of the GS antigen varied in the heterocysts depending on the nitrogen source, whereas the GS level was similar in all vegetative cells. In N2- and NO3+ grown cells, where nitrogenase was expressed, the GS level was ca 100% higher in the heterocysts compared to vegetative cells. In NH4+ grown cells, where nitrogenase was repressed, the GS level was similar in the two cell types. The enhanced level of GS expressed in heterocysts of N2 and NO3? grown cultures apparently is related to nitrogenase expression and has a role in assimilation of N2derived ammonia. 相似文献
7.
The cyanobacterium Anabaena variabilis showed a pH dependent uptake of ethylenediamine. No uptake of ethylenediamine was detected at pH 7.0. At higher pH values (e.g. pH 8.0 and pH 9.0) accumulation did occur and was attributed to diffusion of uncharged ethylenediamine in response to a pH gradient. A biphasic pattern of uptake was observed at these higher pH values. Treatment with l-methionine-d,l-sulphoximine (MSX) to inactivate glutamine synthetase (GS) inhibited the second slower phase of uptake without any significant alteration of the initial uptake. Therefore for sustained uptake, metabolism of ethylenediamine via GS was required. NH
4
+
did not alter the uptake of ethylenediamine. Ethylenediamine was converted in the second phase of uptake to an analogue of glutamine which could not be detected in uptake experiments at pH 7.0 or in uptake experiments at pH 9.0 following pretreatment of cells with MSX. Ethylenediamine treatment inhibited nitrogenase activity and this inhibition was greatest at high pH values.Abbreviations EDA
1,2-diaminoethane (ethylenediamine)
- GS
glutamine synthetase
- HEPES
4-(2-hydroxyethyl)-1 piperazine ethanesulphonic acid
- MSX
l-methionine-dl-sulphoximine
-
membrane potential
- Tricine
N-tris(hydroxymethyl) methylglycine 相似文献
8.
9.
The nitrogenase activity of the cyanobacterium Anabaena cylindrica was repressed upon addition of ammonium salts after preincubation in the presence of a concentration of L-methionine-DL-sulfoximine sufficient to totally inhibit glutamine synthetase. Repression was also observed when urea was added to cells in the presence of the glutamine synthetase inhibitor. Measurements of ammonia concentrations were made in each case and provided evidence that ammonia itself is a primary regulator of nitrogenase levels in A. cylindrica. 相似文献
10.
Anabaena variabilis ATCC 29413 belongs to the cyanobacteria that use a specific cell type, heterocysts, for fixation of atmospheric nitrogen under aerobic conditions. Nitrogen fixation under anaerobic conditions is catalyzed by a Mo-dependent nitrogenase (Nif2) that is expressed in the vegetative cells. We demonstrate here using immunolocalization/light microscopy (LM) that the synthesis of NifH2 is mainly initiated in dividing vegetative cells along the trichomes. Blocking cell division by cephalexin abolished nitrogenase synthesis under anaerobic conditions. 相似文献
11.
Surendra Singh 《FEMS microbiology letters》1988,56(3):281-283
Abstract The utilization of urea was studied in the cyanobacterium Anabaena doliolum . The uptake of urea was unaltered in the presence of ammonium. The cells receiving ATP exogenously showed an induced level of urea-uptake as compared with the control cells. Urease inhibitor acetohydroxamic acid and hydroxyurea as well as glutamate analogue, MSO, did not affect the uptake of urea. These results suggest: (1) urea and ammonia have different uptake sites, (2) urea-uptake is an energy dependent process, and (3) during short-term experiments, urea uptake is not linked with the enzyme urease or the ammonium assimilating enzyme glutamine synthetase. 相似文献
12.
The photophobic responses in the Cyanobacterium Anabaena variabilis which belongs to the Nostocaceae have been studied with aid of a population method as well as by single trichome observations. In white light experiments both step-up and step-down photophobic responses were observed. The wavelength dependence was examined at a constant fluence rate. The photophobically active light is absorbed by the photosynthetic pigments, mainly by the phycobiliproteins and chlorohyll a. Above 690 nm only negative reactions were observed, i.e. the trichomes left the light trap. In white light experiments DCMU strongly inhibited the photophobic responses, whereas photokinesis was not affected to the same extent indicating that the reaction is coupled with the non cyclic photosynthetic electron transport. DBMIB impaired the photophobic behaviour only slightly. It seems that the photophobic responses of A. variabilis are controlled by a similar mechanism as in Phormidium uncinatum (Oscillatoriaceae) although the two families and, hence, the two species differ in their movement mechanism as well as in their photoactic behaviour. 相似文献
13.
Teresa Thiel 《Archives of microbiology》1988,149(5):466-470
The amino acid leucine was transported by the cyanobacterium Anabaena variabilis. The K
m for transport was 10.8 M; the V
max was 8.7 nmoles min–1 mg–1 chlorophyll a. Transport of leucine was energy dependent: uptake of leucine was inhibited in the dark, and by DCMU and cyanide. Transport was neither dependent on nor enhanced by Na+. Prior growth of cells with leucine did not repress transport of [14C]-leucine. Alanine, glycine, valine, and methionine were strong competitive inhibitors of leucine uptake; serine, threonine, isoleucine, norleucine, and d-alanine competitively inhibited to a lesser degree. Other amino acids or amino acid analogues, including d-leucine, -aminoisobutyrate, and d-serine did not inhibit the transport of leucine.Abbreviations Chl a
chlorophyll a
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- TES
N-tris(hydroxymethyl)-2-aminoethane-sulfonic acid
- TCA
trichloroacetic acid
- Tris
N-tris(hydroxymethyl)aminoethane 相似文献
14.
UDP-N-acetylmuramyl-pentapeptide (UDP-MurNAc-pentapeptide) is well known to be a key intermediate of bacterial peptidoglycan biosynthesis. We first detected the occurrence of UDP-MurNAc-pentapeptide in the cyanobacterium Anabaena cylindrica (NIES-19), and identified the structure of this pentapeptide by two-dimensional 1H-1H and 1H-13C NMR correlation experiments and mass spectra. 相似文献
15.
16.
In the cyanobacterium Anabaena variabilis the dependence of photoinhibition on fluence rate, duration and wavelength of irradiation were studied by measurements of oxygen production and fluorescence emission spectra. The analysis of the photosynthetic activity revealed that photoinhibition affects exclusively photosystem II (PS II), whereas photosystem I (PS I) remained largely unimpaired. Furthermore, PS II fluorescence emission decreased much faster in bleached than in unbleached controls.Studying the wavelength dependence of photoinhibition it was found that only radiation between 520 and 680 nm causes photoinhibition. This is about the same range of wavelengths which causes photobleaching. Fluorescence emission spectra of samples exposed to high fluence rates of 582 and 662 nm, respectively, essentially agree with those samples exposed to high fluence rates of white light, whereas the fluorescence emission spectra of samples exposed to blue light resemble those exposed to dim white light.NaN3, a substance which prevents photobleaching, inhibits the photosynthetic O2 production of Anabaena and, hence, enhances the photoinhibitory effect. 相似文献
17.
Birgitta Bergman 《Planta》1981,152(4):302-306
Raising the pO2 reduced nitrogenase activity (C2H2 reduction) of Anabaena cylindrica for both glyoxylate-treated (5 mM) and untreated cells. The stimulation caused by glyoxylate, however, increased with increases of pO2 from 2 to 99 kPa. As the pO2 increased the net CO2 fixation was lowered (Warburg effect) while the CO2 compensation point increased. Glyoxylate partly relieved this sensitivity of net photosynthesis to oxygen and reduced the compensation point considerably. The cells used were preincubated in the dark to exhaust photosynthetic pools. A more pronounced reduction in sensitivity of nitrogenase to oxygen for glyoxylate-treated cells was evident when a preincubation in air with reduced pCO2 (13 l l-1) was used. This was, however, not evident until after a 10-h incubation in air. Before this point 2 kPa O2 sustained the highest nitrogenase activity. Addition of 0.5 and 5 mM of HCO
3
-
to Anabaena cultures preincubated at low CO2 levels (29 l l-1) abolished the stimulatory effect of glyoxylate on the nitrogenase. Thus, the results sustain the suggestion that glyoxylate may act as an inhibitor of photorespiratory activities in cyanobacteria and can be used as a means of increasing their nitrogen and CO2 fixation capacities.Abbreviation RuBP
ribulose 1,5-bisphosphate 相似文献
18.
Yael J. Avissar 《Physiologia plantarum》1985,63(1):105-108
Filaments of Anabaena variabilis Kütz strain ATCC 29413 grown in the absence of nitrate contain nitrate reductase that is active in permeabilized filaments, but not in intact, living filaments until they have been incubated for about 40 min in the presence of nitrate. The delayed acquisition of the ability to reduce nitrate is insensitive to chloramphenicol. Thus, switching on of enzyme activity in the presence of nitrate does not involve protein synthesis and nitrate reductase activity is not regulated by the amount of enzyme present. 相似文献
19.
Abstract The urea uptake system was studied with regard to its repression and derepression in the cyanobacterium, Anabaena doliolum . The uptake of urea was energy-dependent and was repressed in ammonia grown cells. Repression of the urea uptake by ammonium did not require ammonium assimilation or de novo protein synthesis, suggesting that ammonium itself was the repressor signal. The derepression of the urea uptake system, however, required de novo protein synthesis and glutamine synthetase activity. 相似文献
20.
Hilary A. Powell Nigel W. Kerby Peter Rowell David M. Mousdale John R. Coggins 《Planta》1992,188(4):484-490
5-Enolpyruvylshikimate 3-phosphate (EPSP) synthase (3-phosphoshikimate 1-carboxyvinyltransferase; EC 2.5.1.9) from the glyphosate-tolerant cyanobacterium Anabaena variabilis (ATCC 29413) was purified to homogeneity. The enzyme had a similar relative molecular mass to other EPSP synthases and showed similar kinetic properties except for a greatly elevated K
i for the herbicide glyphosate (approximately ten times higher than that of enzymes from other sources). With whole cells, the monoisopropylamine salt of glyphosate was more toxic than the free acid but the effects of the free acid and monoisopropylamine salt on purified EPSP synthase were identical.Abbreviations EPSP
5-enolpyruvylshikimate 3-phosphate
- Mr
relative molecular mass
- PEP
phosphoenolpyruvate
- SDS-PAGE
sodium dodecyl sulphate-polyacrylamide gel electrophoresis
- S3P
shikimate 3-phosphate
The funding of this work by the Agricultural and Food Research Council and the University of Dundee Research Initiatives Programme is gratefully acknowledged. 相似文献