• KSBB Journal
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• v.20 no.6
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• pp.418-424
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• 2005

Photoheterotrophic evolution of molecular hydrogen by Rhodobacter sphaeroides is mediated by nitrogenase that is regulated transcriptionally and post-translationally by ammonium ion. Two PII-like proteins, GlnB and GlnK, play key roles in mediating inhibition and repression of nitrogenase in the presence of ammonium ion. glnB and glnK of R. sphaeroides were interrupted to abolish the ammonium ion effect controlling nitrogenase. Ammonium ion effect was still observed in mutant having an interruption in either glnB or glnK. However, the nitrogenase activity of glnB-glnK double mutant is not affected by ammonium ion. $H_2$ evolution was improved by increasing gene dosages of nitrogenase-coding genes, nifHDK in trans in glnB-glnK double mutant.

• Microbiology and Biotechnology Letters
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• v.14 no.5
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• pp.385-389
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• 1986

Both hydrogenase and nitrogenase were found to be involved in hydrogen evolution independently in Rhodopseudomonas sp. KCTC 1437. The hydrogen formation in this bacterium was independent on light illumination and presence of N $H_4^{+}$ After establishment of conditions to measure the amount of hydrogen evolved by each of the enzymes in vivo, the several factors affecting on the hydrogen evolution, e.g. presence of gases ( $C_2$ $H_2$, $H_2$, $O_2$ or $N_2$), C/N ratio, were investigated, Hydrogenase was less inhibited than nitrogenase under $O_2$ and was active independent on the presence of $N_2$ or $C_2$ $H_2$ which were the strong inhibitor of nitrogenase. Besides, the hydrogenase activity was increased after incubation with $H_2$. And it was verified that this bacterium consume hydrogen and photoreduce $CO_2$ by hydrogenase. From above results, it is concluded that hydrogenase in Rhodopseudomonas sp. KCTC 1437 can produce hydrogen under more favorable condition that nitrogenase.e.

• Korean Journal of Microbiology
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• v.26 no.3
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• pp.215-222
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• 1988

The effect of ammonia and glutamine on nitrogenase activity of Rhodopseudomonas sphaeroides was examined. The nitrogenase activity of this strain was inhibited by ammonia and glutamine. When ammonia and glutamine were exhausted, nitrogenase activity promptly resumed at its original rate. Methionine sulfoximine (MSX), irreversible glutamine synthetase (GS) inhibitor, is a structural analogue of glutamate. MSX was used in order to know whether the nitrogenase activity was inhibited by ammonia and glutamine directly or not. The ability of MSX to prevent nitrogenase switch-off by ammonia was found to be dependent upon the phase of culture. When the cells were sampled after 12 hour culture, $500{\mu}M$ MSX would not prevent the nitrogenase switch-off by ammonia. Twenty one percents of GS actibity was inhibited by $500{\mu}M$ of MSX and concentration of released ammonia decreased. But nitrogenase activiy was still inhibited by ammonia. However, nitrogenase switch-off after 20 hours would be prevented by $100{\mu}M$ of MSX. On the other hand, GS activity was ingibited completely by $100{\mu}M$ MSX and concentration of released ammonia somewhat increased. But nitrogenase activity was not inhibited. The data indicated that the inhibition of in vivo nitrogenase actibity of Rp. sphaeroides by ammonia seemed to be mediated by products of ammonia assimilation rather than by ammonia itself.

• Microbiology and Biotechnology Letters
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• v.11 no.3
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• pp.211-216
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• 1983

Rhodopseudomonas sphaeroides K-7 evolves large quantities of molecular hydrogen under anaerobic and light illuminated conditions in the presence of utilizable organic compounds as electron donors. Photoevolution of molecular hydrogen was strictly dependent on light as the activity of nitrogenase in this organism. Both of these were inhibited to the nearly same extent at varying concentrations of ammonium ion which also depressed nitrogenase synthesis. In the reaction mixtures devoid of molybdenum ion which is known as the component of nitrogenase, hydrogen evolution also decreased similarly like nitrogenase activity. Photoevolution of molecular hydrogen appeared to have no relationship with hydrogenase activity and bacteriocholophyll content and it was markedly inhibited under the atmosphere of $C_2$H$_2$, $N_2$ or $O_2$. The results strongly indicate that hydrogen evolution by R. sphaeroides K-7 might be catalyzed by nitrogenase. Both hydrogen evolution and nitrogenase activity were largely influenced by the nutritional history of the resting cells. From which we propose that glutamate might play an important role in the regulation of nigrogenase activity in vivo.

• The Korean Journal of Food And Nutrition
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• v.5 no.2
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• pp.137-143
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• 1992

As a research for developing biofertilizers, Klebsiella oxytoca, an associative nitrogen fixer in the rhizosphere of rice plant in the soil of paddy field, was subjected to molecular breeding. The results obtained were as followings. 1). By transforming pbIC71A, Nif A overproducing plasmid, into Klebsiella oxytoca NGl3, Klebsiell6f oxytoca SH3l, and Klebsiella oxytoca SH161, nitrogenase activities in the absence of nitrogen source in the medium were increased 6.4, 17.2, and 13.5 times, respectively, in comparison with the parent strains. 2). Nitrogenase activity of Klebgiella oxytoca NGl3, Klebsiella oxytoca SH3l, and Klebsiella oxytoca SH161 was completely repressed In the presence of 15mM NH4+. But, nitrogenase activities of Klebsiella oxytoca NGl3/PMC71A, Klebsiella oxytoca SH3l /PMC71A, and Klebsiella oxytoca SH 161/pMC714 harboring PMC71A, were 13.7%, 7.7%, and 6.2% of the nitrogenase activities in the absence of nitrogen source in the medium, respectively.

• Journal of Life Science
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• v.14 no.5
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• pp.752-760
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• 2004

The function of the [4Fe-4S] cluster containing iron (Fe-) protein in nitrogenase catalysis is to serve as the nucleotide-dependent electron donor to the MoFe protein which contains the sites for substrate binding and reduction. The ability of the Fe protein to function in this manner is dependent on its ability to adopt the appropriate conformation for productive interaction with the MoFe protein and on its ability to change redox potentials to provide the driving force required for electron transfer. The MgADP-bound (or off) conformational state of the nitrogenase Fe protein structure described reveals mechanisms for long-range communication from the nucleotide-binding sites to control affinity of association with the MoFe protein component. Two pathways, termed switches I and II, appear to be integral to this nucleotide signal transduction mechanism. In addition, the structure of the MgADP bound Fe protein provides the basis for the changes in the biophysical properties of the [4Fe-4S] observed when Fe protein binds nucleotides. The structures of the nitrogenase Fe protein with defined amino acid substitutions in the nucleotide dependent signal transduction pathways of the Switch I and Switch II have been determined by X-ray diffraction methods. These two pathways have been also implicated by site directed mutagenesis studies, structural analysis and analogies to other proteins that utilize similar nucleotide dependent signal transduction pathways. We have examined the validity of the assignment of these pathways in linking the signals generated by MgATP binding and hydrolysis to macromolecular complex formation and intermolecular electron transfer. The results provide a structural basis for the observed biophysical and biochemical properties of the Fe protein variants and interactions within the nitrogenase Fe protein-MoFe protein complex.

• Korean Journal of Soil Science and Fertilizer
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• v.12 no.1
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• pp.43-46
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• 1979

Curing the studies on the mechanism of the nodule formation and the infection of rhizobia using the continously cultured plant cell tissues, it was found that some calluses possess high nitrogen fixation activity. This experiment was conducted to know the differences among the calluses and the Rhizobia. The results obtained were as follows; 1) In a single inoculation the nitrogenase activity of soybean cell cultures-rhizobium was moderately higher than non-leguminous cell cultures, however, in the mixing inoculation that was reversely found. 2) Host factor, which was characteristics for the nodule formation and the nitrogenase activity, was not appeared generally in the plant cell cultures except for Kuamusume and Toyozuzu in soybean, and Datura in non-leguminous cell cultures. 3) In the 012 rhizoblium cultured on soybean cell cultures and in the 010, 023 and 024 rhizobia cultured on non-leguminous cell cultures the nitrogenase activity higher than the others.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.5
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• pp.361-368
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• 2003

The responses of five varieties and three cultivars of pea (Pisum sativum) to Rhizobium inoculation on nodulation, growth, nitrogenase activity, dry matter production and N uptake were investigated. The pea varieties were IPSA Motorshuti-l, IPSA Motorshuti-2, IPSA Motorshuti-3, BARI Motorshuti-l, BARI Motorshuti-2 and the cultivars were 063, Local small and Local white. Fifty percent seeds of each pea variety/cultivar were inoculated with a mixture of Rhizobium inoculants at rate of 15g/kg seed and the remaining fifty percent seeds were kept uninoculated. The plants inoculated with Rhizobium inoculant significantly increased nodulation, growth, nitrogenase activity, dry matter production and N uptake. Among the varieties/cultivars, BARI Motorshuti-l performed best in almost all parameters including nitrogenase activity of root nodule bacteria of the crop. There were positive correlations among the number and dry weight of nodules (r=$0.987^{**}$, $0.909^{**}$), nitrogenase activity of root nodule bacteria (r=$0.944^{**}$, $0.882^{**}$), dry weight of shoot (r=$0.787^{**}$, $0.952^{**}$), N content (r=$0.594^{**}$, $0.605^{**}$) and N uptake (r=$0.784^{**}$, $0.922^{**}$) by shoot both at flowering and pod filling stages of the crop, respectively. It was concluded that BARI Motorshuti-l in symbiotic association with Rhizobium inoculant performed best in recording nitrogenase activity, dry matter production and N uptake by pea.

• Microbiology and Biotechnology Letters
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• v.31 no.1
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• pp.18-24
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• 2003

For researching nitrogen-fixing bacteria associated with gramineous crops, we collected growing roots of rices, wheats, oats, barleys, ryes, and maizes at 19 sites of southern Korean peninsula. Endophytes and free living bacteria were isolated from those crop roots. Sixty-three isolates were classified on the basis of different morphology, size, color, host of colony, and the 16S rDNAs sequence. The analyses of PCR amplification for nifH gene and nitrogenase activity assay, revealed that all isolates contained nitrogen-fixing abilities. In addition, most of them have cellulase activity which is one of the common features of endophytic bacteria from plant.

• Korean Journal of Microbiology
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• v.24 no.2
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• pp.113-118
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• 1986

Optimum temperature and pH of glutamine synthetase activity (E.C. 3.6.1.2.) of R. sphaeroides D-230 was $35^{\circ}C$ and 6.8, respectively. The adenylated state of GS in R. sphaeroides D-230 was stabilized by addition of 0.2mg/ml of cethyltrimethylammoniumbromide. Valine, histidine, proline, isoleucine, and lysine were good nitrogen source for the growth of R. sphaeroides D-230. The growth of R. sphaeroides D-230 in $N_2,\;NaNO_3\;or\;NH_4Cl$ as sole nitrogen source was lower than in any otherculture conditions. GS activity was inhibited, more or less, by various amino acid. THe relative inhibition rate of the enzyme by added 7mM arginine, $NH_4Cl,\;N_2,\;and\;NaNO_3$ was 63.8%, 26.79%, 6.24%, and 10.64%, drespectively. THe hydrogen evolution of R. sphaeroides D-230 grown in N-limited media was inhibited by 0.1mM MSX, irreversible GS inhibitor. GS activity was completely inhibited by 1.0mM MSX but ammonia released maximally at the same concentration of MSX. Ammonia release by added MSX was increased up to 1.0mM MS, but decreased above 1.0mM MSX. It is probably due to inhibition of nitrogenase actixity by MSX. Nitrogenase activity was not inhibited at low concentration of MSX. These results suggests that the inhibition of nitrogenase activity by ammonia is mediated by products of ammonia assimilation rather than by ammonia itself.