• Journal of Life Science
• /
• v.22 no.8
• /
• pp.1009-1017
• /
• 2012

The orf282 gene of Rhodobacter sphaeroides is located between the ccoNOQP operon encoding $cbb_3$ terminal oxidase and the fnrL gene encoding an anaerobic activator, FnrL. Its function remains unknown. In an attempt to reveal the function of the orf282 gene, we disrupted the gene by deleting a portion of the orf282 gene and constructed an orf282-knockout mutant. Two FnrL binding sites were found to be located upstream of orf282, and it was demonstrated that orf282 is positively regulated by FnrL. The orf282 gene is not involved in the regulation of spectral complex formation. The $cbb_3$ oxidase activity detected in the orf282 mutant was comparable to that in the wild-type sample, indicating that the orf282 gene is not involved in the regulation of the ccoNOQP operon and the biosynthesis of the cbb3 cytochrome c oxidase. The elevated promoter activity of the nifH and nifA genes, which are the structural genes of nitrogenase and its regulator, respectively, in the orf282 mutant, suggests that the orf282 gene product acts as a negative effector for nifH and nifA expression.

• BMB Reports
• /
• v.29 no.1
• /
• pp.88-91
• /
• 1996

The anaerobically expressed gene aeg-46.5, which had been identified by the operon fusion technique with a hybrid bacteriophage of ${\lambda}$ and Mu, ${\lambda}$placMu53, was studied for its expression pattern and growth. The expression of aeg-46.5 was studied in the wild-type cell and mutant cells that have mutation (s) in the control gene of anaerobic respiration (fnr) and nitrate response (narL and narP). The ${\beta}$-galactosidase reporter gene showed maximum expression in narL host after two hours of aerobic to anaerobic switch in M9-Glc-nitrate medium. Both 40 mM and 100 mM concentrations of nitrate ion in the medium had little effect on expression level. We propose that aeg-46.5 is subject to multiple regulations of anaerobic activation by Fnr, nitrate activation by NarP and repression mediated by NarL.

• Journal of Microbiology and Biotechnology
• /
• v.17 no.2
• /
• pp.218-225
• /
• 2007

A lactic acid bacterium capable of anaerobic respiration was isolated from soil with ferric iron-containing glucose basal medium and identified as L. garvieae by using 16S rDNA sequence homology. The isolate reduced ferric iron, nitrate, and fumarate to ferrous iron, nitrite, and succinate, respectively, under anaerobic $N_2$ atmosphere. Growth of the isolate was increased about 30-39% in glucose basal medium containing nitrate and fumarate, but not in the medium containing ferric iron. Specifically, metabolic reduction of nitrate and fumarate is thought to be controlled by the specific genes fnr, encoding FNR-like protein, and nir, regulating fumarate-nitrate reductase. Reduction activity of ferric iron by the isolate was estimated physiologically, enzymologically, and electrochemically. The results obtained led us to propose that the isolate metabolized nitrate and fumarate as an electron acceptor and has specific enzymes capable of reducing ferric iron in coupling with anaerobic respiration.

• Journal of Environmental Health Sciences
• /
• v.38 no.6
• /
• pp.568-574
• /
• 2012

Objectives: The purpose of this experiment is to understand the phosphorus removal ratio effects of iron plates per unit of surface area through the iron electrolysis system, which consists of an anoxic basin, aerobic basin, and iron precipitation apparatus. Methods: Iron electrolysis, which uses an iron precipitation reactor in anoxic and oxic basins, consisted of iron plates with total areas of 400 $cm^2$, 300 $cm^2$ and 200 $cm^2$ respectively. The FNR process was operated with a hydraulic retention time and a sludge retention time of 12 hours and three days, respectively. Wastewater used in the experiments was prepared by dissolving $KH_2PO_4$ in influent water. Results: The iron plates 400 $cm^2$ (16.6 $mA/cm^2$), 300 $cm^2$ (13.3 $mA/cm^2$) and 200 $cm^2$ (7.3 $mA/cm^2$) in surface area in the phosphorus reactor had respective phosphorus of 2.4 mg/l, 2.7 mg/l and 3.2 mg/l in the effluent and phosphorus removal respective efficiencies of 90.3%, 89.1% and 87.1%. The effluent in the reactor, where the iron plate was not used, had relatively very low phosphorus removal efficiency showing phosphorus concentration of 15.3 mg/l and a phosphorus removal efficiency about 38.3%. Phosphorus removal per ferrous was 0.472 mgP/mgFe in the iron electrolysis system where the surface area of iron was low. Phosphorus pollution load per active surface area and the phosphorus removal efficiency had an interrelation of RE = -0.27LS + 89.0 (r = 0.85). Conclusion: With larger iron plate surface area, the elution of iron concentration and phosphorus removal efficiency was higher. The removal efficiency of phosphorus has decreased by increasing the initial phosphate concentration in the iron electrodes. This shows a tendency of decreasing phosphorus removal efficiency because of decreasing of iron deposition as the phosphorus pollution load per active surface area increases.

• Journal of Life Science
• /
• v.16 no.4
• /
• pp.632-639
• /
• 2006

Here we examined the expression patterns and regulation of seven photosynthesis (PS) genes (puf, puc, puhA, bchC, bchE, bchF, and bchI) in the anoxygenic photosynthetic bacterium, Rhodobacter sphaeroides, based on lacZ reporter gene assay. Expression of the tested PS genes, except puhA and bchI, were strongly induced in R. sphaeroides grown under anaerobic conditions relative to that under aerobic conditions. The puhA and bchI genes appear to form the operons together with bchFNBHLM-RSP0290 and crtA, respectively. Expression of the puf, puc, and bchCXYZ operons in R. sphaeroides grown photosynthetically was proportional to the incident light intensity, whereas that of bchFNBHLM(RSP0290-puhA) was inversely related to light intensity. Expression of bchEJG was lowest under medium-light photosynthetic conditions $(10\;W/m^2)$ and highest under high light conditions $(100\;W/m^2)$. The regulation of PS genes by the three major regulatory systems involved in oxygen- and light-sensing in R. sphaeroides is as following: puf and bchC are regulated by both the PpsR repressor and the PrrBA two-component system. The puc operon is under control of PpsR, FnrL, and PrrBA system. Expression of bchE is controlled by FnrL and PrrBA two-component system, whereas bchF is regulated exclusively by PpsR. It was demonstrated that the PpsR repressor is responsible for high-light repression of bchF and that FnrL might be involved in perceiving the cellular redox state in addition to sensing $O_2$ itself.

• Journal of Microbiology and Biotechnology
• /
• v.9 no.4
• /
• pp.436-442
• /
• 1999

The aeg-46.5 operon of Escherichia coli is induced by nitrate and anaerobic conditions. Positive regulators Fnr and NarP, and a negative regulator NarL control the expression of the aeg-46.5. It has two symmetry regions [6], one of which is located between +37 and +56 bp from the 5'end of the anaerobic transcription initiation site. In this study, mutagenized symmetry regions were transferred from plasmid to chromosome by homologous recombination to evaluate the mutation as a single copy in the fnr, narL, narP, and narL-narP double mutant background. The expressions of the aeg-46.5 operon with these mutations indicated that the control was not through the possible stem-loop structure. Whether there is a protein that mediates this control remains to be seen. The results from the narL-narP double mutant indicated that the anaerobic Fill induction was independent of NarL repression.

• BMB Reports
• /
• v.29 no.1
• /
• pp.92-97
• /
• 1996

The age-46.5 gene of Escherichia coli is induced by nitrate ion and regulated by Fnr, NarL, and NarP during anaerobic growth. aeg-46.5::lacZ fusion gene shows its maximum expression in narL host after two hours of aerobic to anaerobic switch in M9-Glc-nitrate medium. Fnr and NarP act as positive regulators, and NarL acts as a negative regulator. The control region of the aeg-46.5 was identified and the binding sites of regulator proteins have been predicted (Reznikoff and Choe (1993)). It has two symmetry regions. One is located at -52~-37 bp from the anaerobic mRNA 5'-end, which is the binding site of NarL and NarP. The other is located at +37~+56 bp from the 5'-end of mRNA. In this study, the downstream symmetry region from the mRNA 5'-end was investigated by site-directed mutagenesis. The destruction of the symmetry region increases the expression level of aeg-46.5. We propose that the symmetry region interferes with the expression of aeg-46.5 possibly by forming a stem-and-loop structure.

• Journal of Environmental Health Sciences
• /
• v.39 no.1
• /
• pp.83-89
• /
• 2013

Objectives: The purpose of this experiment was to illuminate the relationship between the phosphorus removal rate of unit operation and the phosphorus removal rate of phosphorus volume loading in the Ferrous Nutrient Removal process, which consists of an anoxic basin, oxic basin, and iron precipitation apparatus. Methods: This study was conducted in order to improve the effect of nitrogen and phosphorus removal in domestic wastewater using the FNR (Ferrous Nutrient Removal) process which features an iron precipitation reactor in anoxic and oxic basins. The average concentration of TN and TP was analyzed in a pilot plant ($50m^3/day$). Results: The removal rate of T-N and T-P were 66.5% and 92.8%, respectively. The $NH_3-N$ concentration of effluent was 2.62 mg/l with nitrification in the oxic basin even though the influent was 17.7 mg/l. The $NO_3$-N concentration of effluent was 5.83 mg/l through nitrification in oxic basin even though the influent and anoxic basin were 0.82 mg/l and 1.00 mg/l, respectively. The specific nitrification of the oxic basin ($mg.NH_3$-Nremoved/gMLVSSd) was 16.5 and specific de-nitrification ($mg.NO_3$-Nremoved/gMLVSSd) was 90.8. The T-P removal rate was higher in the oxic basin as T-P of influent was consumed at a rate of 56.3% in the anoxic basin but at 90.3% in the oxic basin. The TP removal rate (mg.TP/g.MLSS.d) ranged from 2.01 to 4.67 (3.06) as the volume loading of T-P was increased, Conclusions: The test results showed that the electrolysis of iron is an effective method of phosphorus removal. Regardless of the temperature and organic matter content of the influent, the quality of phosphorus in the treated water was both relatively stable and high due to the high removal efficiency. Nitrogen removal efficiency was 66.5% because organic matter from the influent serves as a carbon source in the anoxic basin.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.4 no.4
• /
• pp.25-36
• /
• 1984

This paper checked up the safety criteria of the steel structural members by LRFD. And it calculated the resistance and load modulus for it by the proposed method, considering our circumstance, by establisting the taget relability index (${\beta}_0$), and compared their calculated modulus with the nominal safety factors of the road-bridge code and analyzed them. Uncertain quantity measurements fnr the resistance of the steel structural members and for the load effect are due to the method of the uncertain quantity analysis of the load and the resistance, of Galambos-Ravindra and SGST. The summary of the results is as follows: 1) Considering our circumstance, taget relibility index(${\beta}_0$) for current steel structural members are appropriate ${\beta}_0=3.5$. 2) Nominal resistance ${\Phi}^{\prime}$ of the strength design formula for 1) and nominal load modulus ${\gamma}_i^{\prime}$ are as follows; a) Both-sides support plate: ${\Phi}{^{\prime}}=0.75$, ${\gamma}_0{^{\prime}}=1.04$, ${\gamma}_L{^{\prime}}=2.08$ b) One-side support plate: ${\Phi}{^{\prime}}=0.82$, ${\gamma}_0{^{\prime}}=1.04$, ${\gamma}_L{^{\prime}}=2.11$.

• KSBB Journal
• /
• v.11 no.4
• /
• pp.431-437
• /
• 1996

The nar promoter of Escherichta coli, which is maximally induced under anaerobic conditions in the presence of nitrate, was characterized to see whether the nar promoter cloned onto pBR322 can be used as an expression promoter. The modified nar promoter, in which several bases in the -10 region was mutated to the consensus sequence by site-directed mutagenesis, was characterized in E. coli, on which chromosome the fnr gene affecting expression of the nar promoter according to dissolved oxygen level was mutated. The E. coli lacZ gene was used as a reporter gene. The following effects were investigated to find optimal conditions to induce the modified nar promoter: induction methods, optimal nitrate concentrations, the amount of ${\beta}$-galactosidase expressed at the different growth conditions, and induction characteristics. The following results were obtained from the experiments : expression of ${\beta}$-galactosidase from the modified nar promoter was not affected much by nitrate concentrations. The maximal specific ${\beta}$-galactosidase activity was obtained when E. coli was grown under aerobic conditions, and then the modified nar promoter was induced at OD600=2.2 under microaerobic conditions (DO=1∼2%), under which conditions the maximal specific ${\beta}$-galactosidase activity was 13,000 Miller units. However, the specific ${\beta}$-galactosidase activity was approximately 6,000 Miller units even before the modified nar promoter was induced. Therefore, the modified nar promoter seemed to be useful when the cloned gene wants to be expressed in E. coli constitutively.