The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
James A Houghton - One of the best experts on this subject based on the ideXlab platform.
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Photoreactivation and excision repair of uv induced pyrimidine dimers in the unicellular cyanobacterium gloeocapsa alpicola synechocystis pcc 6308
Photochemistry and Photobiology, 2008Co-Authors: Philip A Obrien, James A HoughtonAbstract:Abstract— The survival curve obtained after UV irradiation of the unicellular cyanobacterium Synecho-cystis is typical of a DNA repair competent organism. Inhibition of DNA replication, by incubating cells in the dark, increased resistance to the lethal effects of UV at higher fluences. Exposure of irradiated cells to near ultraviolet light(350–500 nm) restored viability to pre-irradiation levels. In order to measure DNA repair activity, techniques have been developed for the chromatographic analysis of pyrimidine dimers in Synechocystis. The specificity of this method was established using a haploid strain of Sacchar-omyces cerevisiae. In accordance with the physiological responses of irradiated cells to photoreactivating light, pyrimidine dimers were not detected after Photoreactivation treatment. Incubation of irradiated cells under non-photoreactivating growth conditions for 15 h resulted in complete removal of pyrimidine dimers. It is concluded that Synechocystis contains Photoreactivation and excision repair systems for the removal of pyrimidine dimers.
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Photoreactivation and excision repair of uv induced pyrimidine dimers in the unicellular cyanobacterium gloeocapsa alpicola synechocystis pcc 6308
Photochemistry and Photobiology, 2008Co-Authors: Philip A Obrien, James A HoughtonAbstract:Abstract— The survival curve obtained after UV irradiation of the unicellular cyanobacterium Synecho-cystis is typical of a DNA repair competent organism. Inhibition of DNA replication, by incubating cells in the dark, increased resistance to the lethal effects of UV at higher fluences. Exposure of irradiated cells to near ultraviolet light(350–500 nm) restored viability to pre-irradiation levels. In order to measure DNA repair activity, techniques have been developed for the chromatographic analysis of pyrimidine dimers in Synechocystis. The specificity of this method was established using a haploid strain of Sacchar-omyces cerevisiae. In accordance with the physiological responses of irradiated cells to photoreactivating light, pyrimidine dimers were not detected after Photoreactivation treatment. Incubation of irradiated cells under non-photoreactivating growth conditions for 15 h resulted in complete removal of pyrimidine dimers. It is concluded that Synechocystis contains Photoreactivation and excision repair systems for the removal of pyrimidine dimers.
Shinichiro Ohgaki - One of the best experts on this subject based on the ideXlab platform.
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Effect of Photoreactivation on ultraviolet inactivation of Microcystis aeruginosa.
Water Science and Technology, 2011Co-Authors: Hiroshi Sakai, Kumiko Oguma, Hiroyuki Katayama, Shinichiro OhgakiAbstract:Microcystis aeruginosa forms algal bloom in lakes. They produce toxic compounds such as microcystin. Against such algal problems, the effect of UV treatment was examined. In UV treatment, the effect of Photoreactivation should be examined. Photoreactivation is a repair mechanism of genomic DNA damage by sunlight irradiation. UV treatment causes DNA damages on target cyanobacteria, however sunlight can repair some of these DNA damages. To examine the effect of Photoreactivation, both white and yellow light incubations were employed. White light allows both Photoreactivation and photosynthesis, while yellow light prohibits Photoreactivation and only allows photosynthesis. Microcystis aeruginosa NIES 98 strain and PCC 7806 strain were used as the test cultures. Those cultures were exposed to low-pressure (LP) or medium-pressure (MP) ultraviolet (UV) lamp, then incubated under white or yellow light. Yellow light incubation method was effective to examine Photoreactivation. It was revealed that almost six times UV fluence was required to inactivate 99% of Microcystis aeruginosa , under Photoreactivation condition, compared with non-Photoreactivation condition. Inhibition of Photoreactivation could greatly enhance UV treatment efficiency against Microcystis aeruginosa . One of the practical suggestions is to conduct UV treatment at night, when Photoreactivation by sunlight rarely takes place. Highly efficient inactivation was achieved by avoiding Photoreactivation.
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spectral impact of inactivating light on Photoreactivation of escherichia coli
Journal of Environmental Engineering and Science, 2005Co-Authors: Kumiko Oguma, Hiroyuki Katayama, Shinichiro OhgakiAbstract:The spectral impact of inactivating light on subsequent Photoreactivation of Escherichia coli K12 was investigated. Ultraviolet-induced pyrimidine dimers in the genome of E. coli were determined, w...
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repressive effects of yeast extract on Photoreactivation of escherichia coli
Water Science and Technology, 2004Co-Authors: J Oguma, Hiroyuki Katayama, Hiroshi Mitani, Shinichiro OhgakiAbstract:Photoreactivation of Escherichia coli K12 (IFO 3301), in the presence or absence of yeast extract (YE), was investigated after inactivation by low-pressure UV lamp. An endonuclease sensitive site (ESS) assay was used to determine the UV-induced pyrimidine dimers in the genome of E. coli , while a colony-forming ability (CFA) test was also used to examine the survival ratio of E. coli . The YE solution reduced the CFA recovery at a final concentration of 125 mg/L. A dialysis of the YE solution indicated that the YE fraction (with nominal molecular weight >1,000 and E. coli without affecting the ESS repair during Photoreactivation.
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Photoreactivation of legionella pneumophila after inactivation by low or medium pressure ultraviolet lamp
Water Research, 2004Co-Authors: Kumiko Oguma, Hiroyuki Katayama, Shinichiro OhgakiAbstract:Photoreactivation of Legionella pneumophila after the inactivation by low-pressure (LP) or medium-pressure (MP) UV lamp was investigated in comparison with that of Escherichia coli. An endonuclease sensitive site (ESS) assay was used to determine the number of UV-induced pyrimidine dimers in the genome DNA of L. pneumophila or E. coli, while the survival ratio of each bacterium was also investigated by cultivation methods. L. pneumophila performed Photoreactivation with almost complete repair of pyrimidine dimers associated with the quick recovery of survival ratio. A 3 log inactivation of L. pneumophila by LP or MP UV lamp was, respectively, resulted in 0.5 log or 0.4 log inactivation when Photoreactivation was completed. Interestingly, L. pneumophila performed equivalent Photoreactivation after LP and MP UV lamp exposures while Photoreactivation of E. coli was significantly repressed after the inactivation by MP UV lamp. This study indicated that an attention would be required to design and operate a UV disinfection system targeting L. pneumophila. It was further implied that E. coli would not correctly indicate the fate of L. pneumophila in UV disinfection systems when Photoreactivation takes place.
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determination of pyrimidine dimers in escherichia coli and cryptosporidium parvum during uv light inactivation Photoreactivation and dark repair
Applied and Environmental Microbiology, 2001Co-Authors: Kumiko Oguma, Hiroyuki Katayama, Tsuyoshi Hirata, Hiroshi Mitani, Shigemitsu Morita, Shinichiro OhgakiAbstract:UV inactivation, Photoreactivation, and dark repair of Escherichia coli and Cryptosporidium parvum were investigated with the endonuclease sensitive site (ESS) assay, which can determine UV-induced pyrimidine dimers in the genomic DNA of microorganisms. In a 99.9% inactivation of E. coli, high correlation was observed between the dose of UV irradiation and the number of pyrimidine dimers induced in the DNA of E. coli. The colony-forming ability of E. coli also correlated highly with the number of pyrimidine dimers in the DNA, indicating that the ESS assay is comparable to the method conventionally used to measure colony-forming ability. When E. coli were exposed to fluorescent light after a 99.9% inactivation by UV irradiation, UV-induced pyrimidine dimers in the DNA were continuously repaired and the colony-forming ability recovered gradually. When kept in darkness after the UV inactivation, however, E. coli showed neither repair of pyrimidine dimers nor recovery of colony-forming ability. When C. parvum were exposed to fluorescent light after UV inactivation, UV-induced pyrimidine dimers in the DNA were continuously repaired, while no recovery of animal infectivity was observed. When kept in darkness after UV inactivation, C. parvum also showed no recovery of infectivity in spite of the repair of pyrimidine dimers. It was suggested, therefore, that the infectivity of C. parvum would not recover either by Photoreactivation or by dark repair even after the repair of pyrimidine dimers in the genomic DNA.
Philip A Obrien - One of the best experts on this subject based on the ideXlab platform.
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Photoreactivation and excision repair of uv induced pyrimidine dimers in the unicellular cyanobacterium gloeocapsa alpicola synechocystis pcc 6308
Photochemistry and Photobiology, 2008Co-Authors: Philip A Obrien, James A HoughtonAbstract:Abstract— The survival curve obtained after UV irradiation of the unicellular cyanobacterium Synecho-cystis is typical of a DNA repair competent organism. Inhibition of DNA replication, by incubating cells in the dark, increased resistance to the lethal effects of UV at higher fluences. Exposure of irradiated cells to near ultraviolet light(350–500 nm) restored viability to pre-irradiation levels. In order to measure DNA repair activity, techniques have been developed for the chromatographic analysis of pyrimidine dimers in Synechocystis. The specificity of this method was established using a haploid strain of Sacchar-omyces cerevisiae. In accordance with the physiological responses of irradiated cells to photoreactivating light, pyrimidine dimers were not detected after Photoreactivation treatment. Incubation of irradiated cells under non-photoreactivating growth conditions for 15 h resulted in complete removal of pyrimidine dimers. It is concluded that Synechocystis contains Photoreactivation and excision repair systems for the removal of pyrimidine dimers.
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Photoreactivation and excision repair of uv induced pyrimidine dimers in the unicellular cyanobacterium gloeocapsa alpicola synechocystis pcc 6308
Photochemistry and Photobiology, 2008Co-Authors: Philip A Obrien, James A HoughtonAbstract:Abstract— The survival curve obtained after UV irradiation of the unicellular cyanobacterium Synecho-cystis is typical of a DNA repair competent organism. Inhibition of DNA replication, by incubating cells in the dark, increased resistance to the lethal effects of UV at higher fluences. Exposure of irradiated cells to near ultraviolet light(350–500 nm) restored viability to pre-irradiation levels. In order to measure DNA repair activity, techniques have been developed for the chromatographic analysis of pyrimidine dimers in Synechocystis. The specificity of this method was established using a haploid strain of Sacchar-omyces cerevisiae. In accordance with the physiological responses of irradiated cells to photoreactivating light, pyrimidine dimers were not detected after Photoreactivation treatment. Incubation of irradiated cells under non-photoreactivating growth conditions for 15 h resulted in complete removal of pyrimidine dimers. It is concluded that Synechocystis contains Photoreactivation and excision repair systems for the removal of pyrimidine dimers.
Kumiko Oguma - One of the best experts on this subject based on the ideXlab platform.
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effects of salinity on Photoreactivation of escherichia coli after uv disinfection
Journal of Water and Health, 2013Co-Authors: Kumiko Oguma, Kentaro Izaki, Hiroyuki KatayamaAbstract:The effects of sodium chloride on Photoreactivation of Escherichia coli were examined, assuming the discharge of ultraviolet (UV)-treated wastewater to water environment at different salinities. Suspensions of E. coli were first exposed to a low-pressure UV lamp in phosphate buffer to achieve 3 log inactivation, followed by an exposure to fluorescent light in NaCl solutions at the concentration of 1.0, 1.4, 1.9, 2.4 and 2.9 weight/volume %. When Photoreactivation was completed in 3 h, survival ratio was recovered about 2 log in 1.0, 1.4, and 1.9% NaCl solutions, which was equivalent to the recovery observed in phosphate-buffered solution. Meanwhile, the recovery was suppressed to 0.8 log and -0.2 log in 2.4 and 2.9% NaCl solutions, respectively, which was significantly less than the recovery in phosphate buffer according to the t-test (p < 0.05). An endonuclease sensitive site assay demonstrated that the suppressed Photoreactivation in 2.9% NaCl solution was due to the failure at repairing UV-induced pyrimidine dimers in the genome. In conclusion, Photoreactivation of E. coli was significantly suppressed in NaCl solution at 2.4% or higher but not affected in NaCl solution at 1.9% or lower. This implies that Photoreactivation of E. coli may potentially occur in brackish and coastal areas where salinity is rather low.
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Effect of Photoreactivation on ultraviolet inactivation of Microcystis aeruginosa.
Water Science and Technology, 2011Co-Authors: Hiroshi Sakai, Kumiko Oguma, Hiroyuki Katayama, Shinichiro OhgakiAbstract:Microcystis aeruginosa forms algal bloom in lakes. They produce toxic compounds such as microcystin. Against such algal problems, the effect of UV treatment was examined. In UV treatment, the effect of Photoreactivation should be examined. Photoreactivation is a repair mechanism of genomic DNA damage by sunlight irradiation. UV treatment causes DNA damages on target cyanobacteria, however sunlight can repair some of these DNA damages. To examine the effect of Photoreactivation, both white and yellow light incubations were employed. White light allows both Photoreactivation and photosynthesis, while yellow light prohibits Photoreactivation and only allows photosynthesis. Microcystis aeruginosa NIES 98 strain and PCC 7806 strain were used as the test cultures. Those cultures were exposed to low-pressure (LP) or medium-pressure (MP) ultraviolet (UV) lamp, then incubated under white or yellow light. Yellow light incubation method was effective to examine Photoreactivation. It was revealed that almost six times UV fluence was required to inactivate 99% of Microcystis aeruginosa , under Photoreactivation condition, compared with non-Photoreactivation condition. Inhibition of Photoreactivation could greatly enhance UV treatment efficiency against Microcystis aeruginosa . One of the practical suggestions is to conduct UV treatment at night, when Photoreactivation by sunlight rarely takes place. Highly efficient inactivation was achieved by avoiding Photoreactivation.
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spectral impact of inactivating light on Photoreactivation of escherichia coli
Journal of Environmental Engineering and Science, 2005Co-Authors: Kumiko Oguma, Hiroyuki Katayama, Shinichiro OhgakiAbstract:The spectral impact of inactivating light on subsequent Photoreactivation of Escherichia coli K12 was investigated. Ultraviolet-induced pyrimidine dimers in the genome of E. coli were determined, w...
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Photoreactivation of legionella pneumophila after inactivation by low or medium pressure ultraviolet lamp
Water Research, 2004Co-Authors: Kumiko Oguma, Hiroyuki Katayama, Shinichiro OhgakiAbstract:Photoreactivation of Legionella pneumophila after the inactivation by low-pressure (LP) or medium-pressure (MP) UV lamp was investigated in comparison with that of Escherichia coli. An endonuclease sensitive site (ESS) assay was used to determine the number of UV-induced pyrimidine dimers in the genome DNA of L. pneumophila or E. coli, while the survival ratio of each bacterium was also investigated by cultivation methods. L. pneumophila performed Photoreactivation with almost complete repair of pyrimidine dimers associated with the quick recovery of survival ratio. A 3 log inactivation of L. pneumophila by LP or MP UV lamp was, respectively, resulted in 0.5 log or 0.4 log inactivation when Photoreactivation was completed. Interestingly, L. pneumophila performed equivalent Photoreactivation after LP and MP UV lamp exposures while Photoreactivation of E. coli was significantly repressed after the inactivation by MP UV lamp. This study indicated that an attention would be required to design and operate a UV disinfection system targeting L. pneumophila. It was further implied that E. coli would not correctly indicate the fate of L. pneumophila in UV disinfection systems when Photoreactivation takes place.
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Photoreactivation of Escherichia coli after low- or medium-pressure UV disinfection determined by an endonuclease sensitive site assay
Applied and Environmental Microbiology, 2002Co-Authors: Kumiko Oguma, Hiroyuki Katayama, Shinji OhgakiAbstract:Photoreactivation of Escherichia coli after inactivation by a low-pressure (LP) UV lamp (254 nm), by a medium-pressure (MP) UV lamp (220 to 580 nm), or by a filtered medium-pressure (MPF) UV lamp (300 to 580 nm) was investigated. An endonuclease sensitive site (ESS) assay was used to determine the number of UV-induced pyrimidine dimers in the genomic DNA of E. coli, while a conventional cultivation assay was used to investigate the colony-forming ability (CFA) of E. coli. In Photoreactivation experiments, more than 80% of the pyrimidine dimers induced by LP or MPF UV irradiation were repaired, while almost no repair of dimers was observed after MP UV exposure. The CFA ratios of E. coli recovered so that they were equivalent to 0.9-, 2.3-, and 1.7-log inactivation after 3-log inactivation by LP, MP, and MPF UV irradiation, respectively. Photorepair treatment of DNA in vitro suggested that among the MP UV emissions, wavelengths of 220 to 300 nm reduced the subsequent photorepair of ESS, possibly by causing a disorder in endogenous photolyase, an enzyme specific for Photoreactivation. On the other hand, the MP UV irradiation at wavelengths between 300 and 580 nm was observed to play an important role in reducing the subsequent recovery of CFA by inducing damage other than damage to pyrimidine dimers. Therefore, it was found that inactivating light at a broad range of wavelengths effectively reduced subsequent Photoreactivation, which could be an advantage that MP UV irradiation has over conventional LP UV irradiation.
Qiao Wang - One of the best experts on this subject based on the ideXlab platform.
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disinfection of municipal secondary effluents with microwave induced electrodeless ultraviolet irradiation for water reuse
Journal of Chemical Technology & Biotechnology, 2017Co-Authors: Yue Zhang, Guangshan Zhang, Peng Wang, Qiao WangAbstract:BACKGROUND Disinfection is an essential way to ensure the safety of recycled water. Ultraviolet (UV) is an effective and environmentally friendly technique suitable for the disinfection of recycled water. However, UV disinfection also leads to Photoreactivation. This work proposes a combined use of UV irradiation and microwave technique to compensate for the limitations of UV disinfection. RESULTS The process of microwave-induced electrodeless ultraviolet (MW-EUV) irradiation was utilized to disinfect municipal secondary effluents. A homemade columnar electrodeless UV lamp was used as the source of UV irradiation. Good disinfection results the under optimal microwave power at 600 W were obtained. There was no Photoreactivation after sufficient irradiation. Cell damage of Escherichia coli by MW-EUV irradiation was investigated by measuring the leakage of K+ and protein from cells and was observed by an atomic force microscope (AFM). CONCLUSION The MW-EUV irradiation is demonstrated to be a faster and more effective disinfection method in this study. The irradiated samples could meet the hygienic standards for the reuse of urban recycling water (Standard Number GB/T 18920–2002) in China. The disinfection mainly depends on UV irradiation. The microwave was the main causes of bacterial breakup and deformation. This irreversible damage offsets the biological self-healing phenomenon in UV disinfection.
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disinfection of municipal secondary effluents with microwave induced electrodeless ultraviolet irradiation for water reuse
Journal of Chemical Technology & Biotechnology, 2017Co-Authors: Yue Zhang, Guangshan Zhang, Peng Wang, Qiao WangAbstract:BACKGROUND Disinfection is an essential way to ensure the safety of recycled water. Ultraviolet (UV) is an effective and environmentally friendly technique suitable for the disinfection of recycled water. However, UV disinfection also leads to Photoreactivation. This work proposes a combined use of UV irradiation and microwave technique to compensate for the limitations of UV disinfection. RESULTS The process of microwave-induced electrodeless ultraviolet (MW-EUV) irradiation was utilized to disinfect municipal secondary effluents. A homemade columnar electrodeless UV lamp was used as the source of UV irradiation. Good disinfection results the under optimal microwave power at 600 W were obtained. There was no Photoreactivation after sufficient irradiation. Cell damage of Escherichia coli by MW-EUV irradiation was investigated by measuring the leakage of K+ and protein from cells and was observed by an atomic force microscope (AFM). CONCLUSION The MW-EUV irradiation is demonstrated to be a faster and more effective disinfection method in this study. The irradiated samples could meet the hygienic standards for the reuse of urban recycling water (Standard Number GB/T 18920–2002) in China. The disinfection mainly depends on UV irradiation. The microwave was the main causes of bacterial breakup and deformation. This irreversible damage offsets the biological self-healing phenomenon in UV disinfection.