Oguma Kumiko, Katayama Hiroyuki, Ohgaki Shinichiro
Department of Urban Engineering, University of Tokyo, Bunkyo-ku, Japan.
Appl Environ Microbiol. 2002 Dec;68(12):6029-35. doi: 10.1128/AEM.68.12.6029-6035.2002.
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.
研究了用低压（LP）紫外线灯（254nm）、中压（MP）紫外线灯（220至580nm）或过滤中压（MPF）紫外线灯（300至580nm）灭活后大肠杆菌的光复活情况。采用内切核酸酶敏感位点（ESS）测定法来确定大肠杆菌基因组DNA中紫外线诱导的嘧啶二聚体数量，同时使用传统培养测定法来研究大肠杆菌的菌落形成能力（CFA）。在光复活实验中，LP或MPF紫外线照射诱导产生的嘧啶二聚体中有80%以上得到修复，而MP紫外线照射后几乎未观察到二聚体的修复。大肠杆菌的CFA比率得以恢复，使得在分别经LP、MP和MPF紫外线照射3对数灭活后，其相当于0.9对数、2.3对数和1.7对数的灭活。体外DNA的光修复处理表明，在MP紫外线发射中，220至300nm的波长降低了ESS随后的光修复，这可能是由于导致了内源性光解酶（一种光复活特异性酶）的紊乱。另一方面，观察到300至580nm波长的MP紫外线照射在通过诱导除嘧啶二聚体损伤之外的其他损伤来降低随后CFA的恢复方面发挥了重要作用。因此，发现宽波长范围的灭活光有效地降低了随后的光复活，这可能是MP紫外线照射相对于传统LP紫外线照射的一个优势。
