Gourmelon M, Cillard J, Pommepuy M
Laboratoire de Microbiologie, IFREMER, DEL, Plouzané, France.
J Appl Bacteriol. 1994 Jul;77(1):105-12. doi: 10.1111/j.1365-2672.1994.tb03051.x.
The effect of visible light on Escherichia coli H10407 in seawater microcosms was investigated. Light damage was estimated by loss of colony-forming ability. Illumination of E. coli suspended in oligotrophic seawater with visible light at an intensity of about 40 klux caused a drastic decrease of culturable bacteria which turned to a viable but non-culturable state. In seawater E. coli exhibited weak metabolic activity as estimated by 3H methyl-thymidine incorporation in the cell. Visible light did not significantly alter this metabolic activity and did not involve detectable oxidation of lipid membranes as evaluated by gas chromatography analysis of fatty acids. The involvement of oxygen and reactive oxygen species in phototoxicity was studied. A decrease of the toxic effect was observed when E. coli was exposed to visible light under anaerobic conditions. Scavengers of reactive oxygen species exhibited variable protective effects. beta-Carotene, a singlet oxygen scavenger, and superoxide dismutase were equally ineffective. On the other hand, catalase, which eliminates hydrogen peroxide and thiourea, a hydroxyl radical scavenger, showed a net protection. In addition desferrioxamine B, an iron chelator, was also effective in reducing phototoxicity, probably by preventing hydroxyl radical generation by decomposition of hydrogen peroxide in the presence of iron (Fenton reaction). Therefore, hydrogen peroxide and hydroxyl radical seem to be reactive intermediates of oxygen-dependent (type II) photosensitized reactions.
研究了可见光对海水微宇宙中大肠杆菌H10407的影响。通过菌落形成能力的丧失来估计光损伤。用强度约为40勒克斯的可见光照射贫营养海水中悬浮的大肠杆菌，导致可培养细菌急剧减少，细菌转变为活的但不可培养的状态。在海水中，通过细胞中3H甲基胸苷掺入估计，大肠杆菌表现出较弱的代谢活性。可见光并未显著改变这种代谢活性，通过脂肪酸气相色谱分析评估，可见光也未引起脂质膜的可检测氧化。研究了氧气和活性氧在光毒性中的作用。当大肠杆菌在厌氧条件下暴露于可见光时，观察到毒性作用降低。活性氧清除剂表现出不同的保护作用。β-胡萝卜素，一种单线态氧清除剂，和超氧化物歧化酶同样无效。另一方面，过氧化氢酶（可消除过氧化氢）和硫脲（一种羟基自由基清除剂）显示出净保护作用。此外，去铁胺B，一种铁螯合剂，也能有效降低光毒性，可能是通过在铁存在下防止过氧化氢分解产生羟基自由基（芬顿反应）。因此，过氧化氢和羟基自由基似乎是氧依赖性（II型）光敏反应的活性中间体。
