Muela A, García-Bringas J M, Seco C, Arana I, Barcina I
Departamento de Inmunología, Microbiología y Parasitología, Facultad de Ciencias, Universidad del País Vasco, Bilbao, Spain.
Microb Ecol. 2002 Nov;44(4):354-64. doi: 10.1007/s00248-002-1027-y. Epub 2002 Oct 14.
We studied the mechanisms by which photosynthetically active radiation (PAR) and ultraviolet (UV-A and UV-B) radiation damage Escherichia coli suspended in water. The roles played by oxygen and exogenous and endogenous sensitizers were analyzed by monitoring changes in the physiological state of irradiated cells. Impairment of the cellular functions was more severe in the case of UV radiations. Radiation caused cellular damage in the absence of oxygen. PAR, UV-A, and UV-B radiation induced photobiological and photodynamic reactions mediated by endogenous sensitizers, which significantly shortened the T90 (time needed to reduce a cellular parameter by 90%) based on the growth ability of the cells. In addition, when exogenous sensitizers were present, the photodynamic reactions also had a negative effect on the operation of the electron transport chains. The presence of oxygen might enhance photoinactivation, affecting both the growth ability and the electron transport chains. Endogenous sensitizers were responsible for the noxious action of oxygen. The presence of dissolved organic material played a protective role against the oxygen by absorbing the incident radiation, thereby reducing the energy that reached the endogenous sensitizers.
我们研究了光合有效辐射（PAR）以及紫外线（UV-A和UV-B）对悬浮于水中的大肠杆菌造成损伤的机制。通过监测受辐照细胞生理状态的变化，分析了氧气以及外源性和内源性敏化剂所起的作用。紫外线辐射对细胞功能的损害更为严重。在无氧情况下辐射也会导致细胞损伤。PAR、UV-A和UV-B辐射诱导由内源性敏化剂介导的光生物学和光动力反应，基于细胞的生长能力，这显著缩短了T90（将细胞参数降低90%所需的时间）。此外，当存在外源性敏化剂时，光动力反应也会对电子传递链的运行产生负面影响。氧气的存在可能会增强光灭活作用，对生长能力和电子传递链均产生影响。内源性敏化剂是氧气产生有害作用的原因。溶解有机物质的存在通过吸收入射辐射对氧气起到保护作用，从而减少到达内源性敏化剂的能量。
