Arana I, Muela A, Iriberri J, Egea L, Barcina I
Departamento de Microbiología e Inmunología, Facultad de Ciencias, Universidad del País Vasco, Bilbao, Spain.
Appl Environ Microbiol. 1992 Dec;58(12):3903-7. doi: 10.1128/aem.58.12.3903-3907.1992.
A study was made of the mechanisms by which visible light produces cell dormancy in Escherichia coli, resulting in loss of culturability. Visible light may act directly on the cells or generate photoproducts with a negative effect on the cells. In nonilluminated microcosms the addition of increasing concentrations of hydrogen peroxide, one of the photoproducts formed in natural aquatic systems, gave rise to the formation of nonculturable cells and injured culturable cells, and this negative effect depended on the concentration of peroxide. On the other hand, in illuminated microcosms the addition of compounds which eliminate hydrogen peroxide (i.e., catalase, sodium pyruvate, and thioglycolate) had a protective effect on the E. coli cells, as the CFU counts on minimal medium and on recuperation medium were significantly higher (P < 0.05) than those detected in the absence of these compounds. Furthermore, when hydrogen peroxide was eliminated, the CFU counts on recuperation medium did not fall significantly, indicating that nonculturable cells did not form. These results rule out the direct effect of visible light on the cells and show that hydrogen peroxide, generated photochemically, may be the cause of the loss of culturability of E. coli in illuminated systems.
对可见光致使大肠杆菌细胞进入休眠状态并导致其失去可培养性的机制进行了研究。可见光可能直接作用于细胞，或者产生对细胞有负面影响的光产物。在未光照的微观环境中，添加浓度不断增加的过氧化氢（天然水生系统中形成的光产物之一）会导致不可培养细胞的形成以及可培养细胞受到损伤，且这种负面影响取决于过氧化氢的浓度。另一方面，在光照的微观环境中，添加能消除过氧化氢的化合物（即过氧化氢酶、丙酮酸钠和巯基乙酸盐）对大肠杆菌细胞具有保护作用，因为在基本培养基和恢复培养基上的菌落形成单位（CFU）计数显著高于（P < 0.05）未添加这些化合物时检测到的计数。此外，当消除过氧化氢时，恢复培养基上的CFU计数没有显著下降，表明未形成不可培养细胞。这些结果排除了可见光对细胞的直接作用，并表明光化学产生的过氧化氢可能是光照系统中大肠杆菌失去可培养性的原因。
