Comisión Nacional de Energía Atómica, Departamento de Radiobiología, Argentina.
J Photochem Photobiol B. 2011 Jan 10;102(1):20-5. doi: 10.1016/j.jphotobiol.2010.08.012. Epub 2010 Sep 7.
Salmonella enterica serovar Typhimurium is an important pathogen, and exhibits considerable resistance to the lethal effects of solar radiation. To evaluate the involvement of the RpoS transcription factor in the defense mechanisms of this organism, the sunlight response of a wild type strain (ATCC14028) was compared with that of an rpoS mutant, which exhibited increased sensitivity. Kinetics of cell death was complex in both strains, probably due to the presence of a variety of targets for the radiation. When ultraviolet radiation was excluded from the incident sunlight, lethal effects were abolished independently of the allelic state of rpoS. Reduction of oxygen concentration in the irradiation medium provided moderate protection to ATCC14028, but notably improved survival of the mutant. Similar assays were developed with another S. enterica strain (DA1468), which is a derivative of strain LT2 and produces low levels of RpoS. In this strain the loss of viability reveals the dependence on solar ultraviolet and oxygen concentration found for ATCC14028, but radiation resistance was slightly reduced. Increased sensitivity was observed in an rpoS mutant derived from DA1468, indicating that RpoS functions related to photoprotection are conserved in this strain. In addition, notable differences in the shape of the survival curves obtained for mutants derived from ATCC14028 and DA1468 were found, suggesting that genes beyond RpoS control are relevant in the sunlight response of these mutants.
鼠伤寒沙门氏菌血清型 Typhimurium 是一种重要的病原体，对太阳辐射的致死效应表现出相当大的抗性。为了评估 RpoS 转录因子在该生物体防御机制中的参与，比较了野生型菌株（ATCC14028）与 rpoS 突变体的阳光反应，后者表现出更高的敏感性。两种菌株的细胞死亡动力学都很复杂，可能是由于存在多种辐射靶标。当将紫外线辐射从入射阳光中排除时，致死效应独立于 rpoS 的等位基因状态而被消除。辐照介质中氧浓度的降低为 ATCC14028 提供了适度的保护，但显著提高了突变体的存活率。用另一种沙门氏菌菌株（DA1468）进行了类似的测定，该菌株是 LT2 菌株的衍生物，产生低水平的 RpoS。在该菌株中，生存能力的丧失揭示了对 ATCC14028 发现的太阳紫外线和氧浓度的依赖性，但辐射抗性略有降低。从 DA1468 衍生的 rpoS 突变体表现出敏感性增加，表明与光保护相关的 RpoS 功能在该菌株中得到保守。此外，还发现源自 ATCC14028 和 DA1468 的突变体获得的生存曲线的形状存在显著差异，表明在这些突变体的阳光反应中，除了 RpoS 控制之外，还有相关的基因。
