Departamento de Radiobiología, Comisión Nacional de Energía Atómica, San Martín, Argentina.
Photochem Photobiol. 2010 Nov-Dec;86(6):1334-42. doi: 10.1111/j.1751-1097.2010.00800.x. Epub 2010 Sep 24.
The role of quorum sensing (QS) in the response of Pseudomonas aeruginosa to UVA radiation was investigated in the PAO1 strain and derivatives defective in the synthesis of the QS signals 3OC12-HSL (lasI strain), C4-HSL (rhlI strain) or both (lasI rhlI strain). Cell viability measurements demonstrated that the double mutant was significantly more sensitive to UVA than single mutants, which in turn showed reduced cell survival with regard to the PAO1 strain. Irradiation under nitrogen atmosphere and chemiluminescence measurements indicated the oxidative nature of the UVA-induced damage. The activity of the antioxidant enzymes catalase and superoxide dismutase was assayed in these strains before and after irradiation, and a strong correlation between catalase levels and UVA sensitivity was observed. When a sublethal UVA dose was applied to PAO1, a growth delay was observed and this mechanism depended on the rhl system. Moreover, low doses of UVA irradiation triplicated the level of C4-HSL in log PAO1 cells. It is concluded that QS is fundamental in the defense against the toxic effects of UVA in P. aeruginosa. The induction of the QS system by UVA independently of cell density could function as an adaptative strategy to withstand this hostile environmental condition.
我们研究了群体感应（QS）在铜绿假单胞菌对 UVA 辐射反应中的作用，以 PAO1 株及其在合成 QS 信号 3OC12-HSL（lasI 株）、C4-HSL（rhlI 株）或两者（lasI rhlI 株）方面有缺陷的衍生物为研究对象。细胞活力测量表明，双突变体对 UVA 的敏感性明显高于单突变体，而单突变体相对于 PAO1 株的细胞存活率降低。在氮气气氛下辐照和化学发光测量表明，UVA 诱导的损伤具有氧化性。在辐照前后测定了这些菌株中抗氧化酶过氧化氢酶和超氧化物歧化酶的活性，观察到过氧化氢酶水平与 UVA 敏感性之间存在很强的相关性。当用亚致死剂量的 UVA 照射 PAO1 时，观察到生长延迟，而这种机制依赖于 rhl 系统。此外，低剂量的 UVA 照射使对数期 PAO1 细胞中的 C4-HSL 水平增加了两倍。结论是，QS 是铜绿假单胞菌抵御 UVA 毒性作用的基础。QS 系统的诱导与细胞密度无关，可能是一种适应这种恶劣环境条件的策略。
