Comisión Nacional de Energía Atómica, Departamento de Radiobiología, Argentina.
J Photochem Photobiol B. 2012 Nov 5;116:95-104. doi: 10.1016/j.jphotobiol.2012.08.011. Epub 2012 Aug 21.
The exposure of Pseudomonas aeruginosa cells to very low UVA fluences induces a growth delay, a phenomenon proposed in Escherichia coli as an adaptive mechanism related to protection against lethal and mutagenic effects of UVA. This paper reports that the treatment with low UVA irradiation fluences protects P. aeruginosa PAO1 strain from a subsequent lethal exposure. This phenomenon depends on the relA gene, coding for the main (p)ppGpp synthetase, and is unrelated to the induction of quorum sensing or catalase activity, two essential factors involved in the response of P. aeruginosa to UVA. Cross-protection between osmotic stress and UVA is observed when a great protective response to lethal UVA is caused by the induction of resistance to osmotic stress. The increase in resistance to osmotic shock observed in the pre-irradiated PAO1 strain but not in its relA derivative, unable to show photo-protection, leads us to hypothesize that the photo-protection could be attributed to an adaptive response to osmotic stress. It is concluded that the exposure of P. aeruginosa to low UVA doses induces a relA-dependent adaptive response that protects against cell death induced by high doses and causes an increase in the resistance to osmotic stress.
铜绿假单胞菌细胞暴露于非常低的 UVA 辐照剂量会导致生长延迟，这一现象在大肠杆菌中被提出是一种与 UVA 的致死和诱变效应保护相关的适应性机制。本文报道了低剂量 UVA 照射可保护铜绿假单胞菌 PAO1 菌株免受随后的致死暴露。这种现象依赖于 relA 基因，该基因编码主要的（p）ppGpp 合成酶，与群体感应的诱导或过氧化氢酶活性无关，这两个因素是铜绿假单胞菌对 UVA 反应的关键因素。当诱导对渗透压胁迫的抗性引起对致死性 UVA 的巨大保护反应时，观察到渗透压胁迫与 UVA 之间的交叉保护。在预先辐照的 PAO1 菌株中观察到的对渗透压冲击的抗性增加，但在其无法表现出光保护的 relA 衍生物中没有观察到，这使我们假设光保护可能归因于对渗透压胁迫的适应性反应。结论是，铜绿假单胞菌暴露于低剂量 UVA 会诱导依赖 relA 的适应性反应，可保护细胞免受高剂量诱导的细胞死亡，并增加对渗透压胁迫的抗性。
