Faculty of Education, Mie University, 1577 Kurimamachiya-cho Tsu, Mie 514-8507, Japan.
Strategic Planning Office for Regional Revitalization, Mie University, 1577 Kurimamachiya-cho Tsu, Mie 514-8507, Japan.
J Photochem Photobiol B. 2022 Jun;231:112448. doi: 10.1016/j.jphotobiol.2022.112448. Epub 2022 Apr 26.
Water disinfection is one of the most important applications of ultraviolet light-emitting diodes (UV-LEDs), though bacterial regrowth remains a serious problem. In this study, we showed that UV-resistant cells, though rare, exist in an Escherichia coli clonal population. The UV-resistance of stationary phase cells was higher than that of exponential phase cells. Regrowth cell populations showed identical UV sensitivity before and after UV treatment, indicating that UV resistance is not acquired genetically, but is generated stochastically. The characteristics of these UV-resistant cells are similar to those of non-heritable antibiotic-resistant cells, termed persisters. The induction of persister formation increased the number of viable cells after UV treatment. The toxin-antitoxin system gene hipA (high persistence A) is a key factor in persister cell formation. We observed that hipA was strongly expressed in the stationary phase cells, while regrowth cells after UV treatment lost hipA expression, suggesting that the regrowth cells lost their persistence. Compared to UV batch radiation, we demonstrated that intermittent UV irradiation, which included the induction of regrowth between UV treatments, significantly reduced the number of viable E. coli cells.
水消毒是紫外线发光二极管（UV-LED）的最重要应用之一，尽管细菌再生仍然是一个严重的问题。在这项研究中，我们表明，尽管稀有，但在大肠杆菌克隆群体中存在抗紫外线的细胞。与对数期细胞相比，静止期细胞的抗紫外线能力更高。经紫外线处理前后，再生细胞群体的紫外线敏感性相同，表明紫外线抗性不是遗传获得的，而是随机产生的。这些抗紫外线细胞的特征与非遗传性抗生素抗性细胞（称为持续细胞）相似。持续细胞形成的诱导增加了紫外线处理后存活细胞的数量。毒素-抗毒素系统基因 hipA（高持续 A）是持续细胞形成的关键因素。我们观察到，hipA 在静止期细胞中强烈表达，而经紫外线处理后的再生细胞失去了 hipA 的表达，这表明再生细胞失去了持续能力。与紫外线批量辐射相比，我们证明了间歇性紫外线照射，包括在紫外线处理之间诱导再生，可显著减少大肠杆菌活细胞的数量。
