Department of Bioscience and Biotechnology, Hankuk University of Foreign Studies, Yong-In, Gyunggi-Do, South Korea.
Department of Bioscience and Biotechnology, Hankuk University of Foreign Studies, Yong-In, Gyunggi-Do, South Korea
Appl Environ Microbiol. 2018 Oct 30;84(22). doi: 10.1128/AEM.02085-18. Print 2018 Nov 15.
When phages infect bacteria cultured in the presence of sublethal doses of antibiotics, the sizes of the phage plaques are significantly increased. This phenomenon is known as phage-antibiotic synergy (PAS). In this study, the observation of PAS was extended to a wide variety of bacterium-phage pairs using different classes of antibiotics. PAS was shown in both Gram-positive and Gram-negative bacteria. Cells stressed with β-lactam antibiotics filamented or swelled extensively, resulting in an increase in phage production. PAS was also sometimes observed in the presence of other classes of antibiotics with or without bacterial filamentation. The addition of antibiotics induced expression in various bacteria, but a deletion mutant strain of also showed filamentation and PAS in the presence of quinolone antibiotics. The phage adsorption efficiency did not change in the presence of the antibiotics when the cell surfaces were enlarged as they filamented. Increases in the production of phage DNA and mRNAs encoding phage proteins were observed in these cells, with only a limited increase in protein production. The data suggest that PAS is the product of a prolonged period of particle assembly due to delayed lysis. The increase in the cell surface area far exceeded the increase in phage holin production in the filamented host cells, leading to a relatively limited availability of intracellular holins for aggregating and forming holes in the host membrane. Reactive oxygen species (ROS) stress also led to an increased production of phages, while heat stress resulted in only a limited increase in phage production. Phage-antibiotic synergy (PAS) has been reported for a decade, but the underlying mechanism has never been vigorously investigated. This study shows the presence of PAS from a variety of phage-bacterium-antibiotic pairings. We show that increased phage production resulted directly from a lysis delay caused by the relative shortage of holin in filamented bacterial hosts in the presence of sublethal concentrations of stress-inducing substances, such as antibiotics and reactive oxygen species (ROS).
当噬菌体感染在亚致死剂量抗生素存在下培养的细菌时，噬菌体斑的大小会显著增加。这种现象被称为噬菌体-抗生素协同作用（PAS）。在这项研究中，使用不同类别的抗生素扩展了 PAS 的观察范围，涉及到广泛的细菌-噬菌体对。在革兰氏阳性和革兰氏阴性细菌中均观察到 PAS。β-内酰胺类抗生素使细胞应激时，细胞会广泛丝状化或肿胀，导致噬菌体产量增加。在其他类别的抗生素存在下，有时也会观察到 PAS，无论是否存在细菌丝状化。抗生素的添加诱导了各种细菌的表达，但即使在喹诺酮类抗生素存在下，缺失突变株也会出现丝状化和 PAS。在抗生素存在下，当细胞表面增大时，噬菌体的吸附效率没有改变，因为它们丝状化了。在这些细胞中观察到噬菌体 DNA 和编码噬菌体蛋白的 mRNA 产量增加，但蛋白产量仅有限增加。数据表明，PAS 是由于延迟裂解导致的颗粒组装延长的产物。细胞表面积的增加远远超过丝状化宿主细胞中噬菌体 holin 产量的增加，导致细胞内 holin 用于聚集并在宿主膜上形成孔的相对可用性有限。活性氧（ROS）应激也导致噬菌体产量增加，而热应激仅导致噬菌体产量有限增加。噬菌体-抗生素协同作用（PAS）已经报道了十年，但潜在的机制从未得到过大力研究。本研究从各种噬菌体-细菌-抗生素配对中显示了 PAS 的存在。我们表明，增加的噬菌体产量直接源于在亚致死浓度的应激诱导物质（如抗生素和活性氧（ROS））存在下，丝状化细菌宿主中 holin 的相对短缺导致的延迟裂解。
