Arbitrium-coding phages use peptides to communicate and coordinate the decision between lysis and lysogeny. However, the mechanism by which these phages establish lysogeny remains unknown. Here, focusing on the SPbeta phage family’s model phages phi3T and SPβ, we report that a six-gene operon called the “SPbeta phages repressor operon” (sro) expresses not one but two master repressors, SroE and SroF, the latter of which folds like a classical phage integrase. To promote lysogeny, these repressors bind to multiple sites in the phage genome. SroD serves as an auxiliary repressor that, with SroEF, forms the repression module necessary for lysogeny establishment and maintenance. Additionally, the proteins SroABC within the operon are proposed to constitute the transducer module, connecting the arbitrium communication system to the activity of the repression module. Overall, this research sheds light on the intricate and specialized repression system employed by arbitrium SPβ-like phages in making lysis-lysogeny decisions.

任意编码噬菌体使用肽来沟通和协调裂解和溶原之间的决定。然而，这些噬菌体建立溶原的机制仍然未知。在这里，我们重点关注 SPbeta 噬菌体家族的模型噬菌体 phi3T 和 SPβ，报道了一种称为“SPbeta 噬菌体阻遏操纵子”（sro）的六基因操纵子，它表达的不是一个而是两个主阻遏物，SroE 和 SroF，后者折叠就像经典的噬菌体整合酶一样。为了促进溶源，这些阻遏物与噬菌体基因组中的多个位点结合。 SroD 作为辅助阻遏蛋白，与 SroEF 一起形成溶源建立和维持所需的阻遏模块。此外，操纵子内的蛋白质 SroABC 被提议构成传感器模块，将仲裁通信系统与抑制模块的活动连接起来。总体而言，这项研究揭示了任意 SPβ 样噬菌体在做出裂解-溶原决策时所采用的复杂且专门的抑制系统。