Colicins are toxins produced and released by Enterobacteriaceae to kill competitors in the gut. While group A colicins employ a division of labor strategy to liberate the toxin into the environment via colicin-specific lysis, group B colicin systems lack cognate lysis genes. In Salmonella enterica serovar Typhimurium (S. Tm), the group B colicin Ib (ColIb) is released by temperate phage-mediated bacteriolysis. Phage-mediated ColIb release promotes S. Tm fitness against competing Escherichia coli. It remained unclear how prophage-mediated lysis is realized in a clonal population of ColIb producers and if prophages contribute to evolutionary stability of toxin release in S. Tm. Here, we show that prophage-mediated lysis occurs in an S. Tm subpopulation only, thereby introducing phenotypic heterogeneity to the system. We established a mathematical model to study the dynamic interplay of S. Tm, ColIb, and a temperate phage in the presence of a competing species. Using this model, we studied long-term evolution of phage lysis rates in a fluctuating infection scenario. This revealed that phage lysis evolves as bet-hedging strategy that maximizes phage spread, regardless of whether colicin is present or not. We conclude that the ColIb system, lacking its own lysis gene, is making use of the evolutionary stable phage strategy to be released. Prophage lysis genes are highly prevalent in nontyphoidal Salmonella genomes. This suggests that the release of ColIb by temperate phages is widespread. In conclusion, our findings shed new light on the evolution and ecology of group B colicin systems.

中文翻译：

---

通过细菌-疟原虫噬菌体相互作用的协同毒素生产的进化稳定。

大肠菌素是肠杆菌科产生并释放以杀死肠道竞争者的毒素。尽管A组大肠菌素采用分工策略通过大肠菌素特异性裂解将毒素释放到环境中，但B组大肠菌素系统缺乏同源裂解基因。在肠炎沙门氏菌血清型鼠伤寒沙门氏菌（S. Tm）中，B类大肠菌素Ib（ColIb）通过温和噬菌体介导的细菌分解作用释放。噬菌体介导的ColIb释放促进S.的Tm健身同台竞技大肠杆菌。尚不清楚在ColIb生产者的克隆种群中如何实现原噬菌体介导的裂解，以及原噬菌体是否有助于S中毒素释放的进化稳定性。Tm值。在这里，我们表明，原噬菌体介导的裂解发生在S.只的Tm亚群，从而引入表型异质到系统。我们建立了一个数学模型来研究S. Tm，ColIb和温和噬菌体在竞争物种存在下的动态相互作用。使用此模型，我们研究了在波动的感染情况下噬菌体裂解率的长期演变。这表明，无论是否存在大肠菌素，噬菌体裂解均以对冲策略发展，使噬菌体扩散最大化。我们得出的结论是，缺乏自身裂解基因的ColIb系统正在利用进化稳定的噬菌体策略进行释放。噬菌体裂解基因在非伤寒沙门氏菌中高度流行基因组。这表明温带噬菌体释放ColIb的现象很普遍。总之，我们的发现为B组大肠菌素系统的进化和生态学提供了新的思路。