Nedialkova Lubov P, Sidstedt Maja, Koeppel Martin B, Spriewald Stefanie, Ring Diana, Gerlach Roman G, Bossi Lionello, Stecher Bärbel
Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336, Munich, Germany.
German Center for Infection Research (DZIF), partner site LMU Munich, Munich, Germany.
Environ Microbiol. 2016 May;18(5):1591-603. doi: 10.1111/1462-2920.13077. Epub 2015 Dec 23.
Bacteria employ bacteriocins for interference competition in microbial ecosystems. Colicin Ib (ColIb), a pore-forming bacteriocin, confers a significant fitness benefit to Salmonella enterica serovar Typhimurium (S. Tm) in competition against commensal Escherichia coli in the gut. ColIb is released from S. Tm into the environment, where it kills susceptible competitors. However, colicin-specific release proteins, as they are known for other colicins, have not been identified in case of ColIb. Thus, its release mechanism has remained unclear. In the current study, we have established a new link between ColIb release and lysis activity of temperate, lambdoid phages. By the use of phage-cured S. Tm mutant strains, we show that the presence of temperate phages and their lysis genes is necessary and sufficient for release of active ColIb into the culture supernatant. Furthermore, phage-mediated lysis significantly enhanced S. Tm fitness in competition against a ColIb-susceptible competitor. Finally, transduction with the lambdoid phage 933W rescued the defect of E. coli strain MG1655 with respect to ColIb release. In conclusion, ColIb is released from bacteria in the course of phage lysis. Our data reveal a new mechanism for colicin release and point out a novel function of temperate phages in enhancing colicin-dependent bacterial fitness.
细菌利用细菌素在微生物生态系统中进行干扰竞争。大肠菌素Ib（ColIb）是一种形成孔道的细菌素，在与肠道中共生的大肠杆菌竞争时，能为鼠伤寒沙门氏菌（S. Tm）带来显著的适应性优势。ColIb从S. Tm释放到环境中，在那里它会杀死易感的竞争者。然而，与其他大肠菌素不同，尚未鉴定出ColIb特异性的释放蛋白。因此，其释放机制仍不清楚。在本研究中，我们建立了ColIb释放与温和性λ样噬菌体的裂解活性之间的新联系。通过使用噬菌体清除的S. Tm突变菌株，我们表明温和性噬菌体及其裂解基因的存在对于将活性ColIb释放到培养上清液中是必要且充分的。此外，噬菌体介导的裂解在与ColIb敏感竞争者的竞争中显著增强了S. Tm的适应性。最后，用λ样噬菌体933W进行转导挽救了大肠杆菌MG1655菌株在ColIb释放方面的缺陷。总之，ColIb在噬菌体裂解过程中从细菌中释放出来。我们的数据揭示了一种大肠菌素释放的新机制，并指出了温和性噬菌体在增强大肠菌素依赖性细菌适应性方面的新功能。
