Prophage-encoded phage defense proteins with cognate self-immunity

• DOI: 10.1101/2020.07.13.199331
• Publication Date: 2020-07-14T13:59:58Z
• Authors: Siân V. Owen; Nicolas Wenner; Charles L. Dulberger; Ella V. Rodwell; Arthur Bowers-Bar...; Natalia Quinones-...; Daniel J. Rigden; Eric J. Rubin; Ethan C. Garner; Michael Baym; Jay C. D. Hinton
• Keywords: 0301 basic medicine; 03 medical and health sciences

SummaryTemperate phages are pervasive in bacterial genomes, existing as vertically-inherited islands called prophages. Prophages are vulnerable to the predation of their host bacterium by exogenous phages. Here we identify BstA, a novel family of prophage-encoded phage defense proteins found in diverse Gram-negative bacteria. BstA drives potent suppression of phage epidemics through abortive infection. During lytic replication, thebstA-encoding prophage is not itself inhibited by BstA due to a self-immunity mechanism conferred by the anti-BstA (aba) element, a short stretch of DNA within thebstAlocus. Inhibition of phage replication by distinct BstA proteins fromSalmonella, KlebsiellaandEscherichiaprophages is functionally interchangeable, but each possesses a cognateabaelement. The specificity of theabaelement ensures that immunity is exclusive to the replicating prophage, and cannot be exploited by heterologous BstA-encoding phages. BstA allows prophages to defend host cells against exogenous phage attack, without sacrificing their own lytic autonomy.