Viral Evasion of a Bacterial Suicide System by RNA-Based Molecular Mimicry Enables Infectious Altruism

Abortive infection,during which an infected bacterial cell commits altruistic suicide to destroy the replicating bacteriophage and protect the clonal population,can be mediated by toxin-antitoxin systems such as the type iii protein-rna toxin-antitoxin system,toxin. a flagellum-dependent bacteriophage of the myoviridae,φte,evolved rare mutants that escaped toxin-mediated abortive infection within pectobacterium atrosepticum. wild-type φte encoded a short sequence similar to the repetitive nucleotide sequence of the rna antitoxin,toxi,from toxin. the φte escape mutants had expanded the number of these pseudo-toxi genetic repeats and,in one case,an escape phage had hijacked toxi from the plasmid-borne toxin locus,through recombination. expression of the pseudo-toxi repeats during φte infection allowed the phage to replicate,unaffected by toxin,through rna-based molecular mimicry. this is the first example of a non-coding rna encoded by a phage that evolves by selective expansion and recombination to enable viral suppression of a defensive bacterial suicide system. furthermore,the φte escape phages had evolved enhanced capacity to transduce replicons expressing toxin,demonstrating virus-mediated horizontal transfer of genetic altruism. © 2012 blower et al.