Viral evasion of a bacterial suicide system by RNA-based molecular mimicry enables infectious altruism

• Published in: PLoS genetics Vol. 8; no. 10; p. e1003023
• Main Authors: Blower, Tim R, Evans, Terry J, Przybilski, Rita, Fineran, Peter C, Salmond, George P C
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.10.2012; Public Library of Science (PLoS)
• Subjects: Altruism; Bacteria; Bacterial genetics; Bacteriology; Bacteriophages - genetics; Bacteriophages - ultrastructure; Base Sequence; Biological Evolution; Biology; DNA, Viral - chemistry; DNA, Viral - genetics; Gene Expression; Gene loci; Gene Order; Genetic aspects; Genome, Viral; Genomes; Health aspects; Infections; Microbiology; Mimicry (Biology); Molecular Docking Simulation; Molecular Mimicry; Molecular Sequence Data; Mutation; Nucleic Acid Conformation; Pectobacterium - genetics; Pectobacterium - virology; Physiological aspects; Plasmids; Protein Conformation; Proteobacteria; Quantitative Trait Loci; RNA; RNA, Bacterial - genetics; Sequence Alignment; Suicides & suicide attempts; Toxins, Biological - chemistry; Toxins, Biological - genetics; Toxins, Biological - metabolism; Transduction, Genetic; New Zealand
• ISSN: 1553-7404; 1553-7390; 1553-7404
• DOI: 10.1371/journal.pgen.1003023

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.