Genomic diversity of large-plaque-forming podoviruses infecting the phytopathogen Ralstonia solanacearum

Abstract

The genome organization, gene structure, and host range of five podoviruses that infect Ralstonia solanacearum, the causative agent of bacterial wilt disease were characterized. The phages fell into two distinctive groups based on the genome position of the RNA polymerase gene (i.e., T7-type and φKMV-type). One-step growth experiments revealed that φRSB2 (a T7-like phage) lysed host cells more efficiently with a shorter infection cycle (ca. 60 min corresponding to half the doubling time of the host) than φKMV-like phages such as φRSB1 (with an infection cycle of ca. 180 min). Co-infection experiments with φRSB1 and φRSB2 showed that φRSB2 always predominated in the phage progeny independent of host strains. Most phages had wide host-ranges and the phage particles usually did not attach to the resistant strains; when occasionally some did, the phage genome was injected into the resistant strain's cytoplasm, as revealed by fluorescence microscopy with SYBR Gold-labeled phage particles.