Host recognition and integration of filamentous phage φRSM in the phytopathogen, Ralstonia solanacearum

Two prophages, called phi RSM3 and phi RSM4, that are closely related to, but differ from, filamentous phage phi RSM1, have been detected in strains of the Ralstonia solanacearum species complex. The prophage phi RSM3, found in host strain MAFF730139, could be converted to infectious phage by means of PCR and transfection. The nucleotide sequence of phi RSM3 is highly conserved relative to phi RSM7 except for open reading frame 2 (ORF2), encoding an unknown protein, and ORF9 encoding the presumed adsorption protein that determines host range. The two host ranges differ dramatically and correlate closely with different gel electrophoresis banding patterns for cell surface fimbriae. Infections by phi RSM1 and phi RSM3 enhance bacterial cell aggregation and reduce the bacterial host virulence in tomato plants. Database searches in the R. solanacearum strains of known genomic sequence revealed two inovirus prophages, one designated phi RSM4 that is homologous to phi RSM1 and phi RSM3, and one homologues to RSS1, in the genome of strain UW551. (C) 2008 Elsevier Inc. All rights reserved.