Location: Floral and Nursery Plants ResearchTitle: Molecular and biological characterization of 'Rs551, a filamentous bacteriophage isolated from a race 3 biovar 2 strain of Ralstonia solanacearum Author
Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2017
Publication Date: 9/21/2017
Citation: Ebrahim, A., Stulberg, M.J., Mershon, J.P., Mollov, D.S., Huang, Q. 2017. Molecular and biological characterization of 'Rs551, a filamentous bacteriophage isolated from a race 3 biovar 2 strain of Ralstonia solanacearum. PLoS One. https://doi.org/10.1371/journal.pone.0815034. Interpretive Summary: A particular type of the bacterial pathogen Ralstonia solanacearum is a quarantine pathogen in the U.S., Canada, and Europe because of the serious threat it poses to agriculture, including brown rot in potato. Detecting and controlling this bacterium is critical for safeguarding crop production. Scientists in Beltsville, MD discovered a virus associated with the bacterium that affects its virulence. We determined the nucleotide and amino acid sequences of this virus and determined its mechanism for entering the bacterium. Our study is important for developing effective strategies to combat this plant pathogen.
Technical Abstract: A filamentous bacteriophage, designated 'Rs551, was isolated and purified from the quarantine and select agent phytopathogen Ralstonia solanacearum race 3 biovar 2 strain UW551 (phylotype IIB sequevar 1) grown under normal culture conditions. Electron microscopy suggested that 'Rs551 is a member of the family Inoviridae, and is about 1200 nm long and 7 nm wide. 'Rs551 has a genome of 7929 nucleotides containing 14 open reading frames, and is the first isolated virion that contains a resolvase (ORF13) and type-2 putative phage repressor (ORF14). Unlike other R. solanacearum phages isolated from soil, the genome sequence of 'Rs551 is not only 100% identical to its prophage sequence in the deposited genome of R. solanacearum strain UW551 from which the phage was isolated, but is also surprisingly found with 100% identity in the deposited genomes of ten other phylotype II sequevar 1 strains of R. solanacearum. Furthermore, it is homologous to genome RS-09-161, resulting in the identification of a new prophage, designated RSM10, in a R. solanacearum strain from India. When ORF13 and a core attP site of 'Rs551 were either deleted individually or in combination, phage integration was not observed, suggesting that similar to other filamentous R. solanacearum 'RSM phages, 'Rs551 relies on its resolvase and the core att sequence for site-directed integration into its susceptible R. solanacearum strain. The integration occurred 4 hours after phage infection. Infection of a susceptible R. solanacearum strain RUN302 by 'Rs551 resulted in less fluidal colonies and reduced motilities of the bacterium. Interestingly, infection of RUN302 by 'Rs551 also resulted in reduced virulence, rather than enhanced or loss of virulence caused by other 'RSM phages. Study of bacteriophages of R. solanacearum contributes to a better understanding of the phage-bacterium-environment interactions in order to develop integrated management strategies to combat R. solanacearum.