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ARS Home » Northeast Area » Washington, D.C. » National Arboretum » Floral and Nursery Plants Research » Research » Publications at this Location » Publication #381730
Research Project: Detection, Identification, and Characterization of New and Emerging Viral and Bacterial Diseases of Ornamental Plants

Location: Floral and Nursery Plants Research

Title: Biological and molecular characterization of a Jumbo bacteriophage infecting plant pathogenic Ralstonia solanacearum species complex strains

Author
item AHMAD, ABDELMONIN - Minia University
item ADDY, HARDIAN - University Of Jember
item Huang, Qi

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2021
Publication Date: 9/27/2021
Citation: Ahmad, A.A., Addy, H.S., Huang, Q. 2021. Biological and molecular characterization of a Jumbo bacteriophage infecting plant pathogenic Ralstonia solanacearum species complex strains . Frontiers in Microbiology. 12:741600. https://doi.org/10.3389/fmicb.2021.741600.
DOI: https://doi.org/10.3389/fmicb.2021.741600

Interpretive Summary: Bacterial wilt caused by the bacterium Ralstonia solanacearum is one of the most devastating bacterial diseases in the world. It is a major limiting factor in the production of many economically important crops including tomato, potato and tobacco, and is very difficult to control. ARS scientists discovered a virus, or phage, in the soil of a tomato field in Florida that can kill this bacterium. They purified and characterized the phage, and determined its nucleotide and amino acid sequences. They found that infection of the bacterium by the phage significantly reduced the virulence of the infected bacterium in tomato plants. This research has led to a better understanding of the phage and is useful in developing effective control of this important bacterial disease.

Technical Abstract: A jumbo bacteriophage infecting Ralstonia solanacearum species complex strains, designated RsoM2USA, was isolated from soil of a tomato field in Florida, United States. Electron microscopy revealed that the phage belongs to the family Myoviridae with an icosahedral head of 142 nm in diameter, a long tail of 125 nm, a base plate of 55 nm, and tail fibers of 70 nm in length. The phage has a long latent period of 270 min and completed its infection cycle in 360 min with a burst size of approximately 32 particles per cell. With a genome size of 343,806 bp, phage RsoM2USA is the largest Ralstonia-infecting bacteriophage sequenced and reported to date. Out of the 486 ORFs predicated for RsoM2USA, 401 ORFs had undiscovered functions due to lack of matches in current databases or annotation as conserved hypothetical proteins. The remaining 85 ORFs were predicated to encode 44 tRNAs and to function in various categories including replication, translation, transcription, and structure with the main structural proteins experimentally confirmed by proteomic analysis of the purified virions. Phylogenetic analyses placed RsoM2USA in the same clade as Xanthomonas phage XacN1, prompting a proposal of a new genus for the two jumbo phages. Study of the transcriptional responses of R. solanacearum susceptible strain RUN302 ten min after infection by phage RsoM2USA revealed that 120 bacterial genes were differentially regulated. Phage RsoM2USA has a wide host range, infecting 14 of the 16 tested R. solanacearum species complex strains in our worldwide collection in each of the three newly established Ralstonia species: R. solanacearum, R. pseudosolanacearum and R. syzygii. Infection of R. solanacearum strain RUN302 by jumbo phage RsoM2USA significantly reduced the virulence of the infected bacterium in tomato plants, suggesting that this jumbo phage has a potential to be developed into an effective control against diseases caused by R. solanacearum species complex strains.