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Poster: Molecular & Cellular Plant-Microbe Interactions: MPMI


Characterization of the T6SS secretion system of Ralstonia solanacearum and its role in virulence at low temperatures
A. BOCSANCZY (1), J. Yuen (1), A. Mangravita-Novo (1), D. Norman (1) (1) University of Florida MREC, U.S.A.

Ralstonia solanacearum is the causal agent of Bacterial Wilt, the worldwide devastating disease of hundreds of plant species. R. solanacearum is a ‘complex’ species due to its genetic diversity and wide host range; however all strains possess conserved secretion systems. The type VI secretion system (T6SS) has been associated with virulence, symbiosis and bacterial competition, however its function is not known in R. solanacearum. Previously, we discovered a functional T6SS in several strains of R. solanacearum, through a proteomic comparison. We created a T6SS related (Vip-B like) gene defective mutant in strain P673. In this work we confirmed that this mutant renders the T6SS non-functional. We show that the T6SS contributes to P673 virulence at low temperatures, only when soil inoculated. We hypothesized that the T6SS contributes indirectly to virulence, either by competition with other bacterial species, or with populations of the same species. To test this hypothesis we performed bacterial competition assays with other bacterial species commonly found in soil, however we did not find a difference. Currently, we are developing intra-species competition assays at 30°C and 18°C in order to determine the T6SS function and its dependency on temperature. We also present a comparative genomics of the T6SS system for all the strains sequenced to date. Characterization of the T6SS system in R. solanacearum will help elucidate its role in virulence at low temperatures.