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Bacteriocin-Like Substances from Tomato Race 3 Strains of Xanthomonas campestris pv. vesicatoria

November 2003 , Volume 93 , Number  11
Pages  1,415 - 1,421

S. M. Tudor-Nelson , G. V. Minsavage , R. E. Stall , and J. B. Jones

Department of Plant Pathology, University of Florida, Gainesville 32611

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Accepted for publication 1 July 2003.

Tomato race 3 (T3) strains of Xanthomonas campestris pv. vesicatoria are antagonistic in vitro to tomato race 1 (T1) strains of the bacterium. All T1 strains and 11 strains of other X. campestris pathovars tested were inhibited by T3 strains. Sensitivity of tomato race 2 (T2) strains was variable. No strains from other bacterial genera tested were inhibited. Cell-free filtrates from T3 strains were inhibitory to sensitive strains. The inhibitory activity of these filtrates was lost after treatment at temperatures above 80°C and with selected protease enzymes. However, treatment with trypsin or DNase had no effect on their activity. Seven cosmid clones from a genomic library of a T3 strain were selected for their ability to consistently inhibit a sensitive indicator strain in plate assays. Southern hybridization analysis placed these into three bacteriocin (BCN)-producing groups designated BCN-A, BCN-B, and BCN-C. The BCN-like groups could be differentiated by variations in inhibitory spectra and levels of activity in plate assays. Mutations that inactivated expression of each BCN group individually in a wild-type T3 strain had inhibitory activity confirming that multiple BCNs are present in the T3 strain. T3 strains were inhibitory to a sensitive indicator strain in tomato leaf tissue, but this effect was observed only when T3 strains were applied in advance of the sensitive strain. BCN-A was the major BCN-like substance involved in the suppression of the sensitive indicator strain in tomato leaf tissues.

© 2003 The American Phytopathological Society