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POSTERS: Bacteriology I

P-029 - Unraveling the Competitive Dynamics Between Xanthomonas euvesicatoria and Xanthomonas perforans in Bacterial Leaf Spot of Pepper and Tomato

Monday, August 4, 2025
3:45 PM - 4:30 PM HST
Location: Exhibit Hall 3
Abstract Text:

Bacterial leaf spot of pepper and tomato is a damaging disease in the southeastern United States. In Florida, the causal agents of the disease are Xanthomonas euvesicatoria and more recently, Xanthomonas perforans, a closely related competitor. X. perforans became the predominant BLS species on tomato by the early 2000s and is now emerging as a pepper pathogen. The competitive relationship between X. euvesicatoria and X. perforans appears to be mediated in part by a density-dependent, volatile-induced bacteriocin. While the bacteriocin is yet uncharacterized, evidence suggests that it may be related to a zinc metalloprotease produced by X. perforans. Interestingly, this metalloprotease is also present and expressed in X. euvesicatoria, but X. euvesicatoria is unable to activate inhibitory activity. However, upon the insertion of a subclone fragment containing the metalloprotease from X. perforans, the altered X. euvesicatoria strain 91-106 was able to inhibit X. euvesicatoria strain ME90. The bacteriocin activity appears to be an interaction between the bacteriocin(s) itself and increasing pH as a result of natural ammonia production. While the effect of pH on the metalloprotease’s inhibitory activity is still not fully understood, it seems that an elevated pH combined with the metalloprotease alters the ability of the strain to inhibit neighboring and closely related Xanthomonas strains. This bacteriocin mechanism may play a role in the changing population dynamics of X. perforans and X. euvesicatoria in bacterial leaf spot infections.