Thirty years ago, I was a graduate student inoculating different lines of tomatoes with Verticillium wilt.

I hated it.

So I became editor of the student newspaper.

But those plant pathogens and tomatoes are still embedded in my DNA, so when I see an abstract like this, I gotta send it out.

Plant pathogen infection is a critical factor for the persistence of Salmonella enterica on plants. We investigated the mechanisms responsible for the persistence of S. enterica on diseased tomato plants by using four diverse bacterial spot Xanthomonas species that differ in disease severities. Xanthomonas euvesicatoria and X. gardneri infection fostered S. enterica growth, while X. perforans infection did not induce growth but supported the persistence of S. enterica. X. vesicatoria-infected leaves harbored S. enterica populations similar to those on healthy leaves. Growth of S. enterica was associated with extensive water-soaking and necrosis in X. euvesicatoria- and X. gardneri-infected plants. The contribution of water-soaking to the growth of S. enterica was corroborated by an increased growth of populations on water-saturated leaves in the absence of a plant pathogen. S. enterica aggregates were observed with bacterial spot lesions caused by either X. euvesicatoria or X. vesicatoria; however, more S. entericaaggregates formed on X. euvesicatoria-infected leaves as a result of larger lesion sizes per leaf area and extensive water-soaking. Sparsely distributed lesions caused by X. vesicatoria infection do not support the overall growth of S. entericaor aggregates in areas without lesions or water-soaking; S. enterica was observed as single cells and not aggregates.

Thus, pathogen-induced water-soaking and necrosis allow S. enterica to replicate and proliferate on tomato leaves. The finding that the pathogen-induced virulence phenotype affects the fate of S. entericapopulations in diseased plants suggests that targeting of plant pathogen disease is important in controlling S. enterica populations on plants.

 Plant Pathogen-Induced Water-Soaking Promotes Salmonella enterica Growth on Tomato Leaves

Applied and Environmental Microbiology, Volume 81, Number 23, December 2015

N Potnis, J Colee, J Jones, J Barak