Project Number: 1907-21000-033-10
Project Type: Reimbursable

Start Date: Feb 01, 2011
End Date: Jan 31, 2014

Objective:
As the number and severity of produce-associated gastroenteritis outbreaks increase, we are coming to recognize that we know little about the ecology of Salmonella and enterovirulent E. coli outside of their animal hosts. It is clear that these human pathogens can contaminate fruits, vegetables, nuts and sprouts, at pre- and/or post-harvest production stages. How these bacteria infect, colonize, and persist within plants and evade reasonably rigorous surface sanitation is much less certain. Some of the ongoing debate focuses on the question of whether plants are true alternate hosts for non-typhoidal S. enterica or E. coli O157:H7, or whether plants are simply matrices where these organisms transiently persist in a resting state. If enteric pathogens enter into a relationship with a plant host as a part of their normal life cycle, then it is important to define differences in genetic and regulatory programs that the enterics require for the two alternating lifestyles (animal pathogen vs plant commensal) and how they might impact important developmental processes of the plant such as fruit ripening. Our goal is to determine what genes and regulatory programs are needed by Salmonella to inhabit tomato plants, and to examine the effects of plant host genotype, developmental stage and fertilization regime on external and internal colonization by Salmonella in addition to its effects on ripening and quality parameters that may provide diagnostic markers. The information obtained may very well have future valuable practical applications in modifying production practices to reduce outbreaks of produce-associated gastroenteritis.

Approach:
Some tomato cultivars are readily colonized by Salmonella while others are not or are greatly reduced in bacterial titer. To establish the basis of the “resistance” of tomato cultivars to Salmonella, we will need to delineate signal transduction mechanisms and responses of the plant host to colonization by this human enteric pathogen. We propose transcriptome characterization of tomato responses to Salmonella to achieve this goal. Specifically, we will perform transcriptome profiling of tomato fruits colonized with S.e. sv Typhimurium 14028 (vs. control fruit) to identify differentially regulated genes that reflect processes and pathways contributing to, or influenced by, colonization and reflect impacts on fruit ripening or quality.