An official website of the United States government.
The objectives of this project are: 1) to characterize at the molecular level, the response of S. enterica and E. coli O157:H7 to the physicochemical conditions resulting from mechanical lesions on fresh-cut lettuce and spinach leaves during postharvest minimal processing, packaging and storage; and 2) to identify components of the plant basal immune system that are involved in the response to mechanical wounding and to colonization by enteric pathogens.
Non-Technical Summary: Minimally processed leafy vegetables are the biggest culprits in produce-linked outbreaks of foodborne illness. Because handling and cutting create new niches for opportunistic colonization of leaves by human pathogens, identification of bacterial and plant attributes that enable or inhibit the bacterial attachment, growth, and interactions with fresh-cut or processed leaves is essential for the development of knowledge-based hurdle strategies that are effective and sustainable. In our recent studies, we have identified a number of bacterial genes and plant factors that are involved in the interactions of human enteric pathogens with injured leaf tissues. The goal of this project is to elucidate more specific molecular mechanisms that underlie the interactions of E. coli O157:H7 and S. enterica with minimally-processed leafy vegetables. Specifically, we will study the mechanisms used by E. coli O157:H7 and S. enterica to attach to and get established on leaves in the face of the various stresses present on minimally-processed leaves using microarray and gene functional analysis. We will also use biochemical, molecular, and genetic approaches to investigate the basal immune defense of leaves in response to bacterial colonization during processing. Results of this study will allow us to gain new knowledge regarding the physiology of enteric pathogens in the plant environment and to uncover plant traits that affect their colonization of fresh-cut leaves. <P> Approach: We will investigate enteric pathogen-plant interactions from two different angles. We will study the mechanisms used by E. coli O157 and S. enterica to attach to and get established on leaves in the face of the various stresses present on minimally-processed leaves using microarray and gene functional analysis. We will also use biochemical, molecular, and genetic approaches to investigate the plant defense in lettuce and spinach leaves in response to bacterial colonization during processing to uncover plant traits that inhibit multiplication of enteric pathogens in damaged tissue. Additionally, we will investigate various EHEC and Salmonella strains that differ in their response to stresses relevant to the processing environment and that of fresh-cut plant tissue. This aspect of strain differences in behavior on plants is critical for a better understanding of the epidemiology of produce-associated enteric illness, yet has been largely unexplored. This project will be led by an expert team of food microbiologists and plant scientists. The combined expertise of this multidisciplinary research team and close collaborations with major fresh produce industry stakeholders will ensure that this project delivers highly novel and useful information to improve produce safety.