2012 Annual Report 1a.Objectives (from AD-416): Identify the molecular mechanisms that underlie the interaction of enteric pathogens with fresh-cut leafy vegetables. 1b.Approach (from AD-416): Transcriptomics in Salmonella and pathogenic E. coli; bacterial population dynamics on fresh-cut lettuce and spinach; and use of lettuce lines and Arabidopsis mutants that are defective in specific basal defense signaling pathways. Documents Reimbursable with National Center for Food Safety and Technology (AFRI).Log 42224. 3.Progress Report: ARS scientists at Albany, CA, have developed a method to perform gene expression profiling by RNAseq to investigate the physiology of E. coli O157:H7 in packaged processed lettuce. Also, parental and mutant lines of the model plant Arabidopsis thaliana were used to identify basal plant defense pathways that have a role in E. coli O157:H7 colonization of wounded leaf tissue, such as is resulting from the fresh-cut processing of lettuce. This research pertains to NP108 Problem Statement 1B, Systems Biology, and addresses the need to understand, utilizing “omics”, the effect of environmental conditions (in this case, MAP fresh-cut lettuce) on human pathogens, and determine how the pathogen may in turn influence conditions in that environment. Monitoring of activities was done through meetings at conferences on produce safety and microbiology, conference calls, and emails.