Objective:
1. Develop strains of Escherichia coli O157:H7 and non-pathogenic E. coli that contain the gfp gene inserted into the bacterial chromosome. 2. Determine the survival and growth of gfp-labeled wild type and rpoS-deficient E. coli O157:H7 populations in internalized tissues. 3. Determine differences in the expression of virulence factors in E. coli O157:H7 grown on leafy greens and ground beef.

Approach:
Strains of pathogenic E. coli O157:H7 and non-pathogenic will be transformed so that the green fluorescent protein is inserted on the bacterial chromosome. These strains will then be applied to soil where lettuce and spinach plants are growing, and these plants will be analyzed by microscopic and culture methods to determine the extent and duration that internalized cells can survive in plant tissues. Changes in virulence of E. coli O157:H7 will also be compared when grown in ground beef and lettuce to determine if these cells are primed to cause illness.