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<ol><li>Develop an in vivo culture system for E. coli O157:H7. Since O157 is exposed to the
rumen before setting up residence in the lower digestive tract, the researchers focused on
studying bacterial growth in this region of the gastrointestinal tract. Bacteria were
inoculated into fistulated cattle and samples were removed at various times to assess the
growth and transcriptional activity of bacterial genes.</li>
<li>Perform transcriptional profiling by DNA microarrays to provide new insights into the
cellular responses of E. coli O157:H7 in its natural environment.</li>
<li>Perform mutational analyses through reverse genetics to allow the researchers to directly
determine to what extent a gene contributes to the survival and persistence of E. coli
O157:H7 in the ruminant.</li></ol>
<p>Findings: E. coli O157:H7 is a well-publicized food-borne pathogen whose source includes cattle. One of the difficulties in eliminating this microorganism from pre-harvest conditions include its prevalence in cattle herds and its apparent ability to persist in the digestive tract of ruminants. This characteristic is likely due to the interplay of specific genes that make this a unique microorganism. Identifying these genes can lead to new, more effective systems for detection and intervention of E. coli O157:H7 growth in its natural environment. To better understand the biology of E. coli O157:H7, we have taken advantage of its recently determined genetic blueprint of over 5,000 genes, along with new experimental methods that allows the activity of each gene to be monitored simultaneously (microarray technology). Many of the genes that show increased activity may also be important for survival of the bacteria in its natural environment that includes the digestive tract of ruminants. By understanding the specific details of how E. coli O157:H7 responds to the rumen environment we hope to identify potential weaknesses in the E. coli that can be exploited by new vaccines, or other treatments to significantly reduce this microorganism from cattle.</p>