The ongoing process of natural selection allows organisms with the appropriate genes to survive and multiply where others cannot. USDA microbiologist Russell has been stationed in Ithaca for more than 17 years and is affiliated with the U.S. Dairy Forage Research Center in Madison, Wisc. Todd Callaway is a Ph.D. candidate in microbiology. Menas Kizoulis, a Cornell senior in biological sciences, was recently awarded a Howard Hughes Undergraduate Fellowship to continue research in Russell's laboratory. The gastrointestinal tract of animals and man is an ideal habitat for the growth of bacteria, and cell densities can be as high as a trillion cells per gram of digesta.
Most gut bacteria are harmless types, and they can even provide essential nutrients to the host.
When animals consume contaminated food, the native bacteria compete with the invaders and provide at least some protection against food-borne illness. Victims may experience severe cramping and abdominal pain, watery or bloody diarrhea, vomiting or low-grade fever for an average of eight days. Fermentation acids increase when cattle are fed large amounts of grain. However it may be possible to process grains to decrease acid production and acid resistance. Schoolnik suggests deliberately infecting cows with the O157 strain, so that researchers can directly compare its incidence in animals fed hay and grain diets rather than focusing broadly on the bacteria as Russell's team did.