Keeping The Beaches Safe

By Sarah Sturmon Dale/ Minneapolis

When public-health authorities close a beach, Michael Sadowsky heads for the shore. It isn't that the microbiologist likes to dip his toes in dirty water. But for Sadowsky, 51, a few drops of contaminated H2O are worth their weight in gold.

Sadowsky, a professor at the University of Minnesota's department of soil, water and climate, is one of the world's foremost experts on tracking the sources of E. coli, the bacterium most commonly responsible for beach closures. E. coli is found in abundance in human fecal matter and represents a significant health threat, which is why the U.S. Environmental Protection Agency requires that E. coli levels in public waters be closely monitored. E. coli also grows in the guts of geese, cows and other animals, but the disease risk from nonhuman fecal bacteria is considerably lower.

Sadowsky and his fellow researchers have found a way to tease out stretches of marker DNA that indicate whether the bacteria came from human or nonhuman sources. With cities and states across the country spending billions on new water-quality systems, the impact of Sadowsky's work could be huge.

It has already started to pay off. Sadowsky is using a robotic system that can sample about 40,000 bacterial colonies at once. Using markers for geese that he pinpointed, he successfully identified geese as the source of contamination at a Lake Superior beach last year--allowing a beach to remain open that otherwise would have been closed. Identifying DNA markers for human fecal bacteria is next on his list.