That's quite different than strawberries, tomatoes and spinach. They had similar surface bacteria, with most coming from one family, the Enterobacteriaiceae. That family includes E. coli, but many, many other harmless and perhaps beneficial bacteria, too. Enterobacteriaiceae was also the most common family, accounting for about one-third of all the microbes overall.
The good news: Most of the bacterial horde is benign.
Still, the sprouts "had a pretty high number of different types of bacteria associated with them, especially alfalfa sprouts," according to Jonathan Leff, an associate scientist at the Cooperative Institute for Research in the Environmental Sciences at the University of Colorado, who led the study.
Dangerous bacteria on sprouts have caused numerous outbreaks, including one in Germany that killed at least 31 people.
The organic-labeled produce had different microbial communities than the conventionally grown food, with the organic microbes generally more diverse, and the conventionally grown having more Enterobacteriaiceae.
Is that good? We don't know. And we also don't know why they're different. "We can't say that this is attributable to the farming practice itself," Leff told The Salt. "It could be transport and storage."
Also on the don't-know list is how the differences in fruit and vegetable microbiomes affect human health. "We can't say how we should act in terms of our daily purchases or how we eat," Leff says.
But understanding the microbiomes of fruits and vegetables, he says, may ultimately make it possible to figure out ways to delay spoilage in fresh produce, or to learn how the food bacteria interact with each other, and with the millions of bacteria in the human gut.
The researchers published their results in the online journal PLoS One.
Copyright 2013 NPR.