Researchers from the University of Colorado, Boulder, examined the microbes found on fresh fruits and vegetables at area grocery stores using 16S ribosomal gene sequencing. As they report in PLOS One, the different types of produce — they sampled apples, grapes, spinach, alfalfa, and more — harbored different microbes. "Mung bean sprouts, for one, harbor very different bacteria than alfalfa sprouts," Nancy Shute at NPR's The Salt notes. "Grapes, apples and peaches house a greater variety of bacteria than veggies." Other produce, though, like strawberries, tomatoes and spinach, she says, appear to contain more similar surface bacteria.
Further, the Boulder scientists found that there were differences between conventional and organic samples of the same types of produce, as the organic varieties typically had more diverse microbes. "We can't say that this is attributable to the farming practice itself," lead author Jonathan Leff tells The Salt. "It could be transport and storage." He adds that how the diversity of microbes on fruits and veggies influences human health is also unknown.