TR: How will this affect development of probiotics as products? Most current studies--and probiotic-labeled foods--contain only one or a few strains of bacteria.

JG: We have to think of microbes as part of a community with properties that result from that community. The types of compounds a community will make might be affected by the host, so types of products might emerge that may only be apparent when you study the whole community.

TR: Several studies have examined probiotic treatment in pregnant women and newborns, and preliminary evidence suggests that this might have a long-term impact on reducing some allergies.

JG: There may be a critical period in development in determining an individual's microbial profile. We need to start thinking about what forces shape the community assembly. There may be a dynamic interplay between microbes and diet that could have a long-term impact on the host.

TR: Your lab has previously shown that obese and lean people have differences in their microbial populations that impact how efficiently foods are digested. What are you working on now?

JG: My lab is trying to place the human gut microbiome in the context of evolution. How was it shaped by evolution? Is it changing with our rapidly changing lifestyle? We're just completing a large global study of the mammalian gut, including species of nonhuman primates, carnivores, herbivores, and omnivores.