Last year, I wrote about an intriguing study which showed that our hordes of gut bacteria tend to cluster into one of three communities. Each individual has one of these three “enterotypes”. As I wrote at the time, “There seem to be just three preferred ways of building a community of gut bacteria.” Or are there? I’ve just spent three days at the International Human Microbiome Congress in Paris, where several hundred scientists gathered to discuss the nature of the several trillion bacteria we carry. One of the most intriguing debates, which ran across the first days of the conference, revolved around whether the enterotypes are actually discrete meaningful entities, or just points along a continuum of gut bacteria. This reflects an age-old debate in science between “lumpers and spliiters” but it matters if, as suggested, the enterotypes could one day be used to stratify patients according to their risk of disease or which treatments they should receive. I wrote about the debate for Nature News. Head over there for more details. Disclosure: MetaHIT, the conference organisers and the scientists behind the enterotype paper, paid for my travel and accommodation to the conference, so that I could chair the final panel on the future of the microbiome.