To help shed light on the role of these bacteria, a team of researchers led by MIT associate professor Eric Alm recently tracked fluctuations in the bacterial populations of two research subjects over a full year. The findings, described in the July 25 issue of the journal Genome Biology, suggest that while these populations are fairly stable, they undergo daily fluctuations in response to changes in diet and other factors.

For one year, the two subjects in the study collected daily stool samples so bacterial populations could be measured. They also used an iPhone app to track lifestyle factors such as diet, sleep, mood, and exercise, generating a huge amount of data.

Analysis of this data revealed that dietary changes could produce daily variations in the populations of different strains of bacteria. For example, an increase in fiber correlated with a boost in the populations of Bifidobacteria, Roseburia, and Eubacterium rectale. Four strains - including Faecalibacterium prausnitzii, which has been implicated in protecting against inflammatory bowel disease - were correlated with eating citrus.

The ultimate goal, Alm says, is to generate data from individual patients that could be analyzed to produce a personalized monitoring system for people suffering from inflammatory bowel disease or other diseases prone to occasional flare-ups. Such a system could detect when someone is heading for a flare-up and recommend dietary changes that could help avoid it.

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