Traditionally, we consider the bacterial load within the intestine as a potential problem, with diarrheal disease a major global burden affecting millions. More recently, we have learned that the extraordinary range of microbes is progressively established in the intestine after birth, but the conditions controlling an individual's selective array of microbes and their seemingly remarkable resilience is unexplained. Now, with evidence emerging of the intestinal microbes' role in immune development, in altering the availability of dietary energy, in synthesizing essential amino acids, and even in altering insulin resistance, the diversity of the microbiome's effects becomes intriguing. There is also discussion about the microbes' potential role both in the propensity to weight gain and on behavior, so clearly there is a need to apply the latest analytical techniques and metabolic research to an area that is becoming of great therapeutic interest.

This was the subject of the 24th Marabou symposium in 2011 attended by 40 international experts. The meeting involved eight main speakers and four short presentations. These contributions are set out in the present supplement, both in the main articles and in special sections of the referenced Discussion. The Discussion captures about 7 hours of recorded, highly interactive discussions, which often dealt with unpublished work and new opportunities for collaboration. The Summary provides an overview of the whole meeting. The individual articles, Discussion, and Summary can also be accessed for further study at the Marabou Website: