• Bifidobacteria
• IBD
• lactobacillus
• probiotics

The influence of the commensal microbiota on intestinal and extra-intestinal development has been evident since the first studies of germ-free animals over a half-century ago. Microbial signals from the lumen of the gut are trophic for the digestive, immune and other systems, including the developing brain.1 2 In later life, reciprocal host–microbe interactions remain critical for mucosal homeostasis. Probiotic therapy is, in essence, an attempt to harness the beneficial effects of the commensal microbiota for the host.3 In most instances, the molecular underpinning of these exchanges remains to be defined but represents an intriguing strategy for identifying therapeutic targets and drug discovery.4 While the therapeutic potential of immunomodulatory molecules from pathogens is well recognised, the pursuit of bioactive molecules from the commensal gut microbiota is a more recent venture; examples include the discovery of bacteriocins with activity against Clostridium difficile and bacterial-derived immunomodulatory molecules.4 However, much more remains to be mined from the commensal microbiota.

The study by Fernandez and colleagues published in this issue of Gut (see page 1050 …