Comment

The intestinal epithelium is the first point of contact for prokaryotic organisms within the gut and plays a pivotal role in both the recognition of microbial species and coordination of the host response. Research on the molecular cross talk between pathogenic organisms and intestinal epithelial cells has occupied centre stage for many years, as gastroenterologists have actively dissected the major signalling cascades, genes, and protein products that underpin intestinal pathogenesis, with the aim of identifying potential therapeutic targets. In recent years however there has been recognition of the importance of the non-pathogenic (commensal) flora in gut health. These organisms are intimately involved in driving the development and maintenance of digestive and immunological functions of the gut,1 ,2 but under predisposing conditions can also trigger inflammatory bowel disease.3 The study of Hooperet al is one of the first to utilise state of the art molecular array technology and laser capture microdissection to investigate the impact of commensal bacteria on intestinal gene expression. Application of these technologies has provided a valuable insight into global gene responses and specific cellular events regulated by the normal intestinal microbiota.

The germ free mouse was used as a model to study the effect of monoassociation with Bacteroides thetaiotaomicron, a dominant anaerobic bacterium found in the gut of adult mice and humans. Following 10 days of colonisation, mRNA from ileal tissue was isolated from treated and untreated animals and microarray studies were undertaken. The technology reported in this study involves high density arrays of 25mer oligonucleotides (probes), designed to ∼25 000 murine gene sequences. One feature of this technology is that multiple probes (a probe set) are designed to each sequence, which provides a mechanism for robust data analysis and for accurate quantification of gene expression levels. The authors identified 118 probe …