Analysis of Microbial Genes Involved in Gut Survival and Host Interaction in Gut Commensal Bacteria.

The intestinal microflora has a key role in human health, and yet few of the predominant groups of anaerobic bacteria colonising the large intestine have been studied in detail. This is particularly true of the most abundant group, the obligately anaerobic low DNA G+C content Gram-positives that comprise more than 50% of the total microbial diversity. <P> In this project we concentrated on one of the key groups of anaerobes isolated at RRI, which form up to 10% of the total anaerobic microflora, namely the Roseburia genus. Members of this genus produce butyrate, an important substrate for growth and differentiation of colonic epithelial cells.
<P>
Growth studies showed that Roseburia spp. were able to utilise a variety of substrates that are available for bacterial growth in the colon, including starch and inulin. A microarray approach was used to identify specific genes that are required to degrade these substrates. These include a gene encoding an extremely large amylase containing several different domains, with different specific functions in starch degradation.<P> A range of enzymes required to degrade inulin, and other growth substrates, were also identified. The same enzyme involved in inulin utilisation was identified from microarray analysis and total protein expression profiles. The advantage of the microarray approach was the ability to identify membrane bound transport genes and regulatory genes, not possible using traditional screening methods. This showed that a number of genes involved in substrate utilisation are arranged in clusters, encoding catalytic and transport proteins, under the control of a single regulatory gene.