Molecular ecological analysis of the succession and diversity of sulfate-reducing bacteria in the mouse gastrointestinal tract

Intestinal sulfate-reducing bacteria (SRB) growth and resultant hydrogen su lfide production may damage the gastrointestinal epithelium and thereby con tribute to chronic intestinal disorders. However, the ecology and phylogene tic diversity of intestinal dissimilatory SRB populations are poorly unders tood, and endogenous or exogenous sources of available sulfate are not well defined. The succession of intestinal SRB was therefore compared in inbred C57BL/6J mice using a PCR-based metabolic molecular ecology (MME) approach that targets a conserved region of subunit A of the adenosine-5'-phosphosu lfate (BPS) reductase gene. The APS reductase-based MME strategy revealed i ntestinal SRB in the stomach and small intestine of 1-, 4-, and 7-day-old m ice and throughout the gastrointestinal tract of 14-, 21-, 30-, 60-, and 90 -day-old mice. Phylogenetic analysis of APS reductase amplicons obtained fr om the stomach, middle small intestine, and cecum of neonatal mice revealed that Desulfotomaculum spp. may be a predominant SRB group in the neonatal mouse intestine. Dot blot hybridizations with SRB-specific 16S ribosomal DN A (rDNA) probes demonstrated SRB colonization of the cecum and colon pre- a nd postweaning and colonization of the stomach and small intestine of matur e mice only. The 16S rDNA hybridization data further demonstrated that SRB populations were most numerous in intestinal regions harboring sulfomucin-c ontaining goblet cells, regardless of age. Reverse transcriptase PCR analys is demonstrated APS reductase mRNA expression in all intestinal segments of 30-day-old mice, including the stomach. These results demonstrate for the first time widespread colonization of the mouse intestine by dissimilatory SRB and evidence of spatial-specific SRB populations and sulfomucin pattern s along the gastrointestinal tract.