The gastrointestinal tract harbors a complex community of bacteria, of which many may be beneficial.
Studies of germ-free animal models have shown that the gastrointestinal microbiota not only assists
in making nutrients available for the host but also contributes to intestinal health and development.
We studied small intestinal protein expression patterns in gnotobiotic pigs maintained germ-free, or
monoassociated with either Lactobacillus fermentum or non-pathogenic Escherichia coli. A common
reference design in combination with labeling with stable isobaric tags allowed the individual
comparison of 12 animals. Our results showed that bacterial colonization differentially affected
mechanisms such as proteolysis, epithelial proliferation, and lipid metabolism, which is in good
agreement with previous studies of other germ-free animal models. We have also found that E. coli
has a profound effect on actin remodeling and intestinal proliferation, which may be related to stimulated
migration and turnover of enterocytes. Regulations related to L. fermentum colonization involved
individual markers for immunoregulatory mechanisms.
Keywords: iTRAQ • gnotobiotic • germ-free • quantitative proteomics • LC−MS/MS • Escherichia coli • Lactobacillus
fermentum • gut • small intestine • pi
