Whole tissues corresponding to the corpus, jejunum, descending colon and rectum were dissected from each mouse, washed with ice-cold PBS, placed into 2ml of RNA-later and flash-frozen in liquid nitrogen. The corpus was defined as the part of the stomach different from the antrum (distinguished by a difference in colour). The jejunum was defined as the tissue between the first 4 cm and the last 2 cm of the small intestinal tube. The descending colon and the rectum were defined as the last 3 cm of the digestive tube, where the first 2 cm was the descending colon and the last centimetre was the rectum. Keywords = gastrointestinal tract, microbiota, germ-free, microarray, gene ontology
