To sample the microbial communities in the gut, fecal samples are generally collected from an individual and DNA is sequenced to identify bacteria that are present. This is an overall effective method, however, it does not provide information of the specific spatial location of bacteria within the gut. In a study published in the journal Gut, researchers in Ireland looked to determine differences in the bacterial composition of specific regions of the large intestine between patients with ulcerative colitis and control patients.
Four volunteers undergoing routine colonoscopies were recruited to serve as the controls for this study. Five patients with ulcerative colitis (UC), who were undergoing colectomies, or surgical removal of the colon, were also involved in the study. Samples were taken at four locations in the colon in all individuals: the caecum, traverse colon, descending colon, and rectum. The four locations were sampled three times at three different levels: luminal brush, whole mucosal biopsy, and laser captured sample of mucus gel layer. A total of twelve samples were taken per individual.
After analysis of the many samples it was discovered that there was more variability between the bacterial compositions between subjects than there was within the different locations of an individual’s colon. The findings showed a difference between the luminal and mucus gel microbiota in both the controls and the ulcerative colitis subjects. Three bacterial families were common between this difference shared by controls and UC subjects, namely Bifidobacteriaceae, Peptostreptococcaceae, and Enterobacteriaceae being more abundant in UC patients.
This study has its limitations because of the small sample size, however the researchers state that the small sample allowed for extensive analysis of the individual samples. So what do the findings of this study mean for patients with ulcerative colitis? Better understanding of differences in the spatial relations of bacteria could lead to the modulation of microbial communities to help treat ulcerative colitis.