Principal components analysis of luminal- and tissue-associated microbiomes. Colon surgery affects the composition of the intestinal microbiota associated with intestinal tissue (B) but not the microbiota associated with luminal contents (A). n = 10 per group. PERMANOVA p values based on 10,000 random permutations of the dataset. Multiple comparisons were performed using the Bonferroni method. Error bars = ±2 standard error.