Proportions of core bacterial taxa in fecal and colonic mucosal samples from healthy individuals. Compared to mucosal samples, fecal samples had a significantly higher abundance of Firmicutes (41.4% vs. 29.1%, FDR < 0.0001, respectively) and of Actinobacteria (22% vs. 12.6%, FDR < 0.0001, respectively) compared to mucosal samples, and a significantly lower abundance of Bacteroidetes (20.2% vs. 26.3%, FDR < 0.05, respectively), and Proteobacteria (9.3% vs. 19.3%, FDR < 0.0001, respectively).