Figure 1: High proteolytic activity (PA) following C. jejuni infection is characterized by reduced microbiota diversity and taxa loss.

a, PA of PI-IBS and healthy volunteers. High PA in 19/52 PI-IBS patients (90^th percentile of healthy volunteers dotted line >1078 BAEE/mg of protein, n=38 healthy, 52 PI-IBS). b, PCoA plot of β-diversity. Microbiota composition in high PA is different from healthy (p=0.05) or low PA PI-IBS (p=0.01) (Bray-Curtis distance, PERMANOVA, with 999 permutations, n= 21 healthy, 12 high PA, 17 low PA PI-IBS). c, Alpha diversity measures between high PA PI-IBS, low PA PI-IBS and healthy volunteers (n=12 high PA PI-IBS, 17 low PA PI-IBS, 21 healthy, linear regressions, *p=0.05,**p=0.01,***p=0.001). d, Higher level taxonomic representation (n=12 high PA PI-IBS, 21 healthy). e, Correlation matrix between fecal PA and taxa. Correlations made taxa with q <0.2 with taxa in red highlighting differential abundance at q<0.1. Spearman correlation coefficient (r) identify taxa correlating with PA. Density reflective of proportions of taxa within healthy or high PA with dots denoting differential at q<0.1. f, Representative scatterplots between logPA and taxa of entire cohort. High PA and healthy volunteers plotted (n=21 healthy, 12 high PA PI-IBS). Grey area: 95% confidence level of linear regression. g, Differentially abundant taxa between healthy and high PA PI-IBS. Alistipes putredinis absent from high PA (n= 21 healthy, 12 high PA, q<0.1). Data are presented as mean + s.d. h, Boruta feature selection algorithm identifying predictive taxa of PA status. Six taxa identified (n=12 high PA, 17 low PA PI-IBS). i, Receiver operating curve of random forests prediction. AUC=0.813, (95% CI 0.69–0.94). Grey area: 95% confidence interval. Boxplots: lower, middle and upper hinges correspond to 25^th, 50^th and 75^th percentiles. Upper and lower whiskers extend to largest and smallest value no further than 1.5 * IQR from respective hinge.