a, b, Diltiazem conversion to desacetyldiltiazem by 28 human gut communities (each colour represents a human donor, lines depict the mean of n = 4 assay replicates). Diltiazem-metabolizing activity of the microbiota does not correlate with total bacterial culture densities or with microbiota abundance of B. thetaiotaomicron (quantified by species-specific 16S RNA quantitative PCR). P values were calculated for the null hypothesis that there is zero correlation, against the two-sided alternative that there is non-zero correlation (see Methods). c, Composition and diversity of the 28 bacterial communities based on metagenomic sequencing. d, Correlation analysis between diltiazem-metabolizing activity of the microbiota and community CFU or metagenomic abundance of BT_4096 homologues, and diltiazem-metabolizing bacterial species, genera and phyla identified in this study. e, f, Correlation analysis identical to that shown in d, but for the metabolism of norethindrone acetate and famciclovir by the 28 bacterial communities (each colour represents a human donor, lines depict the mean of n = 4 replicate assays). P values were calculated for the null hypothesis that there is zero correlation, against the two-sided alternative that there is non-zero correlation (see Methods). Data are available in Supplementary Tables 16–19.