<i>TrpA1</i>-dependent defecation is required for bacteria expulsion from the gut.

<p><b>A</b> Defecation of indicated <i>Drosophila</i> lines fed with either Ecc15 <i>pyrE</i> or Ecc15 wild-type (WT) was presented as output/input denoting the fecal spot number normalized by ingestion volume (n = 5–17). <b>B</b> Quantitative representation of (A) as defecation fold difference of indicated genotypes. <i>Left</i>, The <i>wcs</i> flies fed with ECC15 WT at OD600 of 10 defecate ~1.5 fold more than those fed with ECC15 <i>pyrE</i>, while <i>TrpA1</i>^<i>ins</i> did not show higher defecation with ECC15 WT. <i>Right</i>, <i>rel</i>^<i>e20</i> lacking the <i>imd</i> pathway show higher defecation frequency with ECC15 WT over <i>pyrE</i>. <b>C</b> Defecation comparison between <i>pyrE</i> ingestions with and without supplementation of 1 mM uracil (n = 5–8). Defecation of ECC15 <i>pyrE-</i>ingested flies is increased by supplementing uracil, and the increase requires <i>TrpA1</i>. #: p<0.05, Student’s <i>t-</i>test between <i>wcs</i> and <i>rel</i>^<i>e20</i> fed with Ecc15 <i>pyrE</i> (<b>A</b>). *: p<0.05, **: p<0.01, Student’s <i>t-</i> or Tukey tests.