Ingestion of opportunistic bacteria rapidly induces visceral muscle spasms.

(A) Pictures of a midgut dissected from a fly having ingested a blue food dye. The lower image shows the method to measure the length of the midgut between the proventriculus and the hindgut. (B) Measurement of midgut length upon intoxication by 104, 106 and 108 CFU of Btk. The length is expressed in function of the control (Ctrl, 100%). Flies were fed for 30 min and the measurements were taken 30 min, 1 h, 2 h and 4 h after the initiation of feeding. (C) Midgut length upon intoxication by 108 CFU of the commensal bacterium L. plantarum. (D) Immunolabelling of posterior midgut 2 h post ingestion of 5% sucrose (Ctrl) or Btk (108 CFU/fly were provided). DAPI labels the nuclei (Blue), Arm marks the basolateral compartment (Red) and Dlg::GFP marks the apical compartment. (E) Caspase3 staining (Red, Casp3) of posterior midgut 2 h after feeding with 5% sucrose (Ctrl) or Btk (108 CFU/fly were provided). Green marks the enterocytes (EC) and blue the nuclei (DAPI). Note the very few presence of apoptotic enterocytes (red arrow) in both conditions. (F) Visceral muscle fibers were labelled by Phalloidin 2 h after feeding with 5% sucrose (Ctrl) or Btk (108 CFU/fly were provided). Note that only the longitudinal fibers are contracted in presence of Btk. Because the images are more apparent in the posterior midgut, this region was chosen to illustrate the visceral contractions in this figure and in all the following images. The vertical bars on the pictures indicate the proportion of intestines with (red) or without (yellow) contractions. (G) Measure of the width of the longitudinal visceral muscle fibers. Data are represented as a function of the control (Ctrl, 100%). Objective is 40X in D and 20X in E and F.