Figure 3. Temporal aspects of the infection process.

(A) Infections are established upon a short exposure to pathogen. Upper: schematic of experiment. Worms are added to the well on the left containing B. thuringiensis and Cry5B. Following either 5 min, 15 min, 30 min, 1 h, 2 h, 4 h, or 8 h, the worms were then moved through a series of five wells lacking Cry5B protein and containing non-infectious B. megaterium instead of B. thuringiensis. Infection outcomes in the final well were scored 48 h later. Lower: results of the experiment depicted in upper schematic. Data shown represent a total of three independent experiments with ∼30 animals per time point per experiment. Error bars indicate SEM. Only the infection rate for a 5-minute pulse is significantly different from the other data points (ANOVA, p<0.05, Tukey's post test). (B) Cry5B acts early in the infection process as temporal addition of Cry5B protein after, and separate from, pathogen exposure results in a significant drop in infections. Upper: schematic of experiment in which worms are exposed to pathogen first and then to Cry5B. Lower: results in which two sets of experiments were set up simultaneously—a normal 15 minute pulse chase with both Cry5B PFP and pathogen added together (light gray bars; see (A) for set up) and pulse chase in which Cry5B was not added until the end (dark gray bars). Error bars represent SEM. ∼30 worms/condition/trial; 3–4 independent trials per condition. (C) The infection process appears to begin with colonization of the anterior intestine. The anterior intestine of a nematode 3 hr after exposure to B. thuringiensis (407-gfp) under pathogenic conditions. The left panel is a DIC image; the right panel deconvolved fluorescent (FITC) of the same animal. Images taken at 600×. Anterior is down.