Fig. 4.

X. nematophila requires SR1 for localization to the AIC and PIV. Nematodes were grown on a GFP-expressing X. nematophila ΔSR1 mutant (green; no bacteria visible) or wild type and actin was visualized with rhodamine phalloidin (actin; red). A) Average (+/− S.E.M.) frequency of nematode colonization for adults, juveniles, pre-IJs, and IJs by X. nematophila wild type (Tn7-SR1) (white bars) or a ΔSR1 mutant (gray bars). Significantly fewer nematodes carried colonizing ΔSR1 mutant bacteria than wild type bacteria in each tested colonization state..Statistical significance was determined using a generalized linear mixed effects model (p < 0.05). B, C) Unlike wild type X. nematophila, the ΔSR1 mutant did not localize to the AIC of most adult (B) or juvenile (C) nematodes. D, E) F2 juvenile nematodes that were developmentally similar to pre-IJs did not display PIV colonization (pre-IJ PIV) either prior to (D) or during pre-IJ intestinal constriction (IC) (E). Abbreviations: basal bulb (bb); pharyngeal-intestinal valve (piv); intestinal lumen (int lumen); intestinal epithelium cells (int), adult AIC (aAIC), juvenile AIC (jAIC), intestinal constriction (const), statistics not determined (n.d.). Nematode actin was stained with rhodamine-phalloidin (red) and bacteria expressed green fluorescent protein (green). Size bars: 10 μm.