FIG. 3.

Y. enterocolitica strain W22703 colonizes the worm intestine. The anterior part of a nematode feeding on OP50 is depicted in panels A and B. Background fluorescence emitted by C. elegans is visible in panel A. (C) Infection with DH5α/pGreenTIR served as a control; no fluorescent bacteria were observed. (D) Distension of the intestinal lumen was observed when worms were fed unlabeled W22703. Four days after infection, an accumulation of W22703/pNT-P_YE2848::gfp was detected in the anterior (E) and posterior (F) intestinal regions proximal to the pharynx and the anus of the nematode, the regions exhibiting maximal luminal distension. Approximately from day 4 after infection with Y. enterocolitica, the whole intestine (G) and finally the nematode body (H) are colonized by bacterial cells. Uptake of the W22703 ΔtcaA/pNT-P_YE2848::gfp strain results in a less distinct phenotype 7 days after infection (I). Bright-field and fluorescence photographs were not overlaid in panels B and G. Representative photographs are shown. Arrows indicate the intestinal lumen of C. elegans. Scale bar, 50 μm.