Intact P. luminescens gets to the C. elegans intestinal lumen. Nomarski DIC (A, B, E, F) or fluorescence (C, D, G, H) images of C. elegans, fed on GFP-labeled E. coli (A-D) or GFP-labeled P. luminescens (E-H) for 24 hours. Intestinal lumen was filled with ground cells when cultured on E. coli (A-D). Intestinal lumen had intact cells when nematodes were cultured on P. luminescens (E-H). Arrows indicate the terminal bulb. Anterior is left. Scale bars, 50 μm.