TEM of C. elegans fed live C. burnetii. After 6 d on a live C. burnetii diet, cross-sections of infected nematodes (a) at low magnification (1,500×) showed a distended intestinal lumen packed with bacteria. Apical membranes of two enterocytes delineate the intestinal lumen boundary, here outlined with a dashed line, showing intestinal distension. A structure resembling an Elb is boxed and magnified as inset. (b) At higher magnification (20,000×), numerous intact C. burnetii were observed in intimate contact with enterocytes, and the microvillar boarder appeared to be shortened and effaced. C. burnetii with distended nucleoids (arrows) were an indicator of C. burnetii vegetative cells, and were intact within the intestinal lumen. IL: intestinal lumen; Ps: pseudocoelom; BL: basal lamina; AM: apical membrane; Mv: microvilli.