FIG. 6.

Differentiation of dot mutant SPFs into MIFs as observed by electron microscopy in T. tropicalis food vacuoles (A and B) or expelled pellets (C to E). (A and C) dotA mutant; (B, D, and E) dotB mutant. (A and B) Early development of MIFs was evident in mid-stage food vacuoles for both mutants. While several bacteria appeared degraded (e.g., black arrowhead in panel B), small groups of bacteria could be seen with irregular shapes, dark cytoplasm, and thick envelopes (white arrowheads in panel B), straight outer membranes with no evidence of periplasm, and inclusions (I). (C to E) In pellets, structurally complete bacteria also exhibited features typical of MIFs, e.g., thick, dark, and nonwavy outer membrane (arrow in panel C), multiple internal membranes (arrows in panel D), a laminated envelope with no obvious periplasm (arrows in panel E), dense cytoplasm, and prominent inclusions (I). Bars in panels C to E, 100 nm.