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One segment of the assembly line used for phagosome membrane growth
in P. caudatum (similar to Fig. 29). Cytopharyngeal ribbons
bring discoidal vesicles to the left lip of the cytopharynx where the
vesicles bind and then fuse with the cytopharyngeal membrane. This
expands the membrane to form the phagosome. The role of the
contractile cytostomal cord (cc) in this process has yet to be
determined. Also brought to this area are acidosomes and carrier
vesicles. Carrier vesicles contain cargo coming into the cell via
parasomal sacs that is sorted from the membrane components that are to
be recycled back to the plasma membrane. Sorting occurs in the early
endosomes. Coated pits on the early endosomes pinch off to form the
carrier vesicles. The carrier vesicles come to lie against the
acidosomes where they fuse. Eventually acidosomes will fuse with the
phagosome to form the phagoacidosome where the acid pH will kill the
bacteria and other food organisms. qar, quadrulus associated
ribbon. EM taken on 5/21/73 by R. Allen with Hitachi HU11A TEM. Neg.
15,250X. Bar = 0.25µm.
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