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Quick-freeze deep-etch of acidosomes show the results of carrier
vesicle fusion with the acidosomes. Both the E-face
(Eac) and P-face (Pac) of the
acidosomes appear to have two areas, the larger area on the E-face has
few IMPs but has pits left by the removal of IMPs during fracturing
and another area that is smooth with fewer pits that resembles a fused
carrier vesicle membrane. A line (arrowheads) marking the
fusion site between these two vesicles is evident. The P-face of the
acidosome has many IMPs while the fused carrier vesicle membrane is
smooth. Presumably these two membrane areas will mix with time. Thus
acidosomes, which are somewhat similar in appearance to multivesicular
bodies in higher organisms, are late endosomes and deliver their
membrane, their contents and their V-ATPase complexes to the phagosome
to transform the phagosome to the phagoacidosome. EM taken on 7/29/88
by C. Schroeder with Zeiss 10A TEM. Neg. 24,800X. Bar = 0.2µm. Part
published in J. Cell Sci. 106:411-422, 1993.
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