Fig. 6. Delivery of endosomal content to the phagosome. (A) A cell fed yeast in the presence of Neutral Red. Within the cell are three phagosomes containing yeast particles, all with Neutral Red accumulation at the bud neck. The upper phagosome also has mounds of Neutral-Red-positive material at sites along its membrane. (There are also two free yeast particles just above the cell; these are not stained.) (B,C) A cell whose endosomes were labeled with TRITC-dextran prior to addition of yeast particles. Mounds of TRITC-dextran are present along the phagosome membrane (B). Subtraction of the red channel shows that VatM-GFP is continuous around the outside of these mounds (C), suggesting that they are sites of fusion between endosomal vesicles and the phagosome membrane. Bar, 10 µm.