Figure 3. Purity of sorted P. carinii cystic and trophic forms.

P. carinii cyst forms were physically separated from trophic forms by cell sorting using high-speed flow cytometry [12]. To check for purity, smears of sorted P. carinii organisms were stained with RAL-555, a panoptic Giemsa-like stain. No cystic forms were noted in the sorted trophic-form fraction (A). No trophic forms were visible within the sorted cystic-form fraction (B). P. carinii cell sorting was reproducible, reaching 99.6% purity [12]. Insets represent a higher magnification. Bars = 10 μm.