MAGNETIC SEPARATION OF PHAGOSOMES OF DEFINED AGE FROM TETRAHYMENA-THERMOPHILA

We describe a new mass isolation procedure for both pure and stage-spe cific phagosomes from Tetrahymena thermophila. We prepared magnetic ir on dextran particles about 1 mum in diameter to label the phagosomes. The oral apparatus of the cells concentrated these particles so readil y that after 1 min the majority of the cells had formed a single phago some. A short wash removed non-ingested particles, enabling us to foll ow the age-dependent changes of a single labeled phagosome through the cell. Phagosomes of different ages, including very young and nascent phagosomes, were removed easily from the non-magnetic cell debris of m echanically homogenized cells by means of a permanent magnet. The isol ated phagosomes are pure as tested by enzymatic assays and tight and e lectron microscopy. Since the yield of pure phagosomes of all ages is high (approximately 90%), this method could be generally applied for p hagosome isolation from ciliates.