Acidification in Digestive Vacuoles is an Early Event Required for Holospora Infection of Paramecium Nucleus

Summary

Specific inhibitors of vacuolar-type H⁺-ATPase, concanamycin A and concanamycin B, inhibited acidification of lysosomes and digestive vacuoles of the ciliate Paramecium caudatum. Holospora obtusa engulfed in the host digestive vacuoles could not escape there and could not infect the host macronucleus in the presence of these antibiotics. Indirect immunofluorescence microscopy with polyclonal antibodies specific for 57 kDa subunit of V-ATPase of chromatin granule showed that antigens were present in the digestive vacuole membranes. These results show that V-ATPase is present in the digestive vacuole membrane and maintains acidic pH inside the vacuole, and that acidification of the digestive vacuole is a required event for bacteria escape from the digestive vacuole and for infection into the host macronucleus.