Characterization of Symbiotic Algae-free Strains of Paramecium bursaria Produced by the Herbicide Paraquat

Abstract

As is well known, Paramecium bursaria has many endosymbiotic algae in its cytoplasm. We already reported that these endosymbiotic algae can be removed from the cytoplasm by using the herbicide paraquat and symbiotic algae-free paramecia were prepared (Hosoya et al. 1995). In this study, we examined the characteristics of symbiotic algae-free paramecia obtained by paraquat treatment. Symbiotic algae-free paramecia had a shorter log phase than those with symbiotic algae, and showed lower cell density at the stationary phase. Additionally, they had the ability to form stable symbiotic relationships with symbiotic algae. Symbiotic algae obtained from P. bursaria in log phase showed a higher infection rate than those from P. bursaria in stationary phase. These results suggest that growth phase of the host influences the reinfection ability of their interior symbiotic algae.