Effect of components released from bacteria on encystment in ciliated protozoan Colpoda sp.

Abstract

Ca-induced encystment of Colpoda sp. was found to be cancelled by bacteria suspended in the surrounding medium. Continuation of the uptake of polystyrene latex particles into the food vacuoles slightly suppressed encystment. When the cells of Colpoda containing a large number of food vacuoles filled with Congo-red stained bacteria were transferred into an encystment-inducing medium, they encysted after promptly expelling the contents of the food vacuoles. Supernatant obtained from bacterial suspension, commercial albumin or polypeptone markedly prevented encystment, although free amino acid did not have much of an affect. Boiling or dialysis (MWCO: 10,000) of the supernatant reduced the encystment-suppression effect. These results suggest that the essential factors for the suppression of encystment are components such as peptides or proteins that are released from bacteria suspended in the surrounding medium. INTRODUCTION