Some Effects of Chloramphenicol and Ethidium Bromide on Tetrahymena pyriformis

SYNOPSIS. Very similar results are obtained by the addition of 300 μg/ml chloramphenicol or of 15 μg/ml ethidium bromide to cultures of Tetrahymena pyriformis strain ST. In such cultures the exponential growth rates and the yields are reduced. Unlike the untreated ciliates, which retain the pyriform shape throughout the exponential and stationary phases, those exposed to either of the drugs become more spherical. In the control organisms progressively less surface area/unit of cell volume is exposed to the environment during the growth cycle; in the drug-treated ciliates this pattern is reversed. Increased endogenous respiration, reduced specific activities of states 3 and 4, and reduction in the levels of cytochromes a, a₃, b , and c + c ₁ are found in mitochondria from ciliates exposed to chloramphenicol and ethidium bromide.