This study describes effects of exposure of the freshwater ciliate Tetrahymena pyriformis to the "classic" weak acid respiratory uncoupler pentachlorophenol (PCP) on the population growth kinetics and membrane lipid profiles. The assessment of growth kinetics of naive populations exposed to PCP, at concentrations eliciting < 50% growth inhibition, showed generation times of exposed cultures similar to generation times of controls but preceded by a short lag phase (< 2 h). Assessment of exposed cultures exhibiting > 50% growth inhibition revealed generation times that increased with increasing concentrations of toxicant. In addition, the relative percentages of selected fatty acid methyl esters (FAMEs) in both pellicle and mitochondrial membranes were examined. Upon exposure to PCP the relative percentages of FAMEs 12:0, 14:0, 16:0, 16:1, and 18:0 did not change. However, with exposure to PCP a decrease was observed for FAMEs 15:0 and 17:0. Conversely, with PCP exposure there was an increase in FAME 18:1. A comparison of these results with those elicited upon exposure to the model narcotic 1-octanol reveals marked differences in both growth kinetics and fatty acid shifts.
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