Bioavailability, biodegradation, and acclimation of Tetrahymena pyriformisto 1-octanol

Previous work has indicated that the ubiquitous freshwater ciliate Tetrahym ena pyriformis acclimates to the presence of hydrophobic chemicals acting b y nonpolar narcosis. Four explanations have been identified to explain this apparent acclimation: (1) genetic adaptation occurs resulting in a resista nt population, (2) T. pyriformis quickly biodegrades hydrophobic chemicals resulting in a perceived acclimation response, (3) hydrophobic chemicals ar e not bioavailable, and (4) T. pyriformis contain an endogenous biochemical adaptation system which can quickly cause cellular changes resulting in ac climation. Results of biodegradation experiments indicated that the total e xtractable 1-octanol did not change over the duration of the experiments. B ioavailability experiments were performed using the solid-phase microextrac tion technique. Although there is a decrease in freely available concentrat ions of 1-octanol over a 2.5 log unit range of Tetrahymena population densi ty, the freely available concentration is constant for the population densi ties used for population growth experiments. Genetic change is highly unlik ely since acclimation occurs in less than the time required for one populat ion division. It is hypothesized that the acclimation response seen in Tetr ahymena results from partitioning of the chemical into the membrane followe d by active changes in the membrane structure to restore homeostasis. (C) 1 999 Academic Press.