Lipid Interrelationships in the Growth of Paramecium aurelia, Stock 299

Abstract

In axenic medium with TEM-4T (a tartaric acid ester of beef tallow monoglyceride) as a source of fatty acids, regulation of the growth of Paramecium aurelia, stock 299, was achieved by varying the relative amounts of TEM-4T and stigmasterol. Optimal populations were reached in 7 days at 27' when the relative proportion of these lipids was 10 : I (w/w) TEM-4T : stigmasterol. Division was inhibited at ratios of 2: I (wiw) or less. The inhibition was annulled by restoration of the ' optimal ' ratios of TEM-4T : stigmasterol to the growth medium even after the protozoa had been exposed to 'inhibitory' ratios for periods up to 6 days. Growth was also inhibited when the relative proportions of TEM-4T : stigmasterol were adjusted to 2 : I (w/w) by the addition of TEM-4T to the culture after a 3-day period during which the organisms had been incubated with stigmasterol alone. No inhibition was observed when the TEM-4T: stigmasterol ratio was adjusted to 2 : I (wlw) by adding stigmasterol to the culture after a period of incubation with TEM-4T alone. It is suggested that under conditions of lipid imbalance in the medium stigmasterol interferes with the utilization of TEM-4T for growth.