%0 Journal Article %A Young, Paul G. %T The SHAM-sensitive Alternative Oxidase in Tetrahymena pyriformis: Activity as a Function of Growth State and Chloramphenicol Treatment %D 1983 %J Microbiology, %V 129 %N 5 %P 1357-1363 %@ 1465-2080 %R https://doi.org/10.1099/00221287-129-5-1357 %I Microbiology Society, %X The SHAM-sensitive alternative oxidase has been studied in Tetrahymena pyriformis strain ST as a function both of growth state and of chloramphenicol treatment. In low density cultures the total alternative oxidase activity, as revealed by SHAM titration in the presence of CN−, is equivalent to 17% of total respiration and is slightly utilized at all times. Stationary phase cells have somewhat less of the oxidase and it is not utilized even in CCCP-uncoupled cells. Respiration in chloramphenicol-treated cells is 100% CN−-resistant. Alternative oxidase activity is equivalent to 30-40% of this total and one third of it is active. The remaining 60% residual respiration is due to unknown oxidases. Following CCCP-uncoupling, a CN−-sensitive pathway is demonstrable and the alternative oxidase is fully utilized. The higher proportion of alternative oxidase in chloramphenicol-treated cells is brought about by its conservation at a time when the cytochrome chain is becoming non-functional. There is no large scale induction of the alternative oxidase. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-129-5-1357