Respiration of early-exponential phase cultures of the ciliate protozoon is inhibited in two stages with increasing concentrations of cyanide. Up to 40 to 50% inhibition occurs at low concentrations (< 15 μ). Maximal inhibition was obtained with 300 μ-cyanide; at this concentration 20% of the respiration was still unaffected. Competitive inhibition of respiration by CO occurs ( = 4.25 μ); azide inhibition of oxygen consumption is uncompetitive ( = 4 to 9 m). A salicylhydroxamic acid-sensitive oxidase is present which is not inhibited by cyanide, azide, CO or HS. Three other pathways of terminal oxidation are present which are insensitive to azide, CO and salicylhydroxamic acid. One of these is cyanide- and sulphide-sensitive, a second is cyanide-insensitive but sulphide-sensitive, and a third is cyanide-sensitive but sulphide-insensitive; these pathways may not possess unique terminal oxidases. No oxidase with a very low affinity for oxygen was detected, but the overall affinity for oxygen of in the absence of inhibitors ( = 2.9 μ) is lower than that of some other protozoa.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error