Aerobically grown Euglena gracilis, a bleached mutant, shows a prompt synthesis of wax esters with the concomitant fall of the paramylon (a β-1,3-glucan) content upon exposure to anaerobiosis. Bringing the anaerobic cells back to aerobiosis causes the reverse conversions. The anaerobic wax ester formation is accompanied by a net synthesis of ATP. The transition between the fermentation and respiration occurs at 10−5–10−7 M of the O2 concentration.
