Respiration of Tritrichomonas foetus: components detected in hydrogenosomes and in intact cells by electron paramagnetic resonance spectrometry.

Electron paramagnetic resonance spectrometry (EPR) techniques revealed a complex set of redox components in intact respiring cells of Tritrichomonas foetus, an aerotolerant anaerobic protozoon which lacks mitochondria. One of the two main systems of terminal respiration of this organism is the hydrogenosomal system, which oxidizes pyruvate and other substrates. EPR analysis of hydrogenosome-enriched fractions, prepared by differential centrifugation, revealed the presence of at least five redox components with midpoint potentials ranging from -305 to -115 mV; most of these are likely to represent iron-sulfur clusters. Signals indicating relatively stable flavin free radicals were also observed. Involvement of these multiple redox components in the electron transport system of T. foetus hydrogenosomes is suggested.