Hybrid respiration in the denitrifying mitochondria of Fusarium oxysporum

Induction of the mitochondrial nitrate-respiration (denitrification) system of the fungus Fusarium oxysporum requires the supply of low levels of oxygen (O-2). Here we show that O-2 and nitrate (NO3-) respiration function simultaneously in the mitochondria of fungal cells incubated under hypoxic, denitrifying conditions in which both O-2 and NO3- act as the terminal electron acceptors. The NO3- and nitrite (NO2-) reductases involved in fungal denitrification share the mitochondrial respiratory chain with cytochrome oxidase. F oxysporum cytochrome c(549) can serve as an electron donor for both NO2- reductase and cytochrome oxidase. We are the first to demonstrate hybrid respiration in respiring eukaryotic mitochondria.