Environmental changes can often result in
oxygen deficiency which influences cellular energy metabolism, but such effects have been insufficiently studied in fungi. The effects of
oxygen deprivation on respiration and
phosphate metabolites in Phycomyces blakesleeanus were investigated by
oxygen electrode and (31)P NMR spectroscopy. Mycelium was incubated in hypoxic and anoxic conditions for 1.5, 3 and 5 h and then reoxygenated. Participation of
alternative oxidase (AOX) in total respiration increased gradually in both treatments and after 5 h of
anoxia exceeded a value 50% higher than in control. Shortly after reintroduction of
oxygen into the system AOX level decreased close to the control level.
Oxygen deprivation also caused a reversible decrease of
polyphosphate/
inorganic phosphate ratio (PPc/Pi), which was strongly correlated with the increase of AOX participation in total respiration. Unexpectedly,
ATP content remained almost constant, probably due to the ability of
PolyP to sustain energy and
phosphate homeostasis of the cell under stress conditions. This was further substantiated by the effects of
azide, a
cytochrome c oxidase inhibitor, which also decreased PPc/Pi ratio, but to a smaller extent in
oxygen deprived than control and reoxygenated specimens.