Effects of High Partial Pressures of Oxygen on Fungi and Bacteria

IN previous articles1–3 attention was directed to the fact that high pressures of pure oxygen have a specific effect on the metabolism of cells of various kinds. In the tissues of higher plants the effect was shown to be the stopping of carbon dioxide output, and this, it was postulated, was the result of the inactivation of the associated enzyme systems. In some fungi and in two species of bacteria it was shown also that exposure to 10 atm. pressure of pure oxygen completely suppressed the growth of the organisms. However, unlike the tissues of higher plants, the fungi, when removed from the pressure and returned to air, recovered and began to grow apparently quite normally if the period of exposure were not too long. In these cases a period of some days normally elapsed before the growth of the colonies in air began again. All the fungi were grown on 2.5 per cent malt agar in Petri dishes and the temperature was maintained at 25° C in a constant-temperature room or in an incubator.