Nitrous Oxide as a Sensitizer of Bacterial Spores to X-rays

SummaryIn N2O-saturated water, spores of Bacillus megaterium exhibit sensitivity to x-rays that is higher than that in N2-saturated water, but lower than that in O2-saturated water. O2-N2O mixtures show O2 sensitivity. Ethyl alcohol present simultaneously at 0·8 Molar prevents the N2O sensitization completely. These results can be interpreted as due to an increase in ·OH radical yield by N2O; and removal of ·OH by ethanol. In dilute solutions of ethanol only partial reversal (or competition) of the N2O effect is observed. This effect is concentration-independent over a wide range of dilute concentrations. An apparent exhaustion of the alcohol is observed at higher doses, producing a two-component survival curve, each component being exponential. The break-points are dose-dependent, with only one being expected on the basis of measured yields in chemical systems; and the slope beyond the break-point is always that of O2-saturated suspensions. The last results can be interpreted as indicating two actions of N2O, only one of which is prevented in dilute solutions of alcohol, and the operation of O2 or an O2-mimicking system after exhaustion of the alcohol.