Correlations between sensitivities to radiation and to hyperoxia in microorganisms

The bactericidal and bacteriostatic effects of hyperoxia from 1 to 15 atm and from 1 to 4 atm, respectively, were measured for Escherichia coli strains E-26, B, B/r, and ${\rm B}_{{\rm s}-1}$. Percentage survival was minimal for all strains in oxygen ( O2) at 4.2 atm (E-26, 51%; B, 1.5%; B/r, 60%; and ${\rm B}_{{\rm s}-1}$, 0.25%). O2 at 1-2 atm produced little killing and O2 at 6 atm or greater was less bactericidal than was 3-5 atm. Strain B/r survived better in all hyperoxic environments than did strain B or ${\rm B}_{{\rm s}-1}$. Survival of E-26 and Micrococcus radiodurans at 4.2 atm O2 was similar to B/r. When ${\rm B}_{{\rm s}-1}$ was exposed to O2 at 4.2 atm without organic nutrients, 66% survived. During the first hour of exposure, the growth rate of strain B/r was inhibited 13.2% per atm O2 with an extrapolated intercept of 100% survival at 0.6 atm; growth inhibition of ${\rm B}_{{\rm s}-1}$ was 12.2% per atm with an intercept of 1.2 atm. We concluded that: (1) strains B and ${\rm B}_{{\rm s}-1}...