Correlations between free radical production and viability of lyophilized bacteria.

When Serratia marcescens cultures were treated with dilute solutions of phenol or hydrogen peroxide before drying or by lyophilization at suboptimal pH, the log of the number of cells surviving lyophilization was correlated with subsequent free radical production by the dried cells. Since the rate of free radical production and rate of death were similarly affected by temperature, the log of the number of cells surviving after 6 days was inversely related to the free radical concentration at that time. Free radicals were produced in proportion to the log of oxygen pressure, and viability was inversely related to oxygen tension; again, free radical concentration appeared to be correlated with the death of organisms.