EFFECT OF SODIUM AZIDE ON RADIATION DAMAGE AND PHOTOREACTIVATION

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Abstract
Growth in suitable concns. of Na azide, or even the mere presence of this compound during u.-v. irradiation, reduces the sensitivity of Chromobacterium violaceum, Escherichia coli, and Micrococcus pyogenes var. aureus to the lethal action of u.-v. radiation and, simultaneously, the degree of photoreactivation. Exposure of resting cells to azide prior to irradiation produces essentially the same effects, whereas exposure following u.-v. irradiation does not affect u.-v. radiation survival, but reduces photoreactivation. Moreover, growth in the presence of Na azide increases the incidence of "sponetaneous" and u.-v. radiation induced mutants for streptomycin-resistance in "catalase-rich" strains of M. pyogenes var. aureus. The blocking or temporary inactivation of heavy-metal enzymes or porphyrin-type pigments by azide is suggested as the mechanism responsible for these effects, and possible relationships between u.-v. inactivation, mutagenesis, and photoreactivation are discussed.