[Mutants of the plaque microbe defective in the dark repair system]

The mutants of plague bacteria deficient in dark repair are described. They are sensitive to UV, mitomycin C, polymixin. Mutants have lost the ability to host cell reactivation in phage T7. The data obtained have shown that the addition of caffeine to the plating medium used to assay post-irradiation viability of UV-sensitive mutants did not influence the survival. Data are also given concerning virulence determinants, biochemical and other properties. The mutants formed P- colonies on hemine medium and Ca+ cells on Higuchi-Smith medium. They are avirulent for albino mice.