CELL-EXTRACTS OF PROPIONIC-ACID BACTERIA REACTIVATE CELLS OF ESCHERICHIA-COLI INACTIVATED BY ULTRAVIOLET-RADIATION

Cell extracts of three Propionibacterium shermanii strains were shown to exert a reactivating effect on cells of E. coli AB 1157 inactivated by ultraviolet radiation. The reactivating effect was revealed after both preincubation and postincubation of the irradiated cells with the extracts. The effect increased with a decrease of the survival rate w ithin the range of 1.8 - 0.006%. The protective factor (or factors) is dialyzable and thermolabile; it was detected both in the fraction of soluble proteins and in the fraction of nucleoproteins and nucleic aci ds. The protective properties of dialyzate disappear after incubation with proteinase K and trypsin, decrease after incubation with alpha-am ylase, deoxyribonuclease-1, or ribonuclease, and do not change under t he influence of lipase. The reactivating factor is believed to be of a polypeptide nature.