Reactivation of Escherichia coli inactivated by ultraviolet light by cell extracts of propionic acid bacteria

For the first time reactivation of cell extract of three strains of Propionibacterium shermanii in UV inactivated not filament-forming strain Escherichia colli AB 1157 is shown. Reactivation was demonstrated in preincubated and postincubated test-culture and increased as survival of E. coli decreased in a range 1.8-0.006%. The factor (factors) of defense is dialysable, thermolabile and is present as in a fraction of nucleoproteins and nucleic acids so in a fraction of soluble proteins. The extracts were inactivated by incubation with proteinase K and trypsin, partly decreased activity by incubation with alpha-amylase and selected nuclease but not with lipase. Polypeptide nature of reactivating factor is supposed.