THE INTERACTION OF A GENE (nur) CONTROLLING NEAR‐UV SENSITIVITY AND THE polA1 GENE IN STRAINS OF E. COLI K12

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Abstract
Abstract— When stationary cell populations of the Escherichia coli W3110 strain and the polA1 mutant (p3478) derived directly from it were compared for their sensitivity to near‐UV (NUV, 300–400 nm) inactivation, the polA1 strain proved to be more sensitive. By appropriate matings and transductions, four essentially isogenic strains have been developed which carry all four possible combinations of genes conferring far‐UV (FUV, 200‐300 nm) sensitivity (polA1 vs. polA+) and NUV sensitivity (nur vs. nur+). Stationary cells of strains carrying either the polA1 or polA+ allele in combination with the nur allele are indistinguishable in their sensitivity to NUV inactivation and are equivalent in their NUV sensitivity to the original polA1 mutant strain (p3478). With the two strains carrying the nur+ allele, stationary cell populations of the polA1 strain are clearly more sensitive to NUV inactivation than is the polA+ strain. The NUV sensitizing effect of the polA1 mutation in a nur+ genetic background is about the same as that of the nur mutation at the 0.37 survival level. This may mean that the polA1 and nur mutations sensitize E. coli stationary cell populations to NUV inactivation by a common mechanism.