A new approach to the isolation of potential transcription mutants of escherichia coli

Abstract

A new approach to the isolation of potential transcription mutants of Escherichia coli is described. This is based on the differences in the utilization of host RNA polymerase for the growth of phages T4 and T7. T4 is dependent on the host enzyme during its entire growth cycle whereas T7 needs the same only for the transcription of the 'early' genes. Subsequent transcription in T7-infected cells is carried out by a phage-specific RNA polymerase which is an early gene product. Therefore, a temperature-sensitive E.coli mutant in which T7 growth, but not T4 growth escapes temperature inhibition after a brief incubation at the permissive temperature, could be tentatively regarded as a transcription mutant. The isolation of such a mutant is described.