Abstract
Because of the nature of their functions, enzymes involved in macromolecule metabolism cannot be studied by analyzing classes of auxotrophic mutants. The genetic approach to these enzymes is presently limited to analysis of conditional-lethal and drug-resistant mutants. We have previously described the isolation of a general population of E. coli temperature-sensitive mutants (Boyd et al., 1968) and, in this paper, we describe the properties of one of these, a temperature-sensitive RNA polymerase mutant.