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Several temperature-sensitive initiation mutants of Escherichia coli were examined for the ability to initiate more than one round of replication after being held at nonpermissive temperature for approximately 1.5 generation equivalents. The capacity for initiation was measured by residual synthesis experiments and rate experiments under conditions where protein synthesis and ribonucleic acid synthesis were inhibited. Results of the rate and density transfer experiments suggest that the cells may initiate more than one round of replication in the absence of protein or ribonucleic acid synthesis. This contrasts with the results of the residual synthesis experiments which suggest that, under these conditions, only one round of synthesis is achieved. These findings suggest that the total amount of residual synthesis achieved in the presence of an inhibitor may be both a function of the number of initiation events which occur and the effect of the inhibitor of protein or ribonucleic acid synthesis on chain elongation. MATERIALS AND METHODS Bacteria. The following strains were utilized: Escherichia coli 15T-ts-489, dnaC (Thy-, Arg-, Met-, Trp-; obtained from K. G. Lark); E. coli K-12, dna252A (2) (Thi-, Thy-, Pro-, StrS; obtained from F.

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