Chromosomal mapping by means of mutational induction in synchronous populations of Streptococcus faecalis

Stonehill, E. H. (Sloan-Kettering Institute for Cancer Research, New York, N.Y. and Dorris J. Hutchison. Chromosomal mapping by means of mutational induction in synchronous populations of Streptococcus faecalis. J. Bacteriol. 92:136-143. 1966.-A new method for mapping genetic loci on the bacterial chromosome, based on the linear progression of the deoxyribonucleic acid-replicating enzyme (replicase) in synchronous cultures of Streptococcus faecalis, is described. Ultraviolet irradiation was used to induce mutations to drug and to bacteriophage resistance at various intervals during the progress of the replicase along the chromosome. The time of duplication of the gene in synchronous populations was determined from reductions in the rates of irradiation-induced mutation. After the replication of various genes, the rates fell to half their former values. The resulting data made possible the construction of a 1-hr time-map indicating the sequence of replication of five genes in S. faecalis.