Recalibrated linkage map of Escherichia coli K-12.

Partitioning of bacterial plasmids during cell division: a cis-acting locus that accomplishes stable plasmid inheritance

Transcription and translation initiation frequencies of the Escherichia coli lac operon.

The DnaA protein determines the initiation mass of Escherichia coli K-12.

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https://science.sciencemag.org/content/sci/190/4215/624.full.pdf

Molecular biology of bacteriophage mu.

Origin and sequence of chromosome replication in Escherichia coli

The origin of replication in Escherichia coli K-12 was mapped by determining the rate of marker replication during a synchronous round of replication. Four isogenic strains were made lysogenic for λind− and for phage Mu-1, with Mu-1 integrated into a different chromosomal location in each strain. Cultures were starved for amino acids to allow completion of chromosome replication cycles and then starved for thymine in the presence of amino acids, and a synchronous cycle of replication was initiated by the addition of thymine. Samples were exposed to radioactive thymidine at intervals, deoxyribonucleic acid was extracted, and the rate of marker replication was determined by deoxyribonucleic acid-deoxyribonucleic acid hybridization to filters containing Mu-1, λ, and E. coli deoxyribonucleic acid. The results confirm that the origin of replication is near ilv. The travel times of the replication forks, calculated from the data obtained for cultures with doubling times of approximately 40 and 61 min, are 40 and 52 min, respectively.

More Precise Mapping of the Replication Origin in Escherichia coli K-12

Early experiments to locate the origin of replication on the E. coli chromosome used a variety of techniques: pulse mutagenesis with nitrosoguanidine, enzyme induction or transduction with bacteriophage PI. They provided the general conclusion that there was a fixed origin of replication, in the lower left quadrant of the E. coli genetic map, and that replication proceeded uni-directionally in a clockwise manner. Some of the data obtained with PI transduction could be viewed however as indicating bi-directional replication (Caro and Berg, 1968). Recently, we have described a more precise method for determining origin and direction of chromosome replication in E. coli (Bird et al., 1972). The origin and the direction of replication were defined in two ways: the gradient of marker frequency in exponential cultures and the sequence of marker replication after partial synchronization. Gene frequency and sequence of replication were assayed by DNA-DNA hybridization using only two markers. The first, the prophage lambda, is fixed and the second, the prophage Mu-1, is moveable. We have constructed an isogenic series of strains, each lysogenic for prophage lambda and for Mu-1 integrated into a different chromosomal site. Mu-1 often integrates within a gene, thus making the identification of its location quite simple.

Jacqueline Louarn

Papers

Origin and sequence of chromosome replication in Escherichia coli

More Precise Mapping of the Replication Origin in Escherichia coli K-12

Pattern of Replication of Various Genes in Exponential and Synchronized Cultures of Escherichia coli