Escherichia coli strains B5 and B/r/l were grown under conditions of periodic glucose starvation in a minimal medium. Such conditions of growth give rise to two synchronous populations that are out of phase regarding their time of division, one dividing shortly after a new supply of fresh medium and the other at a later stage of the feeding cycle. Preferential selection of one of the two populations using heat treatment resulted in a homogeneous synchronized culture that exhibited in a non-limiting medium of a high degree of synchrony that was long lasting. Synchrony and its persistence could survive preservation of such a synchronized culture by freeze drying. An explanation of the synchrony persistence was put forward and the practical implications of these findings were discussed.

Cell Division↗

PubMed1976

DNA synthesis by Escherichia coli B/r/l synchronized and grown under conditions of slow growth.

Escherichia coli B/r/l was synchronized by a novel method and its growth was followed in a minimal salts medium containing glucose, acetate, aspartate or succinate as the sole carbon source. Thymine incorporation experiments showed agreement with the Cooper-Helmstetter model for DNA synthesis, during the division cycle, both in glucose grown culture with a doubling time 57.5 min and in acetate, aspartate and succinate where the doubling time was extended up to 90 min. The ratio C/C + D was identical or close to that predicted by the model. Prolonged growth of the synchronized cultures prior to each experiment was practised in order to ensure their physiological state without causing any considerable deterioration of synchrony.

Cell Division↗

PubMed1975

Growth of escherichia coli B/r/1 in a semi-continuous system designed for the synchronization of cell division.

Escherichia coli B/r/1 was grown under conditions of periodic feeding. Glucose, the only carbon source, was supplied at intervals longer than the generation time of the organism. Thus, each period of glucose availability was followed by a period of depletion. This process gave rise to two synchronous populations, one dividing shortly after a new supply of fresh medium and the other dividing at a later stage within the feeding cycle. Thymine incorporation experiments suggested that the double population emerged as the result of a discriminatory blockage of DNA replication.

Bacteriological Techniques↗

PubMed1975

Defining synchrony of cell cultures.

A method was developed for the statistical analysis of growth data from synchronized growth experiments. The analysis provided a firm basis for the recognition of synchrony and the objective graphical presentation of the growth pattern of a synchronized culture. The latter could then supply reliably the parameters required for the calculation of a synchronization index, i.e. for the synchrony evaluation.

Cell Count↗

PubMed1975