Analysis of the Growth of Recombination-Deficient Strains of Escherichia coli K-12

Abstract

Cultures of' recombination-deficient strains of Escherichia coli are composed of' three classes of cells: (i) viable cells, which can undergo 20 or more generations, (ii) residually dividing cells, which can undergo fewer than 20 generations (probably an average of' f'ewer than 6). and (iii) nondividing cells, which are incapable of' a single division. The nonviable but residually dividing cells contribute to the mass increase of the culture, but not to the viability, thus accounting for the apparent dissimilarity in the effects of' rec mutations on growth rates and viabilities. We have determined the frequencies of cells in each of' the three classes, and, by making a simplifying assumption concerning the relative division times of viable and residually dividing cells, we have been able to describe mathematically the growth of the rec-cultures.Strains of' Escherichia coli K-12 with lesions in either the recA, recB, or recC genes exhibit a variety of phenotypic alterations when compared with isogenic rec+ strains. recA mutants are characterized by high sensitivity to ultraviolet (UV) irradiation, sensitivity to X-irradiation, excessive deoxyribonucleic acid (DNA) breakdown, both during normal growth and after UV irradiation, low spontaneous production of lambda phage from lysogens, no detectable recombination prof'iciency in bacterial crosses, and alterations in cell division processes (9,11,14,21). recB and recC mutants are characterized by moderate UV sensitivity, sensitivity to X-irradiation, reduced DNA breakdown after UV irradiation, normal spontaneous production of' lambda phage f'rom lysogens, reduced recombination proficiency, and the absence of' an adenosine triphosphate-dependent deoxyribonuclease (exonuclease V) (1, 16. 19, 21). Strains carrying both a recA and a recB or a recC mutation retain the high sensitivity to UV irradiation and undetectable recombination proficiency characteristic of recA mutants, but have lost exonuclease V activity and no longer degrade their DNA excessively either during normal growth or after UV irradiation (21).In addition to the above defects, mutants with lesions in any of the three rec genes grow more slowly and have significantly lower viability than isogenic rec+ strains (4,8,9,22). Previously obtained data on the relative growth

Replication arrests during a single round of replication of the Escherichia coli chromosome in the absence of DnaC activity

“…This does not seem to be consistent with the general belief that pausing of a replication fork leading to replication arrest is quite frequent during normal chromosome replication (reviewed by Cox et al, 2000;Michel, 2000;Rothstein et al, 2000). The observation that RecA deficiency causes massive chromosome degradation (Skarstad and Boye, 1993) and renders over 50% of the cells non-viable (Capaldo-Kimball and Barbour, 1971;Capaldo et al, 1974;S. Maisnier-Patin et al unpublished observation) supports the frequent occurrence of DSBs from replication arrest and dependence on homologous recombination for reactivation (Cox, 1999;Marians, 2000).…”

Host strain influences on supercoiled plasmid DNA production in Escherichia coli: Implications for efficient design of large‐scale processes

“…The recA mutation leaves about 10% of cells anucleate at each cell division and can generate up to 50% dead cells (Capaldo et al, 1974), yet the majority of the recA strains used here gave fast growth rates and only DH10b and XL10 Gold had slow growth out of the 7 recA strains in Table I.…”

A broadening view of recombinational DNA repair in bacteria

“…A defect in DNA replication and cell division in recA cells was first reported by Inouye (Inouye 1971). Over 50% of the cells in a culture of a recA null mutant are nonviable under at least some conditions (Capaldo et al 1974). The frequency of productive replication initiation at oriC is significantly reduced (Skarstad & Boye 1988).…”