Significance of Folded Chromosomes Released from Amino‐Acid‐Starved Escherichia coli Cells

Abstract

1. Folded chromosomes from amino-acid-starved Escherichia coli DG 75 cells are to a large extent released as envelope-bound complexes which sediment more rapidly than envelope-bound complexes from exponentially growth cells. A minor fraction (about 3%) represents relatively slow sedimenting envelope-free nucleoids. 2. Morphological analysis of the sensitivity of amino-acid-starved cells to the action of lysozyme and/or detergents indicates that these cells are less susceptible to lysis than exponentially grown cells. This results in the production of fast sedimenting envelope-bound complexes from non-dividing cells. We infer that it is not the amount of DNA, as suggested by Ryder and Smith (1974), but the low degree of envelope fragmentation that causes the high sedimentation rate. 3. After prolonged periods of starvation about 3% of cells in the process of division persist in the population. The results indicate that these cells release their (terminated) chromosomes in the envelope-free form. At this stage it is impossible to conclude whether these chromosomes are released because of their detachment from the membrane in situ (cf. Worcel and Burgi, 1974) or because of an enhanced susceptibility of dividing cells to lysis.