A cytoplasmic membrane preparation that stimulates septation in irradiated Escherichia coli

Exposure of cells of Escherichia coli K-12 defective at the lon locus to ionizing radiation prevented cell division by inhibiting septation. Properties of a cytoplasmic membrane preparation that stimulated septation in irradiated Escherichia coli K-12 lon cells plated in complex medium were investigated. It was determined that each resultant colony was derived from a single, irradiated cell that had undergone a septation event. It was, also, determined that the cytoplasmic membrane preparation stimulated septation and, therefore, reversed the effects of radiation by providing two necessary conditions. One condition was anaerobiosis of the plating medium produced by the reduction of O₂ to water via enzymatic processes of the electron transport system contained in the cytoplasmic membrane preparation. The other condition was an alteration of the medium, most probably reflecting an inactivation of a septation-inhibitory substance (still unidentified) that was normally present in the plating medium. An understanding of these properties may increase our knowledge of the mechanism of septation and, furthermore, may increase our knowledge of the mechanism by which cells recover from the deleterious effects of radiation.