Mischkolonien auxotropher und Wildtypzellen nach Behandlung von Esdierichia coli-Zellen mit salpetriger Säure

Abstract

Cells of E. coli incubated in nitrous acid give rise 1. to unchanged wildtype colonies, 2. to colonies composed of wildtype and auxotrophic cells and 3. to colonies consisting of auxotrophic cells only. The mixed colonies are considered to originate from single cells each of them harbouring hybrid DNA with one subunit, probably a sisterstrand, changed by deamination of a cytosine or adenine, the other one with unchanged wildtype composition. In cells producing type 3 colonies this wildtype strand is mutated lethally by a separate deamination of a cytosine or adenine. A mathematical treatment of this hypothesis leads to predictions which are in good agreement with experimental evidence. The data obtained are used for an estimation of the number of gene-loci of E. coli.