The selection of mutants of escherichia coli with impaired cell division at elevated temperature

Abstract

1. 1. After treatment of a strain of Escherichia coli K 12 with the mutagenic agent N-methyl- N′-nitro- N-nitrosoguanidine, mutants were selected which divide normally at 30° but which show a strong inhibition of cell division during growth at 42°. 2. 2. According to their phenotype at elevated temperature the mutants were divided into the following classes. 1. I. Mutants that showed a complete inhibition of cell division and had no colony forming ability at 42°. 2. II. Mutants that showed an incomplete inhibition of cell division and formed colonies at 42° that consisted essentially of long filaments. 3. III. Mutants with no colony forming ability at 42° and in which the inhibition of cell division was accompanied and probably caused by an inhibition of nucleic acid synthesis. 1. 3. Mutants falling into the first class and not subject to inhibition of nucleic acid synthesis were studied in more detail. The temperature-induced inhibition of cell division, unlike the inhibition of cell division induced by ultraviolet irradiation, was not reversed by treatment with the agent pantoyl-lactone. Both inherited properties, sensitivity of temperature-induced and radiation-induced inhibition of cell division, are chromosomally determined; the corresponding genes however are located at different sites on the bacterial chromosome.