Genetical and Physiological Studies on a Thermosensitive Mutant of Escherichia coli Defective in Cell Division

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Abstract
A new temperature-sensitive mutant of E. coli, defective in cell division, was isolated after selection for tolerance to colicin E2. The mutant strain, ASH124, growing in minimal or complex medium, begins filament formation immediately upon shift to high temperature. High densities of bacteria or the presence of 0.44 M-sucrose prevent filament formation at 42.degree. C, and division continues. Filament formation in the mutant is reversible, and upon return to 29.degree. C the multinucleate filaments divide up into normal-sized bacteria by a series of rapid but sequential divisions. In the presence of chloramphenicol at 29.degree. C, 25% of these division sites are still expressed. A genetic locus designated ftsH, apparently controlling temperature sensitivity and filament formation, was provisionally mapped at 80 min on the E. coli K12 map.