TEMPERATURE LIMITS, GENEALOGICAL ORIGIN, DEVELOPMENTAL COURSE, AND ULTIMATE FATE OF HEAT-INDUCED FILAMENTS IN ESCHERICHIA COLI MICROCULTURES

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Abstract
The heat induction of filaments in micro-cultures of Escherichia coli occurred through a wide range of temperature, with 43.5 C being the upper limit at which all cells continued to grow. The lower temperature limit was not determined, but filaments were obtained at room temperature in overnight cultivations. The evidence from genealogical histories, growth rates and cell and filament lengths strongly suggested that the filaments are collections of morphologically undifferentiated but quasi-independent cell units which continue to grow and multiply while retaining the capacity eventually to break off completely as normal nonfilamented cells. Filaments which failed to give off a daughter by the end of the second generation after their inception lyse explosively. The evidence obtained contradicts the hypothesis that the mother cell of a clonal microcolony becomes a filament and eventually lyses, although the cell length patterns upon which this hypothesis is based were reproduced. A high degree of synchronization of division was obtained and maintained through the entire period of incubation, which in some cultivations extended into the tenth generation.