Effects of temperature shift on growth rate of Escherichia coli BB at lower glucose concentration.
Although a shift in nutritinal conditins brings about transient unbalanced growth in normally grown Escherichia coli, a shift in temperature without changing the nutritional conditions results in immediate adaptation to the new conditions. However, when a medium contained an insufficient amount of nutrient, such as glucose, a temperature shift caused a lag time in temperature shiftup was primarily determined by the postshift temperature. These situatins were quite similar to those observed in nutrient shiftup, but a growth profile during the lag time was more distorted than that found in the nutrient shiftup. The transient unbalanced growth appeared to be caused by a difference in physiological states of bacteria, as expressed by macromolecule content per cell characterized by the pre and postshift environments, and was capable of expressing theoretically its profile and duration according to the model of Cooper and Helmstetter. On the other hand, the shiftdown in temperature in the presence of a limiting concentration of glucose caused extraordinarily long lag time, and transient cessation of cell division during that period. This response was unable to explain by the Cooper and Helmstetter model. In contrast to the temperature shiftup, the duration of lag time in the shiftdown was expresed as functions of the poshift temperature and the difference in physiological states of the pre- and postshift environments.
Department of Chemical Engineering, Faculty of Technology, Kanazawa University, Kanazawa 920, Japan.
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Chohji
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Sawada
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Kuno