Lethal Environmental Factors Within the Natural Range of Growth

Abstract

Young cells of Bacterium coli may be killed by abrupt environmental changes within their natural growth range. When young cultures growing at 45[degree] C are suddenly changed to 10[degree], about 95% of the cells are killed within 1 hr. Those in cultures growing at 10[degree] withstand better a sudden change to 45[degree]; in this case, relatively few cells are killed, and the survivors soon become adjusted, so that rapid growth ensues within 1 hr. Drastic killing action is also obtained with abrupt changes in osmotic pressure, without going beyond the limits suitable for growth, e.g., transfer from 1% peptone to 1% peptone plus 5% NaCl, and vice versa. While sudden changes within the growth range have a lethal effect on young bacterial cells, there is no apparent killing by gradual changes.