A Study of the Effects of Hydrostatic Pressure on Macromolecular Synthesis in Escherichia coli

In cultures of Escherichia coli 15 (thymine^-, leucine^-) which were incubated at high hydrostatic pressures, cell division occurred only at pressures below 430 atm but in a somewhat synchronous fashion at around 250 atm. The rate of leucine-¹⁴C incorporation into a macromolecular fraction of the cells diminished to a zero value at about 580 atm and that of uracil-¹⁴C incorporation to a zero value at about 770 atm. The rate of thymine-¹⁴C incorporation at pressures around 330 atm was that to be expected with a culture in which DNA synthesis is somewhat synchronous. At pressures above 500 atm, thymine-¹⁴C was incorporated only over the initial part of the pressure incubation and further incorporation under pressure was not observed no matter how long the duration of the incubation. We present evidence along several lines that the thymine incorporation kinetics reflect an effect of pressure on a locus at the origin (or termination) of a replication of the bacterial chromosome. The recovery of cell division and of the incorporation rates upon release of pressure were found to depend on the magnitude of the pressure and the duration of the pressure incubation.