The effects of hydrostatic pressure on ribosome conformation in Escherichia coli: an in vivo study using differential scanning calorimetry

Differential scanning calorimetry of whole Escherichia coil cells allowed t he detection in vivo of changes in ribosome conformation. This enabled for the first time an analysis of the effects of high hydrostatic pressures on ribosomes in living cells. A correlation was observed between loss of cell viability and decrease in ribosome-associated enthalpy in cells subjected t o pressures of 50-250 MPa for 20 min. Cell death and ribosome damage were t herefore closely related phenomena. In pressure-treated cells, the thermogr am peak temperatures decreased, suggesting that the remaining ribosomes had adopted a less stable conformation. During subsequent incubation of the cu ltures at 37 degrees C, peak temperatures and enthalpies gradually increase d over a period of 5 h. This change in ribosome conformation had no apparen t effect on cell survival, as viability continued to decrease. The addition of 5 mM MgCl2 before pressure treatment of cells prevented the reduction i n stability of surviving ribosomes but had no effect on the initial loss of enthalpy or on cell viability.