Decrease in High Pressure Tolerance of Resting Cells of Escherichia coli K-12 by Pretreatment with Alternating Current

Abstract

The effects of 50 Hz alternating current (a.c.) pretreatment on the high pressure tolerance of Escherichia coli K-12 cells were found to be dependent on the composition of the solutions suspending the cells during treatment with pressure up to 4000 kg/cm² at room temperature for 10min. When pressurized in a 8/15 M NaCl solution (pH 7.0) at 3000 kg/cm² after a.c. exposure of 600mA/cm² for 2 hr at 35°C, the exposed cells could not survive as well as those pressurized in a 8/15 M phosphate buifer (pH 7.0): the value of the ratio of the exposed cells surviving to that of the unexposed ones was less than 0.1 in an NaCl solution and about 0.5 in a buffer. The lethal action of high pressure on the cells suspended in M/15 buffer was appreciably counteracted by 8/15 M buffer but not by 8/15 M NaCl solution.