EFFECT OF CENTRIFUGATION ON THE PRESSURE RESISTANCE OF EXPONENTIAL PHASE CELLS OF ESCHERICHIA-COLI-8164

Exponential phase cells of Escherichia coli NCTC 8164 that were centri fuged at 2000g for 20 min at 4 degrees C were more resistant to subseq uent pressure treatment than cells grown in trypticase soya broth (TSB ) and treated without any centrifugation steps. The effects of mild pr essure stress (200 kPa for 20 min) and temperature stress (a shift fro m 37 degrees C to 4 degrees C) involved in the centrifugation procedur e were analysed separately. It appeared that the increase in pressure resistance obtained following centrifugation was mainly due to the gra dual temperature decrease during centrifugation, while the mild pressu re stress seemed to play a smaller role in the response.