Studies on Freeze injury in Enterohemorrhagic E. coli 0157

Viability of the E. coli O157 has been determined on TSA and CT-SMAC after frozen storage atD1C in various media. The unwashed O157 cells showed The highest viability in saline，虽然washed cells showed the lowest viability in the medium. the decrease in viability in the decrease in viabilitywater,phosphate buffer和TSB medium was lower in washed cells than in unwashed cells. The decrease inviability was the lowest in 200mm phosphate buffer when E. coli O157 cells were frozen stored inphosphate buffers with various concentration.这些结果suggest that O157 cells acquire freezetolerance when it is washed with water.Injury of E. coli O157 cells was largest at pH3 and 3.5. Theviability of the cells after frozen storage for 3 days was highest when the cells were frozen inbuffers with pH's from 5.5 to 6.5. The viability of The washed cells was higher than that of The7. unwashed cells. The decrease of The amount of a 7.9 kDa protein of The whole cells被监测after frozen storage in buffers above pH . in contrast，a whole cell protein with 12.5kDa increased after frozen storage.The viability was determined bothmicroscopically by using fluorescence dye and plating method. After frozen storage for 3 days atD1C in phosphate buffer (pH 6.5)，70% of the unwashed E. coli lost its ability for colony formation.These results suggest that E. coliO157 cells increase freeze tolerance when the cells are washed with water。

Viability of the E. coli O157 has been determined on TSA and CT-SMAC after frozen storage at -20ィイD1゜ィエD1C in various media. The unwashed O157 cells showed the highest viability in saline, though the washed cells showed the lowest viability in the medium. The decrease in viability in water, phosphate buffer and TSB medium was lower in washed cells than in unwashed cells. The decrease in viability was the lowest in 200mM phosphate buffer when E. coli O157 cells were frozen stored in phosphate buffers with various concentration. These results suggest that O157 cells acquire freeze tolerance when it is washed with water.Injury of E. coli O157 cells was largest at pH3 and 3.5. The viability of the cells after frozen storage for 3 days was highest when the cells were frozen in buffers with pH's from 5.5 to 6.5. The viability of the washed cells was higher than that of the unwashed cells. The decrease of the amount of a 7.9 kDa protein of the whole cells was observed after frozen storage in buffers above pH 6. In contrast, a whole cell protein with 12.5kDa increased after frozen storage.The viability was determined both microscopically by using fluorescence dye and plating method. After frozen storage for 3 days at -20ィイD1゜ィエD1C in phosphate buffer (pH 6.5), 70% of the unwashed E. coli lost its ability for colony formation.These results suggest that E. coli O157 cells increase freeze tolerance when the cells are washed with water.