Cold shock and its effect on ribosomes and thermal tolerance in Listeria monocytogenes

Differential scanning calorimetry (DSC) and fatty acid analysis were used t o determine how cold shocking reduces the thermal stability of Listeria mon ocytogenes, Additionally, antibiotics that can elicit production of cold or heat shock proteins were used to determine the effect of translation block age on ribosome thermal stability. Fatty acid profiles showed no significan t variations as a result of cold shock, indicating that changes in membrane fatty acids were not responsible for the cold shock-induced reduction in t hermal tolerance. Following a 3-h cold shock from 37 to 0 degrees C, the ma ximum denaturation temperature of the 50S ribosomal subunit and 70S ribosom al particle peak was reduced from 73.4 +/- 0.1 degrees C (mean +/- standard deviation) to 72.1 +/- 0.5 degrees C (P less than or equal to 0.05), indic ating that cold shock induced instability in the associated ribosome struct ure. The maximum denaturation temperature of the 30S ribosomal subunit peak did not show a significant shift in temperature (from 67.5 +/- 0.4 degrees C to 66.8 +/- 0.5 degrees C) as a result of cold shock, suggesting that ei ther 50S subunit or 70S particle sensitivity was responsible for the intact ribosome fragility. Antibiotics that elicited changes in maximum denaturat ion temperature in ribosomal components also elicited reductions in thermot olerance. Together, these data suggest that ribosomal changes resulting fro m cold shock may be responsible for the decrease in D value observed when L . monocytogenes is cold shocked.