HEAT-SHOCK INDUCES THERMOTOLERANCE AND INHIBITION OF LYSIS IN A LYSOGENIC STRAIN OF LACTOCOCCUS-LACTIS

In this preliminary work, the heat shock response of lactic acid bacteria was investigated and characterized. Log-phase Lactococcus lactis cells pre-incubated at 40-degrees-C before heat challenge at 52-degrees-C for 30 min demonstrated increased thermotolerance as compared with cells pre-incubated at 30-degrees-C. The response persisted for at least 60 min. Additionally, we demonstrated that: (i) the physiological expression of the heat shock response is temperature dependent; (ii) ethanol 4.0% (v/v) caused, to a lesser extent, a response similar to the heat shock; and (iii) hydrogen peroxyde failed to induce a detectable response. Furthermore, we suggest that the induction of the heat shock response increases the resistance of a lysogenic strain of L. lactis, treated by mitomycin C (1.25-mu-g/ml), to lysis by the bacteriophage.