Impact of multiple stress factors on the survival of dairy lactobacilli

in order to understand growth, stability and behaviour in response to cultu ring conditions of dairy lactobacilli, we investigated the impact of Variou s conditioning stress treatments on the survival of selected strains. Heat- treatment or a sublethal osmotic shock improved the resistance to subsequen t freeze-drying and storage. The groES/groEL chaperone operon was found in these strains. Furthermore, a second chaperone machine (dnaK, dnaJ, grpE an d hrcA) was detected and a model for their regulation was adapted. The tran scription activity of the two major chaperone machines in response to vario us stresses was evaluated (Dot-Blot and Northern-Blot). Initial results sug gested improved viability under certain stress-conditions. We observed that the induction of stress-proteins might improve survival of bacterial strai ns, including dairy lactobacilli used as starter-cultures. Consequently, th e assessment of the genetic basis for this physiological behaviour requires further investigation.