Lactococcus lactis, a bacterial model for stress responses and survival

The dairy organism, Lactococcus lactis, is continuously exposed to stress c onditions generated during industrial processes. To identify the mechanisms that confer resistance to the lethal effects of oxygen and thermal stress, we isolated resistant strains by insertional mutagenesis. Mutated genes we re identified and mutations were shown to confer resistance to multiple str esses (including non-selected stresses such as carbon starvation). Our resu lts revealed that metabolic flux plays an important role in L. lactis stres s response, and suggested that phosphate and guanine pools may be intracell ular stress sensors. As previously shown, we also observed an increase of s tress resistance during the stationary phase. We have evidence that station ary phase actually initiates very early during growth. Taken together; thes e data show that the stationary phase is a very complex system with multipl e participants interacting altogether. These results reinforce the idea of the interdependence of stress response and the intimate relation between me tabolic flux and stress responses in L. lactis. (C) 2000 Elsevier Science B .V. All rights reserved.