Lactobacillus sakei is a lactic acid bacterium belonging to the natural flora of fresh meat and is used as starter for the manufacturing of fermented sausages. Added at the beginning of the process it is developing rapidly. Its acid production leads to protein coagulation and takes part in development of the characteristic flavour of these products. It has also an inhibitory effect towards pathogenic or spoilage bacterial species. To understand its adaptation to meat and factors favouring its implantation, we studied the response developed by this bacterium to its environment with two examples corresponding to situations found during technological processes: presence of NaCl or low temperature, We first studied the physiological consequences of temperature and salt concentration in a chemically defined medium on L. sakei 23K, a strain isolated from sausage. In order to study the targets of this adaptation, we have used the two-dimensional electrophoresis technique for a proteomic approach. We focused on proteins with significant expression variations. One of them was identified as 6-phosphofructokinase (PFK), an enzyme of the glycolytic pathway. The gene coding for PFK (pfk) was cloned and a mutant was constructed. The growth of this mutant was modified in the presence of salt or at low temperature.