Relationships between arginine degradation, pH and survival in Lactobacillus sakei

Lactobacillus sakei is one of the most important lactic acid bacteria of me at and fermented meat products, It is able to degrade arginine with ammonia and ATP production by the arginine deiminase pathway (ADI). This pathway i s composed of three enzymes: arginine deiminase, ornithine transcarbamoylas e and carbamate kinase, and an arginine transport system. The transcription of the ADI pathway is induced by arginine and subjected to catabolite repr ession. In order to understand the physiological role of the degradation of this amino acid we investigated the growth of bacteria under various condi tions. We show that arginine degradation is responsible for an enhanced via bility during the stationary phase when cells are grown under anaerobiosis. Arginine is necessary for the induction of the ADI pathway but in associat ion with another environmental signal. Using a mutant of the L-lactate dehy drogenase unable to lower the pH we could clearly demonstrate that (i) low pH is not responsible for cell death during the stationary phase, so surviv al is due to another factor than elevated pH, (ii)neither low pH nor oxygen limitation is responsible for the induction of the ADI pathway together wi th arginine since the ldhL. mutant is able to degrade arginine under aerobi osis. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.