Lactobacillus sakei is a lactic acid bacterium widely represented in the natural flora of fresh meat. The aim of this study was to analyze the differences in protein expression during environmental changes encountered during technological processes in which L. sakei is involved in order to gain insight into the ability of this species to grow and survive in such environments. Using two-dimensional electrophoresis, we observed significant variation of a set of 21 proteins in cells grown at 4°C or in the presence of 4% NaCl. Six proteins could be identified by determination of their N-terminal sequences, and the corresponding gene clusters were studied. Two proteins belong to carbon metabolic pathways, and four can be clustered as general stress proteins. A phenotype was observed at low temperature for five of the six mutants constructed for these genes. The survival of four mutants during stationary phase at 4°C was affected, and surprisingly, one mutant showed enhanced survival during stationary phase at low temperatures.

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Lactobacillus sakei is a lactic acid bacterium belonging to the natural flora of fresh and vacuum-packed meat, and is used as the starter for manufacturing fermented sausages. This species is now being studied at the genetic level. We investigated uracil prototrophy of strain 23K in order to validate the proteomic approach to study metabolism regulations. Cells grown without uracil had lower growth rates than with uracil. Protein analysis by 2D gel electrophoresis showed that at least three polypeptides were specifically induced in the absence of uracil. Two of these polypeptides were identified as orotate phosphoribosyl transferase, catalyzing the fifth step of pyrimidine biosynthesis, and PyrR, the transcriptional regulator of the pyr operon, respectively.

Lactobacillus sakei is a lactic acid bacterium belonging to the natural flora of meat products. It constitutes the main flora of vacuum-packed meat and is largely used in western Europe as a starter for the manufacturing of fermented sausages. This species is able to grow both under aerobiosis and anaerobiosis. In many technological processes involving it, oxygen is scarce. The aim of this study was to identify the major proteins affected by growth under anaerobiosis. Using two-dimensional electrophoresis, we showed that one spot was 10-fold overexpressed when cells were grown under anaerobiosis. By N-terminal sequencing it was identified as a peptidase (PepR), and the pepR gene was cloned. Northern analysis revealed that pepR was expressed as a single 1.27-kb transcript induced under anaerobiosis. A mutant was constructed by single crossover in the pepR gene, and its growth and survival were not affected by anaerobiosis.