RESUMO
AIMS: Growth of the lactic acid bacterium (LAB) Oenococcus oeni, which is involved in malolactic fermentation during the winemaking process, is stimulated by peptides originating from yeast. In this study, we investigated the impact of peptides on O. oeni growth, peptidase activity and the expression of genes encoding the studied peptidases. METHODS AND RESULTS: Low levels of PepN activity and very high levels of PepI activity were observed in O. oeni, whereas levels of PepX activity were intermediate. The level of biosynthesis of these O. oeni peptidases was shown to depend on peptides present in the culture medium. These results were confirmed by transcriptional analyses of putative pep genes. The mechanism of repression by peptides did not involve a CodY-like regulator. CONCLUSIONS: Peptides from yeast decrease the levels of enzymatic activity and relative gene expression of O. oeni peptidases. Peptidases specific for proline-containing peptides are important for O. oeni nitrogen metabolism. SIGNIFICANCE AND IMPACT OF THE STUDY: We report here for the first time that the enzymes involved in the assimilation of proline-containing peptides by O. oeni differ from the well-described proteolytic system of milk LAB. This may reflect a specific adaptation to the wine environment.
Assuntos
Oenococcus/enzimologia , Peptídeo Hidrolases/metabolismo , Cromatografia Líquida de Alta Pressão , Primers do DNA , Ensaio de Desvio de Mobilidade Eletroforética , Regulação da Expressão Gênica , Nitrogênio/metabolismo , Oenococcus/genética , Peptídeo Hidrolases/genética , Regiões Promotoras Genéticas/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Análise de Sequência de DNARESUMO
AIMS: Oenococcus oeni is a slow-growing wine bacterium with a low growth yield. It thrives better on complex nitrogen sources than on free amino-acid medium. We aimed to characterize the oligopeptide use of this micro-organism. METHODS AND RESULTS: Several peptides of two to eight amino-acid residues were able to provide essential amino acids. The disappearance of various peptides from extracellular medium was assessed with whole cells. Initial rates of utilization varied with the peptide, and free amino acids were released into the medium. CONCLUSIONS: Oenococcus oeni was able to transport the oligopeptides with two to five amino-acid residues tested and to hydrolyse them further. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has clear implications for the relationship between wine nitrogen composition and the ability of O. oeni to cope with its environment.