Adaptation to high salt in Lactobacillus: Role of peptides and proteolytic enzymes

PIURI M; SANCHEZ RIVAS C; RUZAL SM

JOURNAL OF APPLIED MICROBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2003 vol. 95 p. 372 - 379

1364-5072

Aims: To study the influence of peptides and proteolytic enzymes in the osmotic adaptation of Lactobacillus casei.Methods and Results: Di- and tri-peptides added individually increased the osmotolerance of Lact. caseiwhen grown in a chemically defined medium (CDM) containing NaCl. Growth stimulation and the reestablishmentin their presence of plasmid DNA supercoiling (recovery of the linking number) in hyperosmoticmedium indicated that they are used as osmocompatible solutes as carnithine a known osmoprotector does.The investigation of the proteolytic system showed that in high osmolarity medium, the cell envelope-associatedproteinase (PrtP), and PepX (X-prolyl-dipeptidyl aminopeptidase) increased activity and lost repression bypeptides. PepI, an iminopeptidase was also derepressed. PepQ, a prolidase that specifically liberated prolinefrom dipeptides, was almost unaffected. Derepression in the presence of peptides took place at the transcriptionallevel. However, the twofold activation of PrtP in CDM hyperosmotic medium was essentially through anincrease of the apparent Vmax of the enzyme.Conclusions: These results strongly suggest a contribution of the proteolytic system peptide supply in theosmotic adaptation.Significance and Impact of the Study: Advances in understanding the role of peptides in the adaptation to highosmolarity particularly involved in dairy processes.