HEBERT Elvira Maria
congresos y reuniones científicas
Regulation of proteolytic system gene expression of Lactobacillus delbrueckii ssp. lactis CRL 581 by the peptide content of the growth medium
Simposio; 11th International Symposium on Lactic Acid Bacteria. HEALTH, SUSTAINABILITY, DIVERSITY, AND APPLICATION; 2014
Since lactic acid bacteria are unable to synthesize many essential amino acids, they possess a specialized proteolytic system that provides cells with essential amino acids during growth in milk, contributes to the development of the organoleptic properties of hard cheeses and can release bioactive health-beneficial peptides from milk proteins. Lactobacillus delbrueckii ssp. lactis CRL 581 possess a specialized proteolytic system that consists of a cell envelope-associated proteinase named PrtL, transport systems to allow the uptake of the resulting peptides, and several intracellular peptidases, which degrade peptides into amino acids. In this study, we demonstrated that PrtL activity was remarkably reduced in cells grown in the peptide-rich MRS medium compared to the proteolytic activity found in CDM, a peptide-free medium. Transcriptional analyses were performed to assess the dynamic response of CRL 581 cells grown in MRS and CDM. Reverse transcription quantitative PCR (qRT-PCR) was used to quantify the transcription level of fifteen genes (prtL, oppB, dppA, dppB, opts, optA, oppA, pepP, pepA, pepC, pepO, pepF, pepM, pepN, pepR) of the proteolytic system of CRL 581 cells grown in both media, with groEL, 16S, and recA as normalizing genes. The prtL gene was repressed 300-fold when CRL 581 cells were grown in MRS compared to the expression in CDM medium. Furthermore, all the transport systems genes evaluated (oppB, dppA, dppB, opts, optA, oppA) presented a significant reduced expression level in MRS (23 to 78 fold). Except pepP, which was repressed by the peptide content, the other aminopeptidases genes did not show difference in the expression levels. This is the first study describing the proteolytic system gene regulation of L. delbrueckii ssp. lactis by the growth media peptide content