Global analysis of the proteolytic system of Lactobacillus delbrueckii subsp. lactis.

BROWN, L.; VILLEGAS, J.M.; SAAVEDRA, L.; MOZZI, F.; HEBERT, E.M.

Simposio; 12th Symposium on Lactic Acid Bacteria.; 2017

Lactobacillusdelbrueckii subsp. lactis CRL 581 is a thermophilic lactic acid bacterium usedas a starter culture in the cheese industry. This strain has a specializedproteolytic system essential for bacterial growth in milk, which is alsoinvolved in flavor development of fermented products and can releasehealth-beneficial bioactive peptides. Considering the industrial importance ofthis system and the scarce information about its regulation in Lactobacillus,we aimed to perform a global analysis of all genes involved in the proteolyticsystem of L. delbrueckii subsp. lactis CRL 581 and to study the effect of thepeptide supply on the expression of several components of this system. Genesencoding the cell envelope-associated proteinase (prtL), peptide transportsystems (opp and opt) and sixteen peptidases (pepM, pepP, pepC, pepA, pepO,pepN, pepF, pepR, pepD, pepG, pepI, pepQ, pepT, pepV, pepX and pepL) wereidentified by in silico analysis. The influence of the peptide supply on thetranscription of these 23 genes when L. delbrueckii subsp. lactis grew in achemically defined medium (CDM) and CDM plus Casitone was examined by qRT-PCRanalysis. prtL, oppA1, optS, optA and the oppDFBC and optBCDF operons were thehighest expressed genes in CDM; their expression being repressed 6- to 115-foldby the presence of Casitone. Consistently, the proteomic approach showed anupregulation of PrtL, PepG, OppD and OptF. Also, growth in CDM led to theupregulation of proteins related to glycolysis, amino acids and purinemetabolism. This is the first report to correlate transcriptional and proteomicanalysis of the proteolytic system of L. delbrueckii subsp. lactisdemonstrating that the biosynthesis of some components are regulated by thenitrogen source of the medium