Modulation of prtL gene expression of Lactobacillus delbrueckii subsp lactis CRL 581 depends on the peptide supply of the growth medium

ESPECHE TURBAY, B; SAVOY DE GIORI, G.; HÉBERT E

San Miguel de Tucumán, Argentina

Simposio; III Simposio Internacional de Bacterias Lácticas. Segundo encuentro Red BAL Argentina; 2009

CERELA

Lactobacillus delbrueckii subsp. lactis CRL 581, a thermophilic lactic acid bacteria used for the manufacture of hard cheeses, depends on a proteolytic system for growth in milk. This proteolytic system consists of a cell envelope-associated proteinase (PrtL), transports systems to allow uptake of the resultant peptides, and several intracellular peptidases for further degradation of the generated peptides. The first step in the breakdown of casein occurs via PrtL activity. The biological properties of PrtL have been previously characterized and its gene determinant was identified in our lab. The aim of this work was to analyze the expression of prtL during growth of L. delbrueckii subsp. lactis CRL 581 in media with different peptide supply, for such a chemically defined medium (CDM), CDM containing 1% Casitone and the complex rich peptide medium MRS were used. Reverse transcription quantitative PCR (RT-qPCR) was used to quantify the prtL transcript levels; the groEL gene was used as housekeeping gene control. The results of the present work indicated that PrtL synthesis is modulated by the peptide supply of the growth medium. The highest expression of prtL was observed during cell growth in basal CDM, while it was repressed in CDM supplemented with the rich peptide source Casitone or in MRS. Gene expression levels were correlated with phenotypic studies, using alpha-casein and a chromogenic peptide as substrates.