HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Courtin, P. Articles by Rul, F. Search for Related Content PubMed PubMed Citation Articles by Courtin, P. Articles by Rul, F. Agricola Articles by Courtin, P. Articles by Rul, F.

Cell-wall proteinases PrtS and PrtB have a different role in Streptococcus thermophilus/Lactobacillus bulgaricus mixed cultures in milk

Unité de Biochimie et Structure des Protéines, INRA, 78352 Jouy-en-Josas Cedex, France¹

Author for correspondence: F. Rul. Tel: +33 1 34 65 21 48. Fax: +33 1 34 65 21 63. e-mail: rul{at}jouy.inra.fr

The manufacture of yoghurt relies on the simultaneous utilization of two starters: Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus (Lb. bulgaricus). A protocooperation usually takes place between the two species, which often results in enhanced milk acidification and aroma formation compared to pure cultures. Cell-wall proteinases of Lactococcus lactis and lactobacilli have been shown to be essential to growth in milk in pure cultures. In this study, the role of proteinases PrtS from S. thermophilus and PrtB from Lb. bulgaricus in bacterial growth in milk was evaluated; a negative mutant for the prtS gene of S. thermophilus CNRZ 385 was constructed for this purpose. Pure cultures of S. thermophilus CNRZ 385 and its PrtS-negative mutant were made in milk as well as mixed cultures of S. thermophilus and Lb. bulgaricus: S. thermophilus CNRZ 385 or its PrtS-negative mutant was associated with several strains of Lb. bulgaricus, including a PrtB-negative strain. The pH and growth of bacterial populations of the resulting mixed cultures were followed, and the Lactobacillus strain was found to influence both the extent of the benefit of Lb. bulgaricus/S. thermophilus association on milk acidification and the magnitude of S. thermophilus population dominance at the end of fermentation. In all mixed cultures, the sequential growth of S. thermophilus then of Lb. bulgarius and finally of both bacteria was observed. Although proteinase PrtS was essential to S. thermophilus growth in milk in pure culture, it had no effect on bacterial growth and thus on the final pH of mixed cultures in the presence of PrtB. In contrast, proteinase PrtB was necessary for the growth of S. thermophilus, and its absence resulted in a higher final pH. From these results, a model of growth of both bacteria in mixed cultures in milk is proposed.

Keywords: bacterial growth, milk fermentation, thermophilic bacteria

Abbreviations: FSDA, Fast Slow Difference Agar; LAB, lactic acid bacterium/bacteria

This article has been cited by other articles:

				S. Sieuwerts, F. A. M. de Bok, J. Hugenholtz, and J. E. T. van Hylckama Vlieg Unraveling Microbial Interactions in Food Fermentations: from Classical to Genomics Approaches Appl. Envir. Microbiol., August 15, 2008; 74(16): 4997 - 5007. [Full Text] [PDF]

				S. Arioli, C. Monnet, S. Guglielmetti, C. Parini, I. De Noni, J. Hogenboom, P. M. Halami, and D. Mora Aspartate Biosynthesis Is Essential for the Growth of Streptococcus thermophilus in Milk, and Aspartate Availability Modulates the Level of Urease Activity Appl. Envir. Microbiol., September 15, 2007; 73(18): 5789 - 5796. [Abstract] [Full Text] [PDF]

				S. Derzelle, A. Bolotin, M.-Y. Mistou, and F. Rul Proteome Analysis of Streptococcus thermophilus Grown in Milk Reveals Pyruvate Formate-Lyase as the Major Upregulated Protein Appl. Envir. Microbiol., December 1, 2005; 71(12): 8597 - 8605. [Abstract] [Full Text] [PDF]

				O. Juille, D. L. Bars, and V. Juillard The specificity of oligopeptide transport by Streptococcus thermophilus resembles that of Lactococcus lactis and not that of pathogenic streptococci Microbiology, June 1, 2005; 151(6): 1987 - 1994. [Abstract] [Full Text] [PDF]

				F. Vaningelgem, M. Zamfir, F. Mozzi, T. Adriany, M. Vancanneyt, J. Swings, and L. De Vuyst Biodiversity of Exopolysaccharides Produced by Streptococcus thermophilus Strains Is Reflected in Their Production and Their Molecular and Functional Characteristics Appl. Envir. Microbiol., February 1, 2004; 70(2): 900 - 912. [Abstract] [Full Text] [PDF]