title: Rerouting of pyruvate metabolism during acid adaptation in Lactobacillus bulgaricus.
abstract: Lactic acid bacteria (LAB) gradually acidify their environment through the conversion of pyruvate to lactate, an essential process to regenerate NAD(+) used during glycolysis. A clear demonstration of acidification can be found in yogurt, the product of milk fermentation by the LAB Lactobacillus delbrueckii ssp. bulgaricus (L. bulgaricus) and Streptococcus thermophilus, where the pH falls to 4.2. Acid adaptation therefore plays an important role in the physiology of LAB. Here we present the results of a proteomic approach to reveal cellular changes associated with acid adaptation in L. bulgaricus. These results were complemented with transcription data for selected genes to show three major effects: (i) induction of the chaperones GroES, GroEL, HrcA, GrpE, DnaK, DnaJ, ClpE, ClpP, and ClpL, and the repression of ClpC; (ii) induction of genes involved in the biosynthesis of fatty acids (fabH, accC, fabI); (iii) repression of genes involved in the mevalonate pathway of isoprenoid synthesis (mvaC, mvaS). Together with changes in the expression of other genes from the local metabolic network, these results for the first time show a coherent picture of changes in gene expression expected to result in a rerouting of pyruvate metabolism to favor fatty acid biosynthesis, and thereby affect membrane fluidity.
authors.affiliation: INRA, Génétique Microbienne, Domaine de Vilvert, Jouy en Josas, France.
authors.forename: Annabelle
authors.initials: A
authors.lastname: Fernandez
authors.forename: Jun
authors.initials: J
authors.lastname: Ogawa
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Penaud
authors.forename: Samira
authors.initials: S
authors.lastname: Boudebbouze
authors.forename: Dusko
authors.initials: D
authors.lastname: Ehrlich
authors.forename: Maarten
authors.initials: M
authors.lastname: van de Guchte
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Maguin
mesh_terms: D000222:Adaptation, Physiological; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018835:Chaperonin 10 / Q000378:metabolism; D018834:Chaperonin 60 / Q000378:metabolism; D003470:Culture Media / Q000494:pharmacology; D015180:Electrophoresis, Gel, Two-Dimensional; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007778:Lactobacillus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D016133:Polymerase Chain Reaction; D019289:Pyruvic Acid / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D018835:Chaperonin 10; D018834:Chaperonin 60; D003470:Culture Media; C068113:GrpE protein, Bacteria; D006360:Heat-Shock Proteins; D019289:Pyruvic Acid