Dual effect of organic acids as a function of external pH in Oenococcus oeni.
In this study we analyzed under various pH conditions including low pH, the effects of L-malic acid and citric acid, combined or not, on the growth, the proton motive force components and the transcription level of selected genes of the heterolactic bacterium Oenococcus oeni. It is shown here that L-malate enhanced the growth yield at pH equal or below 4.5 while the presence of citrate in media led to a complete and unexpected inhibition of the growth at pH 3.2. Nevertheless, whatever the growth conditions, both L-malate and citrate participated in the enhancement of the transmembrane pH gradient, whereas the membrane potential decreased with the pH. These results suggested that it was not citrate that was directly responsible for the inhibition observed in cultures done at low pH, but probably its end products. This was confirmed since, in media containing L-malate, the addition of acetate substantially impaired the growth rate of the bacterium and slightly the membrane potential and pH gradient. Finally, study of the expression of genes involved in the metabolism of organic acids showed that at pH 4.5 and 3.2 the presence of L-malate led to an increased amount of mRNA of mleP encoding a malate transporter.
Augagneur
Yoann
Y
Laboratoire de Microbiologie, UMR UB/INRA 1232, ENSBANA, Université de Bourgogne, 1 Esplanade Erasme, 21000, Dijon, France.
Ritt
Jean-François
JF
Linares
Daniel M
DM
Remize
Fabienne
F
Tourdot-Maréchal
Raphaëlle
R
Garmyn
Dominique
D
Guzzo
Jean
J
D001426:Bacterial Proteins / Q000235:genetics; D019343:Citric Acid / Q000494:pharmacology*; D015964:Gene Expression Regulation, Bacterial; D006863:Hydrogen-Ion Concentration; D007934:Leuconostoc / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D008293:Malates / Q000494:pharmacology*; D053858:Metabolic Networks and Pathways; D027361:Organic Anion Transporters / Q000235:genetics; D018892:Proton-Motive Force
D001426:Bacterial Proteins; D008293:Malates; D027361:Organic Anion Transporters; C098940:malate permease protein, Bacteria; D019343:Citric Acid; C030298:malic acid