Glycerol is metabolized in a complex and strain-dependent manner in Enterococcus faecalis.
Enterococcus faecalis is equipped with two pathways of glycerol dissimilation. Glycerol can either first be phosphorylated by glycerol kinase and then oxidized by glycerol-3-phosphate oxidase (the glpK pathway) or first be oxidized by glycerol dehydrogenase and then phosphorylated by dihydroxyacetone kinase (the dhaK pathway). Both pathways lead to the formation of dihydroxyacetone phosphate, an intermediate of glycolysis. It was assumed that the glpK pathway operates during aerobiosis and that the dhaK pathway operates under anaerobic conditions. Because this had not been analyzed by a genetic study, we constructed mutants of strain JH2-2 affected in both pathways. The growth of these mutants on glycerol under aerobic and anaerobic conditions was monitored. In contrast to the former model, results strongly suggest that glycerol is catabolized simultaneously by both pathways in the E. faecalis JH2-2 strain in the presence of oxygen. In accordance with the former model, glycerol is metabolized by the dhaK pathway under anaerobic conditions. Comparison of different E. faecalis isolates revealed an impressive diversity of growth behaviors on glycerol. Analysis by BLAST searching and real-time reverse transcriptase PCR revealed that this diversity is based not on different gene contents but rather on differences in gene expression. Some strains used preferentially the glpK pathway whereas others probably exclusively the dhaK pathway under aerobic conditions. Our results demonstrate that the species E. faecalis cannot be represented by only one model of aerobic glycerol catabolism.
Bizzini
Alain
A
Laboratoire de Microbiologie de l'Environnement, Université de Caen, EA956 USC INRA2017 IFR 146, 14032 Caen Cedex, France.
Zhao
Chen
C
Budin-Verneuil
Aurélie
A
Sauvageot
Nicolas
N
Giard
Jean-Christophe
JC
Auffray
Yanick
Y
Hartke
Axel
A
D000332:Aerobiosis; D000693:Anaerobiosis; D013293:Enterococcus faecalis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D005990:Glycerol / Q000378:metabolism*; D005993:Glycerolphosphate Dehydrogenase / Q000235:genetics / Q000502:physiology; D006861:Hydrogen Peroxide / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017384:Sequence Deletion; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D013401:Sugar Alcohol Dehydrogenases / Q000235:genetics / Q000502:physiology
D006861:Hydrogen Peroxide; D005993:Glycerolphosphate Dehydrogenase; D013401:Sugar Alcohol Dehydrogenases; C020672:glycerol dehydrogenase; C098831:glycerol-3-phosphate oxidase; D005990:Glycerol