Glycerol is metabolized in a complex and strain-dependent manner in Enterococcus faecalis

Area of Science:

• Microbiology
• Metabolic Engineering
• Molecular Biology

Background:

• Enterococcus faecalis possesses two glycerol dissimilation pathways: glpK and dhaK.
• The glpK pathway involves glycerol kinase and glycerol-3-phosphate oxidase.
• The dhaK pathway involves glycerol dehydrogenase and dihydroxyacetone kinase.

Purpose of the Study:

• To genetically investigate the roles of the glpK and dhaK pathways in E. faecalis glycerol metabolism.
• To determine the aerobic and anaerobic utilization of these pathways.
• To explore the diversity in glycerol catabolism among different E. faecalis isolates.

Main Methods:

• Construction of E. faecalis JH2-2 mutants deficient in both glycerol dissimilation pathways.
• Monitoring bacterial growth on glycerol under aerobic and anaerobic conditions.
• BLAST searching and real-time reverse transcriptase PCR for gene expression analysis.

Main Results:

• E. faecalis JH2-2 utilizes both glpK and dhaK pathways simultaneously under aerobic conditions, challenging the existing model.
• The dhaK pathway is confirmed as the primary route for anaerobic glycerol metabolism.
• Significant diversity in glycerol utilization strategies exists among E. faecalis strains, primarily due to differential gene expression rather than gene content variations.

Conclusions:

• The aerobic glycerol catabolism model for E. faecalis needs revision, as both glpK and dhaK pathways are active.
• Anaerobic glycerol metabolism predominantly relies on the dhaK pathway.
• Strain-specific gene expression patterns dictate the aerobic utilization of glycerol pathways in E. faecalis, highlighting species-level metabolic heterogeneity.