Extracellular Electron Transfer Powers Enterococcus faecalis Biofilm Metabolism

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Metabolic Engineering

Background:

• Enterococci are common human bacteria that can cause opportunistic infections.
• Biofilm formation by enterococci leads to chronic, treatment-resistant infections.
• The biofilm matrix alters bacterial properties, increasing tolerance to antimicrobials.

Purpose of the Study:

• To investigate iron-dependent metabolic pathways in Enterococcus faecalis.
• To understand how metabolic factors influence biofilm formation and pathogenicity.
• To elucidate the role of l-lactate dehydrogenase in iron-augmented biofilm growth.

Main Methods:

• Studied iron-dependent metabolism in Enterococcus faecalis.
• Analyzed biofilm matrix composition and depth.
• Investigated the role of the ldh gene in energy production and extracellular electron transfer (EET).

Main Results:

• Iron, in the absence of heme, enhances Enterococcus faecalis biofilm growth.
• Extracellular electron transfer (EET) and increased ATP production are key to iron-augmented biofilm growth.
• The l-lactate dehydrogenase (ldh) gene is essential for iron-augmented energy production, biofilm formation, and EET.

Conclusions:

• The biofilm matrix can immobilize iron, making it accessible for bacterial metabolism.
• Enterococcus faecalis utilizes matrix-associated iron for EET via l-lactate dehydrogenase when heme is unavailable.
• Iron availability within the biofilm matrix significantly promotes enterococcal biofilm growth and persistence.