Figure 6. Model of the role of respiration in L. monocytogenes pathogenesis.

On the left, an intracellular bacterium with the ability to oxidize NADH and transfer electrons through the aerobic and extracellular electron transfer electron transport chains can regenerate and maintain high NAD⁺ levels allowing the bacterium to grow and be virulent. On the right, an intracellular bacterium unable to regenerate NAD⁺, by lacking the electron transport chains, is avirulent because it lyses in the cytosol of infected cells.