Understanding LrgAB Regulation of Metabolism.

Lack of LrgAB renders cariogenic more sensitive to oxidative stress, as well as limits the capacity of this organism to re-uptake pyruvate upon starvation. This study was aimed at investigating the ecological and metabolic contribution of LrgAB to competitive fitness, using strains, that either lack or overexpress . These experiments revealed that impaired aerobic growth of the Δ mutant can be effectively restored by supplementation of pyruvate, and that perturbated expression of significantly affects pyruvate flux and the conversion of pyruvate to acetyl-CoA by the Pdh pathway, verifying that LrgAB is closely linked to pyruvate catabolism. competition assays revealed that LrgAB plays an important role in competition with HO-producing , an interaction which can also be modulated by external pyruvate. However, no obvious competitive disadvantage was observed against by either the mutant or overexpression strain using a mouse caries model. Organic acid analysis of mouse dental biofilms revealed that metabolites produced by the host and/or dental plaque microbiota could complement the deficiency of a mutant, and favored establishment compared to . Collectively, these results reinforce the importance of the oral microbiota and the metabolic environment in the oral cavity battleground, and highlight that pyruvate uptake through LrgAB may be crucial for interspecies competition that drives niche occupancy.