Propionic acid toxicity and utilization of α-ketobutyric acid in <i>Neisseria meningitidis</i> via the methylcitrate cycle under specific conditions

Meningococci are metabolically versatile organisms, switching between intracellular and extracellular lifestyle during colonization and invasive disease. Niche switching impacts on how bacteria communicate with host to find a balance between nutrient assimilation and protection against toxicity of some metabolites. The methylcitrate pathway fulfills this function, providing a compromise between propionate assimilation and propionate detoxification, in relation to the colonized host microenvironments. In this study, we revealed an unexpected difference in the sensitivity of meningococci to propionate when grown with different carbon sources. We also characterized the function of a gene located within the prp operon that encodes a transporter of α-ketobutyrate, an α-ketoacid abundant in host cells. These results contribute to extending our understanding of the metabolic adaptation mechanisms, which are crucial for meningococcal infection and virulence within the host microenvironments.