The pentose phosphate pathway constitutes a major metabolic hub in pathogenic Francisella.

Metabolic pathways are now considered as intrinsic virulence attributes of pathogenic bacteria and thus represent potential targets for antibacterial strategies. Here we focused on the role of the pentose phosphate pathway (PPP) and its connections with other metabolic pathways in the pathophysiology of Francisella novicida. The involvement of the PPP in the intracellular life cycle of Francisella was first demonstrated by studying PPP inactivating mutants. Indeed, we observed that inactivation of the tktA, rpiA or rpe genes severely impaired intramacrophage multiplication during the first 24 hours. However, time-lapse video microscopy demonstrated that rpiA and rpe mutants were able to resume late intracellular multiplication. To better understand the links between PPP and other metabolic networks in the bacterium, we also performed an extensive proteo-metabolomic analysis of these mutants. We show that the PPP constitutes a major bacterial metabolic hub with multiple connections to glycolysis, the tricarboxylic acid cycle and other pathways, such as fatty acid degradation and sulfur metabolism. Altogether our study highlights how PPP plays a key role in the pathogenesis and growth of Francisella in its intracellular niche. Author summary: Metabolic pathways are intimately associated with the virulence of pathogenic bacteria and are therefore interesting antibacterial targets. Here we focused on the role of the pentose phosphate pathway (PPP) in the intracellular life cycle of the bacterium Francisella novicida. We were able to show, by combining genetic and imaging approaches, that this pathway was a major contributor to the intracellular survival of the bacterium. Complementary proteomics and metabolomics approaches revealed that PPP was at the crossroads of many other metabolic pathways. This work has thus allowed us to better understand the key role played by the PPP in the survival of Francisella in its intracellular niche. [ABSTRACT FROM AUTHOR]