Romestaing, C. | Search bioRxiv

bioRxiv2026

The functional plasticity of the YhdWXYZ ABC transporter enables antibiotic homeostasis and host colonisation in enteric bacteria

ABC transporters are key determinants of bacterial adaptation, yet their functional plasticity remains poorly understood. Here, we characterize the type I ABC transporter YhdWXYZ and uncover a striking functional divergence linked to the presence of its substrate-binding protein (SBP). In Escherichia coli K-12, where yhdW is a pseudogene, deletion of yhdWXYZ increases susceptibility to mecillinam and lomefloxacin and leads to intracellular accumulation of lomefloxacin, indicating a role in antibiotic homeostasis. In contrast, in Citrobacter rodentium, which encodes a complete YhdWXYZ system, deletion of the transporter does not affect antibiotic susceptibility. Biochemical analyses demonstrate that the YhdW SBP of C. rodentium binds asparagine with high affinity; however, genetic and physiological assays indicate that YhdWXYZ is not a primary asparagine importer under laboratory conditions, suggesting redundancy with other transport systems. Importantly, in vivo infection experiments reveal that YhdWXYZ contributes to early colonization and persistence in the host, as mutants display reduced bacterial loads and altered intestinal pathology in mice. Together, these findings show that loss of the SBP in E. coli is associated with a functional shift of YhdWXYZ toward antibiotic homeostasis, whereas in C. rodentium, the complete transporter contributes to host adaptation. This work highlights the evolutionary and functional flexibility of ABC transporters in bacterial physiology and pathogenesis.

microbiology↗

bioRxiv2019

Erythroid differentiation displays a peak of energy consumption concomitant with glycolytic metabolism rearrangements

It has been suggested that a switch from glycolysis, with lactate production, toward mitochondrial oxidative phosphorylation (OXPHOS) could be a driving force during stem cell differentiation.\n\nBased upon initial results, from our previous work, showing a drop in LDHA mRNA level during the differentiation of chicken erythroid progenitors, we studied metabolism behavior to question whether such switch might also be operating in those cells.\n\nWe first analyzed the level of 9 enzymes, including LDHA, involved either in glycolysis or OXPHOS, in self-renewing and differentiating cells. Our results suggest that erythroid differentiation might be accompanied by an enhancement of the respiratory chains and glycolysis activities at 12h, followed by a strong decline of the glycolytic pathway and a stabilization of OXPHOS.\n\nTo confirm that OXPHOS might be increased and glycolysis decreased during erythroid differentiation, we measured lactate concentration and mitochondrial membrane potential (MMP) of self-renewing and differentiating cells. Our findings show that at 12h-24h of differentiation, a surge of energy is needed, which could be fueled jointly by glycolysis and OXPHOS. Then the energy demand comes back to normal and might be supplied by OXPHOS instead of lactate production through glycolysis.\n\nThese results support the hypothesis that erythroid differentiation is associated with a metabolic switch from glycolysis to OXPHOS.\n\nWe also assessed LDHA role in erythroid progenitors self-renewal and the metabolic status changes. Inhibition experiments showed that LDHA activity could be involved in the maintenance of erythroid progenitors self-renewal, and its decline could influence their metabolic status.\n\nFinally, we investigated whether these metabolic rearrangements were necessary for erythroid differentiation. The addition of an inhibitor of the respiratory chains affected progenitors ability to differentiate, suggesting that the metabolic switch from glycolysis toward OXPHOS might act as a driving force for erythroid differentiation.\n\nAuthor summarySingle-cell based gene expression data from one of our previous publication pointed out significant variations of LDHA level, an important metabolism player, during erythroid differentiation. Deeper investigations highlighted that a metabolic switch occurred along differentiation of erythroid cells as previously emphasized in stem cell differentiation. More precisely our finding showed that self-renewing progenitor cells relied mostly upon a glycolytic, lactate-productive, metabolism and required LDHA activity, whereas differentiating cells, mainly involved the aerobic mitochondrial oxidative phosphorylation (OXPHOS). However our careful kinetic study demonstrated that these metabolic rearrangements were coming along with a particular temporary event, occurring within the first 24h of erythroid differentiation. The activity of glycolytic metabolism and OXPHOS rose jointly with ATP production at 12-24h of the differentiation process before lactate-productive glycolysis sharply fall down and energy needs decline. Finally, our results showed that the metabolic switch mediated through LDHA drop and OXPHOS upkeep might be necessary for erythroid differentiation. We also discuss the possibility that metabolism, gene expression and epigenetics could act together in a circular manner as a driving force for differentiation.

cell biology↗