Distinct Roles of Transketolase (TktA) and Transaldolase (talB) in Metabolism, Biofilm Formation, and Flea Colonization in Yersinia pestis.

The flea-borne transmission of Yersinia pestis relies on biofilm formation and metabolic adaptation within the insect gut. The pentose phosphate pathway (PPP) is central to these processes, yet the contribution of its non-oxidative branch remains poorly defined. Here, we investigated the roles of transketolase (TktA) and transaldolase (TalB) in plague bacillus physiology, metabolism, and flea colonization. TktA was essential for growth, preventing assessment of its role in biofilm formation and in vivo colonization. In contrast, TalB was dispensable for growth but required for optimal biofilm formation. In fleas, the ΔtalB mutant colonized the proventriculus but displayed a lower bacterial load than the wild-type strain at later time points, indicating a defect in sustained colonization. Metabolomic analyses revealed that disruption of tktA severely impairs PPP-associated metabolism, whereas loss of talB is associated with disruption of nucleotide homeostasis, carbon redistribution toward glycolysis, and a redox imbalance. These findings demonstrate a functional partitioning of the non-oxidative PPP and identify it as a key metabolic control node linking metabolism to colonization dynamics in Y. pestis.