Rescue of pyrimidine-defective through metabolic complementation.

Unlabelled: Chronic infections harbor multiple pathogens where dynamic interactions between members of the polymicrobial community play a major role in determining the infection outcome. For example, in a nutrient-rich polymicrobial infection, bacteria have the potential to undergo evolutionary changes that impair their ability to synthesize essential metabolites. This adaptation may facilitate metabolic interdependencies between neighboring pathogens and lead to difficult-to-treat chronic infections. Our research group previously demonstrated that (PA) and (SA), typically considered classical competitors, can adopt a cooperative lifestyle through bi-directional purine exchange medicated by exogenous DNA (eDNA) release. To further validate our initial findings, in this study, we investigated the potential exchange of pyrimidine between PA and other pathogens, which is another constituent of DNA. In our findings, we observed that a pyrimidine-deficient transposon mutant strain of PA showed improved growth when co-cultured with wild-type PA, SA, (AB), and (EF). Additionally, improved fitness of pyrimidine-deficient PA was further observed in chemical complementation with eDNA and uridine-5'-monophosphate. Interestingly, the rescue of PA growth through eDNA complementation is not as effective as in intact cells, such as SA, AB, EF, and wild-type PA, implying that eDNA is a lesser contributor to this metabolic complementation. Also, the exchange mechanism between pathogens involves more active mechanisms beyond simple eDNA or metabolite release. Our data further highlights the importance of cell-to-cell contact for effective and increased metabolic complementation.

Importance: This research holds crucial implications for combating chronic infections, where multiple pathogens coexist and interact within the same environment. By uncovering the dynamic exchange of pyrimidines between (PA) and (SA), our study reveals a previously unrecognized aspect of interspecies cooperation. The observed enhanced growth of a pyrimidine-deficient PA strain when co-cultured with SA suggests potential avenues for understanding and disrupting bacterial metabolic interdependencies in chronic infection settings. Furthermore, our findings highlight the mechanisms involved in metabolic exchange, emphasizing the importance of cell-to-cell contact. This research explored essential metabolic interactions to address the challenges posed by difficult-to-treat chronic infections.