GNPS - Mechanism for Utilization of the Populus-Derived Metabolite Salicin by a Pseudomonas—Rahnella Co-Culture

Pseudomonas sp. GM16 associates with Populus, a model plant in biofuel production. Populus releases abundant phenolic glycosides such as salicin, but Pseudomonas sp. GM16 cannot utilize salicin whereas Pseudomonas strains are known to utilize compounds similar to the aglycone moiety of salicin – salicyl alcohol. We propose that the association of Pseudomonas to Populus is mediated by another organism (such as Rahnella sp. OV744) that degrades the glucosyl group of salicin. In this study, we demonstrate that in the Rahnella-Pseudomonas salicin co-culture model, Rahnella grows by degrading salicin to glucose 6-phosphate and salicyl alcohol which is secreted out and is subsequently utilized by Pseudomonas for its growth. Using various quantitative approaches, we elucidate the individual pathways for salicin and salicyl alcohol metabolism present in Rahnella and Pseudomonas, respectively. Furthermore, we were able to establish that the salicyl alcohol cross-feeding interaction between the two strains on salicin medium is carried out through combination of their respective individual pathways. The research presents one of the potential advantages of salicyl alcohol release by strains such as Rahnella, and how phenolic glycosides could be involved in attracting multiple types of bacteria into the Populus microbiome.