Pseudomonas putida as saviour for troubled Synechococcus elongatus in a synthetic co-culture – Interaction studies based on a multi-OMICs approach

Abstract In their natural environments, microbes rarely exist in isolation; instead, they thrive in consortia where diverse interactions take place. In this study, a defined synthetic co-culture of the cyanobacterium S. elongatus cscB , which feeds the heterotrophic P. putida cscRABY with sucrose, was investigated to identify potential interactions. In initial experiments, a remarkable growth-promoting effect brought about by the presence of the heterotrophic partner on the cyanobacterium was observed, leading to a growth rate increase of up to 80% and increased photosynthetic capacity. Vice versa, the cyanobacterium had a neutral effect on P. putida cscRABY , highlighting the resilience against stress of pseudomonads and their potential as co-culture partners. A suitable reference process reinforcing the growth-promoting effect was established in a parallel operating photobioreactor system, which sets the basis for the analysis of the co-culture at transcriptional, proteomic, and metabolomic level. This multi-OMICs approach revealed several moderate changes, including alterations in the metabolism, transportation, and stress response in both microbes, indicating multi-level interactions. These findings provide valuable insights into the complex dynamics within the co-culture system, suggesting the exchange of further molecules beyond the unidirectional feeding with sucrose.