Pseudomonas kielensis strain:KPP123 Genome sequencing. Pseudomonas kielensis strain:KPP123

The goal of this project was to develop a screen that can identify bacterial redox-active metabolites at the plant root. Many interactions both between and among plants and microbes is governed by small bioactive molecules or "secondary metabolites". It is incredibly difficult to study these secondary metabolites, given that under most standard laboratory conditions, secondary metabolite biosynthesis genes are silent or weakly expressed. To address this challenge, we developed a screen that leverages phosphorus limitation to stimulate secondary metabolite biosynthesis and uses a colorimetric (ferrozine) iron-reduction assay to identify redox activity. From this screen, multiple bacteria, including a Pseudomonas kielensis soil isolate, were found to produce redox-active metabolites in response to phosphorus limitation. Our work reveals that redox-active metabolite production in response to phosphorus limitation is common across diverse soil bacteria and provides an approach to screen for these small molecules rapidly.