Determinants of coumarin tolerance in Pseudomonas simiae WCS417

Abstract

Plants are in contact with many microbes, some of which can have a positive impact, while others might have a negative impact on plant health and growth. This makes it important for plants to be able to select for microbes inhabiting their direct surroundings. The plant-root exuded coumarin scopoletin appears to be part of such a selection mechanism by differentially inhibiting bacteria and fungi. Here, a plant-growth promoting bacterium showing high tolerance to scopoletin, Pseudomonas simiae WCS417, is investigated for its mechanism of tolerance for scopoletin, as well as its derivative fraxetin, by screening for random mutants showing increased susceptibility. Here, several mutants with reduced tolerance are isolated, but the genetic background has not yet been investigated. Additionally, the ability of P. simiae WCS417 to catabolize scopoletin is shown. Moreover, an iron-dependent growth-promoting effect of fraxetin on P. simiae WCS417 is shown. Furthermore, a new isolation and pre-screening method using the Isolation Bio Prospector system is explored, as well as a novel method for assessing chemotaxis in plant-microbe interactions studies by using a two-layer agar system.