Invasion and Persistence of Root-colonizing Beneficial Rhizobacterium Pseudomonas simiae Strain WCS417 in Arabidopsis thaliana

<p class="MsoNormal" style="margin: 0in; text-align: justify; text-indent: 0.5in; line-height: 32px;">Food insecurity is becoming an urgent problem as the world&rsquo;s population continues to grow amid worsening climate change. Heightened global greenhouse gas emissions annually increase the Earth&rsquo;s global average surface temperature and affect precipitation patterns, impairing plant physiology, ecosystem interactions, and crop distribution resulting in drought-stressed plants. Beneficial microbes isolated from soil or plant rhizospheres are a promising and eco-friendly solution to rescue plants from detrimental abiotic stress conditions. However, a major challenge lies in the successful application of microbial products from controlled, lab-based settings to natural, agricultural field environments. It was hypothesized that this unsuccessful administration may be due to failure to invade and persist in field settings, given there are heterogeneous plant-associated microbial communities already associated with crops in which inoculants must be able to invade and persist. In this experiment, we use&nbsp;<em>Pseudomonas simiae</em>&nbsp;WCS417, a model plant growth promoting rhizobacteria (PGPR) to understand the parameters controlling invasion and persistence of microbes in drought-stressed plants. We first confirmed the ability of WCS417 to rescue plants from drought stress using&nbsp;<em>in vitro&nbsp;</em>and soil-based screening assays. Next, a multi-soil assay of 13 diverse soil profiles from across the United States was employed to study WCS417 invasion and persistence in native bacterial communities. It was observed that despite varying survival success in diverse soils, WCS417 still consistently colonized&nbsp;<em>A. thaliana</em>&nbsp;seedlings<em>.</em>&nbsp;To further study invasion processes in depth, a complex bacterial synthetic community (SynCom) of 34 taxonomically diverse strains representing an approximate phylum level distribution observed in wild-type roots of&nbsp;<em>A. thaliana&nbsp;</em>will be used along with other publicly available collections. These strains will be used to study relationships between the invading PGPR and SynCom members individually and in association with the end goal of creating a rescuing and non-rescuing commensal SynCom to further study invasion and persistence of WCS417. These findings have important implications for agriculture because understanding how natural community members work together with PGPRs is essential to translating biostimulants from the lab into real agricultural field settings to promote plant growth under adverse stress conditions.