Soil Dwelling Streptomyces Inhibit Arabidopsis Seed Germination

Abstract

Streptomyces are a cosmopolitan and economically important genus of Actinobacteria known for producing an array of secondary metabolites, including many clinically relevant antibiotics. Streptomyces are ubiquitous in soil environments throughout the world and have been identified as prominent members of the microbiomes of diverse plant species. The presence of Streptomyces around and within plants has been shown to provide a wide variety of fitness benefits including increases in disease resistance and abiotic stress tolerance. Despite recent increased interest in the benefits of these bacteria to associated plants, relatively little is known about the genetic basis for the plant growth promotion capabilities shown by Streptomyces, or about the traits that facilitate plant interaction. In this work plant phenotypes resulting from inoculation with isogenic bacterial cultures are quantified and correlated with the genetic background of the bacteria used. The 9 isolates of soil derived Streptomyces influence the early growth phenotypes of co-cultured Arabidopsis thaliana Columbia-0 seedlings in a manner consistent with previously identified phylogenetic clade associations. Quantification of phenotypes of seedlings growing in association with bacterial cultures, and correlation of those phenotypes with the genetic backgrounds of associated isolates, demonstrates how results from an in vitro plant assay can be used to elucidate genomic regions with implication for plant colonization and interaction among closely related Streptomyces bacteria.