A Call for Research: A Resource of Core Microbial Symbionts of the Arabidopsis thaliana Microbiome Ready and Awaiting Experimental Exploration

The characterization of specific subsets of soil microbiota in the rhizosphere and endosphere has led to the recognition of plant species-specific microbiomes. Most attention has been given to microbial prokaryotes and fungi. Only recently was convincing evidence for the existence of plant species-specific protist microbiomes presented. Although protists are expected to shape the composition of bacterial and fungal communities and, thereby, directly impact plant health, a lack of cultures of these important plant-symbiotic protists has hampered their experimental exploration. To facilitate empirical plant microbiome research, we sampled Arabidopsis thaliana, established 79 cultures covering nearly all major groups of plant-symbiotic Cercozoa (protists), and have made these publicly available. We discuss our findings and propose potential roles that these protists may have in structuring the plant microbiome.