Shared features and reciprocal complementation of the Chlamydomonas and Arabidopsis microbiota

Microscopic algae release organic compounds to the region immediately surrounding their cells, known as the phycosphere, constituting a niche for colonization by heterotrophic bacteria. These bacteria take up algal photoassimilates and provide beneficial functions to their host, in a process that resembles the establishment of microbial communities associated with the roots and rhizospheres of land plants. Here, we characterize the microbiota of the model alga Chlamydomonas reinhardtii and reveal extensive taxonomic and functional overlap with the root microbiota of land plants. Using synthetic communities derived from C. reinhardtii and Arabidopsis thaliana, we show that phycosphere and root bacteria assemble into taxonomically similar communities on either host. We show that provision of diffusible metabolites is not sufficient for phycosphere community establishment, which additionally requires physical proximity to the host. Our data suggest the existence of shared ecological principles driving the assembly of the A. thaliana root and C. reinhardtii phycosphere microbiota, despite the vast evolutionary distance between these two photosynthetic organisms. Plants and algae associate with microbial communities that affect their growth and development. Here, the authors characterize the microbiota associated with a unicellular alga in soil, revealing extensive taxonomic and functional overlap with the root microbiota of land plants.

Automated summary

The study reveals the extensive similarity between the microbiota associated with microscopic algae and the root microbiota of land plants. Both algae and plants attract heterotrophic bacteria by releasing organic compounds and establish symbiotic relationships with them. Furthermore, the assembly process of microbial communities associated with algae and plant roots shares common ecological principles.