Like animals, plants are colonised inside and out by diverse microbial communities that influence their health and nutrition. A key difference, however, is that plants have a limited ability to vertically transmit microorganisms between generations. Furthermore, plants have limited mobility and generally remain at a single place their entire lives. Consequently, plant associated microbes have to be primarily drawn from the immediate environment.

We wondered given such restrictions, whether plants preferentially recruit subsets of microorganisms from complex soil communities to their roots, and if the outcome was consistent across locations and plant species. To address these questions, we journeyed to the Great Sandy National Park in Cooloola, Australia. This location is ideally suited with a progressive series of dune systems that have developed over several hundred thousand years within close proximity. We collected root and soil samples from non-seed and seed plant lineages - lycopods, ferns, cycads, conifers and flowering plants - that co-occur across dune systems, and surveyed the resident bacterial communities.

A number of bacterial genera were consistently enriched in the roots of the surveyed plants when compared to their abundance in soil. Most of these genera are well-known lineages with nitrogen-fixing Rhizobium and Burkholderia, but we also detected genera not previously known to be associated with plant roots. Interestingly, we found Bradyrhizobium were enriched in the roots of most of the surveyed plants. Bradyrhizobium species are best known as root-nodulating bacteria specifically associated with legumes, whereas our study suggests they have far more widespread associations with plant lineages.

We also compared the overall root community compositions to their hosts’ phylogeny inferred by the ribulose bisphosphate carboxylase large subunit (rbcL) gene and found a small but significant correlation. These findings suggest that plant genetics influences the recruitment of root communities in a manner consistent with their evolution albeit secondary to the much larger environmental influence. Where might this research take us? Similar to recent revelations on the importance of gut microbial communities in animals, there is good evidence that plant growth and vigour is dependent on favourable microbes. Increasingly, farmers want to capitalise on beneficial microbes to support their crops, and science has to assist in the design of effective crop probiotics. Having identified the core plant microbiome, our next challenge is to find out how they affect plant development, nutrient acquisition and protect plants from attack. These developments will undoubtedly bring new opportunities for agriculture and its associated industries to thrive more sustainably into the future.

The article can be found here: https://www.nature.com/article...