How Plants Modulate Their Rhizosphere Microbiome

Rhizosphere, the soil zone in close proximity with plant roots, is a very special environment for soil microorganisms. The plant secretes a variety of nutrients and bioactive compounds. These have a direct influence on any microbe, and in recent years it has become clear that plant signals shape the rhizosphere microbiome. Plant microbe coevolution has, no doubt, produced interactions that benefit all the partners. The complexity of the microbiome, though, would preclude a simple positive-negative interaction, so that to reach a complete understanding, a full network of interactions needs to be studied. This would be difficult, but recent studies have extracted some of the principles. Thus, the microbiome is shaped in a specific way by the phytochemical composition of the exudates, which in turn reflect the developmental stage of the plants that are present in a given soil neighborhood, their physiological state, as well as the consequences of interactions in the soil. Soil microbes, as assemblies of microbiome populations, can, indeed program the composition of the phytochemicals released by the plant. There is, therefore, a continuous exchange of signals between plants and their associated bacteria and fungi.