Soil Protists and plants: who is in control?

Plants depend on the community of microbes around and in their roots, which is named the microbiome. There is increasing awareness that plants can control their microbiome in a species-specific way, however, little is known about the capacity of plants to steer functioning of the microbiome to their own benefit. Protists influence nutrient supply to plants by feeding on bacteria and fungi. Protists are usually overlooked in plant-microbiome studies, because of the specific expertise needed to experimentally handle this group of microbes. My aim is to elucidate plant control of their microbiome functioning through structuring protist community composition

First, I will examine whether plant species with different traits differentially shape the community composition of protists in their rhizosphere. I will test the hypothesis that slow growing, mid-successional plant species promote a higher protist diversity than fast growing, early-successional plant species, due to tighter predator-prey dynamics. I will study how plant species influence protist community composition in their rhizosphere both from plants sampled in the field and in controlled-greenhouse experiments after inoculating different communities created from over 100 cultures of common soil protist species.

Second, I will identify whether protist functioning depends on protist diversity, as diversity and functioning of many other species groups are often positively correlated. I will test the hypothesis that a higher protist diversity more strongly benefits mid- than early-successional plant species due to tighter predator-prey dynamics. I will measure performance of mid- and early-successional plant species in a greenhouse experiment after inoculating increasing numbers, up to a maximum of 100 protist species.

Finally, I will compare my results on early- and mid-successional plant species to related crop species in order to learn from nature how to enhance crop growth by smartly using the soil microbiome for plant nutrition.