Predatory protist promotes disease suppression against bacterial wilt through enriching plant beneficial microbes at the early stage of plant growth

Plant health is closely associated with the rhizosphere microbial community. Predatory protists can regulate the rhizosphere microbes and thereby affect plant health. However, there is limited research on how the exogenous addition of predatory protists influences plant rhizosphere microbiome across plant growth.

Here, we isolated a predatory protist species, named Naegleria sp. QL92, from healthy tomato rhizosphere soil, which can effectively suppress bacterial wilt. We investigated the impact of predatory protist addition on the rhizosphere bacterial community across tomato growth stages in pots.

We found that the predatory protist of Naegleria significantly altered the community structure and composition of the rhizosphere bacteria during the seedling, flowering and fruiting stages of tomato growth. Moreover, the relative abundances of bacterial phylum of Proteobacteria, Gemmatimonadetes, and Nitrospirae as well as majority bacterial genera, especially Pseudomonas were increased during the seedling stage after Naegleria addition. Naegleria inoculation reduced the density of the Ralstonia solanacearum pathogen, which was negatively correlated with Pseudomonas relative abundance. The addition of Naegleria also increased the connections within rhizosphere bacterial communities, resulting in a complex microbial network.

Overall, our study highlighted the application of predatory protists as puppet masters of rhizosphere bacterial communities with enriching plant beneficial microbes, which offer new venues to manage rhizosphere microbial communities to support healthy plant growth in sustainable agriculture.