COS 270-5 - Parasitism vs. predation: Species interactions within microbiomes and their impact on host population size and ecosystem function

Abstract: Plant microbiomes, consisting of diverse microorganisms such as prokaryotes, eukaryotes, and viruses, play a crucial role in determining plant growth and ecosystem function. Despite their importance, the effects of interactions between microbes from different domains, especially trophic interactions, on plant-microbiome symbiosis are not fully understood.

Our approach to addressing this knowledge gap involves performing an experimental study using the duckweed Lemna minor. We extracted the microbiomes from two natural duckweed populations, separate the bacteria, bacteriophage, and protozoa in the microbiomes, and inoculate them into the microbiomes of laboratory germ-free duckweed lines. We experimentally manipulated the presence/absence of parasitism (by bacteriophage) and predation (by bacterivorous protozoa) within the microbiomes and examined their influences on host plant population size and phosphorus removal. Using 16S amplicon sequencing, we also investigated the changes in microbiome properties, including microbiome abundance, richness, and composition, in response to parasitism and predation.

Here, we show that parasitism reduced plant population size and phosphorus removal, while parasitism had the opposite effect. We used structural equation modeling to demonstrate that the impacts of parasitism and predation on plant growth and ecosystem function were both mediated by microbiomes and occurred via different pathways.

In conclusion, our study highlights the crucial role of understanding microbial trophic interactions in predicting the outcomes and ecosystem impacts of plant-microbiome symbiosis. By investigating the microbial trophic interactions within microbiomes, we can gain insights into how to promote healthy and sustainable plant growth and ecosystem functioning.