Project description:Anthropogenic nutrient inputs alter soil biodiversity; however, it remains largely unknown whether changes in soil microeukaryotes (fungi and protists) are primarily driven by direct effects, such as modifications in soil properties, or by indirect effects, such as plant diversity loss. To disentangle these mechanisms, we investigated the long-term effects (11 years) of fertilization and manipulated plant diversity (1, 2, or 4 plant species) on soil microeukaryote communities in a temperate grassland experiment using long-amplicon rRNA sequencing. Our results indicate that fertilization generally had a stronger influence on microeukaryote communities than plant species richness. Fertilization altered the community composition of fungi and protists, increased OTU richness by 20.8% and 52.7%, respectively, and shifted community dominance from fungi to protists. Regarding plant diversity, we observed an effect exclusively on the protist community. Changes were primarily explained by increased plant biomass (driven by both fertilization and plant diversity) and by higher soil phosphorus and lower soil pH levels (driven exclusively by fertilization). Regarding life strategies, we observed synergistic treatment effects: fertilization primarily enhanced fungal saprophytes (only richness), fungal animal pathogens, and protist consumers, whereas plant diversity affected phototrophic protists (reduction) and protist animal pathogens (enhancement). Notably, fertilization and plant diversity decline together led to a cumulative increase in fungal plant pathogens. In conclusion, we highlight that fertilisation alone has a significant effect on soil microeukaryotes, while the additional decline in plant diversity affects different soil groups that are not directly affected by fertilisation. This synergistic pattern indicates that fertilization can influence the entire microeukaryote community through direct and indirect mechanisms, with a cumulative enhancement on certain groups, such as plant pathogens.
Project description:Predatory interactions among microbes are a major evolutionary driving force for biodiversity. The fungivorous amoeba Protostelium aurantium has a wide fungal food spectrum including major pathogenic members of the genus Candida. Phagocytic feeding by P. aurantium is highly effective with C. parapsilosis, a major pathogenic yeast. Here we show that upon ingestion by the amoeba C. parapsilosis is confronted with an oxidative burst and undergoes phagosomal lysis within minutes. On the fungal side, a functional genomic approach identified the fungal copper and redox homeostasis as primary targets of amoeba predation with the highly expressed copper exporter Crp1 and the peroxiredoxin Prx1 contributing to survival when encountering P. aurantium. The fungolytic activity was largely retained in intracellular vesicles of the amoebae. Following their isolation, the content of these vesicles induced immediate killing and lysis of C. parapsilosis. A proteomic analyses identified 56 vesicular proteins. Although fully unknown proteins were dominant, many of them could be categorized as hydrolytic enzymes presumably targeting the fungal cell wall, indicating that fungal cell wall structures are under predatory selection pressure in natural environments.