Protists regulate microbially-mediated organic carbon turnover in soil aggregates

Soil protists, the major predator of bacteria and fungi, shape the taxonomic and functional structure of soil microbiome via trophic regulation. However, how trophic interactions between protists and their prey influence microbially mediated soil organic carbon turnover remains largely unknown. Here, we investigated the protistan communities and microbial trophic interactions across different aggregates-size fractions in agricultural soil with long-term fertilization regimes. Our results showed that aggregate sizes significantly influenced the protistan community and microbial hierarchical interactions. Bacterivores were the predominant protistan functional group and were more abundant in macroaggregates and silt + clay than in microaggregates, while omnivores showed an opposite distribution pattern. Furthermore, partial least square path modeling revealed positive impacts of omnivores on the C-decomposition genes and soil organic matter (SOM) contents, while bacterivores displayed nega..., , , #### Sample information

**Id**

**Sample_ID**

**Aggregate**: LA, macroaggregates (250-2000 μm); MA, microaggregates (53-25 μm); SA, silt + clay (< 53 μm).

**Fertilization type**: Control, non-fertilization; NPK, chemical fertilization; M, organic manure; MNPK, a combination of chemical and organic fertilization.

#### Abiotic factors

* The abiotic factors of of different soil aggregates were determined.

**TC**: total carbon (g/kg); **TN**:total nitrogen (g/kg); **C/N**: the ratio of soil total carbon to total nitrogen;
**SOM**: soil organic matter (g/kg); **AN**: ammonium-nitrogen (mg/kg); **TP**: total phosphor (g/kg); **AP**:
available phosphorus (mg/kg); **pH**: soil pH.

#### Protistan functional groups

* The protistan ASVs were assigned into functional groups based on their feeding modes. Then, the relative abundances of the protistan functional groups in soil aggregates were caculated, including:

**Bacterivore, Eukaryvore, Omnivore, Parasites, Phototrophs, Plantpatho...