The relationship between protist consumers and soil functional genes under long-term fertilization.

Protists play a crucial role in terrestrial ecosystems by participating in biogeochemical cycles and contributing to ecological balance and stability. However, much remains to be understood about the intricate interactions between soil protists and biogeochemical processes. Here, we collected rhizosphere soil samples from seven distinct fertilization treatments to investigate the responses of bacteria, protists and functional genes to these varying fertilization practices during sorghum's maturity season. The community composition of both protists and bacteria were significantly affected by different fertilization treatments, with organic fertilization increasing protist diversity but not affecting bacterial diversity. There were noticeable variations in the compositions of functional genes across different fertilization treatments, with organic fertilization enhancing the relative abundance of carbon and phosphorus cycling genes. While fertilization generally increased the relative abundance of protistan consumers, it was observed that organic fertilizers decreased the relative abundance of phototrophs. A substantial number of bacterial taxa, including Acidibacter, Steroidobacter, Lysobacter and Agromyces, which correlated positively with functional genes, were found to be prey for protistan consumers, indicating their crucial role in predicting soil functional genes. Altogether, this study highlights the significant impact of fertilization treatments, especially organic fertilization, on the diversity and functional dynamics of protist and bacterial communities, emphasizing the key role of protistan consumers in regulating the soil microbial community and modulating soil biogeochemical cycles.