Fig. 1: Experiment workflow of this study and the overall profile of soil protist and bacterial communities.

A Experiment workflow of this study. Firstly, we obtained indigenous (i) protist and bacterial suspension and (ii) bacterial suspension from a forest soil through a series of filtration. Secondly, we created a gradient of three protist concentrations (low, medium and high) by diluting the collected protist and bacterial suspensions, and then inoculated them into sterilized forest soil samples. The soil microcosms were incubated at 25 °C for 90 days. Thirdly, soil samples were destructively collected at days 0, 15, 30, 45, 60, and 90, and then DNA was extracted for high-throughput quantitative PCR (HT-qPCR), qPCR and Illumina amplicon sequencing to characterize the profiles of ARGs and microbial communities. B Relative abundance of soil protists at the class level and trophic functional group in protist treatments across all time points. C Relative abundance of bacteria at the class level in protist treatments across all time points. D Principal coordinate analysis showing differences in bacterial community composition at different protist treatments over time. E Temporary alteration in alpha diversity (Shannon index) of bacteria over the incubation time. Letters indicate the significant difference in alpha diversity among different treatments in each time point (one-way ANOVA, post hoc LSD test, p < 0.05). Photo. Phototrophs, Para. Parasites, L Low, M Medium, H High protist concentrations.