Phagotrophic protists affect the metabolic function of bacterial communities by regulating phytopathogenic bacteria

Ping Zhou¹Xuebo Zheng²Jiewang He¹Tiantian Zhang¹Yinghui Zhou¹Xiangyun Li^2*Jianxin Dong^2*Wenjing Song²

• ¹China Tobacco Hubei Industrial LLC, Wuhan, China
• ²Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao, China

Soil-borne phytopathogenic bacteria pose a major threat to agricultural productivity and food security. However, their biogeographic patterns and functional impacts on soil microbial communities remain poorly understood. Here, we combined large-scale soil sampling with high-throughput sequencing to investigate how phagotrophic protists regulate phytopathogenic bacterial communities (PPB) and their downstream effects on microbial metabolic functions in tobacco-cultivated soils. We found that, compared to phytopathogenic fungal communities (PPF), the abundance and diversity of PPB were more strongly influenced by changes in climate or soil factors. Moreover, community compositions of both PPB and PPF were more strongly associated with phagotrophic protists than with soil or climatic factors, with PPF showing greater host dependence than those of PPB. Additionally, increased PPB abundance was associated with enhanced carbohydrate and amino acid metabolism metabolic functions but suppressed energy and nucleotide metabolism metabolic pathways, and higher dissimilarity in PPB structure was linked to greater variation in metabolic profiles. Structural equation modeling further revealed that phagotrophic protists shape microbial metabolic function by modulating both PPB abundance and diversity. These findings provide novel insights into how microbial predators structure pathogen communities and influence soil functions in intensively managed agroecosystems, offering a foundation for microbiome-informed strategies to enhance soil health and disease suppression in fields.