Soil commensal bacteria with pathogens reveal complex community effects

The complete suite of microbial interactions in natural soil is vast and complex. As such, it is of interest to systematically dissect convoluted microbe-microbe interactions and examine intricate mechanisms. Ralstonia solanacearum is a plant pathogen causing bacterial wilt which damages economically valuable crops. Biological control agents (BCAs) are a promising strategy to suppress such pathogenic activities by applying beneficial microbes. We selected taxonomically diverse commensal bacteria from the root of healthy Arabidopsis thaliana and tested potential community-wise effects on the pathogen. We demonstrated a high-throughput quantification system to evaluate in vitro microbe interactions. We found one of the commensals, Acinetobacter was a key player promoting other members' growth, and multiple bacteria grouped with Streptomyces induced the maximum hindrance effects on the pathogen. Our findings revealed the low abundant species unexpectedly delivered the highest impact on the community-wise interactions and the pathogen, highlighting the complexity of microbial interactions.