Rhizosphere Metabolites and Microbial Communities Shape Lettuce Responses to Oxytetracycline Stress

Oxytetracycline (OTC), a persistent antibiotic frequently detected in agricultural soils, can influence plant growth and rhizosphere ecology. Using lettuce (Lactuca sativa L.) as a model, this study compared the effects of OTC under hydroponic and soil cultivation systems and integrated physiological, metabolomic, and microbiome analyses. Hydroponic exposure consistently inhibited growth, whereas soil culture showed a biphasic, dose-dependent pattern─low OTC doses stimulated growth while high doses suppressed it. In soil systems, OTC exposure reprogrammed rhizosphere metabolites and reshaped microbial networks, enriching taxa associated with OTC degradation and plant growth promotion (Chryseolinea, Nitrospira, Devosia, Haliangium). Structural equation modeling indicated that rhizosphere diversity and metabolite profiles mediate plant biomass responses. These findings reveal that rhizosphere metabolite–microbe networks play a key role in modulating plant hormetic responses to antibiotic stress, providing mechanistic insight into antibiotic–plant–microbe interactions in agroecosystems.