Metabolic Regulation of Phenanthrene-Degrading Strain Sphingobium abikonense GHP1 in Response to Phenanthrene Stress and Its Effects on Endorhizosphere Microbiota of Lettuce

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants with high ecotoxicity and bioaccumulation potential, and plant-microbe-assisted remediation is a promising green strategy for their removal. This study investigated Sphingobium abikonense GHP1, a phenanthrene-degrading bacterium isolated from a municipal solid waste incineration site, to elucidate its potential remediation mechanism using untargeted metabolomics and root endophytic bacterial community analysis. GHP1 completely degraded phenanthrene (50 mg L−1) within 3 days using it as the sole carbon source. During degradation, aromatic intermediates, including 1-hydroxy-2-naphthoic acid, salicylic acid, and hydroxybenzoic acid derivatives, accumulated, while central carbon metabolism, 2-oxocarboxylic acid metabolism, aromatic compound degradation, and benzoate degradation pathways were activated. Increased levels of NAD, purine metabolites, phosphatidylcholine, and phosphatidylethanolamine suggested enhanced redox regulation, energy metabolism, and membrane homeostasis under phenanthrene stress. In lettuce, GHP1 inoculation promoted plant growth, increased biomass and chlorophyll content, and reduced phenanthrene residues in roots and leaves. Moreover, GHP1 increased the richness of the root endophytic bacterial community and enriched Actinobacteriota, Firmicutes, and other bacterial taxa. These findings demonstrate that GHP1 enhances phenanthrene remediation through coordinated pollutant degradation, metabolic regulation, and plant-microbe interactions, providing a promising microbial resource for the remediation of PAH-contaminated environments.