Degradation effects and mechanism of o-chlorotoluene by Raoultella planticola and Escherichia fergusonii

o-Chlorotoluene ( o -CT) is a representative organic pollutant that poses potential risks to ecosystems and human health. Currently, microbial degradation of o -CT remains inefficient and requires improvement. Therefore, in this study, two novel o-chlorotoluene-degrading bacteria— Raoultella planticola OCT-DM2 and Escherichia fergusonii OCT-DM4—were successfully isolated from chemically contaminated soil, and an efficient degrading bacterial community (OCT-MC) was constructed by combining these strains. After optimization, OCT-MC achieved an 80.5% degradation of o -CT under the following conditions: pH 7, 35 °C, 15% (v/v) inoculum, and an initial o -CT concentration of 200 mg L −1 . Gas chromatography-mass spectrometry (GC-MS) analysis identified five key metabolites, based on which a degradation pathway of o -CT by the consortium OCT-MC was proposed. In this pathway, o -CT was initially transformed into toluene via reductive dechlorination, followed by aromatic ring cleavage and oxidative reactions, ultimately leading to complete mineralization. Integrated genomic and transcriptomic analyses further revealed that redox-related genes within OCT-MC acted synergistically to facilitate o -CT degradation. Notably, genes encoding key enzymes, such as benzylsuccinate synthase (BSS), were significantly upregulated at the transcriptional level, providing molecular-level insights into the high degradation efficiency of the OCT-MC consortium. Overall, the constructed consortium OCT-MC exhibits considerable potential for the bioremediation of o-chlorotoluene–contaminated environments and offers a theoretical basis for elucidating the molecular mechanisms underlying chlorinated aromatic hydrocarbon degradation by mixed microbial consortia.