Synergistic division of labor in a bacterial consortium for enhanced phenanthrene mineralization under cadmium stress: mechanisms of degradation-detoxification coordination

The remediation of co-contamination by polycyclic aromatic hydrocarbons (PAHs) and heavy metals poses a significant challenge. Although microbial consortia present a promising approach, their synergistic mechanisms under stress conditions are not fully understood. To address this gap, we constructed a functionally specialized bacterial consortium (KZ) by assembling Klebsiella sp. CW-D3T and Arthrobacter sp. SZ-3, which synergistically enhanced phenanthrene (PHE) degradation and mineralization under cadmium stress (25 mg/L Cd 2+ ), outperforming monocultures by 1.2–1.9-fold. Through biomass-normalized enzyme activity assays, we uncovered a structured division of labor: SZ-3 exhibited superior upstream catalytic activity (50 % higher 2H1N conversion), while CW-D3T dominated downstream mineralization (>80 % contribution). Mechanistic investigations via metagenomics revealed that CW-D3T utilized high-expression efflux pumps (ZntA/zinT) and antioxidant genes ( yhcN ) to mitigate cadmium toxicity, whereas SZ-3 employed the frnE -mediated oxidative stress response and limited Cd 2+ uptake via mntH . This study elucidates a synergistic mechanism for concurrent PAH degradation and heavy metal detoxification, offering a novel bioresource for remediating co-contaminated environments.