The role of multi-low molecular weight organic acids on phenanthrene biodegradation: Insight from cellular characteristics and proteomics.

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic and ubiquitous pollutants that need to be solved. The low-molecular-weight organic acid (LMWOA) holds the promise to accelerate the capacity of microbes to degrade PAHs. However, the degradation mechanism(s) with multi-LMWOAs has not been understood yet, which is closer to the complex environmental biodegradation in nature. Here, we demonstrated a comprehensive cellular and proteomic response pattern by investigating the relationship between a model PAH degrading strain, B. subtilis ZL09-26, and the mixture LMWOAs (citric acid, glutaric acid, and oxalic acid). As a result, multi-LMWOAs introduced a highly enhanced phenanthrene (PHE) degradation efficiency with up to 3.1-fold improvement at 72 h, which is accompanied by the enhancement of strain growth and activity, but the releasement of membrane damages and oxidative stresses. Moreover, a detailed proteomic analysis revealed that the synergistic perturbation of various metabolic pathways jointly governed the change of cellular behaviors and improved PHE degradation in a network manner. The obtained knowledge provides a foundation for designing the artificial LMWOAs mixtures and guides the rational remediation of contaminated soils using bio-stimulation techniques.