Enhance bioremediation mechanism of alicylic acid as a pathway inducer in oil-contaminated saline-alkali soil by chemotactic Pseudomonas stelleri M3

The microbial remediation of petroleum-contaminated soil is hindered by lower efficiency of mass transfer between pollutants and beneficial microorganisms, and persistent high-molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs). In this study, chemotactic strain named as Pseudomonas stelleri M3 was screened for automatic target tracking of petroleum hydrocarbons, thereby improving the efficiency of mass transfer in soil matrix. Meanwhile, salicylic acid act as a pathway inducer for enhancing the microbial degradation of petroleum hydrocarbons, particularly PAHs. The addition of an appropriate concentration of salicylic acid significantly enhanced the activities of alkane hydroxylase and catechol 1,2-dioxygenase, as well as the biodegradation rate of petroleum hydrocarbons. Furtherly, the inputs of salicylic acid reshaped microbial community, and obviously affected their cooperative metabolic process by increasing the relative abundance of petroleum hydrocarbon-degrading bacteria, such as Stutzerimonas, Pontibacillus, Halobacillus and Virgibacillus. Metagenomic analysis furtherly confirmed that overall metabolic pathways of microbial communities and expression of functional genes associated with petroleum degradation (e.g., fad, cat and nah) were enhanced. Furthermore, the addition of salicylic acid significantly increased the chemotactic gene expression in strain M3, thereby facilitating the bacteria's ability to further degrade petroleum hydrocarbons. These findings enhance our comprehension of the bioaugmentation remediation mechanism for polycyclic aromatic hydrocarbons and provide theoretical basis for bioremediation at PAHs-contaminated sites.