Sensitive indicator microorganisms and C,N-cycle processes in soil with different petroleum hydrocarbon pollution levels

Abstract

Total petroleum hydrocarbon(TPH) is toxic to soil microorganisms and humans and has become a serious public concern. This study employed chemical analysis, high-throughput sequencing, and KEGG database functional gene annotation to investigate microbial responses to TPH contamination and identify potential bioindicators for soil toxicity assessment. Our results demonstrated that TPH stress significantly altered soil microbial community stability and functional structure. In contaminated soils, the relative abundance of Actinomycetes increased by 14.03–25.06 %, while Ascomycetes and Mortieres increased by 0.85–2.2 % and 1.62–2.39 %, respectively, compared to uncontaminated soil. The Mantel test analysis identified that Nocardioides, unclassified-Micrococcaceae, Streptomyces, and Gibberella as robust bioindicators petroleum contamination(p < 0.05). Network analysis revealed that petroleum hydrocarbons enhanced microbial community complexity, with network edges increasing by 20–90 % in contaminated soils. PICRUSt2 functional prediction showed that TPH pollution altered microbial metabolic pathways, with bacterial metabolic processes and fungal biosynthesis processes dominating (>60 %) the total pathways. The abundance of nitrification genes involved in nitrogen transformation was positively correlated with soil oil content, denitrification, and nitrogen-fixing genes showed a negative correlation with TPH content. Expressions of functional genes involved in carbon photosynthesis fixation are inhibited in oil-contaminated soil with the hydroxypropanoate-hydroxybutylate cycle (M00375) being the main carbon cycle pathway.