Dynamic responses in Pseudomonas stutzeri M3 bioaugmentation of crude-oil-contaminated soil: hydrocarbons, microbial community structures, and functional genes

Bioaugmentation is a cost-effective and environmentally friendly method for dealing with hazardous pollutants. However, bioaugmentation has some drawbacks, including poor bioactivities, inconsistent effects, and uncontrollability. Understanding the inter-relationships between actual microbial communities and various petroleum hydrocarbon components remains a key challenge for effective and efficient decontamination in oilfield soil. Here, dynamic changes of reconstructed PIONA (paraffins, iso-paraffins, olefins, naphthenes, and aromatics) fractions and microbial community structures were investigated in a 60-day laboratory-scale experiment with exogenous Pseudomonas stutzeri M3 supplementation. The results showed that effective biodegradation occurred between the 15th and 30th days of bioaugmentation, and the biodegradation efficiency of paraffin reached 96.5% after 60 days in 1% oil-contaminated soil. Moreover, supplementation with strain M3 significantly altered the microbial community structures, promoting the enrichment of Balneolaceae, Halolalama, and Woeserchaeia, while delaying the colonization of Alcanivorax. Weighted gene co-expression network analysis (WGCNA) showed that the positive interactions between hub bacteria were more significant than the negative interactions and revealed the synergistic degradation of petroleum constituents. The abundance of alcohol dehydrogenase, aldehyde dehydrogenase, catechol cleavage enzyme, cytochrome P450, gentisate dioxygenase, and benzoate/toluate dioxygenase increased abruptly in the initial 7 days with the inoculation of strain M3. This study provides insights into the inner mechanisms of petroleum hydrocarbon metabolism under the combined action of exogenous and indigenous microbes in oilfield soil.