Microbial Community Succession During Bioremediation of Petroleum-Contaminated Soils Using Rhodococcus sp. OS62-1 and Pseudomonas sp. P35.

Oil pollution poses a persistent threat to soil ecosystems globally, and bioremediation using bacterial consortia has emerged as a cost-effective remediation strategy. However, the role of weak petroleum-degrading bacteria in enhancing the efficiency of specialized petroleum-degrading bacteria remains unclear. This study explores the synergy and remediation potential of a two-bacterial consortium: the petroleum-degrading bacterium Rhodococcus sp. OS62-1 and the weak petroleum-degrading bacterium Pseudomonas sp. P35. A 25-day microcosm experiment was conducted with petroleum-contaminated soil, and four treatments were set: (1) uninoculated control, (2) inoculation with Rhodococcus sp. OS62-1 alone, (3) inoculation with Pseudomonas sp. P35 alone, and (4) inoculation with the consortium. Soil samples were collected periodically to analyze petroleum degradation efficiency, soil enzyme activities (dehydrogenase, catalase, polyphenol oxidase, and lipase), and microbial community composition (16S rRNA gene sequencing). Inoculating the soils with this consortium produced a higher petroleum degradation rate, microbial activity, and soil enzyme activity than inoculation with strain OS62-1 or P35 alone. Inoculation with strain P35 also contributed to the maintenance of strain OS62-1 during bioremediation. The study of microbial community structure found that the relative abundance of phylum Acidobacteriota (57.6 ± 5.3% to 75.6 ± 8.1%) and the Nocardioides genus (36.4 ± 4.5% to 53.0 ± 9.2%) increased dramatically during the bioremediation process. Pearson's correlation analysis revealed that inoculation with strain OS62-1 and/or strain P35 increases the soil enzyme activity, boosts native oil-degrading bacteria, and accelerates the degradation of petroleum contaminants. Molecular ecological networks analysis revealed that inoculation with strain OS62-1 and/or strain P35 increased the complexity and robustness of the microbial network. These findings confirm that weak petroleum-degrading bacteria can synergistically enhance the bioremediation efficiency of specialized petroleum-degrading bacteria, providing a practical strategy for optimizing the design of bacterial consortia in the bioremediation of oil-polluted soils.