Abstract: To solve the problem of low degradation efficiency of petroleum hydrocarbon degrading bacteria in oil contaminated soil and oily sludge with low nitrogen, we screened and isolated four bacterial strains from oil contaminated soil in Dongying, using nitrogen-free and nitrogen-containing liquid media. According to the morphological, physiological and biochemical characteristics and 16S rRNA sequence analysis, the four strains were identified as Acinetobacter venetiae (W), Agromyces sp. (B), Brevibacillus invocatus (G), and Stenotrophomonas maltophilia (T). GC-MS results showed that all the four strains had high nitrogenase activity (224.41-324.63 nmol·mL^-1·h^-1). Compared to nitrogen-containing conditions, the degradation of petroleum hydrocarbons by strains B and T increased slightly under the nitrogen-free conditions, but still significantly lower than the degradation rate of petroleum hydrocarbons by strains W and G. Under nitrogen-free conditions, the degradation rates of petroleum hydrocarbons by the “W+T”, “G+T”, and “W+B+G+T” combinations decreased to different degrees, but the “B+T” combination maintained close to 60%. The results of degradation products in liquid medium showed that strain W could degrade long-chain alkanes (C₂₂-C₄₀) to short-chain alkanes (C₁₄-C₁₉), strain B had the best degradation effect on short-chain alkanes (C₁₀-C₂₁), while strain G and T showed good degradation effect on petroleum hydrocarbon components (C₁₀-C₄₀). In the actual soil remediation experiments, the degradation efficiency of petroleum hydrocarbons by the combination of “W+B+G+T” (56.9%) was much higher than that of single strain (≤32.1%). The relative abundance of microorganisms associated with the degradation of petroleum hydrocarbons increased in the treatments with the addition of strains compared to the control. The relative abundance of A. venetianus with petroleum hydrocarbons degradation ability increased by 21.23% and 2.58% in the treatment with strain W and “W+B+G+T”, respectively. Meanwhile, the relative abundances of Agromyces sp. (B) and S. maltophilia (T) also increased to varying degrees.

Key words: petroleum hydrocarbon degrading bacteria, low nitrogen stress, strain screening, degradation characteristics