Abstract: A laboratory simulation test was conducted to study the microbial remediation of soils contaminated by medium and low concentration polycyclic aromatic hydrocarbons (PAHs), and the relationships between the degradation of PAHs and the inoculated and indigenous microbes. The addition of high-effective PAHs-degrading bacteria promoted the biodegradation of soil PAHs, and the effect was remarkable in the first two weeks. The biodegradation of test PAHs was phenanthrene<anthracene<pyrene<benzo［a］pyrene<chrysene, and negatively correlated with the diversity/abundance of soil bacterial population. In the same treatments, soil bacterial population structure varied less with time, and hence, to increase the activity of indigenous microbes would be an effective way to remediate the farmland soils contaminated by medium and low concentration PAHs.

Key words: polycyclic aromatic hydrocarbons (PAHs), soil, bacteria, biodegradation, diversity, colistin sulfate, soil microbial biomass carbon, community structure, phospholipid fatty acid.