Effect of inoculation of functional bacteria on the remediation of petroleum polluted soil and the microbial community

The dibenzothiophene (DBT) degrading bacteria screened and domesticated based on previous culture experiment was inoculated into the petroleum contaminated soil for a 40 day simulated soil remediation experiment. The degradation effect of functional bacteria (Rhodococcus sp. ZYL-1) and the succession of bacterial community in the petroleum contaminated soil was analyzed. The results showed the addition of Rhodococcus sp. ZYL-1 increased significantly the degradation efficiency of DBT compared to control during the incubation at 25 ℃ in the dark chamber (P<0.001). The DBT degradation in the bioaugmentation treatment (BIOEIF) mainly occurred in the first 10 days after soil incubation, in which DBT degradation rate was close to 60% at the end of incubation, higher than that in the control, i.e., natural attenuation treatment (NAT) relying on soil indigenous microorganisms. Compared with the bacterial community composition between BIOEIF treatment and NAT treatment in the soil incubating process, the Shannon diversity index and phylogenetic diversity index of BIOEIF were significantly lower than that in NAT, but the inoculation of Rhodococcus sp. ZYL-1 did not affect significantly the composition of the soil bacterial community. Micromonospora, Bacillus, and unclassified_f_Planococcaceaeis were detected as the dominated taxa in the petroleum contaminated soil, but Rhodococcus which was inoculated did not have an obviously high abundance in soils. Network analysis showed that key functional bacteria for DBT degradation had significantly improved in the contaminated soil in BIOEIF, which might be due to the symbiosis of Shimazuella with indigenous microorganism. In conclusion, the inoculated functional bacteria (Rhodococcus sp. ZYL-1) could obviously improve the biodegradation of DBT in petroleum hydrocarbon contaminated soil based on enhancing the degradation function of indigenous microorganisms.