TPH degradation difference during the 77-day incubation
For oil-pollution remediation, the absence of a universal indicator for predicting microbial biodegradation potential and assessing remediation effects, restricts the generalization of bioremediation. The community-level ribosomal RNA gene operon (rrn) copy number, an important functional trait, has the potential to serve as a key proxy in organic pollutants bioremediation. To investigate the relationship between hydrocarbon microbial biodegradation and the community-level rrn copy number, a meta-analysis based on 16S rRNA high-throughput sequencing data from hydrocarbon-polluted situations was performed, and a positive relationship was observed in soil, seawater and culture ecosystems. To further prove the indicative role of the community-level rrn copy number in hydrocarbon microbial bioremediation, an oil-polluted soil microcosm was performed to decipher the community-level rrn copy number pattern during the total petroleum hydrocarbon (TPH) biodegradation. Straw combined with Rpf showed the best biodegradation effect compared with other treatments, the initial TPH (20,000 mg/kg) was reduced by 67% after 77-day incubation and showed the highest community-level rrn copy number at every time point. The biodegradation rate of the different stages was positively correlated with the community-level rrn copy number (P < 0.0003, R2 = 0.6506) . Community analysis and meta-analysis showed that the rrn copy number may reflect hydrocarbon degradation and dormancy ability. Our findings provide insight into the applicability of the community-level rrn copy number to assess bacterial biodegradation in pollutant bioremediation.