Identification and characteration of nitrogen-fixing bacteria and oligotrophic-nitrogen bacteria from the polluted petroleum

Abstract:

Bioremediation in petroleum pollution has attracted wide attention due to its advantages including no secondary pollution and low cost. However, due to the large input of petroleum hydrocarbons into the environment, the relative shortage of nitrogen sources in the environment has become one of the key factors that restricted the efficiency of bioremediation. Therefore, screening microorganisms that can grow in the oligotrophic-nitrogen environments has important ecological significance. [Objective] To screen microorganisms that can grow on nitrogen-free conditions from the Liaohe Oilfield reservoir, and to provide candidate strains for the bioremediation of petroleum- contaminated environments. [Methods] The strains were isolated using modified nitrogen-free medium, followed by the analysis of 16S rRNA gene sequence and nitrogenase activity, and amplication of nitrogen fixation genes and petroleum degradation genes. [Results] 21 microorganisms were screened, belonging to 16 different genera, among which Pseudomonas accounted for the highest proportion. The analysis of nitrogenase activity showed that 8 microorganisms could detect acetylene reduction activity, 3 microorganisms successfully amplified the nitrogen-fixing gene nifH, and the remaining 13 microorganisms defined them as oligotrophic-nitrogen bacteria. Amplification of petroleum degradation-related genes in these 21 strains revealed that 5 strains have alkB monooxygenase genes or cytochrome P450 genes in their genomes. [Conclusion] The bacteria isolated from the reservoir water of the Liaohe Oilfield in this study can adapt to the oligo-nitrogen environment, coupled with the potential to degrade oil. This study enrichs the microbial diversity in oil-contaminated areas and provide bacterial foundation for microbial remediation.