Isolation, Characteristics And Mechanism Of Bacteria With High Phenanthrene And Naphthalene Degradation Ability

Polycyclic aromatic hydrocarbons (PAHs) are toxic, mutagenic and carcinogenic pollutants that exist extensively in the environment. Microbial degradation is the main method of PAHs eradication in natural environment and therefore is of importance to investigate.Two strains with high phenanthrene and naphthalene degradation ability were separated from the polluted soil nearby the Xi'an coke-oven plant using phenanthrene or naphthalene as sole carbon source. The two strains belong to Acinetobacter sp. and Pseudomonas sp. respectively by 16SrDNA analysis and named A and B.Together with a PAO1 strain, C, stored in the lab, degradation characteristics were investigated including temperature, pH, dissolved oxygen, surfactants etc. Surfactants such as Tween-80 and Triton X-100, could facilitate the biodegradation. Addition of antibiotics at subinhibitory concentrations, such as Tc and Van, also facilitate the degradation because of the increasing secretion of biosurfactant rhamnolipid. Mixed cultivation of the three strains could increase the degradation of phenanthrene and naphthalene. The degradation rate of phenanthrene by A, B, C strains reached 80.4%,86.6% and 85.7% respectively in two days under optimized conditions. The degradation rate of naphthalene reached 83.1%,92.7% and 90.2% respectively.The degradation pathway was explored using salicylate and phthalate, the different kinds of metabolic intermediates in phenanthrene biodegradation, as substrates. Salicylate pathway could be the degradation pathway in A strain, while both salicylate pathway and protocatechuate pathway could be the degradation pathways in B, C strains. The degradation enzymes were also checked by PCR.The related phenanthrene and naphthalene biodegradation genes of P. aeruginosa were researched through screening P. aeruginosa random promoter library which contained a promoterless luminescence regulon luxCDABE as a reporter. The uncovered genes included biosynthesis-related and energy-related proteins encoding genes such as geneF, geneG and geneJ, transport proteins encoding genes such as geneB, membrane proteins encoding genes such as geneT, hypothetical proteins encoding genes such as geneP, totally 20 genes. Also the expressions of five RND pumps genes were affected by phenanthrene. The results showed that both degradation genes and degradation interrelated genes have played important roles in PAHs degradation. The combination of two kinds of genes ensured bacteria to realize the degradation of PAHs eventually.The results will promote further researchs and applications of PAHs microbial degradation technology.