Microorganisms, <i>e.g., </i>bacteria and microalgae, play an important role in removing organic pollutants, including polycyclic aromatic hydrocarbons (PAHs) in the environment. Commonly, the microorganisms faced a complicated situation that there coexist a large variety of PAHs in the real environments. By investigating pyrene degradation by Mycobacterium sp. strain A1-PYR in the presence of nutrient broth, phenanthrene and fluoranthene respectively, we found that indigenous PAH-degrading bacteria could process refractory PAHs via rapid growth with enough nutrients, otherwise via inducing expression of genotypic enzymes by easily-degradable PAH homologues in the absence of nutrients. Needs for bacterial growth determine that the most efficient way as well as relating enzymes is selected for converting PAHs into effective carbon sources in the PAH-only substrates.  Microbes could interact with each other during PAH degradation in the environments. To understand the general potential mechanisms of interactions between microbes under PAH stress, we constructed a consortium of PAH-degrading microalgae (Selenastrum capricornutum) and bacterium (Mycobacterium sp. strain A1-PYR). The result showed that the algal-bacterial consortium exhibited a higher degradation rate of pyrene than either of single species. Rapid bacterial degradation of pyrene might not only mitigate the toxicity of pyrene to algea, but also provide phenolic acid, which could serve as the phytohormone for promoting algal growth. In turn, bacteria growth was also enhanced by the algea presented in the mixing culture. Consequently, the growth of algea and bacteria resulted in the faster degradation of pyrene.  Nevertheless, microorganism could be able to remove PAHs even after loss of biological activity. We found that the remove speed of benzo[a]pyrene (BaP) by dead algal cells was faster than that by the alive algea. The chlorophyII released by dead algal cells could generate a high level of singlet oxygen and catalyse the photo-transformation of BaP under visible light irradiation. According to various BaP metabolites formed, the degradation mechanism was proposed as that chlorophyII in dead algal cells photo-oxidized BaP to quinones via photocatalytic of singlet oxygen.

Biodegradation of polycyclic aromatic hydrocarbons in the Mangrove environment

256th National Meeting (2018)

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