The syntrophic network of pyrene degradation by the synthetic halophilic consortium PES

Abstract

Owing to the high osmotic pressure, the degradation of high-molecular-weight polycyclic aromatic hydrocarbons (HMW-PAHs) in saline environments is quite difficult, leading to a scarcity of research on halophilic PAH-degrading bacteria. In this study, a halophilic synthetic consortium, PES, comprising Pelagerythrobacter sp. N7 and Salinicola sp. A11, was constructed on the basis of the bottom-up strategy. The syntrophic network for pyrene degradation by the consortium PES was investigated on the basis of genomic sequencing, functional gene annotation and expression, intermediates detection and bioemulsifier synthesis analysis. Consortium PES completely degraded 50 mg/L pyrene at 5% salinity in 10 days. Neither of strain N7 or strain A11 was identified able to complete degrade pyrene alone. Among which, strain N7 was responsible primarily for the upstream degradation of pyrene with a slow degradation rate and a low degradation efficiency. Intermediate 4,5-dicarboxyphenanthrene was detected highly accumulated in the pyrene degradation process by strain N7. Strain A11 exhibits no direct pyrene-degrading capability. Combined with the results from bioinformatic analysis and RT-PCR, strain A11 was proposed to supplies a candidate 4,5-dicarboxyphenanthrene decarboxylase to cooperate with strain N7 for complete pyrene degradation. Meanwhile, strain A11 was predicted able to produce bioemulsifier, further improving the pyrene degradation efficiency of PES consortia. Genes encoding gentisate 1,2-dioxygenase in strain N7, catechol 1,2-dioxygenase in strain N7 and A11 were detected highly expressed in pyrene degradation process. To our knowledge, this is the first study in which a syntrophic network of HMW-PAH degradation by a halophilic synthetic consortium was proposed, and 4,5-dicarboxyphenanthrene was identified as the key intermediate during pyrene syntrophic degradation. The halophilic synthetic consortium, PES, exhibited good environmental tolerance, providing an important theoretical basis and valuable microbial resources for the removal of PAHs from saline environments.