Polycyclic aromatic hydrocarbon-induced structural shift of bacterial communities in mangrove sediment

Mangrove sediment is well known for its susceptibility to anthropogenic pollution, including polycyclic aromatic hydrocarbons (PAHs), but knowledge of the sediment microbial community structure with regards to exposure to PAHs is limited. The study aims to assess the effects of PAHs on the bacterial community of mangrove sediment using both 16s rDNA polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and traditional enrichment methods. Both the exposure time and the PAH concentration reduced the microbial diversity, as determined by the DGGE bands. Although PAHs could act as carbon sources for microorganisms, PAHs, at a concentration as low as 20 mg l(-1), posed a toxic effect to the microbial community. Sequencing of DGGE bands showed that marine bacteria from the genera of Vibrio, Roseobacter, and Ferrimonas were most abundant after PAH exposure, which suggests that both marine and terrestrial bacteria coexisted in the mangrove sediment, but that the marine microbes were more difficult to isolate using the traditional culture method. DGGE determination further demonstrated that the consistency among triplicates of the enriched consortia was significantly less than that of the sediment slurries. The present study reveals that the mangrove sediment microbial structure is susceptible to PAH contamination, and complex microbial community interactions occur in mangrove sediment.