Microbial Communities and the Bioremediation of Polycyclic Aromatic Nitrogen Heterocycle-Contaminated Soil

Azaarenes are nitrogen heterocyclic compounds comparable to the more commonly known polycyclic aromatic hydrocarbons. These nitrogen heterocycles tend to co-exist with polycyclic aromatic hydrocarbons in contaminated soils. Despite their known toxicity and relatively high bioavailability, little research exists on the bioremediation of these chemicals in soil. This study used high-performance liquid chromatography to detect a decline in azaarene concentration in microcosms of soil samples from a former wood treatment facility in Andalucía, Spain, to which a specific azaarene was spiked. Seven azaarenes were studied: quinoline, isoquinoline, phenanthridine, acridine, benzohquinoline, benzoaacridine, and benzocacridine. Differences in the microbial communities among the microcosms were first analyzed by denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes. High-throughput sequencing of community 16S rRNA genes was then conducted to determine the organisms that responded to the addition of a given azaarene. The results suggest that the microbial communities among triplicate incubations were similar to one another, and that both the molecular weight and the position of the nitrogen in the ring structure of the azaarene can influence the microbial community responsible for degradation.