Fungal and bacterial microbial community assessment during bioremediation assays in an aged creosote-polluted soil

Abstract

The application of bioremediation technologies to polycyclic aromatic hydrocarbon (PAH)-contaminated soils does not remove the excess of the high-molecular-weight fraction (HMW-PAHs), as has been widely reported. Taking into account the metabolic capacities of white-rot fungi, their bioaugmentation has been extensively assayed on polluted soils, but with controversial results. The aim of this study is to gain insight into how fungal bioaugmentation assays affect both PAH degradation and autochthonous microbial populations in a previously biotreated aged creosote-polluted soil contaminated with HMW-PAHs. To this end, we performed a set of slurry bioassays encompassing different biostimulation and bioaugmentation strategies. The results show that the autochthonous microbial populations degraded PAHs the most; specifically, the 4-ring PAHs under carbon-limiting conditions (26% and 28% degradation for benzo(a)anthracene and chrysene respectively). Although Trametes versicolor amendment produced the highest depletion of benzo(b + k)fluoranthene and benzo(a)pyrene concentrations in an autoclaved soil, it did not improve either the 4-ring or the 5-ring PAH degradation, when active native PAH-degrading microbiota was present. Microbial community analysis of fungal and eubacterial populations, based on the 16SrRNA gene and ITS1 region respectively, revealed that the ribotypes closely related to the eubacterial genera Chryseobacterium, Pusillimonas and Sphingobium, that are concomitant with the autochthonous fungal genus Fusarium, could be important in HMW-PAH degradation processes in polluted soils. Antagonistic effects or resource competition resulting from the effects of active native soil microbiota on augmented white-rot fungi should be evaluated in polluted soil before scaling up the remediation process to field scale.