Authors: Anirudra Parajuli, Mira Grönroos and Aki Sinkkonen
Abstract: Objective Long-term exposure to polyaromatic hydrocarbons (PAHs) in living environment has been connected to chronic health disorders in humans. Almost 90% of the PAHs emitted into the environment naturally or as a result of human activity end up in the top 20 cm of the soil. Microbial degradation and abiotic disappearance of PAHs favor certain microbial taxa, while others become less prevalent as a result of resource competition and direct PAH toxicity. Bacterial species that prosper under PAH exposure vary from soil to soil. Assuming that the goal is to understand microbial shifts in PAHs polluted soils, it is necessary to study microbial community changes in several soils concurrently. This study intended to study the bacterial communities that are altered as a result of creosote treatment and PAH degradation. The rationale behind our study is to facilitate reconsidering factors leading to bioremediation of creosote contaminated soils. Methodology Large containers filled with either spruce forest soil, pine forest soil, peat or glacial sand were contaminated with creosote or left intact. The degradation of PAHs, primarily fluoranthene, phenanthrene and pyrene, was followed for 27 weeks. The degradation was monitored at 4, 13 and 27 weeks using gas chromatography-mass spectroscopy (GC-MS), and bacterial community composition was analysed using 454 pyrosequencing. Results and Discussion Relative abundance and richness of Proteobacteria, particularly Betaproteobacteria and Deltaproteobacteria, was higher while Bacteroidetes and several genuses under the phylum Bacteroidetes including Sphingobacteriia was less abundant in creosote contaminated soils. This finding could be turn out to be important in bioremediation approach of creosote or PAH contaminated sites.
Keywords: Creosote Proteobacteria Betaproteobacteria Bacteroidetes Polyaromatic hydrocarbons (PAHs) Bacterial community composition Microbial degradation pristine soil