Impact of diesel and biodiesel contamination on soil microbial community activity and structure

Soil contamination as a result of oil spills is a serious issue due to the global demand for diesel fuel. As an alternative to diesel, biodiesel has been introduced based on its high degradability rates and potential for reducing of greenhouse gases emissions. This study assessed the impacts diesel and biodiesel contamination on soil microbial community activity and structure. Our results suggest higher microbial activity in biodiesel contaminated soils and analysis of PLFA profiles confirmed shifts in microbial community structure in response to contamination. High-throughput 16S rRNA amplicon sequencing also revealed a lower bacterial richness and diversity in contaminated soils when compared to control samples, supporting evidence of the detrimental effects of hydrocarbons on soil microbiota. Control samples comprised mostly of Actinobacteria, whereas Proteobacteria were predominantly observed in diesel and biodiesel contaminated soils. At genus level, diesel and biodiesel amendments highly selected for Rhodococcus and Pseudomonas spp., respectively. Moreover, predicted functional profiles based on hydrocarbon-degrading enzymes revealed significant differences between contaminated soils mostly due to the chemical composition of diesel and biodiesel fuel. Here, we also identified that Burkholderiaceae, Novosphingobium, Anaeromyxobacter, Pseudomonas and Rhodococcus were the main bacterial taxa contributing to these enzymes. Together, this study supports the evidence of diesel/biodiesel adverse effects in soil microbial community structure and highlights microbial taxa that could be further investigated for their biodegradation potential.

Automated summary

The study found higher microbial activity in biodiesel-contaminated soils compared to diesel-contaminated ones, while contaminated soils had lower bacterial richness and diversity. Actinobacteria were predominant in control samples, whereas Proteobacteria were predominantly observed in diesel and biodiesel contaminated soils. Genus-level analysis showed Rhodococcus and Pseudomonas spp. were highly selected in diesel and biodiesel amendments, respectively. Predicted functional profiles based on hydrocarbon-degrading enzymes showed significant differences between contaminated soils, with Burkholderiaceae, Novosphingobium, Anaeromyxobacter, Pseudomonas and Rhodococcus identified as main bacterial taxa contributing to these enzymes.