It’s complicated – microbial hydrocarbon degradation in sandy soils based on contamination history

Anthropogenic chemicals like polycyclic aromatic hydrocarbons (PAH) require quick removal from contaminated ecosystems. Therefore, it is crucial to investigate microbial community compositions of contaminated ecosystems to identify microbes with biodegrading capabilities for bioremediation.

Schwarz et al. (2018) predicted contamination responsiveness based on community structure in (shallow/deep) pristine and previously contaminated soil before adding phenanthrene as a proxy for PAH contamination. DNA and RNA stable isotope probing (SIP) was used in combination with temperature gradient electrophoresis to identify hydrocarbon-degrading microbes and assess community structures based on the 16S rRNA gene and the fungal ITS region. 

Fungal and bacterial baseline communities were similar across all sample types and included prominent hydrocarbon-degrading species in both soil types. Incubation with phenanthrene caused a decrease in fungal and bacterial diversity and evenness, leading to increased functional organisation. As expected, SIP identified several bacterial Gammaproteobacteria and fungal Basidiomycota as key degraders. Additionally, fungal community profiles of the samples with the highest degradation rates, deep pristine and shallow contaminated, were very similar in contrast to bacterial communities. Therefore, high degradation seemed to be neither related to contamination history, nor sample depth, indicating a more complex underlying causality than just microbial community structure, including an adaptable fungal community.

Schwarz, A., Adetutu, E. M., Juhasz, A. L., Aburto-Medina, A., Ball, A. S., & Shahsavari, E. (2018). Microbial Degradation of Phenanthrene in Pristine and Contaminated Sandy Soils. Microbial Ecology, 75(4), 888–902. https://doi.org/10.1007/s00248-017-1094-8