Diesel is a significant anthropogenic pollutant within Antarctica . While management practices and disposal have improved, accidental spills still occur and ‘legacy spills’ persist in the terrestrial environment for decades. Remediation approaches such as biostimulation are essential to clean-up these contaminated sites. Biostimulation is a form of bioremediation that enhances the metabolic activity of endemic hydrocarbon degrading microorganisms by optimisation of environmental conditions, through the supplementation of key nutrients and if required, moisture and oxygen addition. Our research aims to understand microbial dynamics during active bioremediation. Hydrocarbon bioremediation was undertaken via the excavation of diesel contaminated soil and the construction of engineered biopiles amended with urea. The addition of urea-based nitrogen fertilizers was indeed effective in stimulating the microbial community, with significant reductions in hydrocarbons observed. But, alongside hydrocarbon degradation was a prolonged accumulation of toxic nitrite, likely caused by the rapid proliferation of ammonia oxidisers and nitrate reducers.
Given the harsh conditions of Antarctica and the need for ongoing remediation efforts, a better understanding of the microbial-metabolic pathways involved in soil bioremediation is critical. The aim of this research was to pioneer a soil metaproteomics approach, alongside metagenomics, to identify key shifts in taxonomy and metabolism over the biopile lifetime. We found that remediated soils that had been returned to the environment contained communities with more diverse metabolic strategies compared to soils undergoing active remediation. With the direct incorporation of ammonia by glutamate dehydrogenase and glutamine synthase minimal despite an abundance of soil ammonia. These findings support our earlier research that suggested existing guidelines on N/C ratios in terrestrial Antarctica are excessive. Furthermore, metaproteomics offers the ability for direct monitoring of nitrogen constraints by microbial communities present during active bioremediation.