Harnessing nature’s hidden alliances: about the oil degradation potential of native procaryotes and algae isolated from natural oil seeps

Crude oil can flow naturally to the earth's surface without human intervention. Such natural oil seeps occur around the world, leaking into marine, freshwater or terrestrial environments through geological processes and fractures in underground rocks. While oil is toxic to most living organisms, many bacteria and some algae can use it as a carbon source and degrade it. From a microbiological perspective, these natural seeps are relatively understudied compared to anthropogenic spills, despite significant biological, chemical and physical differences.
In our research, we study the native microorganisms and species interactions, including prokaryotes and eukaryotic microalgae, isolated from natural oil seeps. We hypothesise that these native organisms are better adapted to oil and can degrade anthropogenic oil spills faster than microorganisms from freshly contaminated sites. In addition, algae harbor oil-degrading prokaryotes in their phycosphere, which helps them survive in harsh, toxic conditions while providing CO2 from oil mineralisation.
We sampled microorganisms and isolated oil-tolerant algae from two natural oil seeps in Germany and set up microcosm experiments to test our hypotheses. Oil degradation was assessed by monitoring visual and microscopic changes, pH, cell numbers (DAPI/flow cytometry), determining microbial community composition via 16/18S rRNA gene sequencing, and measuring CO2 evolution using our proprietary reverse stable isotope labelling (RSIL) method. RSIL allows us to measure the mineralisation of complex oils without the need to know their exact chemical composition.
Our results show that adding microbes from natural oil seeps to an oil spill can accelerate oil degradation rates by up to 60%. In addition, prokaryotic algal (Euglena sp.) cultures degrade oil effectively, but the RSIL method needs further development to account for CO2 fixation by algae.
Understudied natural oil seeps provide a diverse habitat with a large potential of well-adapted oil-degrading microorganisms and consortia that could accelerate the degradation of anthropogenic oil spills and contribute to carbon cycling. Prokaryotic-algal interactions appear to be important in creating more stable conditions for both to thrive in toxic oil environments.