Euglena sp. and its associated prokaryotic community degrade light crude oil

Oil enters the environment through natural and anthropogenic sources and poses a serious threat to water and soil. We hypothesized that algae and their associated prokaryotic communities from natural oil seeps are robust systems capable of surviving and degrading anthropogenic oil spills. We isolated Euglena sp. together with its closely associated prokaryotes from a natural oil seep in Germany and tested its oil degradation potential in laboratory cultivation experiments. Oil mineralization was monitored using reverse stable isotope labeling (RSIL), and the associated microbiome was characterized by 16S rRNA gene amplicon sequencing over a 76-day incubation. Dark incubations of Euglena sp. showed significantly higher oil degradation than day/night light cycle incubations. The RSIL data and microbial community dynamics indicated that oil degradation was primarily driven by Euglena sp. itself rather than by the associated prokaryotes. We conclude that the Euglena sp. culture SLN082 is a promising model for studying algal oil degradation and has potential for bioremediation applications. Comprehensive information on Euglena sp. isolation and experimental protocols, such as cultivation, RSIL measurements, DNA extraction and 16S rRNA gene amplicon sequencing, and subsequent bioinformatic analyses, is available in the supplementary text.