Insights into the degradation of diesel-contaminated seawater through natural microbiota and culturable microorganisms: The overlook role of extracellular polymeric substances (EPS)

The role of EPS produced during biodegradation diesel-contaminated seawater, as well as the effect of EPS on natural microbiota and culturable microorganisms, remains unknown. Here, natural microbiota (pre and post enrichment with diesel) from 5 islands' seawater in Jiaozhou Bay were explored through metagenomic and culture-dependent approaches. EPS response degradation was mainly characterized by the following aspects: 1) The post-enrichment samples contained significantly fewer dominant bacterial genera than the pre-enrichment samples, and EPS or PS (polysaccharides) promoted degradation of C16-C24 hydrocarbon fractions; 2) EPS caused higher increases in aromatic compound degradation functional genes copies; 3) EPS enhanced the enzymatic activity of alkane hydroxylase and ethanol dehydrogenase; 4) Diesel degradation by mono and mixed cultures of culturable bacteria (B1 and B2) with extracted EPS showed a higher biomass, biosurfactant production, expression of PAH-RHD alpha GN and cytochrome P450 genes, degradability and emulsification capacity. The above innovations provided new perspectives for oil-spill bioremediation.