Labelling of eicosapentaenoic acid with stable isotope 13C in the marine bacterium Shewanella marinintestina

Eicosapentaenoic acid (EPA) is an essential omega-3 polyunsaturated fatty acid that plays a critical role in marine life. It is present in several marine animals, including fish, but the primary producers of EPA are phytoplankton and specific marine bacteria. Although most of the EPA present in marine animals come from phytoplankton, the bacterial input into the marine EPA food web is still unknown. The labelling of EPA within a bacterial strain could be a viable strategy to help revealing this contribution. In this work, Shewanella marinintestina IRL 567, a marine bacterium isolated from fish guts and known to produce EPA, was labelled with the stable isotope 13C at small (250-mL shake flask), bench (2.5-L shake flask), and pilot scale (50-L stirred tank bioreactor). Growing the bacterium with 13C-acetate in the culture medium demonstrated that EPA was de-novo synthesized utilizing acetate as precursor. 13C incorporation into the EPA molecule resulted in values as high as 95.5% of the syn-thesized EPA being labelled in small scale, 95.9% in bench scale and 91.5% in pilot scale. This simple method to label EPA proved to be effective and therefore it could be a valuable tool to follow the fate of bacterial EPA into higher trophic levels.

Automated summary

EPA is an essential omega-3 polyunsaturated fatty acid that plays a critical role in marine life, primarily produced by phytoplankton and specific marine bacteria. Labelling a marine bacterium with stable isotope 13C proved to be an effective method to reveal the contribution of bacterial EPA, showing potential for further research.