The use of stable isotope (SI) labelling and tracing of live diets is currently considered one of the most comprehensive tools to detect their uptake and assimilation by aquatic organisms. These techniques are indeed widely used in nutritional studies to follow the fate of specific microbial dietary components, unraveling trophic interactions. Nevertheless, to the current date, our understanding of aquatic trophic relationships has yet to include a whole domain of life, the Archaea. The aim of the present research was therefore to describe a halophilic Archaea (haloarchaea) labelling procedure. To do this, the SI 13C and 15N were used, in order to enable the application of SI tracing in future studies of haloarchaea consumption by aquatic metazoans. To this end, three 13C enriched carbon sources (glucose; sodium acetate and glycerol, 99% 13C-enriched) and two 15N enriched nitrogen sources ((NH4)2SO4 and NH4Cl, 99% 15N-enriched) were tested as potential labels to enrich cells of three haloarchaea strains when supplemented to the culture medium. Our overall results indicate 13C-glycerol as the most effective carbon source to achieve an efficient 13C enrichment in haloarchaea cells, with Δδ13C values above 5000‰ in all tested haloarchaea strains. As for 15N enriched nitrogen sources, both (15NH4)2SO4 and 15NH4Cl seem to be readily assimilated. This is also resulting in efficient 15N enrichment in haloarchaea cells, with Δδ15N values higher than 20000‰. We believe that the proposed methodology will allow for the use of SI labelled haloarchaea biomass in feeding tests. This will potentially provide unambiguous confirmation of the assimilation of haloarchaea biomass by aquatic metazoans.
If you would like to know more about this study, please read the full article available at https://link.springer.com/article/10.1007%2Fs00792-019-01084-w.
Reference: Lopes-Dos-Santos RMA, De Troch M, Bossier P, Van Stappen G (2019) Labelling halophilic Archaea using (13)C and (15)N stable isotopes: a potential tool to investigate haloarchaea consumption by metazoans. Extremophiles 23(3), pp. 359-365