Analysis of subcellular localization of celestine (SrSO4) crystals in marine unicellular eukaryotes

Organisms highly concentrate certain elements from their environment. Far less about this is known in unicellular eukaryotes (= protists) than in multicellular organisms, although protists constitute the majority of eukaryotic diversity. We have found large amount of celestine (SrSO4) with admixtures of barite (BaSO4) crystals enclosed in vacuoles of unicellular marine protists belonging to the group Diplonemidae. Micro-XRF in frozen-hydrated intact cells will allow artefact-free intracellular localization of Sr and Ba or celestine and barite (e.g. in cytoplasm, vacuoles, cell surface incrustations etc.), with much better resolution and quantification than previous EDX analyses of diplonemids. Furthermore, assessing intraspecific and intrastagial differences in their distribution and morphology will hint to the uptake, formation and function of celestine and barite. We believe that such an in-depth study of these elements in eukaryotic cells is unprecedented.