Exploring the potential of Gloeomargarita lithophora for radionuclides bioremediation

Current physico-chemical techniques for remediating ⁹⁰Sr traces from effluents are costly and can exhibit a low selectivity for Sr over Ca. Therefore, there is an incentive to develop an alternative method. In this study, we demonstrate that the cyanobacterium Gloeomargarita lithophora can rapidly remove more than 90 % of the ⁹⁰Sr activity from a nuclear plant effluent within 24 h. This process occurs through two steps: a first rapid and passive phase of ⁹⁰Sr sorbtion to the cell surface, followed by an active phase of ⁹⁰Sr accumulation within the cells, partially driven by photosynthesis. We show that ⁹⁰Sr sequestration within G. lithophora cells is stable with no release of ⁹⁰Sr into the surrounding medium. Furthermore, we evidence that incorporation of 2.05 × 10⁷ Bq g^-1DCW of ⁹⁰Sr and exposure to an estimated dose rate of 1.7 mGy h^-1 for 5 days did not result in cell death. To go further in the development of a bioremediation method, we established the capacity to sequester ⁹⁰Sr in a synthetic medium mimicking the radioactivity and mineral composition of a real industrial nuclear effluent. These results highlight G. lithophora as a promising solution for effective bioremediation of water contaminated with ⁹⁰Sr, especially from nuclear plant effluents.