Radium is a highly radioactive element that occurs naturally as a decay product of uranium and thorium. Exposure to radium has been linked to human cancers (ToxFAQs: Radium). Radium is found in highest concentrations in uranium ores, and Ra⁺ can be mobilized from uranium mine waste by the activity of sulfate-reducing (Landa et al, 1986) or iron(III)-reducing bacteria (Landa et al, 1991). Some growing cyanobacteria and algae have been found to accumulate radium (Havlik and Robertson, 1973), and biosorption of radium by bacterial (Satvatmanesh et al, 2003) and fungal (Tsezos and Keller, 1983) biomass has been described.

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Landa ER, Phillips JP, Loveley DR. Release of radium-226 from uranium mill tailings by microbial iron³⁺ reduction. Appl Geochem. 1991;6:647-52.

Satvatmanesh DF, Siavoshi F, Beitollahi MM, Amidi J, Fallahian N. Biosorption of ²²⁶ in high level natural radiation areas of Ramsar, Iran. J Radioanal Nucl Chem. 2003;258:483-86.

Tsezos M, Keller DM. Adsorption of radium-226 by biological origin absorbents. Biotechnol Bioeng. 1983;25:201-215.