Interaction of uranium with a filamentous, heterocystous, nitrogen-fixing cyanobacterium, Anabaena torulosa

The filamentous, heterocystous, diazotrophic cyanobacterium, Anabaena torulosa was found to bind uranium from aqueous solutions containing 100 μM uranyl carbonate at pH 7.8. The uranyl sequestration kinetics exhibited (a) an initial rapid phase, binding 48% uranium within 30 min resulting in a loading of 56 mg U g−1 of dry wt, followed by (b) a slower phase, binding 65% uranium with resultant loading of 77.35 mg U g−1 in 24 h. Energy Dispersive X-ray fluorescence spectroscopy of uranium loaded biomass revealed all components of UL X-rays (ULl, ULα, ULβ1 and ULβ2). Heat killed cells or extracellular polysaccharides derived from live cells exhibited limited uranyl binding (∼26%) highlighting the importance of cell viability for optimum uranyl binding. The present study revealed the involvement of acid soluble polyphosphates in uranium accumulation by this brackish water cyanobacterium.