Solid phase capture of strontium by the iron reducing bacteria Shewanella alga strain BrY

The impact of the Fe (III)-reducing bacteria Shewanella alga on the solid p hase partitioning of dissolved Sr2+ was investigated in a series of experim ents using live cells, dead cells (heat-treated at 80 degrees C) and isolat ed cell envelope fractions, The synthetic hydrous ferric oxide (HFO) used i n the experiments was prepared in the laboratory by titration of FeCl3 with NaOH, The presence of dissolved Fe (II) was observed only in response to t he reductive dissolution of HFO by S. alga in experiments conducted with li ve cells, nor was the production of dissolved Fe (II) by the live cells inh ibited by 1 mM Sr2+ pH increased in each of the bacterial systems (live, de ad, cell envelope) as well as in the abiotic control (HFO, no bacteria) ove r the time course of the experiment (5 days) due presumably to a pCO(2) dra wdown of the culture medium in response to equilibration with the N-2 atmos phere of the anaerobic chamber used in the investigation. In the presence o f the live Fe (III)-reducing bacteria, the pH increase was sufficient to br ing about supersaturation with respect to siderite after approximately 2 da ys. Solid phase Sr2+ capture was greatest in the live cell systems (60%) fo llowed by dead cell and cell envelope treatments (40%), and least in the ab iotic control (10%). The greater percentage solid phase capture of Sr2+ i, the presence of the live cells is due to both sorption and precipitation pr ocesses occurring in this experimental system. These results show that non- viable S, alga cells and cell envelopes can sorb significantly greater quan tities of Sr2+ compared to HFO alone, and that siderite precipitation in li ve S. alga cultures enhances the solid phase partitioning of Sr2+. (C) 2000 Elsevier Science B.V. All rights reserved.