Characterization of deinococcus radiodurans for actinide precipitation
- Author(s): Nitsche, Heino;
- et al.
Deinococcus radiodurans, a nonpathogenic prokaryote able to withstand high doses of ionizing radiation, is being engineered for bioremediation and biostabilization of heavy metals and actinides. An actinide bioprecipitation system for D. radiodurans capable of polyphosphate accumulation, inducible degradation and secretion, and uranyl precipitation, is being developed. The radioresistance of D. radiodurans to ionizing gamma radiation has been well studied, yet the effects of light-ion irradiation in aqueous suspension have not been characterized. The survivability in Helium and Nitrogen nuclei fields has been studied using the 88" cyclotron at the Lawrence Berkeley National Laboratory and increasing lethality corresponding to increasing linear energy transfer (LET) values of the radiation is seen. To understand the sorption chemistry of D. radiodurans, the interaction of strain R1 with UO22+ has been studied. The Gram-negative R1 uranyl sorption load is an order of magnitude less than that of non-engineered Gram-positive Bacillus sphaericus under similar conditions, and more than two orders of magnitude less than a polyphosphate accumulation engineered strain of Gram-negative Pseudomonas aeruginosa. Chemical studies of the cell-uranyl binding strength and pH sorption edges support spectroscopic data indicating that a carboxyl surface group, consistent with known characteristics of D. radiodurans' S-layer, interacts with and binds the uranyl. A strain engineered with the putative polyphosphate kinase gene shows promise for use in applications of uranyl bioprecipitation and its efficacy and contrast to the non-engineered strain will be discussed.