We study Deinococcus radiodurans, a nonpathogenic prokaryote able to withstand high doses of ionizing radiation, for bioremediation and biostabilization of heavy metals and actinides to limit the migration of these contaminants. Our goal is to develop a system for D. radiodurans to bioprecipitate actinides similar to that of a genetically engineered strain of Pseudomonas aeruginosa capable of polyphosphate accumulation, inducible degradation and secretion, and UO22+ precipitation. The radioresistance of D. radiodurans to ionizing gamma radiation has been well studied, yet is not well understood1. Several DNA repair mechanisms have been discovered, yet survivability studies are typically done under nutrient-rich conditions at a single growth stage. Although a minimal irradiation medium has been described2, a clear study of the effect of different variables on survivability in a nutrient-starved environment has not been performed. We have shown that D. radiodurans grown in typical TGY complex media displays increasing radioresistance with increasing age of the culture at the time of harvest; however, the dose below which there is little loss of reproductive viability does not change significantly with growth phase. Higher irradiation rates in nutrient-starved medium display higher survivability. These results indicate that there is a threshold below which the radiation dose is not sufficient to overcome the cells' passive defense mechanisms, such as radical scavenging by carotenoids in the cell wall. Additional radiation resistance is then due to active resistance induced by cell damage, which can be related to aging. Using the 88" cyclotron at the Lawrence Berkeley National Laboratory, we also studied the effects of light-ion irradiation inaqueous suspension and show increasing lethality corresponding to increasing linear energy transfer (LET) values of the radiation. Previous studies only examined heavy ion effects on cells supported on solid medium3. To better understand the chemistry of non-engineered D. radiodurans, we studied the interaction of strain R1 with UO22+ in dilute salt solution. R1 sorbs uranyl more than two orders of magnitude less than the engineered P. aeruginosa. We are increasing the ability of D. radiodurans to sequester uranium via metabolic engineering. Chemical studies of the cell-uranyl binding strength and pH optima support spectroscopic data indicating that a carboxyl surface group, consistent with known characteristics of D. radiodurans' S-layer4, interacts with and binds the uranyl. Studies including Infrared Spectroscopy, Laser Fluorescence Spectroscopy, and Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS) are underway to further elucidate the mechanism of uranyl complexation to the cell surface and to further characterize a strain provided that has been engineered to accumulate polyphosphate.

BACKGROUND:Behavioral economics interventions have been shown to effectively reduce the rates of inappropriate antibiotic prescriptions for acute respiratory infections (ARIs). OBJECTIVE:To determine the cost-effectiveness of three behavioral economic interventions designed to reduce inappropriate antibiotic prescriptions for ARIs. DESIGN:Thirty-year Markov model from the US societal perspective with inputs derived from the literature and CDC surveillance data. SUBJECTS:Forty-five-year-old adults with signs and symptoms of ARI presenting to a healthcare provider. INTERVENTIONS:(1) Provider education on guidelines for the appropriate treatment of ARIs; (2) Suggested Alternatives, which utilizes computerized clinical decision support to suggest non-antibiotic treatment choices in lieu of antibiotics; (3) Accountable Justification, which mandates free-text justification into the patient's electronic health record when antibiotics are prescribed; and (4) Peer Comparison, which sends a periodic email to prescribers about his/her rate of inappropriate antibiotic prescribing relative to clinician colleagues. MAIN MEASURES:Discounted costs, quality-adjusted life years (QALYs), and incremental cost-effectiveness ratios. KEY RESULTS:Each intervention has lower costs but higher QALYs compared to provider education. Total costs for each intervention were $178.21, $173.22, $172.82, and $172.52, and total QALYs were 14.68, 14.73, 14.74, and 14.74 for the control, Suggested Alternatives, Accountable Justification, and Peer Comparison groups, respectively. Results were most sensitive to the quality-of-life of the uninfected state, and the likelihood and costs for antibiotic-associated adverse events. CONCLUSIONS:Behavioral economics interventions can be cost-effective strategies for reducing inappropriate antibiotic prescriptions by reducing healthcare resource utilization.

To understand the possible environmental interactions of uranium with the radioresistant bacterium Deinococcus radiodurans we have characterized its sorption complex chemically and spectroscopically. The binding strength, pH sorption edge, selective blocking of cell-surface functional groups, and competition with known complexors support laser fluorescence and infrared spectroscopic data indicating that a carboxyl surface group, consistent with known characteristics of D. radiodurans' S-layer, interacts with and binds the uranium. Although its high survivability in gamma radiation fields has been well studied, the effects of alpha particles from uranium bound to its surface may affect its survivability and interaction with the environment. Using Helium and Nitrogen nuclei cyclotron beams to mimic the effect of typical actinide alpha particles, we explored the ability of D. radiodurans to survive ion irradiation. In addition, a Co-60 gamma source was used to study the effects of environmental conditions on survivability.

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 UO22+ precipitation, is being developed.The radioresistance of D. radiodurans to ionizing gamma radiation has been well studied, yet is not well understood. Several DNA repair mechanisms have been discovered, yet survivability studies are typically done under nutrient-rich conditions at a single growth stage. Although a minimal irradiation medium has been described, the effect of different variables on survivability in a nutrient-starved environment has not been systematically studied. Results indicate that there is a threshold below which the radiation dose is not sufficient to overcome the cells' passive defense mechanisms, such as radical scavenging and constitutive repair proteins. Additional radiation survivability is then from active resistance induced by cell damage, possibly related to aging. The effects of light-ion irradiation in aqueous suspension have also 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. Previous studies only examined heavy ion effects on cells supported on solid medium.To better 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 accumulation genes shows promise for use in applications of uranyl bioprecipitation and its efficacy and contrast to the non-engineered strain will be discussed.