Application Progress of Deinococcus radiodurans in Biological Treatment of Radioactive Uranium-Containing Wastewater

Insulin like growth factor binding protein 7 activate JNK/ERK signaling to aggravate uranium-induced renal cell cytotoxicity

Acute kidney injury (AKI) can occur primarily by exposing kidneys to uranium (U). Insulin-like growth factor binding protein 7 (IGFBP7) can regulate sepsis-induced AKI and epithelial-mesenchymal transition through ERK1/2 signaling. In vitro, the IGFBP7's role and mechanism of action in uranium-induced NRK-52E cells, however, remains unknown. To evaluate the effect of U exposure on kidneys, rat kidney proximal cell line NRK-52E was treated with different concentrations (200, 400, and 800 µmol/L) of it. Subsequently, three siRNAs targeting IGFBP7 were transfected with the HiPerFect reagent. The role of the JNK/ERK signaling pathway in uranium-induced kidney cytotoxicity was examined by a series of cell function experiments, including CCK-8 assay, TUNEL staining, RT-qPCR, Western blot, and flow cytometry analysis. Uranium inhibited NRK-52E cell viability and enhanced IGFBP7 expression in a dose-dependent manner. Silencing of IGFBP7 promoted cell cycle progression and inhibited cell apoptosis of uranium-treated cells. Mechanistically, silencing of IGFBP7 inhibited the uranium-activated JNK/ERK signaling pathway. The ERK1/2 signaling inhibitor PD98059 suppressed the IGFBP7-activated JNK/ERK signaling pathway. Furthermore, knockdown of IGFBP7 exerted a similar effect with PD98059 on uranium-induced NRK-52E cell cycle arrest and apoptosis. Silencing IGFBP7 inhibited the JNK/ERK signaling pathway to attenuate uranium-induced cytotoxicity and necrosis of NRK-52E cells.

A review of uranium (U) elemental detection methods

With the increasing demand for energy, nuclear energy has been developing rapidly. The quantitative detection and qualitative identification of uranium (U) are of great significance for the comprehensive and efficient use of U resources and the control of nuclear and radioactive substances. In this study, the detection of U is divided into liquid sample detection, solid sample detection, gas sample detection, and industrial detection from the perspectives of the sample state and detection environment. For liquid samples, the advantages and disadvantages of various detection methods are summarized. The application of different detection methods for different samples is also analyzed. For solid samples, the application of laser-induced breakdown spectroscopy and X-ray fluorescence in powder compaction and U-containing solid samples is presented. The problems of low instrumental resolution and poor accuracy of quantitative analyses are discussed, and methods to solve the above problems are proposed. For gas samples, UF6 can be analyzed for U isotopes using laser-induced breakdown spectroscopy. U abundance (235U/(235U + 238U)) is obtained quickly, directly and without the need for sample preparation. Finally, the application of remote detection and in situ detection techniques in industrial detection of U is also discussed in this study. In the future, rapid, high-precision and portable U detection methods can be developed by coupling multiple detection methods to meet the needs of different scenarios.

Enhanced uranium sequestration through selenite-modified nano-chitosan loaded with melatonin: Facilitating U(IV) conversion

The combined chemotoxicity and radiotoxicity associated with uranium, utilized in nuclear industry and military applications, poses significant threats to human health. Among uranium pollutants, uranyl is particularly concerning due to its high absorptivity and potent nephrotoxicity in its + 6 valence state. Here, we have serendipitously found Na2SeO3 facilitates the conversion of U(VI) to U(IV) precipitates. A novel approach involving nano-chitosan loaded internally with melatonin and externally modified with selenite (NPs Cs-Se/MEL) was introduced. This modification not only enhances the conversion of U(VI) to U(IV) but also preserves the spherical nanostructure and specific surface area, leading to increased adsorption of U(VI) compared to unmodified samples. Selenite modification improves lysosomal delivery in HEK-293 T cells and kidney distribution of the nanoparticles. Furthermore, NPs Cs-Se/MEL demonstrated a heightened uranium concentration in urine and exhibited remarkable efficiency in uranium removal, resulting in a reduction of uranium deposition in serum, kidneys, and femurs by up to 52.02 %, 46.79 %, and 71.04 %, respectively. Importantly, NPs Cs-Se/MEL can be excreted directly from the kidneys into urine when carrying uranium. The results presented a novel mechanism for uranium adsorption, making selenium-containing nano-materials attractive for uranium sequestration and detoxification.

16S amplicon-based microbiome biomapping of a commercial broiler hatchery

Hatcheries, where eggs from multiple breeder farms are incubated and hatched before being sent to different broiler farms, represent a nexus point in the commercial production of broilers in the United States. Considering all downstream microbial quality and safety aspects of broiler production (live production, processing, consumer use) can be potentially affected by the hatchery, a better understanding of microbial ecology within commercial hatcheries is essential. Therefore, a commercial broiler hatchery was biomapped using 16S rRNA amplicon-based microbiome analyses of four sample type categories (Air, Egg, Water, Facility) across five different places in the pre-hatch, hatch, and post-hatch areas. While distinct microbiota were found for each sample type category and hatchery area, microbial community analyses revealed that Egg microbiota trended towards clustering with the facility-related samples when moving from the prehatch to post-hatch areas, highlighting the potential effect of the hatchery environment in shaping the pre-harvest broiler-related microbiota. Prevalence analyses revealed 20 ASVs (Core20) present in the core microbiota of all sample types and areas, with each ASV possessing a unique distribution throughout the hatchery. Interestingly, three Enterobacteriaceae ASVs were in the Core20, including Salmonella. Subsequent analyses showed that Salmonella, while a minor prehatch and hatch Core20ASV, dominated the Enterobacteriaceae niche and total microbiota in the chick pad feces in the post-hatch area of the hatchery, and the presence of this Salmonella ASV in the post-hatch feces was associated with swabs of breakroom tables. These findings highlight the complexity of commercial hatchery microbiota, including identifying chick pad feces and breakroom tables as potentially important sampling or disinfection targets for hatchery managers to focus their Salmonella mitigation efforts to reduce loads entering live production farms.

Developing a new host-vector system for Deinococcus grandis

Deinococcus spp. are known for their radiation resistance, toxic compound removal, and production of valuable substances. Therefore, developing gene expression systems for Deinococcus spp. is crucial in advancing genetic engineering applications. To date, plasmid vectors that express foreign genes in D. radiodurans and D. geothermalis have been limited to plasmid pI3 and its derivatives. In contrast, plasmid vectors that express foreign genes in D. grandis include plasmid pZT23 and its derivatives. In this study, we developed a new system for the stable introduction and retention of expression plasmids for D. grandis. Two cryptic plasmids were removed from the wild-type strain to generate the TY3 strain. We then constructed a shuttle vector plasmid, pGRC5, containing the replication initiation region of the smallest cryptic plasmid, pDEGR-3, replication initiation region of the E. coli vector, pACYC184, and an antibiotic resistance gene. We introduced pGRC5, pZT23-derived plasmid pZT29H, and pI3-derived plasmid pRADN8 into strain TY3, and found their coexistence in D. grandis cells. The quantitative PCR assay results found that pGRC5, pZT29H, and pRADN8 had relative copy numbers of 11, 26, and 5 per genome, respectively. Furthermore, we developed a new plasmid in which the luciferase gene was controlled by the promoter region, which contained radiation-desiccation response operator sequences for D. grandis DdrO, a stress response regulon repressor in D. grandis, hence inducing gene expression via ultraviolet-C light irradiation. These plasmids are expected to facilitate the removal and production of toxic and valuable substances, in D. grandis, respectively, particularly of those involving multiple genes.

Research on the Properties of Wasteforms after Direct Involvement of Uranium-Containing Silica Gel in Glass Network Formation

Uranium-containing silica gel (UCSG) is a secondary waste generated during the advanced treatment of nuclear wastewater. In order to reduce the growing storage pressure for UCSG, from the perspective of building a borosilicate glass network, UCSG was used to replace SiO2 in the glass-cured formula to directly achieve the immobilization of UCSG. SEM-EDS results showed that uranium was uniformly distributed in the matrix, and the maximum solid solubility of UCSG (two components: silica gel and uranyl ions) in the formula was as high as 55 wt %. At the same time, TG-MS proved that silica gel lost OH groups (down about 4.61 wt %) and formed Si-O-Si bond by condensation. FT-IR and XPS proved a change in the number of Si-O-Si bond, and new Si-O-B and Si-O-Al bond appeared on the spectrum. This was evidence that silica gel could self-involved participate in the construction of glass networks. EPR analysis obtained the changes in the coordination environment of U atom, the U atom decreased spin electrons number in the glass than in uranyl crystals. The glass also has good physical properties (hardness: 6.51 ± 0.23 GPa; density: 2.3977 ± 0.0056 g/cm3) and chemical durability (normalized leaching rate: LRU = 2.34 × 10-4 ± 2.05 × 10-6 g·m2·days-1 after 42 days), this research provided tactics for simple treatment of uranium-containing silica gel in one step.

Construction of oxime-functionalized PCN-222 based on the directed molecular structure design for recovering uranium from wastewater

The directed construction of productive adsorbents is essential to avoid damaging human health from the harmful radioactive and toxic U(VI)-containing wastewater. Herein, a sort of Zr-based metal organic framework (MOF) called PCN-222 was synthesized and oxime functionalized based on directed molecular structure design to synthesize an efficient adsorbent with antimicrobial activity, named PCN-222-OM, for recovering U(VI) from wastewater. PCN-222-OM unfolded splendid adsorption capacity (403.4 mg·g-1) at pH = 6.0 because of abundant holey structure and mighty chelation for oxime groups with U(VI) ions. PCN-222-OM also exhibited outstanding selectivity and reusability during the adsorption. The XPS spectra authenticated the -NH and oxime groups which revealed a momentous function. Concurrently, PCN-222-OM also possessed good antimicrobial activity, antibiofouling activity, and environmental safety; adequately decreased detrimental repercussions about bacteria and Halamphora on adsorption capacity; and met non-toxic and non-hazardous requirements for the application. The splendid antimicrobial activity and antibiofouling activity perhaps arose from the Zr6(μ3-O)4(μ3-OH)4(H2O)4(OH)4 clusters and rich functional groups within PCN-222-OM. Originally proposed PCN-222-OM was one potentially propitious material to recover U(VI) in wastewater on account of outstanding adsorption capacity, antimicrobial activity, antibiofouling activity, and environmental safety, meanwhile providing a newfangled conception on the construction of peculiar efficient adsorbent.

Antioxidant defense of Deinococcus radiodurans: how does it contribute to extreme radiation resistance?

PURPOSE

Deinococcus radiodurans is an extremely radioresistant bacterium characterized by D10 of 10 kGy, and able to grow luxuriantly under chronic ionizing radiation of 60 Gy/h. The aim of this article is to review the antioxidant system of D. radiodurans and its possible role in the unusual resistance of this bacterium to ionizing radiation.

CONCLUSIONS

The unusual radiation resistance of D. radiodurans has apparently evolved as a side effect of the adaptation of this extremophile to other damaging environmental factors, especially desiccation. The antioxidant proteins and low-molecular antioxidants (especially low-molecular weight Mn2+ complexes and carotenoids, in particular, deinoxanthin), as well as protein and non-protein regulators, are important for the antioxidant defense of this species. Antioxidant protection of proteins from radiation inactivation enables the repair of DNA damage caused by ionizing radiation.

Compositional Changes in Sediment Microbiota Are Associated with Seasonal Variation of the Water Column in High-Altitude Hyperarid Andean Lake Systems

The lacustrine systems of La Brava and La Punta, located in the Tilopozo sector in the extreme south of Salar de Atacama, are pristine high-altitude Andean lakes found along the central Andes of South America. This shallow ecosystem suffers from permanent evaporation, leading to falling water levels, causing it to recede or disappear during the dry season. This dynamic causes physicochemical changes in lakes, such as low nutrient availability, pH change, and dissolved metals, which can influence the composition of the microbial community. In this study, we used a metataxonomic approach (16S rRNA hypervariable regions V3 to V4) to characterize the sedimentary microbiota of these lakes. To understand how the water column affects and is structured in the microbiota of these lakes, we combined the analysis of the persistence of the water column through satellite images and physicochemical characterization. Our results show a significant difference in abiotic factors and microbiota composition between La Punta and La Brava lakes. In addition, microbiota analysis revealed compositional changes in the ecological disaggregation (main and isolated bodies) and antagonistic changes in the abundance of certain taxa between lakes. These findings are an invaluable resource for understanding the microbiological diversity of high Andean lakes using a multidisciplinary approach that evaluates the microbiota behavior in response to abiotic factors. IMPORTANCE In this study, we analyzed the persistence of the water column through satellite images and physicochemical characterization to investigate the composition and diversity in High Andean Lake Systems in a hyperarid environment. In addition to the persistence of the water column, this approach can be used to analyze changes in the morphology of saline accumulations and persistence of snow or ice; for example, for establishing variable plant cover over time and evaluating the microbiota associated with soils with seasonal changes in plants. This makes it an ideal approach to search for novel extremophilic microorganisms with unique properties. In our case, it was used to study microorganisms capable of resisting desiccation and water restriction for a considerable period and adapting to survive in ecological niches, such as those with high UV irradiation, extreme drought, and high salt concentration.

Electrocatalytic and green system coupling strategy for simultaneous recovery and purification of uranium from uranium-containing wastewater

The recycling of uranium in wastewater is not only beneficial to the protection of ecological safety but also has great significance for the sustainable development of nuclear energy. However, there is no satisfactory method to recover and reuse uranium efficiently up to now. Here, we have developed an efficient and economical strategy that can achieve uranium recovery and direct reuse in wastewater. The feasibility analysis verified that the strategy still had good separation and recovery ability in acidic, alkaline, and high-salinity environments. The purity of uranium recovered from the separated liquid phase after electrochemical purification was up to about 99.95%. Ultrasonication could greatly increase the efficiency of this strategy, and 99.00% of high-purity uranium could be recovered within 2 h. We further improved the overall recovery rate by recovering the residual solid-phase uranium, and the overall recovery of uranium was increased to 99.40%. Moreover, the concentration of impurity ions in the recovered solution met the World Health Organization guidelines. In summary, the development of this strategy is of great importance for the sustainable use of uranium resources and environmental protection.

Application of radiological assessment as water quality criterion for effluent release in a Brazilian uranium mine

Uranium mining causes several radiological impacts on the surrounding environment, notably in the water bodies, mainly due to the release of long half-life radionuclides from the ²³⁸U and ²³²Th series. The Ore Treatment Unit, an old uranium mine undergoing decommissioning, has three points of liquid effluent release (#014, #025, and #076). For current study, 78 samples of water were collected at #014, 33 samples at #025, and 63 samples at #076. The radionuclides were analyzed by gross alpha count, gross beta count, and by arsenazo spectrophotometry. Analyses were carried out using the radiological water quality criterion established by World Health Organization and other organizations, together with the Brazilian legislation, to assess if the released effluents may be used unrestrictedly by the individuals of the public. At #014, the mean values of activity concentration (AC), in Bq·L^-1, were as follows: U_nat = 0.107, ²²⁶Ra = 0.035, ²¹⁰Pb = 0.031, ²³²Th = 0.007, and ²²⁸Ra = 0.049. At #025 the mean values of AC, in Bq·L^-1, were as follows: U_nat = 0.086, ²²⁶Ra = 0.015, ²¹⁰Pb = 0.028, ²³²Th = 0.006, and ²²⁸Ra = 0.032. Finally, at point #076, the mean AC values, in Bq·L^-1, were as follows: U_nat = 3.624, ²²⁶Ra = 0.074, ²¹⁰Pb = 0.054, ²³²Th = 0.013, and ²²⁸Ra = 0.069. The current study showed that natural radionuclides were not in secular equilibrium. Despite uranium presented its values outside the limits of guidance levels, it can be state that the unrestricted use of effluents released in the three water bodies is authorized from the radiological point of view. In terms of dose rate, the releases at three points were within the radiological limits of potability. On the other hand, in an additional analysis, #76 presented chemical toxicity above the authorized value, pointing the need of restricted use of water from the point of view of chemical toxicity.

A strategy for bioremediation of nuclear contaminants in the environment

Radionuclides released from nuclear contamination harm the environment and human health. Nuclear pollution spread over large areas and the costs associated with decontamination is high. Traditional remediation methods include both chemical and physical, however, these are expensive and unsuitable for large-scale restoration. Bioremediation is the use of plants or microorganisms to remove pollutants from the environment having a lower cost and can be upscaled to eliminate contamination from soil, water and air. It is a cheap, efficient, ecologically, and friendly restoration technology. Here we review the sources of radionuclides, bioremediation methods, mechanisms of plant resistance to radionuclides and the effects on the efficiency of biological adsorption. Uptake of radionuclides by plants can be facilitated by the addition of appropriate chemical accelerators and agronomic management, such as citric acid and intercropping. Future research should accelerate the use of genetic engineering and breeding techniques to screen high-enrichment plants. In addition, field experiments should be carried out to ensure that this technology can be applied to the remediation of nuclear contaminated sites as soon as possible.

Functionalized maghemite nanoparticles for enhanced adsorption of uranium from simulated wastewater and magnetic harvesting

Maghemite (γ-Fe₂O₃) nanoparticles (MNPs) were functionalized with 3-aminopropyltriethoxysilane (APTES) to give APTES@Fe₂O₃ (AMNP) which was then reacted with diethylenetriamine-pentaacetic acid (DTPA) to give a nanohybrid DTPA-APTES@Fe₂O₃ (DAMNP). Nano-isothermal titration calorimetry shows that DTPA complexation with uranyl ions in water is exothermic and has a stoichiometry of two DTPA to three uranyl ions. Density functional theory calculations indicate the possibility of several complexes between DTPA and UO₂²⁺ with different stoichiometries. Interactions between uranyl ions and DAMNP functional groups are revealed by X-photoelectron and Fourier transform infrared spectroscopies. Spherical aberration-corrected Scanning Transmission Electron Microscopy visualizes uranium on the particle surface. Adsorbent performance metrics were evaluated by batch adsorption studies under different conditions of pH, initial uranium concentration and contact time, and the results expressed in terms of equilibrium adsorption capacities (q_e) and partition coefficients (PC). By either criterion, performance increases from MNP to AMNP to DAMNP, with the maximum uptake at pH 5.5 in all cases: MNP, q_e = 63 mg g^-1, PC = 127 mg g^-1 mM^-1; AMNP, q_e = 165 mg g^-1, PC = 584 mg g^-1 mM^-1; DAMNP, q_e = 249 mg g^-1, PC = 2318 mg g^-1 mM^-1 (at 25 °C; initial U concentration 0.63 mM; 5 mg adsorbent in 10 mL of solution; contact time, 3 h). The pH maximum is related to the predominance of mono- and di-cationic uranium species. Uptake by DAMNPs follows a pseudo-first-order or pseudo-second-order kinetic model and fits a variety of adsorption models. The maximum adsorption capacity for DAMNPs is higher than for other functionalized magnetic nanohybrids. This adsorbent can be regenerated and recycled for at least 10 cycles with less than 10% loss in activity, and shows high selectivity. These findings suggest that DAMNP could be a promising adsorbent for the recovery of uranium from nuclear wastewaters.

Adsorption performance of Enterobacter cloacae towards U(VI) ion and application of Enterobacter cloacae/carbon nanotubes to preconcentration and determination of low-levels of U(VI) in water samples

Keeping the high potential of some microorganisms in adsorption of radionuclides in view, the adsorption properties of Enterobacter cloacae towards uranium were attentively scrutinized, and then it was used for preconcentration of uranium in different samples, using Enterobacter cloacae/carbon nanotube composite. First, using ultrasonic agitation, the effects of operational factors on biosorption of uranium on the inactive Enterobacter cloacae were appraised and modeled by central composite design, and a comprehensive study was performed on the equilibrium, kinetics, thermodynamic, and selectivity aspects of biosorption. The optimization studies along with the evaluations of the adsorption properties revealed that Enterobacter cloacae have a high affinity for fast and selective biosorption of uranium ions, at pH 5.1. Second, the Enterobacter cloacae/carbon nanotube was synthesized, characterized, and utilized for preconcentration of uranium in different samples, using a mini-column packed with the composite. The optimization of operational factors on recovery of uranium, using the central composite design, showed that uranium can be quantitively adsorbed at a sample flow rate lower than 4.5 mL min^-1 and the desorption could be accomplished with 3.0 mL HCl 0.6 M solution. Finally, the mini-column was exploited for preconcentration and determination of uranium in different samples. The results revealed the low detection limit (0.015 μg.L^-1), high precision (RSDs ≤3.92%), and good accuracy of the proposed procedure.

Highly selective extraction of uranium from wastewater using amine-bridged diacetamide-functionalized silica

A major environmental concern related to nuclear energy is wastewater contaminated with uranium, thus necessitating the development of pollutant-reducing materials with efficiency and effectiveness. Herein, highly selective mesoporous silicas functionalized with amine-bridged diacetamide ligands SBA-15-ABDMA were prepared. Different spectroscopy techniques were used to probe the chemical environment and reactivity of the chelating ligands before and after sorption. The results showed that the functionalized SBA-15-ABDMA had a strong affinity for uranium at low pH (pH = 3) with desirable sorption capacity (68.82 mg/g) and good reusability (> 5). It showed excellent separation performance with a high distribution coefficient (K_d,U > 10⁵ mL/g) and separation factors SF_U/Ln > 1000 at a pH of 3.5 in the presence of lanthanide nuclides, alkaline earth metal and transition metal ions. In particular, SiO₂spheres-ABDMA was used as a column material, which achieved excellent recovery of U(VI) (> 98%) and good reusability for samples of simulated mining and nuclear industries wastewater. XPS and crystallography studies clearly illustrated the tridentate coordination mode of U(VI)/PEABDMA and the mechanism and origin behind the high selectivity for U.

Bio-enrichment of heavy metals U(VI) in wastewater by protein DSR A

Uptaking U(VI) from the environment by biological method is an environmental friendly and efficient way. In this work, we have acquired and isolated the protein DSR A by genetic engineering, then assessed its capacity and mechanisms to absorb U(VI) from wastewater. As results, we proved that protein DSR A can precisely recognize, enrich and remove uranyl ions in simulated wastewater solution. Its great removal potential was demonstrated in the adsorption experiments, the adsorption capacity of protein DSR A can reach 182.3 mg/g in the condition at 10 mg/L U(VI) and pH = 6. The Langmuir isotherm model and the pseudo-first-order kinetic equation were used to better describe the absorption process. We can confirm that Na⁺, Sr²⁺ and K⁺, these three metal ions have less effect on the enrichment of U(VI) by protein DSR A compared with other common cations. Besides, we can educe some mechanisms for the removal of U (VI) by protein DSR A from the results of FTIR, SEM-EDS, XPS (binding energy = 2.0 ~ 4.0ke V), MAP and XRD analysis before and after adsorption. This work has demonstrated the great potential of genetic engineering and biological methods in dealing with environmental heavy ion pollution.

Molecular Mechanisms Underlying Bacterial Uranium Resistance

Environmental uranium pollution due to industries producing naturally occurring radioactive material or nuclear accidents and releases is a global concern. Uranium is hazardous for ecosystems as well as for humans when accumulated through the food chain, through contaminated groundwater and potable water sources, or through inhalation. In particular, uranium pollution pressures microbial communities, which are essential for healthy ecosystems. In turn, microorganisms can influence the mobility and toxicity of uranium through processes like biosorption, bioreduction, biomineralization, and bioaccumulation. These processes were characterized by studying the interaction of different bacteria with uranium. However, most studies unraveling the underlying molecular mechanisms originate from the last decade. Molecular mechanisms help to understand how bacteria interact with radionuclides in the environment. Furthermore, knowledge on these underlying mechanisms could be exploited to improve bioremediation technologies. Here, we review the current knowledge on bacterial uranium resistance and how this could be used for bioremediation applications.