Enhanced rare-earth separation with a metal-sensitive lanmodulin dimer.

Technologically critical rare-earth elements are notoriously difficult to separate, owing to their subtle differences in ionic radius and coordination number1-3. The natural lanthanide-binding protein lanmodulin (LanM)4,5 is a sustainable alternative to conventional solvent-extraction-based separation6. Here we characterize a new LanM, from Hansschlegelia quercus (Hans-LanM), with an oligomeric state sensitive to rare-earth ionic radius, the lanthanum(III)-induced dimer being >100-fold tighter than the dysprosium(III)-induced dimer. X-ray crystal structures illustrate how picometre-scale differences in radius between lanthanum(III) and dysprosium(III) are propagated to Hans-LanM's quaternary structure through a carboxylate shift that rearranges a second-sphere hydrogen-bonding network. Comparison to the prototypal LanM from Methylorubrum extorquens reveals distinct metal coordination strategies, rationalizing Hans-LanM's greater selectivity within the rare-earth elements. Finally, structure-guided mutagenesis of a key residue at the Hans-LanM dimer interface modulates dimerization in solution and enables single-stage, column-based separation of a neodymium(III)/dysprosium(III) mixture to >98% individual element purities. This work showcases the natural diversity of selective lanthanide recognition motifs, and it reveals rare-earth-sensitive dimerization as a biological principle by which to tune the performance of biomolecule-based separation processes.

GENTANGLE: integrated computational design of gene entanglements.

SUMMARY: The design of two overlapping genes in a microbial genome is an emerging technique for adding more reliable control mechanisms in engineered organisms for increased stability. The design of functional overlapping gene pairs is a challenging procedure, and computational design tools are used to improve the efficiency to deploy successful designs in genetically engineered systems. GENTANGLE (Gene Tuples ArraNGed in overLapping Elements) is a high-performance containerized pipeline for the computational design of two overlapping genes translated in different reading frames of the genome. This new software package can be used to design and test gene entanglements for microbial engineering projects using arbitrary sets of user-specified gene pairs. AVAILABILITY AND IMPLEMENTATION: The GENTANGLE source code and its submodules are freely available on GitHub at https://github.com/BiosecSFA/gentangle. The DATANGLE (DATA for genTANGLE) repository contains related data and results and is freely available on GitHub at https://github.com/BiosecSFA/datangle. The GENTANGLE container is freely available on Singularity Cloud Library at https://cloud.sylabs.io/library/khyox/gentangle/gentangle.sif. The GENTANGLE repository wiki (https://github.com/BiosecSFA/gentangle/wiki), website (https://biosecsfa.github.io/gentangle/), and user manual contain detailed instructions on how to use the different components of software and data, including examples and reproducing the results. The code is licensed under the GNU Affero General Public License version 3 (https://www.gnu.org/licenses/agpl.html).

Prolonging genetic circuit stability through adaptive evolution of overlapping genes.

The development of synthetic biological circuits that maintain functionality over application-relevant time scales remains a significant challenge. Here, we employed synthetic overlapping sequences in which one gene is encoded or 'entangled' entirely within an alternative reading frame of another gene. In this design, the toxin-encoding relE was entangled within ilvA, which encodes threonine deaminase, an enzyme essential for isoleucine biosynthesis. A functional entanglement construct was obtained upon modification of the ribosome-binding site of the internal relE gene. Using this optimized design, we found that the selection pressure to maintain functional IlvA stabilized the production of burdensome RelE for >130 generations, which compares favorably with the most stable kill-switch circuits developed to date. This stabilizing effect was achieved through a complete alteration of the allowable landscape of mutations such that mutations inactivating the entangled genes were disfavored. Instead, the majority of lineages accumulated mutations within the regulatory region of ilvA. By reducing baseline relE expression, these more 'benign' mutations lowered circuit burden, which suppressed the accumulation of relE-inactivating mutations, thereby prolonging kill-switch function. Overall, this work demonstrates the utility of sequence entanglement paired with an adaptive laboratory evolution campaign to increase the evolutionary stability of burdensome synthetic circuits.

QuickStroop Predicts Time to Development of Overt Hepatic Encephalopathy and Related Hospitalizations in Patients With Cirrhosis.

Cirrhosis-related neurocognitive impairment caused by covert or minimal hepatic encephalopathy (CHE) affects psychosocial function, increases risk of overt hepatic encephalopathy (OHE) development, and worsens survival.1,2 However, detection in clinical practice is challenging.2 One modality used for screening and prediction of outcomes related to cirrhosis is the EncephalApp Stroop, but it can require up to 10 minutes. Furthermore, the assessment comprises of distinct stages of difficulty, with an easier "Off" stage and a more challenging "On" stage.3 To alleviate these concerns, QuickStroop, which takes <1 minute, was developed. This uses only the first 2 runs of the Off stage of the EncephalApp Stroop, where number signs presented in red, green, or blue need to be matched quickly to their respective colors.4 A prior study showed these versions were comparable cross-sectionally to diagnose CHE.4 However, the utility of QuickStroop to predict cirrhosis-related outcomes is unclear.5-7 Our aim was to determine the ability of QuickStroop to determine time to development of OHE and OHE-related hospitalizations, all-cause hospitalizations, and death in outpatients with cirrhosis.

Scalable and Consolidated Microbial Platform for Rare Earth Element Leaching and Recovery from Waste Sources.

Chemical methods for the extraction and refinement of technologically critical rare earth elements (REEs) are energy-intensive, hazardous, and environmentally destructive. Current biobased extraction systems rely on extremophilic organisms and generate many of the same detrimental effects as chemical methodologies. The mesophilic methylotrophic bacterium Methylobacterium extorquens AM1 was previously shown to grow using electronic waste by naturally acquiring REEs to power methanol metabolism. Here we show that growth using electronic waste as a sole REE source is scalable up to 10 L with consistent metal yields without the use of harsh acids or high temperatures. The addition of organic acids increases REE leaching in a nonspecific manner. REE-specific bioleaching can be engineered through the overproduction of REE-binding ligands (called lanthanophores) and pyrroloquinoline quinone. REE bioaccumulation increases with the leachate concentration and is highly specific. REEs are stored intracellularly in polyphosphate granules, and genetic engineering to eliminate exopolyphosphatase activity increases metal accumulation, confirming the link between phosphate metabolism and biological REE use. Finally, we report the innate ability of M. extorquens to grow using other complex REE sources, including pulverized smartphones, demonstrating the flexibility and potential for use as a recovery platform for these critical metals.

Left Ventricular Diastolic Dysfunction and Pulmonary Hypertension: Outcomes in SAVR.

BACKGROUND: Severe pulmonary hypertension (PH) and left ventricular diastolic dysfunction (LVDD) are independently associated with poor outcomes in cardiac surgery. We evaluated the relationship of several measures of LVDD, PH, and hemodynamic subtypes of PH including precapillary pulmonary hypertension(pcPH) and isolated post-capillary pulmonary hypertension(ipcPH) and combined pre and post capillary pulmonary hypertension(cpcPH) capillary PH to postoperative outcomes in a cohort of patients who underwent elective isolated-AVR. METHODS: We evaluated (n = 206) patients in our local STS database who underwent elective isolated-AVR between 2014 and 2018, with transthoracic echocardiogram (n = 177) or right heart catheterization (n = 183) within 1 year of operation (or both, n = 161). The primary outcome was a composite end point of death, prolonged ventilation, ICU readmission, and hospital stay >14 days. RESULTS: Severe PH was associated with worse outcomes (moderate: OR, 1.1, p = 0.09; severe: OR, 1.28, p = 0.01), but degree of LVDD was not associated with worse outcomes. Across hemodynamic subtypes of PH, odds of composite outcome were similar (p = 0.89), however, patients with cpcPH had more postoperative complications (67 vs. 36%, p = 0.06) and patients with ipcPH had greater all-cause mortality at 1 (8 vs. 1%, p = 0.03) and 3 years (27 vs. 4%, p = 0.008). CONCLUSION: Severe PH conferred modestly greater risk of adverse events, and both LVDD grade and the combination of severe PH and LVDD were not associated with worse outcomes. However, hemodynamic stratification of PH revealed higher postoperative complications and worse long-term outcomes for those with cpcPH and ipcPH. Preoperative stratification of PH by hemodynamic subtype in valve replacement surgery may improve our risk stratification in this heterogenous condition. Further evaluation of the significance of LVDD and PH in other cardiac operations is warranted.

Reduction in Nosocomial Infections in Patients With Cirrhosis During the COVID-19 Era Compared with Pre-COVID-19: Impact of Masking and Restricting Visitation.

Nosocomial infections (NIs) in critically ill patients with cirrhosis result in higher death and transplant delisting. NIs are promoted by staff, visitors, and the environment, all of which were altered to reduce pathogen transmission after COVID-19. Two cohorts of intensive care unit patients with cirrhosis from March 2019 to February 2020 (pre-COVID, n = 234) and March 2020 to March 2021 (COVID era, n = 296) were included. We found that despite a higher admission MELD-Na, qSOFA, and WBC count and requiring a longer intensive care unit stay, COVID-era patients developed lower NIs (3% vs 10%, P < 0.001) and had higher liver transplant rates vs pre-COVID patients. COVID-era restrictions could reduce NIs in critically ill patients with cirrhosis.

Bristol Stool Scale as a Determinant of Hepatic Encephalopathy Management in Patients With Cirrhosis.

INTRODUCTION: Bowel movement (BM) frequency is used to titrate lactulose for hepatic encephalopathy (HE). However, stool consistency using the Bristol stool scale (BSS, 0-7) is often ignored. METHODS: The study included pre-BSS and post-BSS cohorts. BSS was incorporated into decision-making after training in outpatients with cirrhosis. Two to 3 BMs/d and BSS 3-4 were considered normal, whereas the rest were considered high or low; concordance between the metrics was evaluated. Medication changes and 6-month admissions were compared between this group (post-BSS) and a comparable previous group (pre-BSS). Concordance and regression analyses for all-cause admissions and HE-related admissions were performed, and comparisons were made for HE-related medication stability. In the longitudinal analysis, an outpatient group seen twice was analyzed for BSS and BMs. RESULTS: In the post-BSS cohort, 112 patients were included with only 46% BSS and BMs concordance and modest BSS/BMs correlation (r = 0.27, P = 0.005). Compared with a pre-BSS cohort (N = 114), there was a lower 6-month total (4% vs 0.36%, P < 0.001) or HE-related admission (1% vs 0.12%, P = 0.002). Regression showed model for end-stage liver disease (odds ratio [OR]: 1.10, P = 0.003) and pre-BSS/post-BSS (OR: 0.04, P < 0.001) for all-cause admissions and HE (OR: 3.59, P = 0.04) and preera/postera (OR: 0.16, P = 0.02) for HE-related admissions as significant. HE medication regimens were more stable post-BSS vs pre-BSS (32% vs 20%, P = 0.04), which was due to patients with BSS > BMs (P = 0.02). In the longitudinal analysis, 33 patients without medication changes or underlying clinical status changes were tested 36 ± 24 days apart. No changes in BSS (P = 0.73) or BMs (P = 0.19) were found. DISCUSSION: BSS is complementary and additive to BM frequency, can modulate the risk of readmissions and stabilize HE-related therapy changes in outpatients with cirrhosis, and could help personalize HE management.

Projection Microstereolithographic Microbial Bioprinting for Engineered Biofilms.

Microbes are critical drivers of all ecosystems and many biogeochemical processes, yet little is known about how the three-dimensional (3D) organization of these dynamic organisms contributes to their overall function. To probe how biofilm structure affects microbial activity, we developed a technique for patterning microbes in 3D geometries using projection stereolithography to bioprint microbes within hydrogel architectures. Bacteria were printed and monitored for biomass accumulation, demonstrating postprint viability of cells using this technique. We verified our ability to integrate biological and geometric complexity by fabricating a printed biofilm with two E. coli strains expressing different fluorescence. Finally, we examined the target application of microbial absorption of metal ions to investigate geometric effects on both the metal sequestration efficiency and the uranium sensing capability of patterned engineered Caulobacter crescentus strains. This work represents the first demonstration of the stereolithographic printing of microbials and presents opportunities for future work of engineered biofilms and other complex 3D structured cultures.

Chrysophanol-Induced Autophagy Disrupts Apoptosis via the PI3K/Akt/mTOR Pathway in Oral Squamous Cell Carcinoma Cells.

Background and Objectives: Natural products are necessary sources for drug discovery and have contributed to cancer chemotherapy over the past few decades. Furthermore, substances derived from plants have fewer side effects. Chrysophanol is an anthraquinone derivative that is isolated from rhubarb. Although the anticancer effect of chrysophanol on several cancer cells has been reported, studies on the antitumor effect of chrysophanol on oral squamous-cell carcinoma (OSCC) cells have yet to be elucidated. Therefore, in this study, we investigated the anticancer effect of chrysophanol on OSCC cells (CAL-27 and Ca9-22) via apoptosis and autophagy, among the cell death pathways. Results: It was found that chrysophanol inhibited the growth and viability of CAL-27 and Ca9-22 and induced apoptosis through the intrinsic pathway. It was also found that chrysophanol activates autophagy-related factors (ATG5, beclin-1, and P62/SQSTM1) and LC3B conversion. That is, chrysophanol activated both apoptosis and autophagy. Here, we focused on the roles of chrysophanol-induced apoptosis and the autophagy pathway. When the autophagy inhibitor 3-MA and PI3K/Akt inhibitor were used to inhibit the autophagy induced by chrysophanol, it was confirmed that the rate of apoptosis significantly increased. Therefore, we confirmed that chrysophanol induces apoptosis and autophagy at the same time, and the induced autophagy plays a role in interfering with apoptosis processes. Conclusions: Therefore, the potential of chrysophanol as an excellent anticancer agent in OSCC was confirmed via this study. Furthermore, the combined treatment of drugs that can inhibit chrysophanol-induced autophagy is expected to have a tremendous synergistic effect in overcoming oral cancer.

Microbe-Encapsulated Silica Gel Biosorbents for Selective Extraction of Scandium from Coal Byproducts.

Scandium (Sc) has great potential for use in aerospace and clean energy applications, but its supply is currently limited by a lack of commercially viable deposits and the environmental burden of its production. In this work, a biosorption-based flow-through process was developed for extraction of Sc from low-grade feedstocks. A microbe-encapsulated silica gel (MESG) biosorbent was synthesized through sol-gel encapsulation of Arthrobacter nicotianae, a bacterium that selectively adsorbs Sc. Microscopic imaging revealed a high cell loading and macroporous structure, which enabled rapid mass transport and adsorption/desorption of metal ions. The biosorbent displayed high Sc selectivity against lanthanides and major base metals, with the exception of Fe(III). Following pH adjustment to remove Fe(III) from an acid leachate prepared from lignite coal, a packed-bed column loaded with the MESG biosorbent exhibited near-complete Sc separation from lanthanides; the column eluate had a Sc enrichment factor of 10.9, with Sc constituting 96.4% of the total rare earth elements. The MESG biosorbent exhibited no significant degradation with regard to both adsorption capacity and physical structure after 10 adsorption/desorption cycles. Overall, our results suggest that the MESG biosorbent offers an effective and green alternative to conventional liquid-liquid extraction for Sc recovery.

The UzcRS two-component system in Caulobacter crescentus integrates regulatory input from diverse auxiliary regulators.

The UzcRS two-component system in Caulobacter crescentus mediates widespread transcriptional activation in response to the metals U, Zn and Cu. Unexpectedly, a screen for mutations that affected the activity of the UzcR-regulated urcA promoter (PurcA ) revealed four previously uncharacterized proteins whose inactivation led to metal-independent induction of PurcA . Using molecular genetics and functional genomics, we find that these auxiliary regulators control PurcA expression by modulating the activity of UzcRS through distinct mechanisms. An ABC transporter with a periplasmic metallo-aminopeptidase domain forms a sensory complex with UzcRS, antagonizing metal dependent stimulation by virtue of its ATPase and peptidase domains. Two MarR-like transcription factors synergistically regulate UzcRS activity by repressing the expression of the membrane proteins UzcY and UzcZ, which stimulate UzcRS activity and enhance its sensitivity to a more environmentally relevant U/Zn/Cu concentration range. Additionally, the membrane protein UzcX, whose expression is positively regulated by UzcR, provides a mechanism of feedback inhibition within the UzcRS circuit. Collectively, these data suggest that UzcRS functions as the core-signaling unit within a multicomponent signal transduction pathway that includes a diverse set of auxiliary regulators, providing further insight into the complexity of signaling networks.

Anti-Atherogenic Effect of Stem Cell Nanovesicles Targeting Disturbed Flow Sites.

Atherosclerosis development leads to irreversible cascades, highlighting the unmet need for improved methods of early diagnosis and prevention. Disturbed flow formation is one of the earliest atherogenic events, resulting in increased endothelial permeability and subsequent monocyte recruitment. Here, a mesenchymal stem cell (MSC)-derived nanovesicle (NV) that can target disturbed flow sites with the peptide GSPREYTSYMPH (PREY) (PMSC-NVs) is presented which is selected through phage display screening of a hundred million peptides. The PMSC-NVs are effectively produced from human MSCs (hMSCs) using plasmid DNA designed to functionalize the cell membrane with PREY. The potent anti-inflammatory and pro-endothelial recovery effects are confirmed, similar to those of hMSCs, employing mouse and porcine partial carotid artery ligation models as well as a microfluidic disturbed flow model with human carotid artery-derived endothelial cells. This nanoscale platform is expected to contribute to the development of new theragnostic strategies for preventing the progression of atherosclerosis.

Selective and Efficient Biomacromolecular Extraction of Rare-Earth Elements using Lanmodulin.

Lanmodulin (LanM) is a recently discovered protein that undergoes a large conformational change in response to rare-earth elements (REEs). Here, we use multiple physicochemical methods to demonstrate that LanM is the most selective macromolecule for REEs characterized to date and even outperforms many synthetic chelators. Moreover, LanM exhibits metal-binding properties and structural stability unseen in most other metalloproteins. LanM retains REE binding down to pH ≈ 2.5, and LanM-REE complexes withstand high temperature (up to 95 °C), repeated acid treatments, and up to molar amounts of competing non-REE metal ions (including Mg, Ca, Zn, and Cu), allowing the protein's use in harsh chemical processes. LanM's unrivaled properties were applied to metal extraction from two distinct REE-containing industrial feedstocks covering a broad range of REE and non-REE concentrations, namely, precombustion coal and electronic waste leachates. After only a single all-aqueous step, quantitative and selective recovery of the REEs from all non-REEs initially present (Li, Na, Mg, Ca, Sr, Al, Si, Mn, Fe, Co, Ni, Cu, Zn, and U) was achieved, demonstrating the universal selectivity of LanM for REEs against non-REEs and its potential application even for industrial low-grade sources, which are currently underutilized. Our work indicates that biosourced macromolecules such as LanM may offer a new paradigm for extractive metallurgy and other applications involving f-elements.

Preliminary data on help-seeking intentions and behaviors of individuals completing a widely available online screen for eating disorders in the United States.

OBJECTIVE: Scaling an online screen that provides referrals may be key in closing the treatment gap for eating disorders (EDs), but we need to understand respondents' help-seeking intentions and behaviors after receiving screen results. This study reported on these constructs among respondents to the National Eating Disorders Association online screen who screened positive or at high risk for an ED. METHOD: Respondents completed the screen over 18 months (February 9, 2018-August 28, 2019). Those screening positive or at high risk for an ED (n = 343,072) had the option to provide data on help-seeking intentions (after screen completion) and behaviors (2-month follow-up). RESULTS: Of eligible respondents, 4.8% (n = 16,396) provided data on help-seeking intentions, with only 33.7% of those reporting they would seek help. Only 7.6% of eligible respondents opted in to the 2-month follow-up, with 10.6% of those completing it (n = 2,765). Overall, 8.9% of respondents to the follow-up reported being in treatment when they took the screen, 15.5% subsequently initiated treatment, and 75.5% did not initiate/were not already in treatment. DISCUSSION: Preliminary results suggest that among the small minority who provided data, only one-third expressed help-seeking intentions and 16% initiated treatment. Online screening should consider ways to increase respondents' motivation for and follow-through with care.

Recovery of Rare Earth Elements from Geothermal Fluids through Bacterial Cell Surface Adsorption.

The increasing demand for rare earth elements (REEs) in the modern economy motivates the development of novel strategies for cost-effective REE recovery from nontraditional feedstocks. We previously engineered E. coli to express lanthanide binding tags on the cell surface, which increased the REE biosorption capacity and selectivity. Here we examined how REE adsorption by the engineered E. coli is affected by various geochemical factors relevant to geothermal fluids, including total dissolved solids (TDS), temperature, pH, and the presence of specific competing metals. REE biosorption is robust to TDS, with high REE recovery efficiency and selectivity observed with TDS as high as 165,000 ppm. Among several metals tested, U, Al, and Pb were found to be the most competitive, causing >25% reduction in REE biosorption when present at concentrations ∼3- to 11-fold higher than the REEs. Optimal REE biosorption occurred between pH 5-6, and sorption capacity was reduced by ∼65% at pH 2. REE recovery efficiency and selectivity increased as a function of temperature up to ∼70 °C due to the thermodynamic properties of metal complexation on the bacterial surface. Together, these data define the optimal and boundary conditions for biosorption and demonstrate its potential utility for selective REE recovery from geofluids.

Microbe Encapsulation for Selective Rare-Earth Recovery from Electronic Waste Leachates.

Rare earth elements (REEs) are indispensable components of many green technologies and of increasing demand globally. However, refining REEs from raw materials using current technologies is energy intensive and enviromentally damaging. Here, we describe the development of a novel biosorption-based flow-through process for selective REE recovery from electronic wastes. An Escherichia coli strain previously engineered to display lanthanide-binding tags on the cell surface was encapsulated within a permeable polyethylene glycol diacrylate (PEGDA) hydrogel at high cell density using an emulsion process. This microbe bead adsorbent contained a homogenous distribution of cells whose surface functional groups remained accessible and effective for selective REE adsorption. The microbe beads were packed into fixed-bed columns, and breakthrough experiments demonstrated effective Nd extraction at a flow velocity of up to 3 m/h at pH 4-6. The microbe bead columns were stable for reuse, retaining 85% of the adsorption capacity after nine consecutive adsorption/desorption cycles. A bench-scale breakthrough curve with a NdFeB magnet leachate revealed a two-bed volume increase in breakthrough points for REEs compared to non-REE impurities and 97% REE purity of the adsorbed fraction upon breakthrough. These results demonstrate that the microbe beads are capable of repeatedly separating REEs from non-REE metals in a column system, paving the way for a biomass-based REE recovery system.

Results of disseminating an online screen for eating disorders across the U.S.: Reach, respondent characteristics, and unmet treatment need.

OBJECTIVE: The treatment gap between those who need and those who receive care for eating disorders is wide. Scaling a validated, online screener that makes individuals aware of the significance of their symptoms/behaviors is a crucial first step for increasing access to care. The objective of the current study was to determine the reach of disseminating an online eating disorder screener in partnership with the National Eating Disorders Association (NEDA), as well to examine the probable eating disorder diagnostic and risk breakdown of adult respondents. We also assessed receipt of any treatment. METHOD: Participants completed a validated eating disorder screen on the NEDA website over 6 months in 2017. RESULTS: Of 71,362 respondents, 91.0% were female, 57.7% 18-24 years, 89.6% non-Hispanic, and 84.7% White. Most (86.3%) screened positive for an eating disorder. In addition, 10.2% screened as high risk for the development of an eating disorder, and only 3.4% as not at risk. Of those screening positive for an eating disorder, 85.9% had never received treatment and only 3.0% were currently in treatment. DISCUSSION: The NEDA online screen may represent an important eating disorder detection tool, as it was completed by >71,000 adult respondents over just 6 months, the majority of whom screened positive for a clinical/subclinical eating disorder. The extremely high percentage of individuals screening positive for an eating disorder who reported not being in treatment suggests a wide treatment gap and the need to offer accessible, affordable, evidence-based intervention options, directly linked with screening.

Identification of a U/Zn/Cu responsive global regulatory two-component system in Caulobacter crescentus.

Despite the well-known toxicity of uranium (U) to bacteria, little is known about how cells sense and respond to U. The recent finding of a U-specific stress response in Caulobacter crescentus has provided a foundation for studying the mechanisms of U- perception in bacteria. To gain insight into this process, we used a forward genetic screen to identify the regulatory components governing expression of the urcA promoter (PurcA ) that is strongly induced by U. This approach unearthed a previously uncharacterized two-component system, named UzcRS, which is responsible for U-dependent activation of PurcA . UzcRS is also highly responsive to zinc and copper, revealing a broader specificity than previously thought. Using ChIP-seq, we found that UzcR binds extensively throughout the genome in a metal-dependent manner and recognizes a noncanonical DNA-binding site. Coupling the genome-wide occupancy data with RNA-seq analysis revealed that UzcR is a global regulator of transcription, predominately activating genes encoding proteins that are localized to the cell envelope; these include metallopeptidases, multidrug-resistant efflux (MDR) pumps, TonB-dependent receptors and many proteins of unknown function. Collectively, our data suggest that UzcRS couples the perception of U, Zn and Cu with a novel extracytoplasmic stress response.

Recovery of Rare Earth Elements from Low-Grade Feedstock Leachates Using Engineered Bacteria.

The use of biomass for adsorption of rare earth elements (REEs) has been the subject of many recent investigations. However, REE adsorption by bioengineered systems has been scarcely documented, and rarely tested with complex natural feedstocks. Herein, we engineered E. coli cells for enhanced cell surface-mediated extraction of REEs by functionalizing the OmpA protein with 16 copies of a lanthanide binding tag (LBT). Through biosorption experiments conducted with leachates from metal-mine tailings and rare earth deposits, we show that functionalization of the cell surface with LBT yielded several notable advantages over the nonengineered control. First, the efficiency of REE adsorption from all leachates was enhanced as indicated by a 2-10-fold increase in distribution coefficients for individual REEs. Second, the relative affinity of the cell surface for REEs was increased over all non-REEs except Cu. Third, LBT-display systematically enhanced the affinity of the cell surface for REEs as a function of decreasing atomic radius, providing a means to separate high value heavy REEs from more common light REEs. Together, our results demonstrate that REE biosorption of high efficiency and selectivity from low-grade feedstocks can be achieved by engineering the native bacterial surface.