High Concentrations Of Magnesium Ions Research Articles

CRISPR-Cas12a exhibits metal-dependent specificity switching.

Cas12a is the immune effector of type V-A CRISPR-Cas systems and has been co-opted for genome editing and other biotechnology tools. The specificity of Cas12a has been the subject of extensive investigation both in vitro and in genome editing experiments. However, in vitro studies have often been performed at high magnesium ion concentrations that are inconsistent with the free Mg2+ concentrations that would be present in cells. By profiling the specificity of Cas12a orthologs at a range of Mg2+ concentrations, we find that Cas12a switches its specificity depending on metal ion concentration. Lowering Mg2+ concentration decreases cleavage defects caused by seed mismatches, while increasing the defects caused by PAM-distal mismatches. We show that Cas12a can bind seed mutant targets more rapidly at low Mg2+ concentrations, resulting in faster cleavage. In contrast, PAM-distal mismatches cause substantial defects in cleavage following formation of the Cas12a-target complex at low Mg2+ concentrations. We observe differences in Cas12a specificity switching between three orthologs that results in variations in the routes of phage escape from Cas12a-mediated immunity. Overall, our results reveal the importance of physiological metal ion conditions on the specificity of Cas effectors that are used in different cellular environments.

Research on Carbon Dioxide-Assisted Electrocoagulation Technology for Treatment of Divalent Cations in Water

In the external drainage water of Xinjiang Karamay Petrochemical Company, the calcium and magnesium ion contents are as high as 630 mg/L and 1170 mg/L, respectively. These ions are subsequently scaled at large quantities in water treatment equipment, which greatly reduces the efficiency of the process. This study used a coupled chemical precipitation (CP) and electrocoagulation (EC) method to deal with external drainage water. The results show that the removal rates of calcium and magnesium were 94.71% and 96.33%, respectively, when the pH was adjusted with sodium silicate and EC was introduced after saturating the water samples with CO2. In this study, a quadratic polynomial equation was developed for predicting the removal of calcium and magnesium ions using this coupled technique under three factors of current density (CD) (15, 20 and 25 mA/cm2), reaction time (RT) (30, 40 and 50 min) and pH (10.0, 10.5 and 11.0). It was found that these three variables have a significant effect on the removal of both the abovementioned ions. The response surface method based on a Box–Behnken design showed that the average removal rates of calcium and magnesium ions could be 96.57% and 98.66% at a CD of 22 mA/cm2, RT of 46 min and pH of 11. This study confirmed the presence of calcium carbonate in the solid product through XRD and SEM analysis. The results indicate that this study is promising, and the developed technique can also be used to remove the high concentrations of calcium and magnesium ions from different wastewaters.

The impact of seawater ions on urea decomposition and calcium carbonate precipitation in the MICP process

As an environmentally friendly biotechnology, the microbial induced calcium carbonate precipitation (MICP) provides a new approach to repair concrete cracks. Most existing studies focused on finding a suitable environment for bacteria to induce as much calcium carbonate as possible, but the effect of actual concrete service environment on the repair of concrete cracks was usually ignored. This work compared the repair quality of cracked specimens via MICP with the original Sporosarcina (Sp.) pasteurii strain and salt-tolerant Sp. pasteurii strain in the deionized water and simulated seawater. Then the adverse effects of seawater ions on the MICP process was investigated. The results showed that the permeability coefficient of repaired specimens was 175.7 % higher, and the bond strength between the calcium carbonate and concrete surface was lower in the simulated seawater as compared with the deionized water environment. The high concentration of sodium, chloride, magnesium, and sulfate ions in the seawater led to the decrease of the urea decomposition rate and calcium carbonate yield rate, which further induced the decreased super-saturation of calcium carbonate and the conversion of the calcium carbonate crystal form from calcite to vaterite. Besides, the salt-tolerant strain with a high salt adaptability showed a higher repair ability in the simulated seawater as compared with the original strain.

Membrane pre-concentration as an efficient strategy to enhance the enrichment of rare earth by MgO precipitation

Taking advantage of the environmentally-friendly properties of a magnesium salt leaching agent, magnesium oxide (MgO) was used as a precipitant to enrich rare earth (RE) from leaching liquor in the magnesium salt system. This approach not only tackles the issue of ammonia–nitrogen pollution but also enables efficient magnesium recycling. However, due to the high concentration of magnesium ions and the low concentration of RE ions in the leaching solution, the precipitation kinetics of RE concentrates are sluggish, leading to low RE purity in the resulting precipitated product. In this work, we proposed a novel strategy that combines complexation-ultrafiltration (UF) pre-concentration with subsequent MgO precipitation to enhance the hydrolysis of MgO, promoting the precipitation of RE. We further improved the RE enrichment efficiency by optimizing membrane type, complexing agent selection, concentration levels, precipitation temperature, and MgO dosage. Under the conditions of concentrating the leaching solution using optimal UF membrane and employing glyphosate as the complexing agent, the RE ions concentration increased from 101 to 3940 mg/L, and we successfully separated magnesium ions with a separation factor of 36.4. A comparison between direct MgO precipitation and the pre-concentration approach revealed an 80 % reduction in precipitation time and an 80 % decrease in MgO usage with pre-concentration. Furthermore, this combined process led to an 8 % increase in RE recovery and a 2.8-fold enhancement in RE purity, and similar results were obtained when using actual mine leaching solutions. Additionally, the glyphosate present in the UF permeate and the precipitated mother liquor can be efficiently reclaimed through resin adsorption. This proposed process holds significant potential for engineering applications aimed at enriching RE.

Citrate Improves Biomimetic Mineralization Induced by Polyelectrolyte-Cation Complexes Using PAsp-Ca&Mg Complexes.

Magnesium ions are highly enriched in early stage of biological mineralization of hard tissues. Paradoxically, hydroxyapatite (HAp) crystallization is inhibited significantly by high concentration of magnesium ions. The mechanism to regulate magnesium-doped biomimetic mineralization of collagen fibrils has never been fully elucidated. Herein, it is revealed that citrate can bioinspire the magnesium-stabilized mineral precursors to generate magnesium-doped biomimetic mineralization as follows: Citrate can enhance the electronegativity of collagen fibrils by its absorption to fibrils via hydrogen bonds. Afterward, electronegative collagen fibrils can attract highly concentrated electropositive polyaspartic acid-Ca&Mg (PAsp-Ca&Mg) complexes followed by phosphate solution via strong electrostatic attraction. Meanwhile, citrate adsorbed in/on fibrils can eliminate mineralization inhibitory effects of magnesium ions by breaking hydration layer surrounding magnesium ions and thus reduce dehydration energy barrier for rapid fulfillment of biomimetic mineralization. The remineralized demineralized dentin with magnesium-doped HAp possesses antibacterial ability, and the mineralization mediums possess excellent biocompatibility via cytotoxicity and oral mucosa irritation tests. This strategy shall shed light on cationic ions-doped biomimetic mineralization with antibacterial ability via modifying collagen fibrils and eliminating mineralization inhibitory effects of some cationic ions, as well as can excite attention to the neglected multiple regulations of small biomolecules, such as citrate, during biomineralization process.

Investigation of the hydrocarbon contamination of the Dibdibba aquifer in Al-Zubair area, southern Iraq

The importance of Al-Zubair area in Basra governorate is highlighted by the presence of agricultural activities. The Dibdibba aquifer is the main supplier of water which used for irrigation, livestock and some different industries are scattered around the region. This research aims to investigate the extent and impact of hydrocarbon contamination of the Dibdibba aquifer in Al-Zubair region, southern Iraq, due to its proximity to oil fields sites. 18 groundwater samples from different locations within the aquifer were collected in dry and wet season to determine their chemical and physical properties and total petroleum hydrocarbon (TPH) including petroleum-based compounds and their derivatives. The analytical results revealed that the Dibdibba groundwater in this area is polluted with TPH and have high levels of electrical conductivity (EC) and total dissolved salts (TDS) due to the high content of salts along with the high concentrations of calcium and magnesium ions. The overall outcomes of the main elements of water showed that it is unfit for human use due to the high levels of the above parameters. All the water tests carried out indicate the presence of contamination with petroleum hydrocarbons, surpassing the allowable limits set by the World Health Organization (2008) and Iraqi Quality Standard (2009). This observed particularly in areas adjacent oil spills, where the TPH concentrations exceeding 35 μg/l in the northwest of Al-Zubair area near the Rumaila oil field. Significantly, this investigation indicated a clear evidence of hydrocarbon contamination in the study area.

Self-Assembly of DNA Nanostructures in Different Cations.

The programmable nature of DNA allows the construction of custom-designed static and dynamic nanostructures, and assembly conditions typically require high concentrations of magnesium ions that restricts their applications. In other solution conditions tested for DNA nanostructure assembly, only a limited set of divalent and monovalent ions are used so far (typically Mg2+ and Na+ ). Here, weinvestigate the assembly of DNA nanostructures in a wide variety of ions using nanostructures of different sizes: a double-crossover motif (76 bp), a three-point-star motif (~134 bp), a DNA tetrahedron (534 bp) and a DNA origami triangle (7221 bp). Weshow successful assembly of a majority of these structures in Ca2+ , Ba2+ , Na+ , K+ and Li+ and provide quantified assembly yields using gel electrophoresis and visual confirmation of a DNA origami triangle using atomic force microscopy. Wefurther show that structures assembled in monovalent ions (Na+ , K+ and Li+ ) exhibit up to a 10-fold higher nuclease resistance compared to those assembled in divalent ions (Mg2+ , Ca2+ and Ba2+ ). Ourwork presents new assembly conditions for a wide range of DNA nanostructures with enhanced biostability.

A two-step green liquid-liquid extraction strategy for selective lithium recovery and application to seawater

Efficiently harvesting lithium from seawater remains a challenge due to the extremely dilute concentration of lithium ions (Li+) and the existence of many foreign metal ions that are far more abundant. Here, a hydrophobic deep eutectic solvent (HDES)-based two-step liquid-liquid extraction (LLE) strategy is developed for the first time that realizes the separation of dilute Li+ (<1 mg/L) from solutions with a high concentration of sodium, potassium, magnesium and calcium ions. This strategy contains the removal of divalent cations and selective recovery of Li+, which minimizes the influence of coexisting metal ions. In the first LLE step, the unwanted divalent cations are removed with a negligible loss of Li+ by the bis(2-ethylhexyl)phosphate/kerosene (DEHPA/KERO) system. Then, the DEHPA/HDES system can selectively extract Li+ from monovalent cations. All solvents used are readily available and low cost with methyltrioctylammonium chloride and decanoic acid at a 1:2 mol ratio (N8881Cl/2DecA) as the main extractant. Extraction equilibrium is reached within 10 s. The single extraction efficiency of Li+ is 66.4%, and the separation coefficient of lithium and sodium (βLi/Na) reaches 11.6 at the optimized extraction conditions. Finally, the proposed two-step LLE strategy is applied to the simulated seawater. The extraction performance of N8881Cl/2DecA-DEHPA was not significantly weakened after being reused ten times.

Fabrication of nanocrystalline magnesium phosphate-based composite bioceramics using magnesium-containing phosphate glass as sintering additives

Magnesium-rich microenvironment is beneficial to both osteogenic and proangiogenic activities. To construct magnesium-rich microenvironment, the magnesium phosphate bioceramics could not be sintered at high temperatures, leading to low mechanical strength. In this study, magnesium phosphate-based composite (AMP/MPG) bioceramics were fabricated at low sintering temperatures (650 and 800 °C) using amorphous magnesium phosphate (AMP) and magnesium-containing phosphate glass (MPG) powders as starting materials. In the sintering of AMP/MPG, the MPG crystallized and reacted with AMP to form new phases. The AMP/MPG showed nanocrystals and pronouncedly higher compressive strength, in contrast with the bioceramics prepared from crystalline magnesium phosphate powders. The AMP/MPG continuously released high concentrations of magnesium ions, which accounted for the remarkably enhanced cell proliferation, osteogenic and angiogenic activities. The AMP/MPG bioceramics with high mechanical strength, osteostimulative and proangiogenic capacity were considered promising biomaterials to effectively regenerate the critical-size bone defects.

Growth characteristics of shallots and absorption of Mg ions dissolved from serpentinites

Magnesium (Mg)-rich water or food is highly beneficial to human health. Shallots are used in cooking, have simple growth conditions and have a short growth cycle. In this study, natural serpentinite was ground into powder (particle size: 50–200 nm), heated at high temperatures (400 and 800°C) and then dissolved in water of different temperatures (25, 60 and 100°C) to prepare natural magnesium-containing water. The experimental results indicated that natural serpentine minerals contain magnesium silicate, which has ionic properties and a high electrical conductivity. The dissolution of magnesium ions increased with the temperature of the distilled water. The heat-treated powder displayed higher crystallinity. However, the dissolution of magnesium was lower for the solution containing the powder heated to 800°C than for the solution containing the powder heated to 400°C. The 400°C powder exhibited favorable crystallinity and a low level of impurities, and its interlayer spacing did not change. The shallots grown with natural magnesium-containing water (magnesium shallots) had a high concentration of magnesium ions in their white and green parts. Such shallots can be provided by food platforms, and eating such shallots can help one meet the daily magnesium intake requirement of 300 mg/l for humans.

Evaluation of Groundwater Quality by Water Quality Index During Successive Periodic Intervals in the Selected Villages of Gara Mandal of Srikakulam District in Andhra Pradesh

The quality of groundwater is assessed using the Water Quality Index method and it is pertinently helpful to transfer the complex data into usable data. In this research study the WQI values have been estimated for each water sample (in total, 66 samples have been collected) based on 9 water quality parameters at periodic intervals in May 2015, 2016 and 2017 in the villages of Gara Mandal of Srikakulam District in Andhra Pradesh. The overall results disclosed that 50-54% of the groundwater samples (WQI lies between 100-200) showed poor quality and 10-13% of water samples (WQI lies between 200-300) showed very poor quality in successive periodic intervals. An assessment of measured physicochemical parameters of 66 sample sites has shown that the majority of the groundwater samples have a high concentration of calcium, magnesium, sodium, chloride and sulfate ions beyond the desirable limits of BIS and WHO standards. Correlation matrix show a strong positive correlation existing between the calcium, magnesium, sodium, chloride and sulfate ions pointing out that groundwater in this region has been contaminated more by these components due to anthropogenic activities and over-exploitation. Hence, in the study region, suitable treatment of water is necessary before consumption, this is because maximum parts of the sampling points have a high WQI value.

Classification of groundwater in the eastern Nineveh Plain

The research dealt with the classification and evaluation of groundwater for the main uses in the eastern Nineveh Plain, and for that the hydrochemical analysis of the water of (25) wells was carried out, and high concentrations of magnesium, calcium, sulfate and bicarbonate ions were observed. The (Rock Works) program that used for the purpose of classification, this program has three methods were adopted, namely Durov, Piper and Stiff method. by the newly methods the study found (8) types of water. The type (Mg - SO4) constituted (32%) of the total varieties Groundwater in the region, which that reflect the natural characteristics of the region groundwater, that are largely controlled by geological characteristics of the water types and its validity of its uses. The evaluation of groundwater in the study area showed validity of (5) Wells, for drinking, that percentage of (20%) of the total wells that were studied, and the percentage reached (100%) in terms of its suitability for irrigation and (96%) for animal consumption as a good and very good quality.

Influence of sea salt on the interfacial adhesion of bitumen–aggregate systems by molecular dynamics simulation

• Sea salt damaged bitumen’s original colloidal structure by disaggregating asphaltenes. • Saturates played the major role by most extensively diffusing to the surface of silica. • SARA fractions’ redistribution was driven by water with ions only acting as catalysts. • Number of SARA fractions in model decreased the adhesion energy in all environments. • Spatiotemporal distribution of SARA fractions at the interface determined the adhesion. This research investigated the influence of sea salt on the adhesion properties of bitumen–aggregate systems by molecular dynamics simulations in order to fundamentally understand the mechanism of damage in the seawater environment. The seawater environment was simulated by high concentrations of chloride, sodium, sulfate, magnesium, and calcium ions in water. Bitumen was represented by 3-, 4-, and 12-component models using the COMPASS force field, while the bitumen–seawater–aggregate interfacial model was discontinued by a vacuum layer of 60 Å in thickness. The results demonstrated that the presence of seawater affected the adhesion by facilitating the molecular migrations of bitumen components and by weakening the agglomeration of asphaltene. Consequently, this gradually damaged the colloidal structure of bitumen in the interfacial zone. Saturates played a dominant role in the adhesion in the seawater environment because they were the most likely to diffuse away from the silica surface. Besides the composition of bitumen, the spatiotemporal distribution of its components in the region of the interface was also identified as extremely important for the interpretation of the intrinsic factors which control the adhesion behaviour of thesesystems.

Stable ionic liquid-based polymer inclusion membranes for lithium and magnesium separation

The separation of lithium and magnesium is crucial for the exploitation of lithium resources with a high concentration of magnesium ions (Mg2+). In this study, polymer inclusion membranes (PIMs) based on the stable ionic liquid (IL) extractant system were developed for separating lithium ions (Li+) from Mg2+ in aqueous solutions. The mixture of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim][NTf2]) and tributylphosphate (TBP) was used as the carrier to transfer Li+, and the cellulose triacetate (CTA) polymer was chosen as the matrix due to its high compatibility with [C4mim][NTf2] via hydrogen bond. The TBP was kept in the membrane matrix without obvious leakage in the membrane extraction process, and the lithium selectivity and extraction percentage of the membranes decrease by less than 10% after five continuous extraction operation cycles. In the transport experiment using the feed containing 7.2 mmol/L Li+ and 2.06 mmol/L Mg2+, the PIM with 40 wt% TBP-[C4mim][NTf2] exhibits the separation factor of 2.24 for Li+/Mg2+ and an initial flux of 0.89 × 10−6 mol m−2 s−1 for Li+, much higher than the results of the pure CTA membranes, indicating that TBP-[C4mim][NTf2] system is efficient for Li+ extraction in PIM membrane. Besides, the PIMs we prepared were applied to extract Li+ from simulative salt-lake brines with a high Li+/Mg2+ selectivity of 23.87. The IL-based PIMs provide a possible membrane technology to extract Li+ from salt-lake brines with high stability, low energy consumption and environment-friendly.

Study on a novel dilute induced inorganic precipitant for conformance control in high salinity reservoirs

ABSTRACT Inorganic precipitant profile control system has good solubility and temperature tolerance compared with the polymer-based gel system. However, the precipitates form rapidly when the reactants contact. In this paper, it is reported a dilute induced inorganic precipitant for profile control for high salinity reservoirs with high total concentrations of calcium and magnesium ions. The experimental results showed that when sodium carbonate and precipitation inhibitor were injected into the high-salinity reservoir, the introduction of precipitation inhibitor can temporarily inhibit the formation of precipitation. When the system was diluted to the initial dilution times for generating the precipitates, the precipitation inhibitor lost the inhibitory effect on the precipitation reaction, and the profile modification system will produce precipitates to play the role of water shutoff. Furthermore, this dilute induced inorganic precipitant system can be injected into the moderate and low permeability reservoirs without blockage in the wellbore, and the water shutoff rate can reach above 60%.

The PhoPQ Two-Component System Is the Major Regulator of Cell Surface Properties, Stress Responses and Plant-Derived Substrate Utilisation During Development of Pectobacterium versatile-Host Plant Pathosystems.

Pectobacterium versatile (formerly P. carotovorum) is a recently defined species of soft rot enterobacteria capable of infecting many plant hosts and damaging different tissues. Complex transcriptional regulation of virulence properties can be expected for such a versatile pathogen. However, the relevant information is available only for related species and is rather limited. The PhoPQ two-component system, originally described in pectobacteria as PehRS, was previously shown to regulate a single gene, pehA. Using an insertional phoP mutant of Pectobacterium versatile (earlier—P. carotovorum), we demonstrate that PhoP regulates at least 115 genes with a majority of them specific for pectobacteria. The functions performed by PhoP-controlled genes include degradation, transport and metabolism of plant-derived carbon sources (polygalacturonate, arabinose-containing polysaccharides and citrate), modification of bacterial cell envelope and stress resistance. We also demonstrated PhoP involvement in establishing the order of plant cell wall decomposition and utilisation of the corresponding breakdown products. Based on experimental data and in silico analysis, we defined a PhoP binding site motif and provided proof for its universality in enteric bacteria. Scanning P. versatile genome for the locations of this motif suggested a much larger PhoP regulon enriched with the genes important for a plant pathogen, which makes PhoP a global virulence regulator. Potential PhoP targets include many regulatory genes and PhoP control over one of them, expI, was confirmed experimentally, highlighting the link between the PhoPQ two-component and quorum sensing systems. High concentrations of calcium and magnesium ions were found to abolish the PhoPQ-dependent transcription activation but did not relieve repression. Reduced PhoP expression and minimisation of PhoP dependence of regulon members’ expression in P. versatile cells isolated from potato tuber tissues suggest that PhoPQ system is a key switch of expression levels of multiple virulence-related genes fine-tuned to control the development of P. versatile-host plant pathosystem.

Expression of an Extracellular Protein (SMU.63) Is Regulated by SprV in Streptococcus mutans.

In Streptococcus mutans, SprV (SMU.2137) is a pleiotropic regulator that differentially regulates genes related to competence, mutacin production, biofilm formation, and the stress tolerance response, along with some other pathways. In this study, we established a link between SprV and an ∼67-kDa protein in the culture supernatant of strain UA159 that was later confirmed as SMU.63 by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) analysis. We discovered that SprV downregulates the transcription and translation of SMU.63. We found that the seven amino acids from the C-terminal region of SprV were also crucial for the expression of SMU.63. Deletion of smu.63 led to increased sucrose-independent biofilm formation and competence. The sprV deletion also increased biofilm formation although this could be partially attributed to the downregulation of smu.63 In an smu.63 sprV double mutant, a synergistic effect was observed in biofilm formation in contrast to effects on competence development. We found that low or excess magnesium ion repressed sprV transcription that, in turn, affected the expression of smu.63 As expected, a magnesium ion-dependent effect of competence and biofilm formation was observed in the UA159 strain. We also replicated the results of SMU.63 expression and competence in S. mutans GS5 that encodes both SprV and SMU.63 homologs and found that the GS5 strain behaves similarly to the UA159 strain, indicating that SprV's effect is strain independent.IMPORTANCE We previously identified a pleiotropic regulator, SprV, in Streptococcus mutans This regulator appears to be highly conserved among streptococci. Here, we showed that SprV regulates the expression of a secreted protein encoded by SMU.63 in S. mutans SMU.63 has been known to impact biofilm formation and genetic competence, two important characteristics that help in colonization of the organism. SMU.63 is also unique since it is known to form amyloid fiber. We found that SprV regulates the expression of SMU.63 at both the transcriptional and translational levels. We also found that the expression of SprV is regulated by magnesium ion concentration. Interestingly, both low and high magnesium ion concentrations affected biofilm formation and genetic competence. Since SMU.63 is also highly conserved among streptococci, we hypothesized that SprV will have a similar effect on its expression.

Experimental investigation of the concomitant effect of potential determining ions Mg2+/SO42− and Ca2+/SO42− on the wettability alteration of oil-wet calcite surfaces

Modifying the concentration of potential determining ions (PDIs) in the brine can result in alteration of the surface wetting properties towards more water-wet state, which is the desired wetting state in fractured carbonate reservoirs. However, few studies have discussed the interactions between these PDIs and their mechanisms of wettability alteration. Accordingly, the aim of this study was to investigate the concomitant effect of PDIs at different molar ratios on the wettability of oil-wet calcite surfaces as well as the interactions between the ions. Two combinations of wettability modifying agents (Mg2+/SO42−) and (Ca2+/SO42−) were considered. Contact angle and zeta potential measurements were performed to evaluate the effect of these combined ions and explore possible wettability alteration mechanisms. Results revealed that both PDIs groups were able to reduce the contact angle significantly and expel carboxylate group from the surface. Besides, combinations of PDIs were more effective in wettability alteration compared to those ions alone. It was also observed that equal concentrations of magnesium and sulfate provide more water-wet state. However, for combinations of calcium and sulfate, the most water-wet state was achieved when lower concentrations of calcium and higher concentrations of sulfate were used. Zeta potential measurements showed that the performance of each PDI in changing surface wettability is critically affected by the concentration of the other ions present in the same solution. Results indicated that when low concentration of magnesium ions is used, the adsorption of sulfate ions on the rock surface and the interaction of magnesium ions with the carboxylate group is the main mechanism of wettability alteration by magnesium and sulfate ions. However, at high concentration of magnesium ions, no adsorption of sulfate ions was detected which means that sulfate serves as a catalyst for wettability alteration by Mg2+/SO42− and the formation of a complex Mg-carboxylate group is the dominant mechanism. Moreover, the use of cationic surfactant along with the combined PDIs resulted in strong water-wet conditions.

An Ionic Limit to Life in the Deep Subsurface.

The physical and chemical factors that can limit or prevent microbial growth in the deep subsurface are not well defined. Brines from an evaporite sequence were sampled in the Boulby Mine, United Kingdom between 800 and 1300 m depth. Ionic, hydrogen and oxygen isotopic composition were used to identify two brine sources, an aquifer situated in strata overlying the mine, and another ambiguous source distinct from the regional groundwater. The ability of the brines to support microbial replication was tested with culturing experiments using a diversity of inocula. The examined brines were found to be permissive for growth, except one. Testing this brine’s physicochemical properties showed it to have low water activity and to be chaotropic, which we attribute to the high concentration of magnesium and chloride ions. Metagenomic sequencing of the brines that supported growth showed their microbial communities to be similar to each other and comparable to those found in other hypersaline environments. These data show that solutions high in dissolved ions can shape the microbial diversity of the continental deep subsurface biosphere. Furthermore, under certain circumstances, complex brines can establish a hard limit to microbial replication in the deep biosphere, highlighting the potential for subsurface uninhabitable aqueous environments at depths far shallower than a geothermally-defined limit to life.

Metal-Assisted Assembly of Protein Containers Loaded with Inorganic Nanoparticles.

Protein containers are suitable building blocks for bioinorganic materials. Here, we show that high concentrations of magnesium ions induce the formation of a unitary protein scaffold, whereas low magnesium concentration leads to a binary protein scaffold. The molecular interactions in the protein scaffold were characterized with X-ray crystallography to high resolution. We show that the unitary framework can be applied for the assembly of inorganic nanoparticles such as metal oxides into highly ordered bioinorganic structures. Our work emphasizes the structural tunability of protein-container-based materials, important for adjusting emerging properties of such materials.