Alkaline Tolerance Research Articles

Mechanism of TonB-dependent transport system in Halomonas alkalicola CICC 11012s in response to alkaline stress.

Halomonas alkalicola CICC 11012s can grow at pH 12.5, the highest pH at which the organisms in the genus Halomonas can grow. Genomic analysis reveals that H. alkalicola adapts to alkaline stress using a variety of adaptive strategies; however, the detailed mechanism for its growth at high-alkaline conditions has not been elucidated. Therefore, in this study, the adaptations of H. alkalicola in response to extreme alkaline stress were investigated. A sharp decrease of alkaliphilic tolerance was observed in mutants E. coli ΔEctonB and H. alkalicola ΔHatonB. Expressions of the gene clusters encoding TonB-dependent transport system and iron complex transport system in H. alkalicola grown under extreme alkaline conditions were markedly up-regulated. We then compared the intracellular ionic iron content and iron-chelating ability of mutant strain with those of wild-type strain to understand the influence of TonB-dependent transport system on the alkaline responses. The results indicated that the presence of TonB-dependent transport system increased the alkaline tolerance of H. alkalicola grown at high-alkaline conditions, but had no effects when the strain was grown at neutral pH and low-alkaline conditions. Meanwhile, the presence of this system increased the transport and accumulation of ionic irons to maintain intracellular metabolic homeostasis, which in turn could increase the tolerance of the strain to extreme alkaline conditions. Based on the results, we established a model representing the interactions between TonB-dependent transport system, alkaline tolerance, and intracellular ionic iron that could help deepen the understanding of the alkaline response mechanism of alkaliphilic bacteria.

Role of TaALMT1 malate-GABA transporter in alkaline pH tolerance of wheat.

Malate exudation through wheat (Triticum aestivum L) aluminium-activated malate transporter 1 (TaALMT1) confers Al3+ tolerance at low pH, but is also activated by alkaline pH, and is regulated by and facilitates significant transport of gamma-aminobutyric acid (GABA, a zwitterionic buffer). Therefore, TaALMT1 may facilitate acidification of an alkaline rhizosphere by promoting exudation of both malate and GABA. Here, the performance of wheat near isogenic lines ET8 (Al+3 -tolerant, high TaALMT1 expression) and ES8 (Al+3 -sensitive, low TaALMT1 expression) are compared. Root growth (at 5 weeks) was higher for ET8 than ES8 at pH 9. ET8 roots exuded more malate and GABA at high pH and acidified the rhizosphere more rapidly. GABA and malate exudation was enhanced at high pH by the addition of aluminate in both ET8 and transgenic barley expressing TaALMT1. Xenopus laevis oocytes expressing TaALMT1 acidified an alkaline media more rapidly than controls corresponding to higher GABA efflux. TaALMT1 expression did not change under alkaline conditions but key genes involved in GABA turnover changed in accordance with a high rate of GABA synthesis. We propose that TaALMT1 plays a role in alkaline tolerance by exuding malate and GABA, possibly coupled to proton efflux.

Cytoplasmic glucose-6-phosphate dehydrogenase plays an important role in the silicon-enhanced alkaline tolerance in highland barley

Glucose-6-phosphate dehydrogenase (G6PDH), as a key enzyme in the pentose phosphate pathway, extensively responds to the biotic and abiotic stresses. In this study we focussed on the G6PDH role in the alleviation of alkaline stress induced by silicon (Si) in highland barley. Application of Si reduced the water loss and malondialdehyde (MDA) and reactive oxygen species (ROS) contents, improved the fresh weight, photosynthesis, K+ content, and the superoxide dismutase (SOD) and catalase (CAT) activities, thus alleviating the damage caused by alkaline stress. The G6PDH activity, especially the cytoplasmic G6PDH, significantly increased under alkaline stress, and was further stimulated by the addition of exogenous Si. Meanwhile, the levels of NADPH and reduced glutathione (GSH) showed similar profiles to G6PDH activity under NaHCO3 and NaHCO3 + Si treatments. The inhibition of G6PDH activity by glucosamine abolished the relieving effect of Si on alkaline stress, which was manifested in the increase of ROS and the decrease of GSH content. Together, our results suggest that Si-enhanced tolerance of alkaline stress may be related to the regulation of GSH levels by the cytoplasmic G6PDH in highland barley.

QTL Mapping and Candidate Gene Analysis for Alkali Tolerance in Japonica Rice at the bud Stage Based on Linkage Mapping and Genome-Wide Association Study

BackgroundSalinity-alkalinity stress is one of the major factors limiting rice production. Damage caused by alkaline salt stress is more severe than that caused by neutral salt stress. Alkali tolerance at the bud stage in rice directly affects seedling survival and final yield when using the direct seeding cultivation model. However, genetic resources (QTLs and genes) for rice breeders to improve alkali tolerance are limited. In this study, we combined linkage mapping and a genome-wide association study (GWAS) to analyze the genetic structure of this trait in japonica rice at the bud stage.ResultsA population of 184 recombinant inbred lines (RILs) was utilized to map quantitative trait loci (QTLs) for the root length under control condition (RL), alkaline stress (ARL) and relative root length (RRL) at the bud stage. A major QTL related to alkali tolerance at the rice bud stage, qAT11, was detected on chromosome 11. Interestingly, a GWAS identified a lead SNP (Chr_21,999,659) in qAT11 that was significantly associated with alkaline tolerance. After filtering by linkage disequilibrium (LD), haplotype analysis, quantitative real-time PCR, we obtained three candidate genes (LOC_Os11g37300, LOC_Os11g37320 and LOC_Os11g37390). In addition, we performed phenotype verification on the CRISPR/Cas9 mutant of LOC_Os11g37390.ConclusionBased on these results, LOC_Os11g37300, LOC_Os11g37320 and LOC_Os11g37390 were the candidate genes contributing to alkaline tolerance in japonica rice. This study provides resources for breeding aimed at improving rice responses to alkalinity stress.

Overexpression of MdATG18a enhances alkaline tolerance and GABA shunt in apple through increased autophagy under alkaline conditions.

Soil alkalization affects apple production in northwest China. Autophagy is a highly conserved degradative protein pathway in eukaryotes. Autophagy in plants can be activated by various abiotic factors. We previously identified the positive role of the autophagy-related gene MdATG18a in drought, nitrogen deficiency and resistance to Diplocarpon mali infection in apple. However, it is still unclear whether ATG18a is related to alkaline stress. In this study, we used hydroponic culture to simulate alkaline stress and found that the overexpression of MdATG18a significantly improved the tolerance of apple to alkaline stress. The overexpression of MdATG18a increased biomass, photosynthetic rate and antioxidant capacity of transgenic plants compared with wild-type plants under alkaline stress. The overexpression of MdATG18a promoted γ-aminobutyric acid (GABA) shunt via an increase in glutamate (GABA precursor) and GABA contents and upregulation of GABA shunt-related genes. In addition, the overexpression of MdATG18a significantly upregulated the expression of other core ATG genes and increased the formation of autophagosomes under alkaline stress. In conclusion, these results suggest that the overexpression of MdATG18a in apple enhances alkaline tolerance and the GABA shunt, which may be owing to the increase in autophagic activity.

Seed germination and early seedling growth of six wetland plant species in saline-alkaline environment

This study focused on the effect of saline and alkaline stress on six typical wetland plant species during seed germination and early seedling growth stages. Based on the indicators of germination, seedling growth and ionic absorption in seedlings, relatively saline and alkaline tolerant plant species were selected and tolerance mechanism was discussed. Results showed that the existence of saline and alkaline stress inhibited the capacity of germination and early seedling growth of most tested plant species to varying degrees, therein effects of saline-alkaline stress were greater than saline stress. Based on the results of principal component analysis (PCA), germination percentage, K+ content, plant height, Na+ content and Na+/K+ ratios can be selected as representative indicators for saline and alkaline tolerance evaluation during seed germination and early seedling growth stages. Among tested species, Juncus effusus and Vetiveria zizanioides exhibited relatively higher saline and alkaline tolerant capacity during their seed germination and early seedling growth. Additionally, both species increase K+ accumulation and retain lower Na+/K+ ratios, which might be their tolerance mechanisms at ion level. In conclusion, V. zizaniodes and J. effusus were recommended as potential plant species for restoring degraded saline-alkaline wetlands and/or establishing constructed wetlands for treating saline wastewater.

Molecular docking and molecular dynamics simulations of a mutant Acinetobacter haemolyticus alkaline-stable lipase against tributyrin

We previously reported on a mutant lipase KV1 (Mut-LipKV1) from Acinetobacter haemolyticus which optimal pH was raised from 8.0 to 11.0 after triple substitutions of surface aspartic acid (Asp) with lysine (Lys). Herein, this study further examined the Mut-LipKV1 by molecular docking, molecular dynamics (MD) simulations and molecular mechanics-Poisson Boltzmann surface area (MM-PBSA) calculations to explore the structural requirements that participated in the effective binding of tributyrin and its catalytic triad (Ser165, Asp259 and His289) and identify detailed changes that occurred post mutation. Mut-LipKV1 bound favorably with tributyrin (−4.1 kcal/mol) and formed a single hydrogen bond with His289, at pH 9.0. Despite the incongruent docking analysis data, results of MD simulations showed configurations of both the tributyrin-Mut-LipKV1 (RMSD 0.3 nm; RMSF 0.05 − 0.3 nm) and the tributyrin-wildtype lipase KV1 (tributyrin-LipKV1) complexes (RMSD 0.35 nm; RMSF 0.05 − 0.4 nm) being comparably stable at pH 8.0. MM-PBSA analysis indicated that van der Waals interactions made the most contribution during the molecular binding process, with the Mut-LipKV1-tributyrin complex (−44.04 kcal/mol) showing relatively lower binding energy than LipKV1-tributyrin (−43.83 kcal/mol), at pH 12.0. All tributyrin-Mut-LipKV1 complexes displayed improved binding free energies over a broader pH range from 8.0 − 12.0, as compared to LipKV1-tributyrin. Future empirical works are thus, important to validate the improved alkaline-stability of Mut-LipKV1. In a nutshell, our research offered a considerable insight for further improving the alkaline tolerance of lipases. Communicated by Ramaswamy H. Sarma

Saline and Alkaline Tolerance of Wetland Plants—What are the Most Representative Evaluation Indicators?

The increasing discharge of wastewater containing inorganic salts, sometimes accompanied by high pH, has been a worldwide environmental problem. Constructed wetlands (CWs) are considered a viable technology for treating saline and/or alkaline wastewater provided that saline-alkaline tolerant plant species are selected and applied. The influence of both saline and alkaline stress on four wetland plant species during their seed germination, early growth, vegetative propagation and continued growth stages was evaluated by three experiments. Principal component analysis (PCA) was conducted for selecting representative indicators for evaluating the saline and alkaline tolerance of plants during vegetative propagation and plant growth stages. The saline and alkaline stress inhibited the vegetative propagation and plant growth of all tested plant species to varying degrees, therein the influences of saline-alkaline stress on plants were more marked than saline stress. The length of new roots, Na+ accumulation in plant tissue, Na+/K+ ratios in aerial tissue and the total dry biomass were selected as most representative indicators for evaluating the saline and alkaline tolerance of plants. Iris sibirica and Lythrum salicaria showed better saline and alkaline tolerance ability among tested species and could be grown in CWs for treating saline and/or alkaline wastewater.

Overexpression of a TIFY family gene, GsJAZ2, exhibits enhanced tolerance to alkaline stress in soybean

Previous studies have indicated the potential role of a TIFY family gene, GsJAZ2, for its response to alkaline stress in Arabidopsis. Here, we transformed GsJAZ2 into an elite soybean (Glycine max) using particle bombardment-based genetic transformation system to assess whether overexpression of GsJAZ2 in soybean improved alkaline tolerance. Results revealed that transgenic soybean overexpressing GsJAZ2 grew well under alkaline conditions, while wild-type (WT) plants exhibited chlorosis, stunted growth, or even death. Higher chlorophyll concentration and lower of Malondialdehyde (MDA) content were detected in the transgenic plants compared to WT under alkaline stress. Moreover, the transcription levels of two alkaline-responsive genes were up-regulated in the GsJAZ2 overexpression at the early or later stage of alkaline stress, respectively, indicating that GsJAZ2 overexpression enhanced tolerance to alkaline stress in soybean, which might modulate intracellular pH homeostasis and osmotic balance through regulating the expression of alkaline-responsive genes. Additionally, GsJAZ2 is a member of the JAZ subfamily that belongs to the TIFY family. Overexpression of GsJAZ2 in soybean conferred JA insensitivity, including JA-mediated root growth inhibition. The transcripts of some JA-responsive genes were examined and altered under alkaline stress, implying that GsJAZ2 overexpression may involve in JA signal pathway for accumulating anti-osmotic substances in defense to alkaline stress. Collectively, the findings of this study facilitate our understanding of GsJAZ2 in response to alkaline stress as well as enrich the function of TIFY genes in crop.

Transcriptome analysis of sugar beet (Beta vulgaris L.) in response to alkaline stress.

RNA-seq was used to analyze the transcriptional changes in sugar beet (Beta vulgaris L.) triggered by alkaline solution to elucidate the molecular mechanism underlying alkaline tolerance in sugar beet. Several differentially expressed genes related to stress tolerance were identified. Our results provide a valuable resource for the breeding of new germplasms with high alkaline tolerance. Alkalinity is a highly stressful environmental factor that limits plant growth and production. Sugar beet own the ability to acclimate to various abiotic stresses, especially salt and alkaline stress. Although substantial previous studies on response of sugar beet to saline stress has been conducted, the expressions of alkali-responsive genes in sugar beet have not been comprehensively investigated. In this study, we conducted transcriptome analysis of leaves in sugar beet seedlings treated with alkaline solutions for 0day (control, C), 3days (short-term alkaline treatment, ST) and 7days (long-term alkaline treatment, LT). The clean reads were obtained and assembled into 25,507 unigenes. Among them, 975 and 383 differentially expressed genes (DEGs) were identified in the comparison groups ST_vs_C and LT_vs_C, respectively. Gene ontology (GO) analysis revealed that oxidation-reduction process and lipid metabolic process were the most enriched GO term among the DEGs in ST_vs_C and LT_vs_C, respectively. According to Kyoto Encyclopedia of Genes and Genomes pathway, carbon fixation in photosynthetic organisms pathway were significantly enriched under alkaline stress. Besides, expression level of genes encoding D-3-phosphoglycerate dehydrogenase 1, glutamyl-tRNA reductase 1, fatty acid hydroperoxide lyase, ethylene-insensitive protein 2, metal tolerance protein 11 and magnesium-chelatase subunit ChlI, etc., were significantly altered under alkaline stress. Additionally, among the DEGs, 136 were non-annotated genes and 24 occurred with differential alternative splicing. Our results provide a valuable resource on alkali-responsive genes and should benefit the improvement of alkaline stress tolerance in sugar beet.

Heterologous expression and characterization of thermostable lipase (Lk1) in Pichia pastoris GS115

A gene encoding thermostable lipase namely LK1 was successfully sub-cloned into expression vector pPICZαA and integrated into a chromosomal fungal host, Pichia pastoris GS115. The recombinant mut+ clones selected on zeocine-YPD plates were heterologically expressed into Pichia pastoris GS115 using 1% methanol as inducer at 30°C during 120 h in BMMY medium. The protein was expressed at molecular mass 35.5 kDa following SDS-PAGE analysis. The enzyme still showed lipase activity on pNP as substrate. Thermostable lipase was purified by affinity chromatography using Ni-NTA column with a purification fold of 11.6 and yield of 31.75%. Further characterization of the enzyme showed that the enzyme has highest spesicificity on pNP-laurate as substrate with optimum temperature at 60 °C, pH 8. In addition, the enzyme still maintained the activity up to 4 h in incubation at 60 °C and maintained 50% activity at 3 h incubation. All of the above data suggested that the enzyme is an alkaline tolerance and thermostable lipase.

A DedA Family Membrane Protein Is Required for Burkholderia thailandensis Colistin Resistance.

Colistin is a “last resort” antibiotic for treatment of infections caused by some multidrug resistant Gram-negative bacterial pathogens. Resistance to colistin varies between bacterial species. Some Gram-negative bacteria such as Burkholderia spp. are intrinsically resistant to very high levels of colistin with minimal inhibitory concentrations (MIC) often above 0.5 mg/ml. We have previously shown DedA family proteins YqjA and YghB are conserved membrane transporters required for alkaline tolerance and resistance to several classes of dyes and antibiotics in Escherichia coli. Here, we show that a DedA family protein in Burkholderia thailandensis (DbcA; DedA of Burkholderia required for colistin resistance) is a membrane transporter required for resistance to colistin. Mutation of dbcA results in >100-fold greater sensitivity to colistin. Colistin resistance is often conferred via covalent modification of lipopolysaccharide (LPS) lipid A. Mass spectrometry of lipid A of ΔdbcA showed a sharp reduction of aminoarabinose in lipid A compared to wild type. Complementation of colistin sensitivity of B. thailandensis ΔdbcA was observed by expression of dbcA, E. coli yghB or E. coli yqjA. Many proton-dependent transporters possess charged amino acids in transmembrane domains that take part in the transport mechanism and are essential for function. Site directed mutagenesis of conserved and predicted membrane embedded charged amino acids suggest that DbcA functions as a proton-dependent transporter. Direct measurement of membrane potential shows that B. thailandensis ΔdbcA is partially depolarized suggesting that loss of protonmotive force can lead to alterations in LPS structure and severe colistin sensitivity in this species.

Improving the catalytic efficiency of thermostable Geobacillus stearothermophilus xylanase XT6 by single-amino acid substitution.

Directed evolution using error-prone polymerase chain reaction was employed in the current study to enhance the catalytic efficiency of a thermostable Geobacillus stearothermophilus xylanase XT6 parent. High-throughput screening identified two variants with enhanced activity. Sequencing analysis revealed the presence of a single-amino acid substitution (P209L or V161L) in each variant. The maximum activity of mutant V161L and P209L was at 85°C and 70°C, respectively. Both mutants exhibited maximum activity at pH 7. The thermal and alkaline tolerance of mutant V161L only were markedly improved. The two mutants were more resistant to ethanol inhibition than the parent. Substrate specificity of the two mutants was shifted from beechwood xylan to birchwood xylan. The potential of the two mutants to hydrolyze rice straw and sugarcane bagasse increased. Both turnover number (kcat) and catalytic efficiency (kcat/kM) increased 12.2- and 5.7-folds for variant P209L and 13- and 6.5-folds for variant V161L, respectively, towards birchwood xylan. Based on the previously published crystal structure of extracellular G. stearothermophilus xylanase XT6, V161L and P209L mutation locate on βα-loops. Conformational changes of the respective loops could potentiate the loop swinging, product release and consequently result in enhancement of the catalytic performance.

Characterization of Na+ exclusion mechanism in rice under saline-alkaline stress conditions

This study was designed to elucidate the physiological responses of two rice genotypes to different pH levels under high saline stress. A salt-tolerant cultivar, FL478, and a salt-sensitive cultivar, IR29, were exposed to saline-alkaline solutions supplemented with 50 mM Na at pH 9 (severe), pH 8 (moderate), and pH 7 (mild) for three weeks. The results indicated that FL478 is relatively saline-alkaline tolerant compared to IR29, and this was evident from its higher dry mass production, lower Na+ concentration in the leaf blades, and maintenance of water balance under both mild and moderate saline-alkaline stress conditions. In both cultivars, Na+ concentrations in the leaf blades were considerably higher at pH 8 than at pH 7, indicating that high alkaline stress promoted Na+ accumulation under highly saline conditions. FL478 plants had lower Na+/K+ ratios in leaf blades and leaf sheaths than IR29 plants under saline-alkaline stress at both pH 7 and pH 8. To understand the mechanisms behind the difference in saline-alkaline tolerance between the two rice genotypes, transcript levels of the genes encoding Na+ transport proteins were analyzed. In response to mild and moderate saline-alkaline stress conditions, salt-tolerant FL478 had highly induced expression of the OsHKT1;5 gene in the roots, corresponding to lower Na+ accumulation in the leaf blades. Induction of high expression of the OsSOS1 gene in the roots of FL478 implied that Na may be effectively exported from cytosols to apoplasts in the roots resulting in sequestration of Na+ to outside of the roots and loading Na+ in xylem transpiration stream. On the other hand, the salt-sensitive IR29 had lower expression of the genes related to Na+ transporters, such as the OsHKT1;5 gene and the OsSOS1 gene, in the roots, leading to higher Na+ accumulation in the shoots. Expression of the determinant genes for alkaline tolerance, such as K+ and Fe acquisition and acidification of the rhizosphere was highly induced in FL478, but not in IR29. Thus, molecular analysis suggested that genes encoding Na+ transport proteins are involved in regulating Na+ transport under saline-alkaline stress in both salt-tolerant and salt-sensitive rice cultivars, and this is useful information for improving saline-alkaline tolerance traits of rice in the future.

Mutagenesis Reveals That the OsPPa6 Gene Is Required for Enhancing the Alkaline Tolerance in Rice.

Alkaline stress (AS) is one of the abiotic stressful factors limiting plant’s growth and development. Inorganic pyrophosphatase is usually involved in a variety of biological processes in plant in response to the abiotic stresses. Here, to clarify the responsive regulation of inorganic pyrophosphatase in rice under AS, the mutagenesis of the OsPPa6 gene encoding an inorganic pyrophosphatase in rice cv. Kitaake (Oryza sativa L. ssp. japonica) was performed by the CRISPR/Cas9 system. Two homozygous independent mutants with cas9-free were obtained by continuously screening. qPCR reveals that the OsPPa6 gene was significantly induced by AS, and the mutagenesis of the OsPPa6 gene apparently delayed rice’s growth and development, especially under AS. Measurements demonstrate that the contents of pyrophosphate in the mutants were higher than those in the wild type under AS, however, the accumulation of inorganic phosphate, ATP, chlorophyll, sucrose, and starch in the mutants were decreased significantly, and the mutagenesis of the OsPPa6 gene remarkably lowered the net photosynthetic rate of rice mutants, thus reducing the contents of soluble sugar and proline, but remarkably increasing MDA, osmotic potentials and Na+/K+ ratio in the mutants under AS. Metabonomics measurement shows that the mutants obviously down-regulated the accumulation of phosphorylcholine, choline, anthranilic acid, apigenin, coniferol and dodecanoic acid, but up-regulated the accumulation of L-valine, alpha-ketoglutarate, phenylpyruvate and L-phenylalanine under AS. This study suggests that the OsPPa6 gene is an important osmotic regulatory factor in rice, and the gene-editing of CRISPR/Cas9-guided is an effective method evaluating the responsive regulation of the stress-induced gene, and simultaneously provides a scientific support for the application of the gene encoding a soluble inorganic pyrophosphatase in molecular breeding.

Hydrophobic side chains to enhance hydroxide conductivity and physicochemical stabilities of side-chain-type polymer AEMs

Anion exchange membranes (AEMs) of side-chain polymers have attracted growing attention recently in the fuel cells. However, their dimensional stability and alkali resistance still not meet the requirements for industrial application of fuel cells. Herein we demonstrate a facile approach to prepare the side-chain-type polymer AEMs with high performances via introducing both hydrophobic and hydrophilic side chains onto the backbone. Grafting hydrophobic side chain into the backbone favor to construct a well-defined micro-phase separation structure and fabricate fast ion transporting pathway. The resulting polyethersulfone (PES) based AEMs display a high hydroxide conductivity and good physicochemical stability. Impressively, the PES-8C0.15-QA0.85 AEM has a 54.3% increase in the hydroxide conductivity and a 45% decrease in the swelling ratio (SR) by introducing a small amount of hydrophobic side chain. Furthermore, the AEMs show good mechanical properties, alkaline tolerance and oxidative stability. The loss of ionic exchange capacity and hydroxide conductivity is less than 15% after alkaline treatment (1 M KOH, 60 °C, 480 h). This approach will be favorable to exploit practical AEMs for fuel cells.

3-Glycidoxy-propylthrimethoxysilane improved anion exchange membranes based on quaternized poly(2,6-dimethyl-1,4-phenyleneoxide)

The organic-inorganic hybrid anion exchange membranes were prepared from quaternary triethylamonium functionalized poly(2,6-dimethyl-1,4-phenyleneoxide) (QPPO) and 3-glycidoxypropylthrimethoxysilane (GOPS) with different ratios. The obtained membranes are termed as QPPOx-Gy, where x and y are the mole ratios of triethylamine and the siloxane GOPS to the bromomethyl groups of the polymer, respectively. The resultant hybrid membranes are thermally stable up to 200 °C and exhibit a tensile stress of around 10 MPa. The incorporated GOPS endows the hybrid membranes with increased water uptake and conductivity due to the more hydroxyl groups containing in the hydrolytic networks of GOPS in the membranes. A conductivity of 46.0 mS cm−1 is achieved by the QPPO0.4-G0.55 membrane in water at 80 °C, which is about 20 mS cm−1 higher than the conductivity of the pristine QPPO0.4 membrane. In addition, the QPPO0.4-Gy hybrid membranes possess enhanced alkaline tolerance toward the attack of hydroxide ions. After soaked in 1 M KOH at 60 °C for 480 h, the hybrid membranes retained more than 16–22% of the initial conductivity compared to the pristine QPPO0.4 membrane.

KnowVolution of a Fungal Laccase toward Alkaline pH.

To date, commercial laccase preparations are used in the food, textile, and paper and pulp industries (mild pH). Laccases are attractive in the synthesis of dye molecules or oxidative lignin treatment, which take place at high pH (≥8.0). So far, one fungal laccase has been reported to be active at alkaline pH. Herein, engineering of the fungal laccase from Melanocarpus albomyces (MaL) for increased activity toward the substrate 2,6-dimethoxyphenol at pH (≥9.0) is reported. Through a knowledge-gaining directed evolution (KnowVolution) campaign, the key positions Leu365 and Leu513 were identified to increase alkaline tolerance. Both positions are located in close proximity of the T1Cu site. Molecular docking and simulations studies reveal that both substitutions act in a synergic way to stabilize and improve laccase activity at higher pH. Kinetic characterization of the final variant MaL-M1 (L365E/L513M) revealed at pH 9.8 a threefold improved kcat (kcat =(6.0±0.2) s-1 ) compared with that of wild-type M. albomyces laccase (kcat =(2.11±0.07) s-1 ).

Super‐Stretchable Zinc–Air Batteries Based on an Alkaline‐Tolerant Dual‐Network Hydrogel Electrolyte

AbstractStretchable devices need elastic hydrogel electrolyte as an essential component, while most hydrogels will lose their stretchability after being incorporated with strong alkaline solution. This is why highly stretchable zinc–air batteries have never been reported so far. Herein, super‐stretchable, flat‐ (800% stretchable) and fiber‐shaped (500% stretchable) zinc–air batteries are first developed by designing an alkaline‐tolerant dual‐network hydrogel electrolyte. In the dual‐network hydrogel electrolyte, sodium polyacrylate (PANa) chains contribute to the formation of soft domains and the carboxyl groups neutralized by hydroxyls as well as cellulose as potassium hydroxide stabilizer are responsible for vastly enhanced alkaline tolerance. The obtained super‐stretchable, flat zinc–air battery exhibits a high power density of 108.6 mW⋅cm−2, increasing to 210.5 mW⋅cm−2 upon being 800% stretched. Similar phenomena are observed for the 500% stretchable fiber‐shaped batteries. The devices can maintain stable power output even after being heavily deformed benefiting from the highly soft, alkaline‐tolerant hydrogel electrolyte developed. A bendable battery‐display system and water proof weavable fiber zinc–air battery are also demonstrated. This work will facilitate the progress of using zinc–air battery powering flexible electronics and smart clothes. Moreover, the developed alkaline‐tolerant super‐stretchable electrolyte can also be applied for many other alkaline electrolyte‐based energy storage/conversion devices.

A Novel Alkaliphilic Streptomyces Inhibits ESKAPE Pathogens.

In an effort to stem the rising tide of multi-resistant bacteria, researchers have turned to niche environments in the hope of discovering new varieties of antibiotics. We investigated an ethnopharmacological (cure) from an alkaline/radon soil in the area of Boho, in the Fermanagh Scarplands (N. Ireland) for the presence of Streptomyces, a well-known producer of antibiotics. From this soil we isolated a novel (closest relative 57% of genome relatedness) Streptomyces sp. capable of growth at high alkaline pH (10.5) and tolerant of gamma radiation to 4 kGy. Genomic sequencing identified many alkaline tolerance (antiporter/multi-resistance) genes compared to S. coelicolor M145 (at 3:1), hence we designated the strain Streptomyces sp. myrophorea, isolate McG1, from the Greek, myro (fragrance) and phorea (porter/carrier). In vitro tests demonstrated the ability of the Streptomyces sp. myrophorea, isolate McG1 to inhibit the growth of many strains of ESKAPE pathogens; most notably carbapenem-resistant Acinetobacter baumannii (a critical pathogen on the WHO priority list of antibiotic-resistant bacteria), vancomycin-resistant Enterococcus faecium, and methicillin-resistant Staphylococcus aureus (both listed as high priority pathogens). Further in silico prediction of antimicrobial potential of Streptomyces sp. myrophorea, isolate McG1 by anti-SMASH and RAST software identified many secondary metabolite and toxicity resistance gene clusters (45 and 27, respectively) as well as many antibiotic resistance genes potentially related to antibiotic production. Follow-up in vitro tests show that the Streptomyces sp. myrophorea, isolate McG1 was resistant to 28 out of 36 clinical antibiotics. Although not a comprehensive analysis, we think that some of the Boho soils’ reputed curative properties may be linked to the ability of Streptomyces sp. myrophorea, isolate McG1 to inhibit ESKAPE pathogens. More importantly, further analysis may elucidate other key components that could alleviate the tide of multi-resistant nosocomial infections.