Tolerance To Metal Ions Research Articles

High acidity organic waste degradation and the potential to bioremediation of heavy metals in soil by an acid-tolerant Serratia sp.

Highly acidic citrus pomace (CP) is a byproduct of Pericarpium Citri Reticulatae production and causes significant environmental damage. In this study, a newly isolated acid-tolerant strain of Serratia sp. JS-043 was used to treat CP and evaluate the effect of reduced acid citrus pomace (RACP) in passivating heavy metals. The results showed that biological treatment could remove 97.56% of citric acid in CP, the organic matter in the soil increased by 202.60% and the catalase activity in the soil increased from 0 to 0.117Ug-1. Adding RACP into soil can increase the stabilization of Cu, Zn, As, Co, and Pb. Specifically, through the metabolism of strain JS-043, RACP was also involved in the stabilization of Zn and Pb, and Residual Fraction in the total pool of these metals increased by 10.73% and 10.54%, respectively. Finally, the genome sequence of Serratia sp. JS-043 was completed, and the genetic basis of its acid-resistant and acid-reducing characteristics was preliminarily revealed. JS-043 also contains many genes encoding proteins associated with heavy metal ion tolerance and transport. These findings suggest that JS-043 may be a high-potential strain to improve the quality of acidic organic wastes that can then be useful for soil bioremediation.

Characteristics of a novel acid-resistant phenol-degrading bacterium Acinetobacter pittii Hly3: Adaptability, kinetics, degradation pathway and long-term performance

The high concentration of phenol in wastewater significantly restrains bioremediation efficiency; intricate environmental conditions further increase the difficulty, constraining further application. In this work, a novel phenol-degrading Acinetobacter pittii Hly3, was isolated and its ability to degrade phenol, environmental adaptability, kinetics and application potential were studied. Strain Hly3 possessed a strong capability on the degradation of phenol (1700 mg L−1 in 56 h) and could remove phenol at a wide range of pH, temperature, and NaCl concentrations, as well as the tolerance of metal ions. Particularly, the Hly3 showed stable cyclic performance. Mass balance and stoichiometric analysis revealed 0.7935 g g−1 conversions of phenol to biomass. Simultaneously, the growth and phenol degradation aligned well with the Haldane model. The degradation pathway demonstrated that phenol hydroxylase (PH) and 2,3-dioxygenase (C23O) were the key enzymes for phenol degradation. In addition, seed germination indicated that the degradation of phenol by Hly3 was an effective detoxification process, which reduced the biological accumulation of phenol in mung bean plants. Therefore, the highly tolerant strain Hly3 could be utilized to treat high-phenol wastewater in high-salt and acidic environments and this study has enriched the knowledge related to Acinetobacter pittii in managing phenol-contaminated environments.

Encapsulation and Characterization of Proanthocyanidin Microcapsules by Sodium Alginate and Carboxymethyl Cellulose.

Proanthocyanidins are important compounds known for their antioxidant and radical scavenging properties, but they are highly sensitive to light, heat, oxygen, and pH. In our study, proanthocyanidin was encapsulated using sodium alginate and carboxymethyl cellulose to enhance controlled release, pH stability, metal ion tolerance, temperature resistance, time release, the microencapsulation of food additives stability, antioxidant capacity analysis, and the storage period tolerance of proanthocyanidin. Fourier transforms infrared (FTIR) analysis and full-wavelength UV scanning indicated the successful immobilization of proanthocyanidins into the polymeric microcapsules. The flowability and mechanical properties of the microcapsules were enhanced. Moreover, proanthocyanidin microcapsules exhibited higher thermal, pH, metal ion, time, and microencapsulation food additive stability. In addition, due to their high antioxidant properties, the proanthocyanidin microcapsules retained a greater amount of proanthocyanidin content during the gastric phase, and the proanthocyanidin was subsequently released in the intestinal phase for absorption. Thus, the study provided a systematic understanding of the antioxidant capabilities and stability of proanthocyanidin microcapsules, which is beneficial for developing preservation methods for food additives.

Synthesis of metal ion-tolerant Mn-doped fluorescence silicon quantum dots with green emission and its application for selective imaging of ·OH in living cells.

Monitoring hydroxyl radical (·OH) in living cells remains a big challenge on account of its high reactivity and short half-life. In this work, we designed a fluorescent probe based on manganese-doped silicon quantum dots (Mn-SiQDs) for detecting and imaging of ·OH with good water solubility. The manganese was doped in its ethylene diamine tetra-acetic acid (EDTA) complex form and effectively improved the metal ion tolerance of fluorescence of SiQDs. And m-dihydroxybenzene was used as the reductant to extend the emission of SiQDs to the green region at 515nm when the excitation wavelength was 424nm. Basing on the fluorescence quenching of Mn-SiQDs, a linear response of ·OH was observed in the range 0.8-50μM with alimit of detection (LOD) of 88.4nM, which is lower than thosereported with SiQDs. The interference from other ROS or RNS has been assessed and no impact was found. In fully aqueous systems, the Mn-SiQDs have been applied to monitor and image the endogenous ·OH in HeLa cells. Our work provided a newstrategy for designing SiQDs with good biocompatibility, high selectivity and long monitoringwavelength. Synthesis of green-emitting silicon quantum dots withN-[3 -(trimethoxysilyl) propyl] ethylenediamine (DAMO), Ethylenediamine tetraacetic acid disodium salt dehydrate (EDTA-2Na·2H2O), manganese acetate tetrahydrate (Mn(CH3COO)2·4H20) and m-dihydroxybenzene. The green fluorescence of the silicon quantum dots can be selectively quenched by hydroxyl radicals.

Whole-genome mining of abiotic stress gene loci in rice.

We projected meta-QTL (MQTL) for drought, salinity, cold state, and high metal ion tolerance in rice using a meta-analysis based on high-density consensus maps. In addition, a genome-wide association analysis was used to validate the results of the meta-analysis, and four new chromosome intervals for mining abiotic stress candidate genes were obtained. Drought, severe cold, high salinity, and high metallic ion concentrations severely restrict rice production. Consequently, the breeding of abiotic stress-tolerant variety is being paid increasingly more attention. This study aimed to identify meta-quantitative trait loci (MQTL) for abiotic stress tolerance in rice, as well as the molecular markers and potential candidate genes of the MQTL regions. We summarized 2785 rice QTL and conducted a meta-analysis of 159 studies. We found 82 drought tolerance (DT), 70 cold tolerance (CT), 70 salt tolerance (ST), and 51 heavy metal ion tolerance (IT) meta-QTL, as well as 20 DT, 11 CT, 22 ST, and 5 IT candidate genes in the MQTL interval. Thirty-one multiple-tolerance related MQTL regions, which were highly enriched, were also detected, and 13 candidate genes related to multiple-tolerance were obtained. In addition, the correlation between DT, CT, and ST was significant in the rice genome. Four candidate genes and four MM-QTL regions were detected simultaneously by GWAS and meta-analysis. The four candidate genes showed distinct genetic differentiation and substantial genetic distance between indica and japonica rice, and the four MM-QTL are potential intervals for mining abiotic stress-related candidate genes. The candidate genes identified in this study will not only be useful for marker-assisted selection and pyramiding but will also accelerate the fine mapping and cloning of the candidate genes associated with abiotic stress-tolerance mechanisms in rice.

Characterization of a New Intracellular Alginate Lyase with Metal Ions-Tolerant and pH-Stable Properties.

Alginate lyases play an important role in alginate oligosaccharides (AOS) preparation and brown seaweed processing. Many extracellular alginate lyases have been characterized to develop efficient degradation tools needed for industrial applications. However, few studies focusing on intracellular alginate lyases have been conducted. In this work, a novel intracellular alkaline alginate lyase Alyw202 from Vibrio sp. W2 was cloned, expressed and characterized. Secretory expression was performed in a food-grade host, Yarrowia lipolytica. Recombinant Alyw202 with a molecular weight of approximately 38.3 kDa exhibited the highest activity at 45 °C and more than 60% of the activity in a broad pH range of 3.0 to 10.0. Furthermore, Alyw202 showed remarkable metal ion-tolerance, NaCl independence and the capacity of degrading alginate into oligosaccharides of DP2-DP4. Due to the unique pH-stable and high salt-tolerant properties, Alyw202 has potential applications in the food and pharmaceutical industries.

Novel thermostable enzymes from Geobacillus thermoglucosidasius W-2 for high-efficient nitroalkane removal under aerobic and anaerobic conditions

In this study, a thermophilic facultative anaerobic strain Geobacillus thermoglucosidasius W-2 was found to degrade nitroalkane under both aerobic and anaerobic conditions. Bioinformatical analysis revealed three putative nitroalkane-oxidizing enzymes (Gt-NOEs) genes from the W-2 genome. The three identified proteins Gt2929, Gt1378, and Gt1208 displayed optimal activities at high temperatures (70, 70, and 80 °C, respectively). Among these, Gt2929 exhibited excellent degradation capability, pH stability, and metal ion tolerance for nitronates under aerobic condition. Interestingly, under anaerobic condition, only Gt1378 still maintained high activity for 2-nitropropane and nitroethane, indicating that the W-2 strain utilized various pathways to degrade nitronates under aerobic and anaerobic conditions, respectively. Taken together, the first revelation of thermophilic nitroalkane-degrading mechanism under both aerobic and anaerobic conditions provides guidance and platform for biotechnological and industrial applications.

Role of extracellular polymeric substances in biosorption of Pb2+ by a high metal ion tolerant fungal strain Aspergillus niger PTN31

It is widely reported that fungal strains show good heavy metal ions tolerance, but the role of fungal extracellular polymeric substances (EPS) in heavy metal ion biosorption and tolerance is still not clear. In this study, a high metal ion tolerant fungal strain PTN31, identified as Aspergillus niger, was isolated, which could grow in the medium with coexistence of various metal ions. The minimum inhibitory concentration (MIC) for Pb was up to 72 mM. Moreover, biosorption behaviors and mechanisms of Pb2+ by PTN31 and extracted EPS were fully tested. Higher pH promoted biosorption of Pb2+ by the both biosorbents due to deprotonation of the functional groups in microorganisms and EPS. High and low temperature affected the physiological and metabolic activity of the biosorbents, leading to low Pb2+ adsorption. The adsorption kinetic process was well described by pseudo-second order model (R2 > 0.98) and the adsorption isotherm fit well with Freundlich model (R2 > 0.95). The maximum monolayer Pb2+ biosorption capacity of extracted EPS form PTN31 was as high as 713.6 mg/g, whereas Pb2+ biosorption capacity of PTN31 was decreased by 40.9%–66.8% after removal of EPS. Therefore, large Pb2+ biosorption capability of EPS is primarily responsible for the high lead tolerance of strain PTN31. EDS and FTIR indicated that EPS with abundant functional groups was highly related to the formation of cell aggregates, which could build a protective barrier for protecting cells from hostile environments.

Molecular and biochemical characterization of a novel cold-active and metal ion-tolerant GH10 xylanase from frozen soil

ABSTRACTA novel xylanase gene of family 10 (xyn27) was obtained from the genomic DNA of frozen soil of Daxinganling in China by Touch-down polymerase chain reaction (PCR) and thermal asymmetric interlaced (TAIL) PCR methods. Xyn27 contained a putative signal peptide (20 residues) and a catalytic motif of GH10 (327 residues) and shared the highest similarity (83%) with the reported GH10 xylanase (XM_003662144). The recombinant xyn27 was successfully expressed in Pichia pastoris GS115 and the optimal induction condition was 30 °C for 48 h. Xyn27 was demonstrated to be a cold-active xylanase, which shows its highest activity at 35 °C and still had 60.25%, 38.70% and 10.8% relative activity at 20 °C, 10 °C and 0 °C. Further analysis showed that Xyn27 has fewer arginine and more alanine residues compared with its mesophilic or thermophilic counterparts. The optimal pH of Xyn27 was 7.0, and it was stable after incubating under the pH range from 3.0 to 9.0 for 1 h. Besides, Xyn27 exhibited superior metal ion tolerance than other GH10 cold-active xylanases, being tolerant to most metal ions and organic solvents, and significantly enhanced by Ca2+, Mn2+ and Zn2+ metal ions. In addition, the Km, Vmax, kcat and kcat Km−1 against beechwood xylan were 13.42 mg mL−1, 9.07 μmol min−1 mg−1, 192.98 min−1 and 14.38 mL min−1 mg−1, and Xyn27 could completely degrade xylan into xylobiose. The features of cold activity and metal-ion tolerance suggested that xylanase Xyn27 could have potential application in basic research and various industries like food possessing.

A flavonoid-based light-up bioprobe with intramolecular charge transfer characteristics for wash-free fluorescence imaging in vivo

Wash-free imaging methods can simplify the experimental procedures and facilitate the continuous observation of the targets by eliminating washing process. In this work, we present a flavonoid-based light-up bioprobe with intramolecular charge transfer characteristics. The probe could be easily synthesized by the methylation of its flavone derivative, which was initially prepared via the Claisen-Schmidt condensation and Algar-Flynn-Oyamada reaction. The probe possessed a large Stokes shift, positive solvatochromism, high photostability, high tolerance for metal ions, and light-up fluorescence properties towards protein and tissue lysate. Moreover, the signal-to-noise ratio of fluorescence bioimaging in living cells and zebrafish by using this probe could reach 4–15 without washing process, providing a new candidate for efficient wash-free imaging method in vivo.

Peroxynitrous-acid-induced chemiluminescence detection of nitrite based on Microfluidic chip

A chemiluminescent method for nitrite detection was developed on microfluidic chip. Carbon dots-NaNO2− acidified H2O2 system was adopted. Chemiluminescence (CL) spectrum of this system was detected. The radiative recombination of hole-injected and electron-injected carbon dots explained their CL property. Spiral microchannels were designed on the microfluidic chip to allow enough reaction time for the carbon dots-NaNO2-acidified H2O2 system. Carbon dots and NaNO2 were premixed in the branch microchannel, then, the mixture reacted with acidified H2O2 in spiral microchannels. Concentrations of H2SO4 and H2O2, dilution ratio of carbon dots in H2O and flow rate were optimized to obtain the best CL signals. The approach presented satisfactory linear relationship between NaNO2 concentration and CL intensity. The tolerance of metal ions in determination of 1×10−5M nitrite was analyzed. The nitrites in water and beverage samples were successfully analyzed on the microfluidic chip with good repeatability. The data were well accordance with the results obtained from GB 5009.33− 2010. This microfluidic CL detection method is believed to be a simple, automatic and agent-save approach for inorganic ion analysis.

Low specificity of metal ion binding in the metal ion core of a folded RNA

The structure and activity of nucleic acids depend on their interactions with metal ions. Fundamental to these interactions is the degree of specificity observed between the metal ions and nucleic acids, and a complete description of nucleic acid folding requires that we understand the nature of the interactions with metal ions, including specificity. The prior demonstration that high concentrations of monovalent cations prevent nonspecific association of divalent ions with nucleic acids provides a novel and powerful means to examine site-specific metal ion binding isolated from complicating effects of the ion atmosphere. Using these high monovalent cation solution conditions we have monitored the affinity of a series of divalent metal ions for two site-specific metal ion binding sites in the P4-P6 domain of the Tetrahymena group I intron ribozyme. The metal ion core of this highly structured RNA binds two divalent metal ions under these conditions. Despite multiple metal ion-RNA interactions observed in the X-ray crystallographic structure of P4-P6 RNA at the metal ion binding sites, these sites exhibit low specificity among Mn(2+), Mg(2+), Ca(2+), Ni(2+), and Zn(2+). Nevertheless, the largest divalent metal ions tested, Sr(2+) and Ba(2+), were excluded from binding, exhibiting affinities at least two orders of magnitude weaker than observed for the other metal ions. Thus, a picture emerges of two metal ion binding sites, each with a high tolerance for metal ions with different properties but also with limits to accommodation. These limits presumably arise from steric or electrostatic features of the metal ion binding sites.

Involvement of an antioxidant defence system in the adaptive response to heavy metal ions in Helianthus annuus L. cells

A relationship between the antioxidant defence system and metal iontolerance in two types of sunflower callus differing in metal ion sensitivitywas studied. The antioxidant defence system of callus subjected to anadaptationtreatment of Cd(II), Al(III) and Cr(III) responded differently to 150μM of each metal compared with the corresponding controls undershock treatment. The GSH/GSSG ratio remained similar to control values for thethree metal-acclimated calli and in the chromium shock treatment, decreasingmoderately in the acute treatment with cadmium and aluminum. In contrast, theAs/DAs ratio was decreased in the two different treatments for the three metalsions, but the decrease was greater with acute stress. The antioxidant enzymesresponded differently according to the metal and treatment used. In chromiumadapted callus, all antioxidant enzymes increased except for glutathionereductase. However, in the shock treatment ascorbate peroxidase activity wasdiminished with each metal ion assayed. Guaiacol peroxidase was decreased bycadmium and chromium and remained similar to control values with aluminum.Glutathione reductase was only decreased by cadmium, and superoxide dismutaseand catalase activities were less increased than in tolerant cells. Theseresults suggest the involvement of an antioxidant defence system in theadaptiveresponse to heavy metal ions in Helianthus annuus L.cells.

Metal-ion tolerance in Escherichia coli: analysis of transcriptional profiles by gene-array technology.

Escherichia coli was adapted to grow in medium containing substantially elevated concentrations of either Zn(II), Cd(II), Co(II) or Ni(II). Whole-genome transcriptional profiles were generated from adapted strains and analysed for significant alteration in transcript abundance with reference to a wild-type strain. Similar alterations in specific message levels were observed for strains adapted to the four metal ions. One unexpected trend was the increase in transcript level of genes involved in transposition of IS elements, particularly insA. Subsequent expression of insA-7 from a heterologous promoter in E. coli conferred tolerance to Zn(II).