High Salt Environment Research Articles

AepG is a glucuronosyltransferase involved in acidic exopolysaccharide synthesis and contributes to environmental adaptation of Haloarcula hispanica

The attachment of a sugar to a hydrophobic lipid carrier is the first step in the biosynthesis of many glycoconjugates. In the halophilic archaeon Haloarcula hispanica, HAH_1206, renamed AepG, is a predicted glycosyltransferase belonging to the CAZy Group 2 family that shares a conserved amino acid sequence with dolichol phosphate mannose synthases. In this study, the function of AepG was investigated by genetic and biochemical approaches. We found that aepG deletion led to the disappearance of dolichol phosphate-glucuronic acid. Our biochemical assays revealed that recombinant cellulose-binding, domain-tagged AepG could catalyze the formation of dolichol phosphate-glucuronic acid in time- and dose-dependent manners. Based on the invivo and invitro analyses, AepG was confirmed to be a dolichol phosphate glucuronosyltransferase involved in the synthesis of the acidic exopolysaccharide produced by H.hispanica. Furthermore, lack of aepG resulted in hindered growth and cell aggregation in high salt medium, indicating that AepG is vital for the adaptation of H.hispanica to a high salt environment. In conclusion, AepG is the first dolichol phosphate glucuronosyltransferase identified in any of the three domains of life and, moreover, offers a starting point for further investigation into the diverse pathways used for extracellular polysaccharide biosynthesis in archaea.

A Positively Selected fur-R88H Mutation Enhances Helicobacter pylori Fitness in a High-Salt Environment and Alters Fur-Dependent Regulation of Gene Expression.

Both Helicobacter pylori infection and a high-salt diet are risk factors for gastric cancer. We previously showed that a mutation in fur (encoding the ferric uptake regulator variant Fur-R88H) was positively selected in H. pylori strains isolated from experimentally infected Mongolian gerbils receiving a high-salt diet. In the present study, we report that continuous H. pylori growth in high-salt conditions in vitro also leads to positive selection of the fur-R88H mutation. Competition experiments with strains containing wild-type fur or fur-R88H, each labeled with unique nucleotide barcodes, showed that the fur-R88H mutation enhances H. pylori fitness under high-salt conditions but reduces H. pylori fitness under routine culture conditions. The fitness advantage of the fur-R88H mutant under high-salt conditions was abrogated by the addition of supplemental iron. To test the hypothesis that the fur-R88H mutation alters the regulatory properties of Fur, we compared the transcriptional profiles of strains containing wild-type fur or fur-R88H. Increased transcript levels of fecA2, which encodes a predicted TonB-dependent outer membrane transporter, were detected in the fur-R88H variant compared to those in the strain containing wild-type fur under both high-salt and routine conditions. Competition experiments showed that fecA2 contributes to H. pylori fitness under both high-salt and routine conditions. These results provide new insights into mechanisms by which the fur-R88H mutation confers a selective advantage to H. pylori in high-salt environments.

Lignin microparticles-reinforced cellulose filter paper for simultaneous removal of emulsified oils and dyes

The presence of multiple pollutants in wastewater, often with complex interactions, poses a significant challenge for conventional membranes to effectively remove multiple pollutants simultaneously. Herein, a lignin microparticles-reinforced cellulose filter paper (FP@AL-LS-DA) was fabricated via an aldol condensation between lignin and cellulose filter paper and cross-linking with dopamine hydrochloride (DA), which showed desired rejection of oil-in-water emulsions and dyes. Characterizations revealed that the addition of lignin and DA effectively narrowed the pore size (from 4.45 μm to 2.01 μm) and enhanced the rigidity and stability of the cellulose filter paper, thus making it not easily damaged in the water environment and showing excellent tolerance to strong acid and high-salt environments. The oil-in-water emulsions removal efficiency was higher than 99 % even after ten times usage, and the oil flux was kept stable at 52.54 L·m−2·h−1, indicating that FP@AL-LS-DA had outstanding reusability and stability. Remarkably, FP@AL-LS-DA showed excellent removal efficiency (>99 %) for complex pollutants containing dyes and oil-in-water emulsions. In this work, we demonstrate a lignin microparticles-reinforced cellulose filter paper that is simple to prepare and can efficiently separate oil-in-water emulsions and remove dyes.

Expression of a Salt-Tolerant Pseudolysin in Yeast for Efficient Protein Hydrolysis under High-Salt Conditions.

Protease biocatalysis in a high-salt environment is very attractive for applications in the detergent industry, the production of diagnostic kits, and traditional food fermentation. However, high-salt conditions can reduce protease activity or even inactivate enzymes. Herein, in order to explore new protease sources, we expressed a salt-tolerant pseudolysin of Pseudomonas aeruginosa SWJSS3 isolated from deep-sea mud in Saccharomyces cerevisiae. After optimizing the concentration of ion cofactors in yeast peptone dextrose (YPD) medium, the proteolytic activity in the supernatant was 2.41 times more than that in the control group when supplemented with 5 mM CaCl2 and 0.4 mM ZnCl2. The extracellular proteolytic activity of pseudolysin reached 258.95 U/mL with optimized expression cassettes. In addition, the S. cerevisiae expression system increased the salt tolerance of pseudolysin to sodium chloride (NaCl)and sodium dodecyl sulfate (SDS) and the recombinant pseudolysin retained 15.19% activity when stored in 3 M NaCl for 7 days. The recombinant pseudolysin was able to efficiently degrade the β-conglycinin from low-denatured soy protein isolates and glycinin from high-denatured soy protein isolates under high temperatures (60 °C) and high-salt (3 M NaCl) conditions. Our study provides a salt-tolerant recombinant protease with promising applications in protein hydrolysis under high-salt conditions.

Mechanism of trehalose-enhanced metabolism of heterotrophic nitrification-aerobic denitrification community under high-salt stress

Heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria are aerobic microorganisms that can remove nitrogen under high-salt conditions, but their performance in practical applications are not satisfactory. As a compatible solute, trehalose helps microorganisms to cope with high salt stress by participating in the regulation of cellular osmotic pressure, and plays an important role in promoting the nitrogen removal efficiency of microbial populations in the high-salt environment. We investigated the mechanism of exogenous-trehalose-enhanced metabolism of HN-AD community under high-salt stress by starting up a membrane aerobic biofilm reactor (MABR) to enrich HN-AD bacteria, and designed a C150 experimental group with 150 μmol/L trehalose addition and a C0 control group without trehalose. The reactor performance and the community structure showed that NH4+-N, total nitrogen (TN) and chemical oxygen demand (COD) removal efficiency were increased by 29.7%, 28.0% and 29.1%, respectively. The total relative abundance of salt-tolerant HN-AD bacteria (with Acinetobacter and Pseudofulvimonas as the dominant genus) in the C150 group reached 66.8%, an 18.2% increase compared with that of the C0 group. This demonstrated that trehalose addition promoted the enrichment of salt-tolerant HN-AD bacteria in the high-salt environment to enhance the nitrogen removal performance of the system. In-depth metabolomics analysis showed that the exogenous trehalose was utilized by microorganisms to improve proline synthesis to increase resistance to high-salt stress. By regulating the activity of cell proliferation signaling pathways (cGMP-PKG, PI3K-Akt), phospholipid metabolism pathway and aminoacyl-tRNA synthesis pathway, the abundances of phosphoethanolamine, which was one of the glycerophospholipid metabolites, and purine and pyrimidine were up-regulated to stimulate bacterial aggregation and cell proliferation to promote the growth of HN-AD bacteria in the high-salt environment. Meanwhile, the addition of trehalose accelerated the tricarboxylic acid (TCA) cycle, which might provide more electron donors and energy to the carbon and nitrogen metabolisms of HN-AD bacteria and promote the nitrogen removal performance of the system. These results may facilitate using HN-AD bacteria in the treatment of high-salt and high-nitrogen wastewater.

The Essential Role of OmpR in Acidithiobacillus caldus Adapting to the High Osmolarity and Its Regulation on the Tetrathionate-Metabolic Pathway.

Acidithiobacillus spp. are prevalent in acid mine drainage, and they have been widely used in biomining for extracting nonferrous metals from ores. The osmotic stress generated by elevated concentrations of inorganic ions is a severe challenge for the growth of Acidithiobacillus spp. in the bioleaching process; however, the adaptation mechanism of these bacteria to high osmotic pressure remains unclear. In this study, bioinformatics analysis indicated that the osmotic stress response two-component system EnvZ-OmpR is widely distributed in Acidithiobacillus spp., while OmpRs from Acidithiobacillus spp. exhibited a far more evolutionary relationship with the well-studied OmpRs in E. coli and Salmonella typhimurium. The growth measurement of an Acidithiobacillus caldus (A. caldus) ompR-knockout strain demonstrated that OmpR is essential in the adaptation of this bacterium to high osmotic stress. The overall impact of OmpR on the various metabolic and regulatory systems of A. caldus was revealed by transcriptome analysis. The OmpR binding sequences of differentially expressed genes (DEGs) were predicted, and the OmpR box motif in A. caldus was analysed. The direct and negative regulation of EnvZ-OmpR on the tetrathionate-metabolic (tetH) cluster in A. caldus was discovered for the first time, and a co-regulation mode mediated by EnvZ-OmpR and RsrS-RsrR for the tetrathionate intermediate thiosulfate-oxidizing (S4I) pathway in this microorganism was proposed. This study reveals that EnvZ-OmpR is an indispensable regulatory system for the ability of A. caldus to cope with high osmotic stress and the significance of EnvZ-OmpR on the regulation of sulfur metabolism in A. caldus adapting to the high-salt environment.

Novel laser cladding FeCoNiCrNb0.5Mox high-entropy alloy coatings with excellent corrosion resistance

In order to improve the properties of the surface corrosion resistance of the load bearing parts of marine equipment in the high salt and high humid environment, novel FeCoNiCrNb0.5Mox (x = 0.00, 0.25, 0.50, 0.75, 1.00) high-entropy alloy coatings were prepared on the 42CrMo steel by laser cladding. The testing results show that the FeCoNiCrNb0.5Mox coatings consist of FCC phase and Laves phase, and the increase of Mo content promotes the formation of the Laves phase. FeCoNiCrNb0.5Mo0.50, FeCoNiCrNb0.5Mo0.75 and FeCoNiCrNb0.5Mo1.00 coatings have complete eutectic structure. The appropriate addition of Mo improves corrosion resistance by promoting the formation of Laves phase. Mo0.75 coating possesses the best corrosion resistance property. Compared with the substrate of the 42CrMo steel, the FeCoNiCrNb0.5Mox coatings possess much better corrosion resistance, which means that they are promising materials for surface protection of marine engineering equipment.

Spatiotemporal dynamics of the microbial diversity on salt-preserved goatskins assessed by culturing and 16S rRNA gene amplicon sequencing

Wet-salted skin, as a special artificial high-salt environment, is rich in protein, fat, collagen and other nutrient substrates, and is a rich resource of halotolerant and halophilic microorganisms. However, knowledge gaps regarding the microbial community structure and inter taxa associations of wet-salted skin are large. In this study, the spatiotemporal dynamics and community structure of microorganisms present on wet-salted goatskins were investigated using 16S rRNA gene amplicon sequencing and culturable technique. Alpha diversity analysis based on Sobs, Chao, Ace and Shannon indices revealed that microbial diversity on the wet-salted goatskins exhibited a trend of ‘down → up → down → flat’ with time. During preservation, genera belonging to the bacteria domain such as Acinetobacter, Weissella and Streptococcus were slowly dying out, whereas those belonging to halophilic archaea such as Natrialba and Haloterrigena were gradually flourishing. Moreover, to resist high-salt stress, microorganisms on the wet-salted goatskin gradually migrated from the outside to the inside, eventually leading to the microbial diversity inside the skin being the same as or even higher than that on the skin surface. Venn diagram analysis revealed that the strains of some genera, including Psychrobacter, Salimicrobium, Salinicola, Ornithinibacillus, Halomonas, Bacillus and Chromohalobacter, were distributed throughout the interior and exterior of the wet-salted goatskin and existed during various periods. Accordingly, 45 protease-producing halophilic or halotolerant microorganisms were isolated and screened from the wet-salted goatskin using the gradient dilution plate method. Importantly, 16S rRNA genes of some bacteria exhibited less than 99.5% similarity to valid published species, indicating that they likely are novel species and have a good potential for application.Graphical

Whole-transcriptome analyses of Sorghum leaves identify key mRNAs and ncRNAs associated with GA3-mediated alleviation of salt stress.

Sorghum has recently attracted much attention for its tolerance in high salt environment. However, the effect and regulatory mechanism of the gibberellic acid (GA3)-mediated alleviation of salt stress in sorghum remains unclear. Herein, we reported that a GA3 concentration of 50 mg/L is optimal for sorghum ("Jitian 3") development under salt stress. We conducted a whole-transcriptome analysis between GA3-treated and control sorghum leaves under salt stress, and we identified 1002 differentially expressed (DE)-messenger RNAs (mRNAs), 81 DE-long non-coding RNAs (lncRNAs), 7 DE-circular RNAs (circRNAs), and 26 DE-microRNA (miRNAs) in sorghum following GA3 treatment. We also identified a majority of DE-mRNAs and non-coding RNAs (ncRNAs) targets that serve essential roles in phenylpropanoid biosynthesis and plant hormone networks. In addition, we generated a competitive endogenous RNA (ceRNA)-miRNA-target gene network, and 3 circRNAs (circRNA_2746, circRNA_6515, circRNA_5622), 4 lncRNAs (XR_002450182.1, XR_002452422.1, XR_002448510.1, XR_002448296.1) and 4 genes (LOC8056546, LOC8062245, LOC8061469, LOC8071960) probably act as valuable candidates for the regulation of the GA3-mediated alleviation of salt stress in sorghum. Our findings uncovered potential mRNA and non-coding RNAs that contribute to GA3 regulation, thus offering a basis for the future investigation of underlying mechanisms of salt stress in sorghum.

Covalent Bonding and Coulomb Repulsion-Guided AuNP Array: A Tunable and Reusable Substrate for Metabolomic Characterization of Lung Cancer Patient Sera.

Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) has gained increased attention in the metabolic characterization of human biofluids. However, the stability and reproducibility of nanoparticle-based substrates remain two of the biggest challenges in high-salt environments. Here, by controlling the extent of Coulomb repulsion of 26 nm positively charged AuNPs, a homogeneous layer of covalently bonded AuNPs on a coverslip with tunable interparticle distances down to 16 nm has been successfully fabricated to analyze small biomolecules in human serum. Compared with the self-assembled AuNP array, the covalently bonded AuNP array showed superior performances on stability, reproducibility, and sensitivity in high-salt environments. The stable attachment of AuNPs maintained a detection reproducibility with a RSD less than 12% and enabled the reusability of the array for 10 experiments without significant signal deterioration (<15%) and carryover effects. Moreover, the closely positioned AuNPs allowed the coupling of photoinduced plasmons to generate an enhanced electric field, which promotes the generation of excited electrons to facilitate the desorption/ionization processes instead of the heat dissipation, thus enhancing the detection sensitivity with detection limits down to the femtomole level. Combined with machine learning methods, the AuNP array has been successfully applied to discover seven biomarkers for differentiating early-stage lung cancer patients from healthy controls. It is anticipated that this simple approach of developing robust AuNP arrays can also be extended to other types of NP arrays for wider applications of SALDI-MS technology.

Bioaccumulation of Heavy Metals by Suaeda salsa in the Tidal Flat of the Liaohe Estuary

In order to explore the bioaccumulation of heavy metals by Suaeda salsa and its ecological restoration capacity in the tidal flat of the Liaohe estuary, the absorption and reduction effect of Suaeda salsa on heavy metals was determined via a combination of on-site monitoring and experimental tests. The results showed that, under a high-salt environment, Suaeda salsa had a decreasing effect on heavy metals zinc, copper and lead, and the bioaccumulation coefficient BCFSs–Zn &gt; BCFSs–Cu &gt; BCFSs–Pb. When the concentration of heavy metal ions was high, Suaeda salsa could still survive, but the absorptivity was low, reducing its ability to repair heavy metal pollution. By correlating the research data with the population density of Suaeda salsa, the total removal of heavy metals was obtained, about 2008.6 kg Zn2+, 347.5 kg Cu2+, 376.1 kg Pb2+. This paper could provide a theoretical basis and technical support for the promotion and application of ecological restoration via Suaeda salsa.

Overexpression of a Malus baccata CBF transcription factor gene, MbCBF1, Increases cold and salinity tolerance in Arabidopsis thaliana

CBFs play a crucial role when plants are in adverse environmental conditions for growth. However, there are few reports on the role of CBF gene in stress responses of Malus plant. In this experiment, a new CBF TF was separated from M. baccata which was named MbCBF1. MbCBF1 protein was found to be localized in the nucleus after subcellular localization. Furthermore, the expression of MbCBF1 was highly accumulated in new leaves and roots due to the high influence of cold and high salt in M. baccata seedlings. After introducing MbCBF1 into A. thaliana, transgenic A. thaliana can better adapt to the living conditions of cold and high salt. The increased expression of MbCBF1 in A. thaliana also increased the contents of proline, remarkablely improved the activities of SOD, POD and CAT, but the content of MDA was decreased. Although the chlorophyll content also decreased, it decreased less in transgenic plants. In short, above date showed that MbCBF1 has a positive effect on improving A. thaliana cold and high salt tolerance. MbCBF1 can regulate the expression of its downstream gene in transgenic lines, up-regulate the expression of key genes COR15a, RD29a/bandCOR6.6/47 related to low temperature under cold conditions and NCED3, CAT1, P5CS1, RD22, DREB2A,PIF1/4, SOS1 and SnRK2.4 related to salt stress under high salt conditions, so as to further improve the adaptability and tolerance of the transgenic plants to low temperature and high salt environment.

Genomic Analysis of Halotolerant Bacterial Strains Martelella soudanensis NC18T and NC20.

Two novel, halotolerant strains of Martelella soudanensis, NC18T and NC20, were isolated from deep subsurface sediment, deeply sequenced, and comparatively analyzed with related strains. Based on a phylogenetic analysis using 16S rRNA gene sequences, the two strains grouped with members of the genus Martelella. Here, we sequenced the complete genomes of NC18T and NC20 to understand the mechanisms of their halotolerance. The genome sizes and G+C content of the strains were 6.1 Mb and 61.8 mol%, respectively. Moreover, NC18T and NC20 were predicted to contain 5,849 and 5,830 genes, and 5,502 and 5,585 protein-coding genes, respectively. Both strains contain the identically predicted 6 rRNAs and 48 tRNAs. The harboring of halotolerant-associated genes revealed that strains NC18T and NC20 might tolerate high salinity through the accumulation of potassium ions in a "salt-in" strategy induced by K+ uptake protein (kup) and the K+ transport system (trkAH and kdpFABC). These two strains also use the ectoine transport system (dctPQM), the glycine betaine transport system (proVWX), and glycine betaine uptake protein (opu) to accumulate "compatible solutes," such as ectoine and glycine betaine, to protect cells from salt stress. This study reveals the halotolerance mechanism of strains NC18T and NC20 in high salt environments and suggests potential applications for these halotolerant and halophilic strains in environmental biotechnology.

Genome-Wide Investigation and Expression Analysis of the Nitraria sibirica Pall. CIPK Gene Family.

The calcineurin B-like-interacting protein kinase (CIPK) protein family plays a key role in the plant calcium ion-mediated signal transduction pathway, which regulates a plant’s response to abiotic stress. Nitraria sibirica pall. (N. sibirica) is a halophyte with a strong tolerance for high salt environments, yet how it is able to deal with salt stress on a molecular level is still unknown. Due to their function as described in other plant species, CIPK genes are prime candidates for a role in salt stress signaling in N. sibirica. In this study, we identified and analyzed the phylogenetic makeup and gene expression of the N. sibirica CIPK gene family. A total of 14 CIPKs were identified from the N. sibirica genome and were clustered into seven groups based on their phylogeny. The promoters of NsCIPK genes contained multiple elements involved in hormonal and stress response. Synteny analysis identified a total of three pairs of synteny relationships between NsCIPK genes. Each gene showed its own specific expression pattern across different tissues, with the overall expression of CIPK6 being the lowest, and that of CIPK20 being the highest. Almost all CIPK genes tended to respond to salt, drought, and cold stress, but with different sensitivity levels. In this study, we have provided a general description of the NsCIPK gene family and its expression, which will be of great significance for further understanding of the NsCIPK gene family function.

A multiple synergistic composite coating with ultrahigh anti-corrosion performance under harsh oxygen environment

Designing effective strategies to satisfy the anti-corrosion requirements in high-pressure oxygen and high salt environment still remains a huge challenge. Herein, the oriented polyaniline nanofibers doped with phytic acid were synthetized on the surface of sericite (PPANI-Ser) by in-situ polymerization to endow epoxy coating with ultrahigh anti-corrosion performance. The |Z|0.01 Hz of PPANI-Ser/EP coating immersed in 12 wt% NaCl solution still maintained above 1011 ohm⋅cm2 after 90 days of immersion at 60 °C. Significantly, after 10 days immersion in the coupling environment of 3 MPa pure O2 and 12 wt% NaCl solution, PPANI-Ser/EP coating had almost no deterioration.

Metagenomic analysis of the soil microbial composition and salt tolerance mechanism in Yuncheng Salt Lake, Shanxi Province.

The soil in Yuncheng Salt Lake has serious salinization and the biogeographic environment affects the composition and distribution of special halophilic and salt-tolerant microbial communities in this area. Therefore, this study collected soils at distances of 15, 30, and 45 m from the Salt Lake and used non-saline soil (60 m) as a control to explore the microbial composition and salt tolerance mechanisms using metagenomics technology. The results showed that the dominant species and abundance of salt-tolerant microorganisms changed gradually with distance from Salt Lake. The salt-tolerant microorganisms can increase the expression of the Na+/H+ antiporter by upregulating the Na+/H+ antiporter subunit mnhA-G to respond to salt stress, simultaneously upregulating the genes in the betaine/proline transport system to promote the conversion of choline into betaine, while also upregulating the trehalose/maltose transport system encode genes to promote the synthesis of trehalose to resist a high salt environment.

Durable superhydrophobic silica/epoxy resin coating for the enhanced corrosion protection of steel substrates in high salt and H2S environments

A superhydrophobic coating composed of epoxy on the bottom and siloxane-modified silica on the top was prepared by employing the scraping and spraying methods. The superhydrophobic coating possesses excellent mechanical properties, is superhydrophobic (water contact angle, WCA = 164.3°), and has low adhesion. The long-term corrosion resistance of the epoxy coating and the superhydrophobic coating in a 3.5 % NaCl solution and hydrogen sulfide environment was assessed using electrochemical impedance spectroscopy (EIS), polarization curve analysis, immersion testing, and X-ray diffraction (XRD). Test results indicate that the superhydrophobic coating has excellent anti-corrosion capability in an H2S environment for 50 days and in a 3.5 % NaCl solution for 60 days. This is of great significance for developing the potential applications of superhydrophobic coatings in H2S environments.

Low feed water temperature effects on RO membrane fouling development for municipal wastewater reclamation

Understanding the RO membrane fouling development at low feed water temperature plays an important role in the membrane fouling control for wastewater reclamation. In this study, RO membrane fouling development at low feed water temperature (10 °C) was investigated using a lab-scale cross-flow RO apparatus by comparing with that at ambient temperature (25 °C). At low temperature, the normalized flux decline of RO membrane was much milder than that at ambient temperature. The final normalized flux was twice of that at 25 °C. The foulants and biofilm gradually accumulated on the RO membrane, while the living bacteria on the membrane remained stable after a period of running time because of the living space limitation. The amount of the foulants and biofilm thickness at 10 °C were approximately 1/2 of that at 25 °C, while the DOC dissolved by alkali on the membranes at 10 °C were higher than and those at 25 °C. Therefore, alkali cleaning might be more effective in alleviating the membrane fouling at low temperature. Under the selection pressure of low temperature, the microbial community on the RO membranes gradually differentiated from that at ambient temperature. Especially, under low temperature condition, relative abundance of Patescibacteria, which was adapted to oligotrophic, low temperature and high salt environments, was found to gradually increase over time.

Isolation and Functional Analysis of MbCBF2, a Malus baccata (L.) Borkh CBF Transcription Factor Gene, with Functions in Tolerance to Cold and Salt Stress in Transgenic Arabidopsis thaliana.

CBF transcription factors (TFs) are key regulators of plant stress tolerance and play an integral role in plant tolerance to adverse growth environments. However, in the current research situation, there are few reports on the response of the CBF gene to Begonia stress. Therefore, this experiment investigated a novel CBF TF gene, named MbCBF2, which was isolated from M. baccata seedlings. According to the subcellular localization results, the MbCBF2 protein was located in the nucleus. In addition, the expression level of MbCBF2 was higher in new leaves and roots under low-temperature and high-salt induction. After the introduction of MbCBF2 into Arabidopsis thaliana, the adaptability of transgenic A. thaliana to cold and high-salt environments was significantly enhanced. In addition, the high expression of MbCBF2 can also change many physiological indicators in transgenic A. thaliana, such as increased chlorophyll and proline content, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activity, and reduced malondialdehyde (MDA) content. Therefore, it can be seen from the above results that MbCBF2 can positively regulate the response of A. thaliana to low-temperature and osmotic stress. In addition, MbCBF2 can also regulate the expression of its downstream genes in transgenic lines. It can not only positively regulate the expression of the downstream key genes AtCOR15a, AtERD10, AtRD29a/b and AtCOR6.6/47, related to cold stress at low temperatures, but can also positively regulate the expression of the downstream key genes AtNCED3, AtCAT1, AtP5CS, AtPIF1/4 and AtSnRK2.4, related to salt stress. That is, the overexpression of the MbCBF2 gene further improved the adaptability and tolerance of transgenic plants to low-temperature and high-salt environments.

Oxidization of benzo[a]pyrene by CYP102 in a novel PAHs-degrader Pontibacillus sp. HN14 with potential application in high salinity environment

Benzo [a]pyrene (BaP) is a type of high-molecular-weight polycyclic aromatic hydrocarbons (PAHs) with potent carcinogenicity; however, there are limited studies on its degradation mechanism. Here, a strain of Pontibacillus sp. HN14 with BaP degradation ability was isolated from mangrove sediments in Dongzhai Port, Hainan Province. Our study showed that biodegradation efficiencies reached 42.15% after Pontibacillus sp. HN14 was cultured with 20 mg L−1 BaP as the sole carbon source for 25 days and still had degradability of BaP at a 25% high salinity level. Moreover, 9,10-dihydrobenzo [a]pyrene-7(8H)-one, an intermediate metabolite, was detected during BaP degradation in the HN14 strain. Genome analysis identified a gene encoding the CYP102(HN14) enzyme. The results showed that the E. coli strain with CYP102(HN14) overexpression could transfer BaP to 9,10-dihydrobenzo [a]pyrene-7(8H)-one with a conversion rate of 43.5%, indicating that CYP102(HN14) played an essential role in BaP degradation in Pontibacillus sp. HN14. Thus, our results provide a novel BaP biodegradation molecule, which could be used in BaP bioremediation in high salinity conditions. This study is the first to show that CYP102(HN14) had the BaP oxidization ability in bacteria. CYP102(HN14) could be essential in removing PAHs in saline-alkali soil and other high salt environments through enzyme immobilization.