A universal fluorescence biosensor based on rolling circle amplification and locking probe for DNA detection.

A stable DNA signal amplification sensor was developed on account of rolling circle amplification (RCA). This sensor includes target DNA-controlled rolling circle amplification technology and locking probe DNA replacement technology, which can be used to detect DNA fragments with genetic information, thus constructing a biosensor for universal detection of DNA. This study takes the homologous DNA of human immunodeficiency virus (HIV) and let-7a as examples to describe this biosensor. The padlock probe is first cyclized by T4 DNA ligase in response to the target's reaction with it. Then, rolling cycle amplification is initiated by Phi29 DNA polymerase, resulting in the formation of a lengthy chain with several triggers. These triggers can open the locked probe LP1 with the fluorescence signal turned off, so that it can continue to react with H2 to form a stable H1-H2 double strand. This regulates the distance between B-DNA modified by the quenching group and H1 modified by fluorescent group, and the fluorescence signal is recovered.

The impact of the Qinghai-Tibet highway on plant community and diversity.

Roads are an increasingly prevalent form of human activity that drives the decrease in plant community functions and threatens global biodiversity. However, few studies have focused on the changes in the function and diversity of alpine meadows caused by road infrastructure in the Tibetan Plateau. In this study, the changes in species diversity, functional diversity, and community stability were examined at different distances from the Qinghai-Tibet highway. The results showed that the road intensified the degradation of vegetation, which significantly altered species diversity and community structure. This effect gradually decreased from near to far from the highway. Plant community cover and species diversity were highest at intermediate distances (50-100 m) from the roadway; species diversity and stability were lowest in the grassland most disturbed by the road (0 m), and species diversity and functional diversity tended to stabilize farther away from the road (250 m). Our findings indicate that changes in species diversity are synchronized with changes in functional diversity, which largely determines the outcome of degraded grassland community diversity and stability. Our results provide a reference point for restoring degraded alpine areas and mitigating the ecological impacts of roads.

Accelerated Discovery of Halide Perovskite Materials via Computational Methods: A Review.

Halide perovskites have gained considerable attention in materials science due to their exceptional optoelectronic properties, including high absorption coefficients, excellent charge-carrier mobilities, and tunable band gaps, which make them highly promising for applications in photovoltaics, light-emitting diodes, synapses, and other optoelectronic devices. However, challenges such as long-term stability and lead toxicity hinder large-scale commercialization. Computational methods have become essential in this field, providing insights into material properties, enabling the efficient screening of large chemical spaces, and accelerating discovery processes through high-throughput screening and machine learning techniques. This review further discusses the role of computational tools in the accelerated discovery of high-performance halide perovskite materials, like the double perovskites A2BX6 and A2BB'X6, zero-dimensional perovskite A3B2X9, and novel halide perovskite ABX6. This review provides significant insights into how computational methods have accelerated the discovery of high-performance halide perovskite. Challenges and future perspectives are also presented to stimulate further research progress.

Detection of MicroRNA-155 based on lambda exonuclease selective digestion and CRISPR/cas12a-assisted amplification.

In numerous malignancies, miRNA-155 is overexpressed and has oncogenic activity because it is one of the most efficient microRNAs for inhibiting apoptosis in human cancer cells. As a result, the highest sensitive detection of the miRNA-155 gene is a technological instrument that can enable early cancer screening. In this study, a miRNA-155 biosensor was created to create a hairpin probe that can bind to the miRNA-155 gene using lambda nucleic acid exonuclease, which can cut the 5' phosphorylated double strand, and by the DNA probe is recognized by the Cas12a enzyme, which then activates Cas12a to catalyze trans-cutting produces strong fluorescence. Research finding, the target concentration's logarithm and corresponding fluorescence intensity have a strong linear connection, and the limit of detection (LOD) of the sensing system was determined to be 8.3 pM. In addition, the biosensor displayed exceptional specificity, low false-positive signal, and high sensitivity in detecting the miRNA-155 gene in serum samples. This study's creation of a biosensor that has high sensitivity, good selectivity, and is simple to operate provides promising opportunities for research into biosensor design and early cancer detection.

Magnetic beads and GO-assisted enzyme-free signal amplification fluorescent biosensors for disease diagnosis.

Cancer detection is still a major challenge in public health. Identification of oncogene is the first step toward solving this problem. Studies have revealed that various cancers are associated with miRNA expression. Therefore, the sensitive detection of miRNA is substantially important to solve the cancer problem. In this study, let-7a, a representative substance of miRNA, was selected as the detection target. With the assistance of magnetic beads commonly used in biosensors and self-synthesized graphene oxide materials, specificity and sensitivity detection of the target gene let-7a were achieved via protease-free signal amplification. The limit of detection (LOD) was as low as 15.015pM. The fluorescence signal intensity showed a good linear relationship with the logarithm of let-7a concentration. The biosensor could also detect let-7a in complex human serum samples. Overall, this fluorescent biosensor is not only simple to operate, but also strongly specificity to detect let-7a. Therefore, it has substantial potential for application in the early diagnosis of clinical medicine and biological research.

Integrated chemical characterization, metabolite profiling, and pharmacokinetics analysis of Zhijun Tangshen Decoction by UPLC-Q/TOF-MS.

Diabetic nephropathy (DN) is the main cause of end-stage renal disease worldwide and a major public issue affecting the health of people. Therefore, it is essential to explore effective drugs for the treatment of DN. In this study, the traditional Chinese medicine (TCM) formula, Zhijun Tangshen Decoction (ZJTSD), a prescription modified from the classical formula Didang Decoction, has been used in the clinical treatment of DN. However, the chemical basis underlying the therapeutic effects of ZJTSD in treating DN remains unknown. In this study, compounds of ZJTSD and serum after oral administration in rats were identified and analyzed using ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q/TOF-MS). Meanwhile, a semi-quantitative approach was used to analyze the dynamic changes in the compounds of ZJTSD in vivo. UPLC-Q/TOF-MS analysis identified 190 compounds from ZJTSD, including flavonoids, anthraquinones, terpenoids, phenylpropanoids, alkaloids, and other categories. A total of 156 xenobiotics and metabolites, i.e., 51 prototype compounds and 105 metabolites, were identified from the compounds absorbed into the blood of rats treated with ZJTSD. The results further showed that 23 substances with high relative content, long retention time, and favorable pharmacokinetic characteristics in vivo deserved further investigations and validations of bioactivities. In conclusion, this study revealed the chemical basis underlying the complexity of ZJTSD and investigated the metabolite profiling and pharmacokinetics of ZJTSD-related xenobiotics in rats, thus providing a foundation for further investigation into the pharmacodynamic substance basis and metabolic regulations of ZJTSD.

Effects of diaphragm electrical stimulation in treating respiratory dysfunction on mechanical ventilation after intracerebral hemorrhage: A single-center retrospective study.

Intracerebral hemorrhage (ICH) is a major cause of death and disability worldwide. The benefits of electrical stimulation in the treatment of respiratory dysfunction in patients on mechanical ventilation is unknown. Nevertheless, there is a dearth of evidence-based medical research concerning its clinical efficacy. From January 2019 to January 2023, every enrolled patients experienced respiratory dysfunction after ICH while being supported by mechanical ventilation. A total of 205 eligible patients were enrolled and then allocated into 2 groups: control group and observation group. 133 patients was selected and administered standard treatment as control group. Based on conventional treatment, other 72 patients were administered diaphragm electrical stimulation (DES) treatment. We examined information from current medical records, encompassing all initial data and predictive follow-up data, such as the weaning success rate, occurrence of ventilator-associated pneumonia (VAP), duration of stay in the intensive care unit (ICU) and hospital, expenses related to hospitalization, and mortality within 30 days. The baseline clinical data of the 2 groups did not exhibit any statistically significant disparities (all P > .05). The rate of successful weaning showed a significant increase in the DES group when compared to the control group (P = .025). In patients with respiratory dysfunction due to ICH, treatment with DES resulted in a significant reduction in the duration of invasive ventilation (9.8 ±â€…2.1 vs 11.2 ±â€…2.6, P < .01) and total ventilation time (9.8 ±â€…2.1 vs 11.2 ±â€…2.6, P < .01). It also led to a decrease in the length of stay in the ICU (15.67 ±â€…3.76 vs 17.53 ±â€…4.28, P = .002) and hospitalization cost (11500 vs 13600, P = .001). Additionally, DES treatment resulted in a lower incidence of VAP (73.61% vs 86.46%, P = .022) and improved 30-day mortality (P < .05), without any significant adverse effects. The findings of this research indicate that DESs have a positive impact on enhancing the rate of successful weaning and reducing the incidence of VAP. It decreases the duration of invasive ventilation and total ventilation time while also improving the mortality rate within 30 days. This therapy could offer a fresh alternative for respiratory impairment in patients undergoing mechanical ventilation.

Berberine Protects Against Dihydrotestosterone-Induced Human Ovarian Granulosa Cell Injury and Ferroptosis by Regulating the Circ_0097636/MiR-186-5p/SIRT3 Pathway.

Polycystic ovarian syndrome (PCOS) is an endocrine syndrome in women of reproductive age. Berberine (BBR) is a Chinese herbal monomer that exhibits many pharmacological properties related to PCOS treatment. This study aims to analyze the effect of BBR on a cell model of PCOS and the underlying mechanism. Human ovarian granulosa (KGN) cells were treated with dihydrotestosterone (DHT) to mimic a PCOS cell model. The RNA expression of circ_0097636, miR-186-5p, and sirtuin3 (SIRT3) was determined by quantitative real-time polymerase chain reaction (qRT-PCR). Protein expression was detected by western blotting. Cell viability was analyzed by CCK-8 assay. Cell proliferation and apoptosis were investigated by 5-ethynyl-2'-deoxyuridine (EdU) assay and flow cytometry assay, respectively. The levels of interleukin-6 (IL-6), IL-1ß, and tumor necrosis factor-α (TNF-α) were analyzed by enzyme-linked immunosorbent assays (ELISAs). Fe2+ concentration was assessed by an iron assay kit. Oxidative stress was assessed by detecting reactive oxygen species (ROS) level and malondialdehyde (MDA) level using commercial kits. The association of miR-186-5p with circ_0097636 and SIRT3 was identified by dual-luciferase reporter assay and RNA pull-down assay. Circ_0097636 expression was downregulated in the follicular fluid of PCOS patients and DHT-treated KGN cells when compared with control groups. BBR treatment partially relieved the DHT-induced inhibitory effect on cell proliferation and promoted effects on cell apoptosis, inflammation, ferroptosis, and oxidative stress in KGN cells. Additionally, circ_0097636 bound to miR-186-5p, and SIRT3 was identified as a target gene of miR-186-5p in KGN cells. BBR treatment ameliorated DHT-induced KGN cell injury by upregulating circ_0097636 and SIRT3 expression and downregulating miR-186-5p expression. Moreover, circ_0097636 overexpression protected KGN cells from DHT-induced injury by increasing SIRT3 expression. BBR ameliorated DHT-induced KGN cell injury and ferroptosis by regulating the circ_0097636/miR-186-5p/SIRT3 pathway.

Development of a separation platform comprising magnetic beads combined with the CRISPR/Cas12a system enabling ultrasensitive and rapid detection of miRNA-21.

A separation platform has been developed mediated by a combination of magnetic beads and the CRISPR/Cas12a system to achieve ultrasensitive and rapid detection of miRNA-21 at a low level. In this system, with the assistance of an auxiliary probe, the target miRNA-21 can be specifically combined with three-stranded probes to initiate the SDR reaction. Abundant aptamer A3 was added to the solution that can activate the CRISPR/Cas12a system and initiate the trans-cleavage reaction to recover the fluorescence signal. Using magnetic beads to mediate the separation considerably greatly improves the signal conversion efficiency and detection sensitivity. At the 492 nm excitation wavelength, and 502-650 nm scan range, through analyzing the fluorescence peak intensity at 520 nm, the biosensor's determination range and limit of detection is 8 fM-250 nM and 2.42 fM, respectively, and the RSD is 19.03-37.80. Compared with other biosensors, the biosensor developed exhibited superior performance and the signal recovered excellently in 1% human serum and the LOD is 12.12 fM. This method provides a novel highly sensitive scheme for detecting miRNA .

Ulinastatin in the treatment of severe acute pancreatitis: A single-center randomized controlled trial.

BACKGROUND: Severe acute pancreatitis (AP) is one of the most common diseases of the gastrointestinal tract and carries a significant financial burden with high disability and mortality. There are no effective drugs in the clinical management of severe AP, and there is an absence of evidence-based medicine concerning the treatment of severe AP. AIM: To explore whether ulinastatin (UTI) can improve the outcome of severe AP. METHODS: The present research included patients who were hospitalized in intensive critical care units (ICUs) after being diagnosed with severe AP. Patients received UTI (400000 IU) or placebos utilizing computer-based random sequencing (in a 1:1 ratio). The primary outcome measures were 7-d mortality, clinical efficacy, inflammatory response, coagulation function, infection, liver function, renal function, and drug-related adverse effects were evaluated. RESULTS: A total of 181 individuals were classified into two groups, namely, the placebo group (n = 90) and the UTI group (n = 91). There were no statistically significant differences in baseline clinical data between the two groups. The 7-d mortality and clinical efficacy in the UTI group were remarkably improved compared with those in the placebo group. UTI can protect against hyperinflammation and improve coagulation dysfunction, infection, liver function, and renal function. UTI patients had markedly decreased hospital stays and hospitalization expenditures compared with the placebo group. CONCLUSION: The findings from the present research indicated that UTI can improve the clinical outcomes of patients with severe AP and has fewer adverse reactions.

Entropy-driven DNA circuit with two-stage strand displacement for elegant and robust detection of miRNA let-7a.

MicroRNAs (miRNAs) research in cancer diagnosis is expanding, on account of miRNAs were demonstrated to be key indicator of gene expression and hopeful candidates for biomarkers. In this study, a stable miRNA-let-7a fluorescent biosensor was successfully designed based on an exonuclease Ⅲ-assisted two-stage strand displacement reaction (SDR). First, an entropy-driven SDR containing a three-chain structure of the substrate is used in our designed biosensor, leading to reduce the reversibility of the target recycling process in each step. The target acts on the first stage to start the entropy-driven SDR, which generates the trigger used to stimulate the exonuclease Ⅲ-assisted SDR in the second stage. At the same time, we design a SDR one-step amplification strategy as a comparison. Expectly, this developed two-stage strand displacement system has a low detection limit of 25.0 pM as well as a broad detection range of 4 orders of magnitude, making it more sensitive than the SDR one-step sensor, whose detection limit is 0.8 nM. In addition, this sensor has high specificity across members of the miRNA family. Therefore, we can take advantage of this biosensor to promote miRNA research in cancer diagnosis sensing systems.

Preparation and Evaluation of Co-Doped Fe7S8/C Composites for Lithium Storage.

Fe7S8 has a high theoretical capacity (663 mAh g-1) and can be prepared at a low cost, making it advantageous for production. However, Fe7S8 has two disadvantages as a lithium-ion battery anode material. The first is that the conductivity of Fe7S8 is not good. The second is that when the lithium ion is embedded, the volume expansion of the Fe7S8 electrode is serious. That is why Fe7S8 has not been used in real life yet. In this paper, Co-Fe7S8/C composites were prepared by doping Co into Fe7S8 through a one-pot simple hydrothermal method. In situ Co is doped into Fe7S8 to produce a more disordered microstructure to improve ion and electron transport performance, thereby reducing the activation barrier of the main material. The Co-Fe7S8/C electrode presents a high specific discharge capacity of 1586 mAh g-1 and a Coulombic efficiency (CE) of 71.34% at an initial cycle at 0.1 A g-1. After 1500 cycles, the specific discharge capacity remains at 436 mAh g-1 (5 A g-1). When the current density returns to 0.1 A g-1, the capacity almost returns to the initial level, showing excellent rate performance.

The effects of miRNA-27a-3p on human epidermal melanocytes.

OBJECTIVE: To characterize the effects of miRNA-27a-3p on the biological properties of human epidermal melanocytes (MCs). METHODS: MCs were obtained from human foreskins and transfected with miRNA-27a-3p mimic (induces the overexpression of miRNA-27a-3p), mimic-NC (the negative control group), miRNA-27a-3p inhibitor, or inhibitor-NC. After transfection, the proliferation of MCs in each group was evaluated by cell counting kit-8 (CCK-8) at 1, 3, 5, and 7 days. Twenty-four hours later, the MCs were transferred onto a living cell imaging platform and cultured for another 12 h to detect their trajectories and velocities. On days 3, 4, and 5 after transfection, the expression of melanogenesis-related mRNAs, protein levels, and melanin contents were measured using reverse transcription-polymerase chain reaction (RT-PCR), Western blotting, and NaOH solubilization, respectively. RESULTS: The RT-PCR results showed that miRNA-27a-3p was successfully transfected into MCs. The proliferation of MCs was restrained by miRNA-27a-3p. There were no significant differences in the movement trajectories of MCs in the four transfected groups, but the cell movement velocity in the mimic group was slightly lower; that is, the overexpression of miRNA-27a-3p inhibited the speed of MCs. The expression levels of melanogenesis-related mRNAs and proteins were decreased in the mimic group and were increased in the inhibitor group. Melanin content in the mimic group was lower than that in the other three groups. CONCLUSIONS: Overexpression of miRNA-27a-3p inhibits the expression of melanogenesis-related mRNAs and proteins, reduces the melanin content of human epidermal MCs, and slightly impacts their movement speed.

Microbial ecological responses of partial nitritation/anammox granular sludge to real water matrices and its potential application.

Granular sludges are commonly microbial aggregates used to apply partial nitritation/anammox (PN/A) processes during efficient biological nitrogen removal from ammonium-rich wastewater. Considering keystone taxa of anammox bacteria (AnAOB) in granules and their sensitivity to unfavorable environments, it is essential to investigate microbial responses of autotrophic PN/A granules to real water matrices containing organic and inorganic pollutants. In this study, tap water, surface water, and biotreated wastewater effluents were fed into a series of continuous PN/A granular reactors, respectively, and the differentiation in functional activity, sludge morphology, microbial community structure, and nitrogen metabolic pathways was analyzed by integrating kinetic batch testing, size characterization, and metagenomic sequencing. The results showed that feeding of biotreated wastewater effluents causes significant decreases in nitrogen removal activity and washout of AnAOB (dominated by Candidatus Kuenenia) from autotrophic PN/A granules due to the accumulation of heavy metals and formation of cavities. Microbial co-occurrence networks and nitrogen cycle-related genes provided evidence for the high dependence of symbiotic heterotrophs (such as Proteobacteria, Chloroflexi, and Bacteroidetes) on anammox metabolism. The enhancement of Nitrosomonas nitritation in the granules would be considered as an important contributor to greenhouse gas (N2O) emissions from real water matrices. In a novel view on the application of microbial responses, we suggest a bioassay of PN/A granules by size characterization of red-color cores in ecological risk assessment of water environments.

Eimeria infections of plateau pika altered the patterns of temporal alterations in gut bacterial communities.

Intestinal parasites, such as Eimeria, are common among plateau pika (Ochotona curzoniae). The gut microbiome is an essential driver of the host response to gastrointestinal parasites. However, the effects of intestinal protozoal parasites on the temporal variations in the gut microbiome and behavioral and physiological activities remain unknown. Our study conducted treatments involving experimental feeding of pika with Eimeria oocysts or anticoccidia under laboratory conditions to focus on the parasite-associated alterations in gut bacterial communities, host behavioral activity, physiology, and host-bacteria relationships. The results showed insignificant differences in bacterial community structures among treatments on the basis of Bray-Curtis distance metrics, whereas the patterns of temporal alterations in the bacterial communities were changed by the treatments. Bacterial alpha diversities did not vary with the treatments, and experimental feeding with Eimeria slowed down the decrement rate of alpha diversity. Furthermore, few bacterial members were significantly changed by the treatments-only the genus Ruminococcus and the species Ruminococcus flavefaciens, which were associated with energy metabolism. Experimental feeding with Eimeria modified the temporal variations in the bacterial members, including a lower loss rate of the relative abundance of the dominant families Muribaculaceae and Ruminococcaceae in the group with Eimeria experimental feeding. Moreover, a shifting energy trade-off was suggested by the parasite-induced increments in thyroid hormones (triiodothyronine and tetraiodothyronine) and decrements in exploration behavior in the group with Eimeria feeding. However, we did not detect specific connections between gut bacterial communities and pika behaviors and physiology in terms of energy trade-offs. Further in-depth research is needed to examine the role of Eimeria-modified differences in the gut bacteria of plateau pika.

The Temporal Lagged Relationship Between Meteorological Factors and Scrub Typhus With the Distributed Lag Non-linear Model in Rural Southwest China.

Background: Meteorological factors can affect the emergence of scrub typhus for a period lasting days to weeks after their occurrence. Furthermore, the relationship between meteorological factors and scrub typhus is complicated because of lagged and non-linear patterns. Investigating the lagged correlation patterns between meteorological variables and scrub typhus may promote an understanding of this association and be beneficial for preventing disease outbreaks. Methods: We extracted data on scrub typhus cases in rural areas of Panzhihua in Southwest China every week from 2008 to 2017 from the China Information System for Disease Control and Prevention. The distributed lag non-linear model (DLNM) was used to study the temporal lagged correlation between weekly meteorological factors and weekly scrub typhus. Results: There were obvious lagged associations between some weather factors (rainfall, relative humidity, and air temperature) and scrub typhus with the same overall effect trend, an inverse-U shape; moreover, different meteorological factors had different significant delayed contributions compared with reference values in many cases. In addition, at the same lag time, the relative risk increased with the increase of exposure level for all weather variables when presenting a positive association. Conclusions: The results found that different meteorological factors have different patterns and magnitudes for the lagged correlation between weather factors and scrub typhus. The lag shape and association for meteorological information is applicable for developing an early warning system for scrub typhus.

Fluorescence biosensing of the leukemia gene by combining Target-Programmed controllable signal inspiring engineering.

Clinical diagnosis urgently requires ultrasensitive, accurate and rapid monitoring of low-abundance biomarkers. A biosensing strategy capable of detecting target genes at the femtomolar scale was designed in this work. In the biosensing strategy, the target can induce the specially designed hairpin probe H1 to self-fold and form a 3' blunt-ended structure. When there are the hybrid double-stranded P1-T1, ligase, polymerase and nickase, the target gene was recycled, and at the same time the system produces a lot of T1 and T2. T1 and T2 can simultaneously trigger HCR, causing the modified fluorophore FAM on the DNA strand to move away from the quencher group BHQ. The amplified fluorescent signal can be captured by a fluorescence instrument. It is exciting for us that three signal amplifications are involved to achieve femtomolar detection of target genes, namely target recycling, dual-triggered HCR of T1 and T2, and HCR. In addition, it still has good detection ability in actual samples simulated by serum. We expect that the sensing strategy proposed in this paper offers great potential for biomarker detection of leukemia for early clinical diagnosis.

A Pax-5a gene analysis approach enabled by selective digestion with lambda exonuclease.

Owing to the rapid increase in acute leukemia patients, the detection of Pax-5a, which is a tumor marker, is very important for the early diagnosis of patients. Therefore, by combining the selective digestion function of lambda exonuclease and the hybridization chain reaction (HCR) enzyme-free amplification system, we design a biosensor to detect the Pax-5a gene with high sensitivity. Lambda exonuclease can cleave the blunt end formed by the hairpin probe and the Pax-5a gene, which exposes the nucleic acid sequence that can initiate the HCR. When the HCR is triggered, the fluorophore and quencher on H1 and H2 move away from each other, so that the fluorescence signal of the quenched fluorophore can be recovered. Under optimal experimental conditions, a good linear relationship was established between the fluorescence intensity and the logarithm of the target concentration, and the limit of detection (LOD) of Pax-5a was calculated to be 7.6 pM. In addition, the biosensor can not only discriminate the base mismatch sequences of the Pax-5a gene, but also be suitable for target detection in complex human serum samples. Therefore, this biosensor, with the advantages of simple operation, high sensitivity, and good selectivity, has a good application prospect and guiding role in the diagnosis of acute B lymphocytic leukemia and the design of biosensors.

Heterologous Expression and Biochemical Analysis Reveal a Schizokinen-Based Siderophore Pathway in Leptolyngbya (Cyanobacteria).

Siderophores are low molecular weight iron-chelating molecules that many organisms secrete to scavenge ferric iron from the environment. While cyanobacteria inhabit a wide range of environments with poor iron availability, only two siderophore families have been characterized from this phylum. Herein, we sought to investigate siderophore production in the marine genus, Leptolyngbya. A 12 open reading frame (14.5 kb) putative nonribosomal peptide synthetase-independent siderophore biosynthesis gene cluster, identified in the genome of Leptolyngbya sp. PCC 7376, was cloned and heterologously expressed in Escherichia coli. Under iron-limiting conditions, expression strains harboring the first seven genes (lidA to lidF), produced a potent siderophore, which was subsequently identified via UPLC-MS/MS and NMR as schizokinen. The enzymes encoded by the remaining genes (lidG1 to lidG5) did not appear to be active in E. coli, therefore their function could not be determined. Bioinformatic analysis revealed gene clusters with high homology to lidA to lidF in phylogenetically and biogeographically diverse cyanobacteria, suggesting that schizokinen-based siderophore production is widespread in this phylum. Siderophore yields in E. coli expression strains were significantly higher than those achieved by Leptolyngbya, highlighting the potential of this platform for producing siderophores of industrial value. IMPORTANCE Iron availability limits the growth of many microorganisms, particularly those residing in high nutrient-low chlorophyll aquatic environments. Therefore, characterizing iron acquisition pathways in phytoplankton is essential for understanding nutrient cycling in our oceans. The results of this study suggest that Leptolyngbya sp. PCC 7376, and many other cyanobacteria, use schizokinen-based iron chelators (siderophores) to scavenge iron from the environment. We have shown that these pathways are amenable to heterologous expression in E. coli, which expands the limited arsenal of known cyanobacterial siderophores and is advantageous for the downstream overproduction of relevant siderophores of ecological and industrial value.

DNAzyme-based cascade signal amplification strategy for highly sensitive detection of lead ions in the environment.

Lead ions are one of many common environmental pollutants, that can cause posing a serious threat to people's health, thus, their efficient and sensitive detection is important. We propose a cascade signal amplification sensor using a DNAzyme-based strand displacement amplification (SDA) and hybridization chain reaction (HCR) for the high-sensitivity detection of Pb2+. In the demonstrated sensor system, the target metal ion can activate DNAzyme to cause a strand displacement reaction. Under the synergistic action of polymerase and nickase, large numbers of DNA strands are generated that can initiate HCR. The subsequent HCR can restore the fluorescence intensity of the FAM quenched for the fluorescence resonance energy transfer effect, which exhibits a strong fluorescence signal. The DNAzyme-based sensor allowed the detection of Pb2+ down to 16.8 pM and resulted in a good dynamic line relationship ranging from 50 pM to 500 nM, and the biosensor also showed good selectivity. Furthermore, we confirmed that the proposed sensor can still detect lead ions in complex environments such as lake water, milk, and serum. We believe these findings will provide new ideas for the detection of toxic elements ions in the environment and food.