Microglia-targeted inhibition of miR-17 via mannose-coated lipid nanoparticles improves pathology and behavior in a mouse model of Alzheimer's disease.

Neuroinflammation and accumulation of Amyloid Beta (Aß) accompanied by deterioration of special memory are hallmarks of Alzheimer's disease (AD). Effective preventative and treatment options for AD are still needed. Microglia in AD brains are characterized by elevated levels of microRNA-17 (miR-17), which is accompanied by defective autophagy, Aß accumulation, and increased inflammatory cytokine production. However, the effect of targeting miR-17 on AD pathology and memory loss is not clear. To specifically inhibit miR-17 in microglia, we generated mannose-coated lipid nanoparticles (MLNPs) enclosing miR-17 antagomir (Anti-17 MLNPs), which are targeted to mannose receptors readily expressed on microglia. We used a 5XFAD mouse model (AD) that recapitulates many AD-related phenotypes observed in humans. Our results show that Anti-17 MLNPs, delivered to 5XFAD mice by intra-cisterna magna injection, specifically deliver Anti-17 to microglia. Anti-17 MLNPs downregulated miR-17 expression in microglia but not in neurons, astrocytes, and oligodendrocytes. Anti-17 MLNPs attenuated inflammation, improved autophagy, and reduced Aß burdens in the brains. Additionally, Anti-17 MLNPs reduced the deterioration in spatial memory and decreased anxiety-like behavior in 5XFAD mice. Therefore, targeting miR-17 using MLNPs is a viable strategy to prevent several AD pathologies. This selective targeting strategy delivers specific agents to microglia without the adverse off-target effects on other cell types. Additionally, this approach can be used to deliver other molecules to microglia and other immune cells in other organs.

Improved Targeting and Safety of Doxorubicin through a Novel Albumin Binding Prodrug Approach.

Human serum albumin (HSA) improves the pharmacokinetic profile of drugs attached to it, making it an attractive carrier with proven clinical success. In our previous studies, we have shown that Caveolin-1 (Cav-1) and caveolae-mediated endocytosis play important roles in the uptake of HSA and albumin-bound drugs. Doxorubicin is an FDA-approved chemotherapeutic agent that is effective against multiple cancers, but its clinical applicability has been hampered by its high toxicity levels. In this study, a doxorubicin-prodrug was developed that could independently and avidly bind HSA in circulation, called IPBA-Dox. We first developed and characterized IPBA-Dox and confirmed that it can bind albumin in vitro while retaining a potent cytotoxic effect. We then verified that it efficiently binds to HSA in circulation, leading to an improvement in the pharmacokinetic profile of the drug. In addition, we tested our prodrug for Cav-1 selectivity and found that it preferentially affects cells that express relatively higher levels of Cav-1 in vitro and in vivo. Moreover, we found that our compound was well tolerated in vivo at concentrations at which doxorubicin was lethal. Altogether, we have developed a doxorubicin-prodrug that can successfully bind HSA, retaining a strong cytotoxic effect that preferentially targets Cav-1 positive cells while improving the general tolerability of the drug.

Different microbial communities in paddy soils under organic and nonorganic farming.

Organic agriculture is a farming method that provides healthy food and is friendly to the environment, and it is developing rapidly worldwide. This study compared microbial communities in organic farming (Or) paddy fields to those in nonorganic farming (Nr) paddy fields based on 16S rDNA sequencing and analysis. The predominant microorganisms in both soils were Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria, and Nitrospirota. The alpha diversity of the paddy soil microbial communities was not different between the nonorganic and organic farming systems. The beta diversity of nonmetric multidimensional scaling (NMDS) revealed that the two groups were significantly separated. Distance-based redundancy analysis (db-RDA) suggested that soil pH and electrical conductivity (EC) had a positive relationship with the microbes in organic paddy soils. There were 23 amplicon sequence variants (ASVs) that showed differential abundance. Among them, g_B1-7BS (Proteobacteria), s_Sulfuricaulis limicola (Proteobacteria), g_GAL15 (p_GAL15), c_Thermodesulfovibrionia (Nitrospirota), two of f_Anaerolineaceae (Chloroflexi), and two of g_S085 (Chloroflexi) showed that they were more abundant in organic soils, whereas g_11-24 (Acidobacteriota), g__Subgroup_7 (Acidobacteriota), and g_Bacillus (Firmicutes) showed differential abundance in nonorganic paddy soils. Functional prediction of microbial communities in paddy soils showed that functions related to carbohydrate metabolism could be the major metabolic activities. Our work indicates that organic farming differs from nonorganic farming in terms of microbial composition in paddy soils and provides specific microbes that might be helpful for understanding soil fertility.

Optimized Liposomal Delivery of Bortezomib for Advancing Treatment of Multiple Myeloma.

Bortezomib (BTZ), a boronic acid-derived proteasome inhibitor, is commonly employed in treating multiple myeloma (MM). However, the applications of BTZ are limited due to its poor stability and low bioavailability. Herein, we develop an optimized liposomal formulation of BTZ (L-BTZ) by employing a remote-loading strategy. This formulation uses Tiron, a divalent anionic catechol derivative, as the internal complexing agent. Compared to earlier BTZ-related formulations, this alternative formulation showed significantly greater stability due to the Tiron-BTZ complex's higher pH stability and negative charges, compared to the meglumine-BTZ complex. Significantly, the plasma AUC of L-BTZ was found to be 30 times greater than that of free BTZ, suggesting an extended blood circulation duration. In subsequent therapeutic evaluations using two murine xenograft tumor models of MM, the NCI-H929 and OPM2 models showed tumor growth inhibition (TGI) values of 37% and 57%, respectively. In contrast, free BTZ demonstrated TGI values of 17% and 11% in these models. Further, L-BTZ presented enhanced antitumor efficacy in the Hepa1-6 HCC syngeneic model, indicating its potential broader applicability as an antineoplastic agent. These findings suggest that the optimized L-BTZ formulation offers a significant advancement in BTZ delivery, holding substantial promise for clinical investigation in not merely MM, but other cancer types.

Iron Fertilization Can Enhance the Mass Production of Copepod, Pseudodiaptomus annandalei, for Fish Aquaculture.

Copepods are proven nutritious food sources for the mariculture/larviculture industry, however, unreliable methods for mass production of copepods are a major bottleneck. In this study, we modified a previously reported inorganic fertilization method (N: 700 µg L-1 and P: 100 µg L-1) by the addition of iron (Fe: 10 µg L-1, using FeSO4·7H2O) (+Fe treatment) and compared its suitability for copepod culture (Pseudodiaptomus annandalei) to the original method (control). The experiment was conducted outdoors in 1000 L tanks for 15 days. The addition of iron prolonged the growth phase of the phytoplankton and resulted in the production of significantly more small phytoplankton (0.45-20 µm, average 2.01 ± 0.52 vs. 9.03 ± 4.17 µg L-1 in control and +Fe, respectively) and adult copepods (control: 195 ± 35, +Fe: 431 ± 109 ind L-1), whereas copepodid-stage was similar between treatments (control: 511 ± 107 vs. +Fe: 502 ± 68 ind L-1). Although adding iron increased the cost of production by 23% compared to the control, the estimated net profit was 97% greater. We concluded that inorganic fertilization, with the addition of iron (Fe: 10 µg L-1), could be an effective method for the mass production of copepods for larviculture.

Functional Prediction of Microbial Communities in Sediment Microbial Fuel Cells.

Sediment microbial fuel cells (MFCs) were developed in which the complex substrates present in the sediment could be oxidized by microbes for electron production. In this study, the functional prediction of microbial communities of anode-associated soils in sediment MFCs was investigated based on 16S rRNA genes. Four computational approaches, including BugBase, Functional Annotation of Prokaryotic Taxa (FAPROTAX), the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt2), and Tax4Fun2, were applied. A total of 67, 9, 37, and 38 functional features were statistically significant. Among these functional groups, the function related to the generation of precursor metabolites and energy was the only one included in all four computational methods, and the sum total of the proportion was 93.54%. The metabolism of cofactor, carrier, and vitamin biosynthesis was included in the three methods, and the sum total of the proportion was 29.94%. The results suggested that the microbial communities usually contribute to energy metabolism, or the metabolism of cofactor, carrier, and vitamin biosynthesis might reveal the functional status in the anode of sediment MFCs.

Antitumor Activity of Anti-miR-21 Delivered through Lipid Nanoparticles.

The ability of lipid nanoparticles (LNPs) to deliver nucleic acids have shown a great therapeutic potential to treat a variety of diseases. Here, an optimized formulation of QTsome lipid nanoparticles (QTPlus) is utilized to deliver an anti-miR-21 (AM21) against cancer. The miR-21 downstream gene regulation and antitumor activity is evaluated using mouse and human cancer cells and macrophages. The antitumor activity of QTPlus encapsulating AM21 (QTPlus-AM21) is further evaluated in combination with erlotinib and atezolizumab (ATZ). QTPlus-AM21 demonstrates a superior miR-21-dependent gene regulation and eventually inhibits A549 non-small cell lung cancer growth in vitro. QTPlus-AM21 further induces chemo-sensitization of A549 cells to erlotinib with a combination index of 0.6 in inhibiting A549 cell growth. When systemically administers to MC38 tumor-bearing mouse model, QTPlus-AM21 exhibits an antitumor immune response with over 80% tumor growth inhibition (TGI%) and over twofold and fourfold PD-1 and PD-L1 upregulation in tumors and spleens. The combination therapy of QTPlus-AM21 and ATZ further shows a higher antitumor response (TGI% over 90%) and successfully increases M1 macrophages and CD8 T cells into TME. This study provides new insights into the antitumor mechanism of AM21 and shows great promise of QTPlus-AM21 in combination with chemotherapies and immunotherapies.

Evolution of Nanometer-Scale Microstructure within Grains and in the Intergranular Region in Thermoelectric Mg3(Sb, Bi)2 Alloys.

n-type Mg3Sb2-Mg3Bi2 alloys have been investigated as one of the most promising thermoelectric materials. To achieve high performance, a detailed understanding of the microstructure is required. Although Mg3Sb2-Mg3Bi2 is usually considered to be a complete solid solution, nanosized compositional fluctuations were observed within a matrix and in the vicinity of the grain boundary. As an inhomogeneous microstructure can be beneficial or detrimental to thermoelectric performance, it is important to investigate the evolution of compositional variations for the engineering and long-term use of these materials. Using scanning transmission electron microscopy and atom probe tomography, a Bi-rich phase and compositional fluctuations are observed in sintered and annealed samples. After annealing, the broad intergranular phase was sharpened, resulting in a greater compositional change in the intergranular region. Annealing considerably reduces the fluctuations of Bi and Mg content within the grain as observed in atom probe tomography. Weighted mobility and lattice thermal conductivity were both increased as a result of the homogenized matrix phase. The combined microstructure features of intragrain and grain boundary effects resulted in an increased thermoelectric figure-of-merit zT of Mg3Sb0.6Bi1.4. These findings imply that the optimization of thermal and electrical properties can be realized through microstructure tuning.

Ivermectin Enhanced Antitumor Activity of Resiquimod in a Co-Loaded Squalene Emulsion.

Immunogenic cell death (ICD) plays an important role in sensitizing tumor cells to antigen-presenting cells followed by antitumor immunity. However, a successful antitumor response by ICD requires both apoptotic tumor microenvironments and activated immune systems. Ivermectin (IVM) has been shown to induce cell apoptosis through autophagy which can be a great candidate for ICD therapy. However, a single treatment of IVM-free drug is not an ideal anticancer therapy due to its anti-inflammatory effects and cytotoxicity. In the present study, IVM was shown to enhance the ICD process in addition to the treatment of resiquimod (R848), a TLR7/8 agonist, when co-loaded in a squalene-based nanoemulsion (NE). R848-IVM co-loaded NE was developed and characterized in vitro. Antitumor activity of R848-IVM NE was also evaluated in vitro and in vivo. R848-IVM NE exhibited long-term stability and reduced cytotoxicity by IVM. In vivo studies demonstrated that IVM significantly augments the ICD by upregulating Cd8a and releasing HMGB1 in tumor tissue, which could enhance R848-driven antitumor immunity. R848-IVM NE treatment showed strong antitumor activity with over 80% tumor growth inhibition, suggesting a potential combination therapy of systemic co-delivering IVM with TLR agonists against solid cancer.

AZD5153, a Bivalent BRD4 Inhibitor, Suppresses Hepatocarcinogenesis by Altering BRD4 Chromosomal Landscape and Modulating the Transcriptome of HCC Cells.

BRD4, a chromatin modifier frequently upregulated in a variety of neoplasms including hepatocellular cancer (HCC), promotes cancer cell growth by activating oncogenes through its interaction with acetylated histone tails of nucleosomes. Here, we determined the anti-HCC efficacy of AZD5153, a potent bivalent BRD4 inhibitor, and elucidated its underlying molecular mechanism of action. AZD5153 treatment inhibited HCC cell proliferation, clonogenic survival and induced apoptosis in HCC cells. In vivo, AZD5153-formulated lipid nanoemulsions inhibited both orthotopic and subcutaneous HCCLM3 xenograft growth in NSG mice. Mapping of BRD4- chromosomal targets by ChIP-seq analysis identified the occupancy of BRD4 with the promoters, gene bodies, and super-enhancers of both mRNA and noncoding RNA genes, which were disrupted upon AZD5153 treatment. RNA-seq analysis of polyadenylated RNAs showed several BRD4 target genes involved in DNA replication, cell proliferation, and anti-apoptosis were repressed in AZD5153-treated HCC cells. In addition to known tumor-promoting genes, e.g., c-MYC, YAP1, RAD51B, TRIB3, SLC17A9, JADE1, we found that NAPRT, encoding a key enzyme for NAD+ biosynthesis from nicotinic acid, was also suppressed in HCC cells by the BRD4 inhibitor. Interestingly, AZD5153 treatment upregulated NAMPT, whose product is the rate-limiting enzyme for NAD+ synthesis from nicotinamide. This may explain why AZD5153 acted in concert with FK866, a potent NAMPT inhibitor, in reducing HCC cell proliferation and clonogenic survival. In conclusion, our results identified novel targets of BRD4 in the HCCLM3 cell genome and demonstrated anti-HCC efficacy of AZD5153, which was potentiated in combination with an NAMPT inhibitor.

Modification of Lipid-Based Nanoparticles: An Efficient Delivery System for Nucleic Acid-Based Immunotherapy.

Lipid-based nanoparticles (LBNPs) are biocompatible and biodegradable vesicles that are considered to be one of the most efficient drug delivery platforms. Due to the prominent advantages, such as long circulation time, slow drug release, reduced toxicity, high transfection efficiency, and endosomal escape capacity, such synthetic nanoparticles have been widely used for carrying genetic therapeutics, particularly nucleic acids that can be applied in the treatment for various diseases, including congenital diseases, cancers, virus infections, and chronic inflammations. Despite great merits and multiple successful applications, many extracellular and intracellular barriers remain and greatly impair delivery efficacy and therapeutic outcomes. As such, the current state of knowledge and pitfalls regarding the gene delivery and construction of LBNPs will be initially summarized. In order to develop a new generation of LBNPs for improved delivery profiles and therapeutic effects, the modification strategies of LBNPs will be reviewed. On the basis of these developed modifications, the performance of LBNPs as therapeutic nanoplatforms have been greatly improved and extensively applied in immunotherapies, including infectious diseases and cancers. However, the therapeutic applications of LBNPs systems are still limited due to the undesirable endosomal escape, potential aggregation, and the inefficient encapsulation of therapeutics. Herein, we will review and discuss recent advances and remaining challenges in the development of LBNPs for nucleic acid-based immunotherapy.

A Squalene-Based Nanoemulsion for Therapeutic Delivery of Resiquimod.

Agonists for toll-like receptors (TLRs) have shown promising activities against cancer. In the present study, a squalene-based nanoemulsion (NE) was loaded with resiquimod, a TLR7/8 agonist for therapeutic delivery. R848 NE was developed and characterized for long-term stability. In vitro and in vivo antitumor immunity of R848 NE were also evaluated in combination with SD-101, a CpG-containing TLR9 agonist. In vitro studies demonstrated strong long-term stability and immune responses to R848 NE. When combined with SD-101, strong antitumor activity was observed in MC38 murine colon carcinoma model with over 80% tumor growth inhibition. The combination treatment showed a 4-fold increase in systemic TNFa production and a 2.6-fold increase in Cd8a expression in tumor tissues, suggesting strong cell-mediated immune responses against the tumor. The treatment not only demonstrated a strong antitumor immunity by TLR7/8 and TLR9 activations but also induced PD-L1 upregulation in tumors, suggesting a potential therapeutic synergy with immune checkpoint inhibitors.

Dynamic Changes in Soil Microbial Communities with Glucose Enrichment in Sediment Microbial Fuel Cells.

To investigate soil microbial community dynamics in sediment microbial fuel cells (MFCs), this study applied nonhydric (D) and hydric (S) soils to single-chamber and mediator-free MFCs. Glucose was also used to enrich microorganisms in the soils. The voltage outputs of both the D and S sediment MFCs increased over time but differed from each other. The initial open circuit potentials were 345 and 264 mV for the D and S MFCs. The voltage output reached a maximum of 503 and 604 mV for D and S on days 125 and 131, respectively. The maximum power densities of the D and S MFCs were 2.74 and 2.12 mW m-2, analyzed on day 50. Clustering results revealed that the two groups did not cluster after glucose supplementation and 126 days of MFC function. The change in Geobacter abundance was consistent with the voltage output, indicating that these bacteria may act as the main exoelectrogens on the anode. Spearman correlation analysis demonstrated that, in the D soils, Geobacter was positively correlated with Dialister and negatively correlated with Bradyrhizobium, Kaistobacter, Pedomicrobium, and Phascolarctobacterium; in the S soils, Geobacter was positively correlated with Shewanella and negatively correlated with Blautia. The results suggested that different soil sources in the MFCs and the addition of glucose as a nutrient produced diverse microbial communities with varying voltage output efficiencies. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12088-021-00959-x.

A novel protein-drug conjugate, SSH20, demonstrates significant efficacy in caveolin-1-expressing tumors.

In recent years, human serum albumin (HSA) has been characterized as an ideal drug carrier in the cancer arena. Caveolin-1 (Cav-1) has been established as the principal structural protein of caveolae and, thus, critical for caveolae-mediated endocytosis. Cav-1 has been shown to be overexpressed in cancers of the lung and pancreas, among others. We found that Cav-1 expression plays a critical role in both HSA uptake and response to albumin-based chemotherapies. As such, developing a novel albumin-based chemotherapy that is more selective for tumors with high Cav-1 expression or high levels of caveolar-endocytosis could have significant implications in biomarker-directed therapy. Herein, we present the development of a novel and effective HSA-SN-38 conjugate (SSH20). We find that SSH20 uptake decreases significantly by immunofluorescence assays and western blotting after silencing of Cav-1 expression through RNA interference. Decreased drug sensitivity occurs in Cav-1-depleted cells using cytotoxicity assays. Importantly, we find significantly reduced sensitivity to SSH20 in Cav-1-silenced tumors compared to Cav-1-expressing tumors in vivo. Notably, we show that SSH20 is significantly more potent than irinotecan in vitro and in vivo. Together, we have developed a novel HSA-conjugated chemotherapy that is potent, effective, safe, and demonstrates improved efficacy in high Cav-1-expressing tumors.

Isolation of endophytic fungi with antimicrobial activity from medicinal plant Zanthoxylum simulans Hance.

Fungal endophytes have been found to exist in many plant species and appear to be important to their plant hosts. However, the diversity and biological activities of these fungi remain largely unknown. Zanthoxylum simulans Hance, a popular natural spice and medicinal plant, commonly known as Szechuan pepper or Chinese-pepper, grows on Kinmen Island, Taiwan. In this study, leaf and stem samples of Z. simulans, collected in summer and winter, were screened for antimicrobial and anti-inflammatory metabolite-producing endophytic fungi. A total of 113 endophytic strains were isolated and cultured from Z. simulans, among which 23 were found to possess antimicrobial activity, belonging to six fungal genera: Penicillium (26.09%, 6), Colletotrichum (21.74%, 5), Diaporthe (21.74%, 5), Daldinia (17.39%, 4), Alternaria (8.70%, 2), and Didymella (4.34%, 1). We also found that the number of species with antimicrobial activity and their compositions differed between summer and winter. Our study demonstrated that Z. simulans might contain large and diverse communities of endophytic fungi, and its community composition varies seasonally. In addition, fungal endophytes produce antimicrobial agents, which may protect their hosts against pathogens and could be a potential source of natural antibiotics.

CpG Oligodeoxynucleotides for Anticancer Monotherapy from Preclinical Stages to Clinical Trials.

CpG oligodeoxynucleotides (CpG ODNs), the artificial versions of unmethylated CpG motifs that were originally discovered in bacterial DNA, are demonstrated not only as potent immunoadjuvants but also as anticancer agents by triggering toll-like receptor 9 (TLR9) activation in immune cells. TLR9 activation triggered by CpG ODN has been shown to activate plasmacytoid dendritic cells (pDCs) and cytotoxic T lymphocytes (CTLs), enhancing T cell-mediated antitumor immunity. However, the extent of antitumor immunity carried by TLR agonists has not been optimized individually or in combinations with cancer vaccines, resulting in a decreased preference for TLR agonists as adjuvants in clinical trials. Although various combination therapies involving CpG ODNs have been applied in clinical trials, none of the CpG ODN-based drugs have been approved by the FDA, owing to the short half-life of CpG ODNs in serum that leads to low activation of natural killer cells (NK cells) and CTLs, along with increases of pro-inflammatory cytokine productions. This review summarized the current innovation on CpG ODNs that are under clinical investigation and explored the future direction for CpG ODN-based nanomedicine as an anticancer monotherapy.

Metallic n-Type Mg3 Sb2 Single Crystals Demonstrate the Absence of Ionized Impurity Scattering and Enhanced Thermoelectric Performance.

Mg3 (Sb,Bi)2 alloys have recently been discovered as a competitive alternative to the state-of-the-art n-type Bi2 (Te,Se)3 thermoelectric alloys. Previous theoretical studies predict that single crystals Mg3 (Sb,Bi)2 can exhibit higher thermoelectric performance near room temperature by eliminating grain boundary resistance. However, the intrinsic Mg defect chemistry makes it challenging to grow n-type Mg3 (Sb,Bi)2 single crystals. Here, the first thermoelectric properties of n-type Te-doped Mg3 Sb2 single crystals, synthesized by a combination of Sb-flux method and Mg-vapor annealing, is reported. The electrical conductivity and carrier mobility of single crystals exhibit a metallic behavior with a typical T-1.5 dependence, indicating that phonon scattering dominates the charge carrier transport. The absence of any evidence of ionized impurity scattering in Te-doped Mg3 Sb2 single crystals proves that the thermally activated mobility previously observed in polycrystalline materials is caused by grain boundary resistance. Eliminating this grain boundary resistance in the single crystals results in a large enhancement of the weighted mobility and figure of merit zT by more than 100% near room temperature. This work experimentally demonstrates the accurate understanding of charge-carrier scattering is crucial for developing high-performance thermoelectric materials and indicates that single-crystalline Mg3 (Sb,Bi)2 solid solutions can exhibit higher zT compared to polycrystalline samples.

Improvement of Low-Temperature zT in a Mg3 Sb2 -Mg3 Bi2 Solid Solution via Mg-Vapor Annealing.

Materials with high zT over a wide temperature range are essential for thermoelectric applications. n-Type Mg3 Sb2 -based compounds have been shown to achieve high zT at 700 K, but their performance at low temperatures (<500 K) is compromised due to their highly resistive grain boundaries. Syntheses and optimization processes to mitigate this grain-boundary effect has been limited due to loss of Mg, which hinders a sample's n-type dopability. A Mg-vapor anneal processing step that grows a sample's grain size and preserves its n-type carrier concentration during annealing is demonstrated. The electrical conductivity and mobility of the samples with large grain size follows a phonon-scattering-dominated T-3/2 trend over a large temperature range, further supporting the conclusion that the temperature-activated mobility in Mg3 Sb2 -based materials is caused by resistive grain boundaries. The measured Hall mobility of electrons reaches 170 cm2 V-1 s-1 in annealed 800 °C sintered Mg3 + δ Sb1.49 Bi0.5 Te0.01 , the highest ever reported for Mg3 Sb2 -based thermoelectric materials. In particular, a sample with grain size >30 mm has a zT 0.8 at 300 K, which is comparable to commercial thermoelectric materials used at room temperature (n-type Bi2 Te3 ) while reaching zT 1.4 at 700 K, allowing applications over a wider temperature scale.

The effect of paclobutrazol on soil bacterial composition across three consecutive flowering stages of mung bean.

Paclobutrazol, (2RS, 3RS)-1-(4-chlorophenyl)-4, 4-dimethyl-2-(1H-1,2,4-triazol-1-yl) pentan-3-ol, is a plant growth retardant that mainly inhibits gibberellins (GAs) biosynthesis. In agricultural practice, paclobutrazol is applied to arrest vegetative growth so as to increase the reproductive growth of many orchard fruit, as well as grain crops. However, due to its over-application and chemical stability, paclobutrazol accumulates in soil and inhibits the growth of subsequent crops, especially those grown for vegetative purposes. The present study focused mainly on the changes in the soil bacterial community following application of paclobutrazol. Mung bean (Vigna radiata) plants were treated with paclobutrazol and cultivated for three consecutive seasons. Soil samples were collected and analyzed by denaturing gradient gel electrophoresis (DGGE) using 16S rDNA gene fragments and clone library analyses. The results obtained through clustering and clonal sequencing analysis showed that the bacterial community was affected by paclobutrazol, and in addition, was more diverse in the third stage of mung bean plant cultivation. The results of the study showed that paclobutrazol affected bacterial composition, and the population of bacteria varied greatly across time.