Transmission Electron Microscopy Observations Research Articles

Transmission electron microscopic study on rutile-type GeO2 film on TiO2 (001) substrate

Rutile-type GeO2 (r-GeO2) with an ultrawide bandgap of ∼4.7 eV has emerged as a promising material for next-generation power-electronic and optoelectronic devices. We performed transmission electron microscopy (TEM) observation to analyze the structural properties of r-GeO2 film on r-TiO2 (001) substrate at an atomic level. The r-GeO2 film exhibits a threading dislocation density of 3.6 × 109 cm−2 and there exist edge-, screw-, and mixed-type dislocations in the film as demonstrated by two-beam TEM. The edge-type dislocations have Burgers vectors of [100] and/or [110]. The bandgap of the r-GeO2 film is 4.74 ± 0.01 eV as determined by electron energy loss spectroscopy.

Hypoxia adaptation mechanism in rats’ peripheral auditory system in high altitude migration: a time series transcriptome analysis

High altitude is characterized by low oxygen, low pressure, and high radiation. When migrates from low to high altitudes, the body’s tissues and organs experience hypoxic stress and will present acoustic adaptation as the protective response. However, the mechanisms of acoustic adaptation at high altitudes remain unclear. In this study, cochlear tissues from Wistar rats were collected at 15, 30, 60, 120, and 180 days after high-altitude migration. Transcriptome sequencing was conducted and DESeq algorithm revealed expression patterns of Differentially Expressed Genes(DEGs) after high altitude migration. Day 60 is a critical stage for cochlear tissue “damage” and “repair” in high-altitude conditions. Transmission Electron Microscopy (TEM) observations of structures also support the findings. A time-series gene co-expression network algorithm was used to investigate gene regulatory patterns and key genes after migration. Immunofluorescence, immunohistochemistry, and qPCR were per-formed for key gene validation and localization. At Day 60, the peak DEG count occurs in rats migrating to high altitude, aligning with the critical phase for cochlear tissue damage and repair at high altitudes. Repair hinges on synaptic plasticity and myelination-linked processes, influencing modules M4 to M6. Module M4’s activation gradually diminishes from its peak. However, the ‘damage’ effect is orchestrated by inflammation-related processes in modules M3 to M5, with module M3’s activation also waning. Key gene module M4, pivotal for repair during this pivotal phase, encompasses Sptbn5, Cldn1, Gfra2, and Lims2 as its core genes. Immunohistochemistry reveals Sptbn5’s presence in cochlear neurons, hair cells, Schwann cells and stria vascularis tissue. Cldn1 and Gfra2 predominantly localize within the cochlear neuron region. These results may suggest new directions for future research on acoustic acclimatization to high altitude.

DDIT4/mTOR signaling pathway mediates cantharidin-induced hepatotoxicity and cellular damage

BackgroundCantharidin (CTD) extracted from the traditional Chinese medicine Mylabris has significant therapeutic effects on various tumors. However, the high toxicity of CTD can cause serious liver damage, although the related molecular mechanisms remain unclear.MethodsIn this study, we established models of CTD-induced liver and L-O2 cell damage in mice in vivo and in vitro. Subsequently, liver function indicators were detected in mouse serum, while liver tissues were subjected to pathological and transmission electron microscopy observations. L-O2 cell activity was investigated using the CCK-8 assay, and the mRNA and protein expression of DNA damage-induced transcription factor 4 (DDIT4) in liver tissue and L-O2 cells was detected using qPCR, immunohistochemistry, and western blotting. Western blotting was also used to detect the expression levels of autophagy- and apoptosis-related proteins in liver tissue and L-O2 cells. After RNAi interference with DDIT4, Rap, and 3-MA treatment, autophagy and apoptosis of L-O2 cells were detected using western blotting, flow cytometry, transmission electron microscopy, and confocal microscopy.ResultsFollowing CTD exposure, the mouse liver showed significant pathological damage and an increase in autophagic lysosomes, while the vitality of L-O2 cells showed a significant decrease. CTD led to a significant increase in the mRNA and protein levels of DDIT4 in both liver tissue and L-O2 cells, as well as a significant increase in LC3-II, Beclin1, and Bax, whereas p-mTOR and Bcl-2 were significantly decreased. Following DDIT4 interference and 3-MA treatment, the levels of autophagy and apoptosis induced by CTD in L-O2 cells were reduced. After Rap treatment, both autophagy and apoptosis of CTD-induced L-O2 cells were significantly enhanced.ConclusionThe molecular mechanism of CTD-induced toxicity in mouse liver and L-O2 cells is mainly through DDIT4/mTOR signaling pathway activation, leading to an increase in autophagy and apoptosis levels.

Unexpected nanoscale CeO2 structural transformations induced by ecologically relevant phosphate species

In the present study, the dissolution and microstructural transformation of CeO2 nanoparticles (NPs) in a phosphate-containing milieu were investigated. The dissolution behaviour of 2 nm and 5 nm CeO2 NPs in phosphate buffer solutions was found to differ markedly from that observed in 0.01 M NaClO4. Through synchrotron X-ray diffraction analysis and X-ray absorption spectroscopy, the interaction between CeO2 NPs and phosphate species was examined, revealing the transformation of the oxide into sodium-cerium double phosphate, with cerium predominantly existing in the Ce(IV) state. According to scanning and transmission electron microscopy observations, thus formed Na-Ce(IV) phosphate consists of spindle-like aggregates of nanocrystalline rods, presumably formed during phosphate anions sorption on the initial CeO2 surface. Pair distribution function analysis revealed that Na-Ce(IV) phosphate has a three-dimensional framework crystal structure, similar to NaTh2(PO4)3, as reported earlier, with large channels along the c-axis containing disordered sodium atoms. This study represents the first detailed analysis of phosphate-induced speciation and microstructural transformation of CeO2 NPs, resulting in the formation of Ce(IV) phosphate. Similar processes may occur in natural ecosystems upon the introduction of CeO2 NPs.

A new nanoindentation approach for determining both indentation size effect and continuous apparent activation volume during loading of nanocrystalline Ni and Ni-20 wt.% Fe alloy

A new nanoindentation approach is developed in this study to determine both indentation size effect (ISE) and continuous apparent activation volume () during loading of nanocrystalline nickel (NC Ni) and nanocrystalline nickel-20 wt.% iron alloy (NC Ni-Fe alloy). This approach involves conducting nanoindentation tests under loading modes controlled by both constant strain rate (CSR) and constant loading rate (CLR). Firstly, a new empirical expression for the parameter in the modified Nix-Gao model is established to study the strain rate dependence of the ISEs created in the CSR and CLR tests. Then, continuous data of each individual sample (indentation) during loading are obtained in the CLR test through the alternative use of continuous stiffness measurement technique. The stress dependence of is analyzed based on Duhamel et al.’s model, which considers the role of vacancies generated during inhomogeneous dislocation nucleation. Finally, based on the above experimental and theoretical work as well as transmission electron microscopy observation, the influences of loading mode, loading rate, and material properties (stacking fault energy) on resulting intrinsic hardness of NC Ni and NC Ni-Fe alloy are analyzed. The nanoindentation approach developed in this study provides profound insights into the mechanical behaviors during loading and underlying mechanisms of materials.

Effect of Ag–Te alloys on pH sensitivity of Ag2O–TeO2 glass/stainless steel enamel

Glass pH sensors are unsuitable for in vivo biomedical, clinical, or food applications because of brittleness of glass, the difficulty in measurement of small volumes and complex matrices, and the need for calibration. Herein, a novel enamel reference electrode for pH sensors is developed using a binary xAg2O·(100–x)TeO2 glass/stainless steel (SUS) electrode. Subsequently, the effects of Ag2O content on the precipitated crystalline phases and pH sensitivity of Ag2O–TeO2 glass/SUS electrodes are examined. The results indicate that the xAg2O·(100–x)TeO2 glass/SUS samples exhibit relatively low pH sensitivity. The pH sensitivities of the samples can be classified into two distinct groups. The first group, comprising samples with an Ag2O content of 25 mol% or more, exhibits a pH sensitivity higher than 10 %. The second group, comprising samples with an Ag2O content of 22 mol% or less, exhibits a pH sensitivity of less than 10 %. The pH sensitivity tends to decrease with increase in stutzite fraction in Ag–Te alloys. Results of X-ray diffraction measurements and transmission electron microscopy observations indicate that the hessite and stutzite Ag–Te alloys, which are minor and conductive, are the primary contributors to the low pH sensitivity observed. Moreover, the pH sensitivity of xAg2O·(100–x)TeO2/SUS is observed to be between those of the Ag–Te alloy and the Ag2O–TeO2 glass matrix. We propose occurrence of an electrical shunt should occur between the Ag–Te alloy and the Ag+-ion conductive Ag2O–TeO2 glass matrix. Regarding xAg2O·(100–x)TeO2 glass/SUS, the 20Ag2O·80TeO2 glass/SUS to 21Ag2O·79TeO2 glass/SUS compositions represent promising candidates as for KCl-leakage-free reference electrodes for pH sensors.

Activation of peroxymonosulfate by MnOOH/g-C3N5: Study on highly selective removal of phenolic pollutants and its non-radical pathway

In this research, the MnOOH/g-C3N5 material was successfully synthesized, demonstrating its efficacy in selectively removing phenolic organic pollutants. This material outperformed traditional free radical pathways, exhibiting higher selectivity, enhanced persulfate utilization efficiency, and strong resistance to background anions and complex organic matter. Using phenol as the target pollutant, the MnOOH/g-C3N5/PMS system achieved 81 % mineralization, a PMS utilization efficiency of 88 %, and a 75 % process unit energy consumption value in degrading phenol. This efficient degradation is attributed to the synergistic effects of high-valence metal oxides (MnV(O)/MnIV(O)), singlet oxygen (1O2), and electron transfer complexes, as confirmed by electrochemical analysis and In-situ EPR. Additionally, Transmission Electron Microscopy observations disclosed the development of an amorphous shell on the MnOOH/g-C3N5 surface post-reaction. Electrochemical Impedance Spectroscopy analysis suggested an enhanced charge transfer resistance, further affirming the role of MnOOH/g-C3N5 as an "electron transfer station" in the electron transfer process, accompanied by the formation of electron transfer complexes. This study provides crucial scientific insights and theoretical guidance for applying MnOOH/g-C3N5 materials in environmental engineering.

Bromodomain and extraterminal domain (BET) promote autophagy in buffalo sertoli cells

Sertoli cells (SCs) play a pivotal role in spermatogenesis, with autophagy modulation being an evolutionarily conserved mechanism for maintaining cellular homeostasis and protecting spermatogenic cells against apoptosis. The bromodomain and extraterminal domain (BET) family are transcriptional regulators of autophagy. This study investigated the relationship between BET inhibition and autophagy in buffalo SCs. Our findings reveal that BET inhibition suppresses cell proliferation and alters the biological characteristics of SCs. RNA-seq analysis demonstrated significant downregulation of autophagy-related genes upon BET inhibition. Moreover, our bioinformatics analysis suggested the involvement of the PI3K-AKT signaling pathway in autophagy regulation within buffalo SCs. Immunofluorescence and Transmission electron microscopy observations indicated that BET inhibition results in autophagosome accumulation and impedes autophagosome-lysosome degradation, thereby compromising autophagy activity and flux. In summary, this study sheds light on the indispensable role of BET proteins in autophagy and paves the way for further investigations into the mechanisms governing BET protein-mediated autophagy regulation and its implications for male reproduction.

Transmission Electron Microscopy of Coral Tissue.

Coral reefs are invaluable ecosystems that are under threat from various anthropogenic stressors. There has been a recent increase in the diagnostic tools utilized to understand how these threats impact coral reef health. Unfortunately, the application of diagnostic tools like transmission electron microscopy (TEM) is not as standardized or developed in coral research as in other research fields. Utilizing TEM in conjunction with other diagnostic methods can aid in understanding the impact of these stressors on the cellular level because TEM offers valuable insight into the structures and microsymbionts associated with coral tissue that cannot be obtained with a conventional light microscope. Additionally, a significant amount of coral tissue ultrastructure has not yet been extensively described, causing a considerable gap in our understanding of cellular structures that could relate to the immune response, cellular function, or symbioses. Moreover, additional standardization is needed for TEM in coral research to increase comparability and reproducibility of findings across studies. Here, we present standardized TEM sample fixation, embedding, and sectioning techniques for coral studies that ensure consistent ultrastructural preservation and minimize artifacts, enhancing the reliability and accuracy of TEM observations. We also demonstrate that these TEM protocols allow for the observation and quantification of bacterial and viral-like particles within the coral tissue as well as the endosymbiotic microalgae, potentially providing insight into their interactions within coral cells and how they relate to overall coral health and resilience. © 2024 The Author(s). Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Primary fixation Basic Protocol 2: Decalcification Basic Protocol 3: Sample dissection, secondary fixation, dehydration, and embedding Basic Protocol 4: Sectioning and grid staining Basic Protocol 5: Imaging.

Superconducting Boride Nb2IrB2 with Variable and Tunable Stacking Behaviors of Two-Dimensional [Nb-Ir-Nb] Triangular Lattices.

In structures with special geometry lattices, variations in stacking sequences are ubiquitous, yielding many novel structures and functionalities. Despite a wealth of intriguing properties and wide-ranging applications, there remains a considerable gap in understanding the correlation between special geometry lattices and functionalities in borides. Here, we design and synthesize a new superconducting boride Nb2IrB2, with a body-centered orthorhombic structure, consisting of alternating two-dimensional [Nb-Ir-Nb] triple-triangular-lattice-layers and B fragment layers. Advanced aberration-corrected scanning transmission electron microscopy observations show variable stacking configurations between [Nb-Ir-Nb] triple-triangular-lattice layers that can be tuned through synthesis conditions. Density functional theory calculations reveal that the coherent low-energy boundary interface plane of {101} between [11̅1] and [010] domains is responsible for the variable stacking behaviors. Energetically favorable structures are thereby reasonably proposed, based on nanoscale imperfect structure units. These findings provide valuable insights for designing and exploring new structures and functionalities within boride systems involving special geometry lattices.

Stress relaxation aging of 7050 aluminum alloy under elastic and plastic loadings: A perspective from the geometrically necessary dislocations

Aerospace integral panels with large curvature often experience not only elastic loading but also plastic loading during creep age forming. However, the stress relaxation aging behaviors and mechanisms under loading stresses ranging from elastic to plastic regions, especially from the perspective of geometrically necessary dislocations (GNDs), have not been fully explored. The stress relaxation aging (SRA) behavior of 7050 aluminum alloy under elastic (200/250/300 MPa) and plastic loadings (350/400 MPa) are studied by uniaxial SRA, hardness and tensile tests, and corresponding mechanisms are clarified by Electron Back Scatter Diffraction (EBSD) tests and transmission electron microscopy (TEM) observations. Regardless of the loading stress, the stress relaxation of 7050 alloy shows a typical two-stage behavior (rapid stress reduction and stable stress relaxation rate). The second stage of stress relaxation under elastic loading shows an abnormal stress rebound, while the stress continuously decreases under plastic loading, and hardness and yield strength at 350 MPa are lower than that at 200 MPa during SRA. These results are attributed to strong dislocation pinning from small and dense precipitates at elastic loading and dislocations shearing large and sparse precipitates at plastic loading, respectively. Furthermore, both the stress reduction and its ratio increase with the increase of initial stress. GNDs contribute to the formation of low-angle grain boundaries (LAGBs) and accumulate at the LAGBs intersection to coordinate grain orientation for creep deformation. Compared to elastic loading, plastic loading promotes global growth of intragranular precipitates by elastic stress field and local heterogeneous nucleation and coarsening of precipitates at subgrain boundaries by more GNDs.

Recrystallization of amorphous AlNbCr coatings irradiated with chromium ions

Applying an AlNbCr layer on the surface of Zr alloys significantly enhances the alloy resistance to oxidation and high-temperature corrosion. However, the effects of irradiation on AlNbCr coating remain largely unexplored. This work investigates the microstructural evolution of Cr ion-irradiated AlNbCr coatings under varying temperatures, utilizing bright-field transmission electron microscopy (TEM) observations and electron diffraction pattern analyses. With increasing Cr ion irradiation dose, the coatings gradually transitioned from an initial amorphous to a crystalline state. The onset of crystallization occurred earlier at higher temperatures, indicating that the crystallization process was significantly influenced by temperature. Moreover, the dynamic crystallization process of the crystalline structure was also analyzed, as well as the different irradiation responses at the Near-Interface Area (NIA) and Far-Interface Area (FIA). These findings provide new insights for understanding and optimizing the performance of AlNbCr coatings in high-irradiation environments.

Selective area epitaxy of in-plane HgTe nanostructures on CdTe(001) substrate

Semiconductor nanowires (NWs) are believed to play a crucial role for future applications in electronics, spintronics and quantum technologies. A potential candidate is HgTe but its sensitivity to nanofabrication processes restrain its development. A way to circumvent this obstacle is the selective area growth technique. Here, in-plane HgTe nanostructures are grown thanks to selective area molecular beam epitaxy on a semi-insulating CdTe substrate covered with a patterned SiO2mask. The shape of these nanostructures is defined by the in-plane orientation of the mask aperture along the <110>, <11¯0>, or <100> direction, the deposited thickness, and the growth temperature (GT). Several micron long in-plane NWs can be achieved as well as more complex nanostructures such as networks, diamond structures or rings. A good selectivity is achieved with very little parasitic growth on the mask even for a GT as low as 140 °C and growth rate up to 0.5 monolayer per second. For <110> oriented NWs, the center of the nanostructure exhibits a trapezoidal shape with {111}B facets and two grains on the sides, while <11¯0> oriented NWs show {111}A facets with adatoms accumulation on the sides of the top surface. Transmission electron microscopy observations reveal a continuous epitaxial relation between the CdTe substrate and the HgTe NW. Measurements of the resistance with four-point scanning tunneling microscopy indicates a good electrical homogeneity along the main NW axis and a thermally activated transport. This growth method paves the way toward the fabrication of complex HgTe-based nanostructures for electronic transport measurements.

Grain rotation mechanisms in nanocrystalline materials: Multiscale observations in Pt thin films.

Near-rigid-body grain rotation is commonly observed during grain growth, recrystallization, and plastic deformation in nanocrystalline materials. Despite decades of research, the dominant mechanisms underlying grain rotation remain enigmatic. We present direct evidence that grain rotation occurs through the motion of disconnections (line defects with step and dislocation character) along grain boundaries in platinum thin films. State-of-the-art in situ four-dimensional scanning transmission electron microscopy (4D-STEM) observations reveal the statistical correlation between grain rotation and grain growth or shrinkage. This correlation arises from shear-coupled grain boundary migration, which occurs through the motion of disconnections, as demonstrated by in situ high-angle annular dark-field STEM observations and the atomistic simulation-aided analysis. These findings provide quantitative insights into the structural dynamics of nanocrystalline materials.

Nanomineralogy of thorite in the supergiant Huayangchuan uranium ore deposit: Revealing a new geochemical behavior of actinide in environment

Thorium (Th) is a naturally occurring radioactive element found in the environment, and recent advancements have been made in identifying and characterizing Th-bearing nanoparticles (NPs). However, the main focus is still on synthesized Th-bearing NPs and knowledge about natural Th-bearing NPs remains limited. Here, high-resolution transmission electron microscopy (HRTEM) observations of thorite from the Huayangchuan uranium ore deposit in Shaanxi Province, Central China, have revealed the nanoscale mineral characteristics of thorite. In this study, thorite NPs ranging from 5–10 nm in size were identified within the uranium ore. A combination of transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS) elemental mapping and corresponding HRTEM images alongside Selected Area Electron Diffraction (SAED) and Fast Fourier Transform (FFT) patterns revealed a complex nanoscale structure in the thorite NPs, consisting of both amorphous and crystalline nanodomains with abundant defects. These nanostructures are associated with a metamictization mechanism in micrometer-sized thorite. Our findings indicate that the metamictization process can generate numerous thorite nanoparticles. Given the high penetrability and mobility of these NPs, the metamictization of thorite poses new challenges for the long-term stability of radioactive substances and the storage containers for radioactive waste. Furthermore, considering the likelihood of environmental release and the chemical toxicity, radioactivity, and nanotoxicity of natural Th-bearing NPs, increased attention should be given to the presence of natural thorite NPs in the ore deposit.

Carvacrol acts on the larval midgut of Spodoptera frugiperda by destroying the tissue structure and altering the bacterial community

The fall armyworm, Spodoptera frugiperda, has become a global invasive pest in recent years, threatening agricultural production. Carvacrol (CAR) is a multifunctional plant-derived compound and exhibited significant bioactivities against many pests. Our previous study found that CAR inhibited growth and development in S. frugiperda. However, the effects of CAR on the midgut of this pest remain unknown. In this study, the actions of CAR on the larval midgut of S. frugiperda were investigated. The results found that 1.0 and 2.0 g/kg CAR treatments destroyed the structure of the larval midgut based on hematoxylin-eosin staining and transmission electron microscope observation. In addition, 2.0 g/kg CAR exposure significantly altered the larval midgut bacterial community composition and structure. The results of the linear discriminant analysis effect size (LEfSe) analysis suggest that six bacterial genera contributed to the different structures of the larval bacterial community. Furthermore, PICRUSt2 analysis found that 16 bacterial function categories were altered by CAR treatment, of which 8 were significantly increased. Our results provided new insight into the toxicological mechanisms of CAR against S. frugiperda larvae and laid the foundation for the field application of S. frugiperda control.

Effect of precipitate evolution on galvanic corrosion behavior of friction stir welded AA6061-T6 joint after post-weld aging

The microstructural transformation of FSW AA6061-T6 joint after post-weld T6 and its effects on the mechanical properties and corrosion behavior was investigated through electrochemical tests, immersion experiments and transmission electron microscopy (TEM) observation. The research results show that the joint efficiency and strength can be enhanced by post-welding aging. The hardness of SZ is recovered to a level close to that of matrix due to the sufficient precipitation of the effective strengthening phase β''. The main β' precipitate in over-aged HAZ coarsens during post-weld aging and cannot effectively restore strength, resulting in the lowest hardness in HAZ and limited tensile strength of the joint. The presence of macro-galvanic effects in the whole joint was confirmed. In SZ, the highest level of aging characteristics is caused by the highest aging drive due to fully solidified atoms, and is confirmed by the continuous grain boundary precipitates (GBPs) and dense matrix precipitates, which lead to the most positive potentials. Whereas, in HAZ, discrete GBPs and coarsened matrix precipitates indicate over-aged features, which lead to the most negative potentials. The potential difference between SZ and HAZ results in a macro-galvanic effect in the joint, where SZ is protected as the cathode and HAZ is corroded faster as the anode.

Eco-friendly drugs induce cellular changes in colistin-resistant bacteria

Abstract Background and objective As a last option, multidrug-resistant Gram-negative infections (caused by Enterobacteriaceae) are treated with the antibiotic colistin, also known as polymyxin E. Colistin-resistant superbugs predispose people to untreatable infections, possibly leading to a high mortality rate. This project aims to study the effect of Acacia nilotica aqueous extract and zinc oxide nanoparticles (ZnO-NPs) on colistin-resistant Klebsiella pneumonia (CRKP). Materials and methods ZnO-NPs were synthesized using the green method and characterized by UV-vis, Fourier transform infrared spectroscopy, and X-ray diffraction. The zone of inhibition (ZI) was measured using the agar-well diffusion method, and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration were estimated to determine the antimicrobial activity of the tested compound. Scanning electron microscopy (SEM) and transmission electronic microscopy (TEM) were used to investigate the alterations in bacterial cells that were treated with the tested drugs. Results The synthesized ZnO-NPs presented good chemical and physical properties, and the plant extract and ZnO-NPs displayed a large ZI. ZnO-NPs had the lowest MIC (0.2 mg·mL−1). SEM and TEM observations revealed various morphological modifications in CRKP cells, including cell shrinkage, cell damage, cytoplasm loss, cell wall thinning, and cell death. Conclusion A. nilotica aqueous extract and ZnO-NPs could be used as alternative natural products to produce antibacterial drugs and to prevent CRKP infection.

Gone but not forgotten: dynamics of sperm storage and potential ejaculate digestion in the black soldier fly Hermetia illucens.

Understanding the dynamics of sperm storage is essential to unravel the complexity of post-copulatory sexual selection processes in internally fertilized species. This physiological process goes from sperm transfer during copulation to its use for fertilization. In this context, the spatiotemporal dynamics of sperm storage were described in the black soldier fly (BSF) with fluorescence and transmission electron microscopy (TEM). BSF females have compartmentalized spermathecae with a transfer compartment, the fishnet canals, and a storage compartment, the reservoirs. Spermatozoa were counted both during and after mating in the two compartments. In addition to seminal fluids, the male transfers a mass of sperm in the fishnet canals, then only 49% of the transferred spermatozoa reach the reservoirs over two days. TEM observations of the fishnet canals revealed potential digestive functions, explaining the decline in the number and viability of spermatozoa in this compartment but not in the reservoirs. After one mating, females laid up to three fertile clutches, showing no constraints on sperm quantity or quality. Spermatic and ultrastructural investigations strongly suggest that BSF ejaculate acts both as a sperm plug and as a nuptial gift, reinforcing the interest in studying this farming insect as a new model for sexual selection.

Biocontrol efficacy of Botrytis cinerea on postharvest tomato fruit by the endophytic bacterium Bacillus velezensis BE1

Endophytic bacteria offer numerous advantages in the control of postharvest diseases. Bacillus velezensis has been identified as a promising biocontrol agent against postharvest pathogens in various fruits and vegetables. In this study, B. velezensis BE1 was identified by 16S rRNA sequencing and caused 76.9 % inhibition against Botrytis cinerea in dual culture assay. The cell-free culture filtrate (CFCF) of B. velezensis strongly inhibited the growth, spore germination, and germ tube elongation of B. cinerea. Moreover, 11 bioactive compounds were identified in the CFCF using gas chromatography-mass spectrometry, and phthalic acid, dioctyl ester was the predominant component by 72.92 %. Scanning and transmission electron microscopy observations revealed that the CFCF causes irreversible morphological and ultrastructural damage to the fungal hyphae and conidia, including deformed, wrinkled, lysis, collapse, and degradation of cytoplasmic organelles. The incidence and severity of gray mold were significantly suppressed after applying CFCF at 50 % in tomato fruit. The application of CFCF caused an increase in the total phenolics and flavonoids content in tomato fruit compared with the control throughout the experiment. Furthermore, the activities of enzymes associated with defense such as phenylalanine ammonia-lyase, polyphenoloxidase, and peroxidase were significantly higher in the treated tomatoes relative to the untreated group. These results indicate that B. velezensis BE1 has significant potential as an effective biocontrol agent against the pathogen B. cinerea, offering a valuable approach for controlling gray mold in postharvest fruit.