Bactericidal effect of low-temperature atmospheric plasma against the Shigella flexneri.

BACKGROUND: Shigella flexneri (S. flexneri) is a common intestinal pathogenic bacteria that mainly causes bacillary dysentery, especially in low socioeconomic countries. This study aimed to apply cold atmospheric plasma (CAP) on S. flexneri directly to achieve rapid, efficient and environmentally friendly sterilization. METHODS: The operating parameters of the equipment were determined by plasma diagnostics. The plate count and transmission electron microscope were employed to calculate bacterial mortality rates and observe the morphological damage of bacterial cells. Measurement of intracellular reactive oxygen species (ROS) and superoxide anions were detected by 2,7-dichlorodihydrofluorescein (DCFH) and Dihydroethidium fluorescence probes, respectively. The fluorescence intensity (a. u.) reflects the relative contents. Additionally, the experiment about the single effect of temperature, ultraviolet (UV), and ROS on bacteria was conducted. RESULTS: The peak discharge voltage and current during plasma operation were 3.92kV and 66mA. After discharge, the bacterial mortality rate of 10, 20, 30 and 40 s of plasma treatment was 60.71%, 74.02%, 88.11% and 98.76%, respectively. It was shown that the intracellular ROS content was proportional to the plasma treatment time and ROS was the major contributor to bacterial death. CONCLUSION: In summary, our results illustrated that the plasma treatment could inactivate S. flexneri efficiently, and the ROS produced by plasma is the leading cause of bacterial mortality. This highly efficient sterilization method renders plasma a highly promising solution for hospitals, clinics, and daily life.

Effects of non-thermal atmospheric plasma on protein.

Currently, the advancement in non-thermal atmospheric plasma technology enables plasma treatments on some heat-sensitive targets, including biological substances, without unspecific damage caused by thermal effect. The significant effects of non-thermal atmospheric plasma modulating biological events have been demonstrated by considerable studies. Protein, one of the most important biomolecules, participates in the majority of the life-sustaining activities in all organisms, whose functions are derived from the diverse biochemical properties of amino acid compositions and four-tiered protein structure hierarchy. Therefore, the knowledge of how non-thermal atmospheric plasma affects protein greatly benefits the understanding and application of the non-thermal atmospheric plasma's effect in biological area. In this review, we summarize recent research progress on the effects of non-thermal atmospheric plasma, particularly its reactive species, on biochemical and biophysical characteristics of proteins at different structural levels that leads to their functional changes. Moreover, the physiological effects of non-thermal atmospheric plasma at cellular or organism level driven by the manipulations on protein and their relative application prospects are reviewed. Despite the exceptional application potential, the exploration of the non-thermal atmospheric plasma's effect on protein still confronts with difficulties due to the limited knowledge of the underlying mechanisms and the complexity of non-thermal atmospheric plasma operation systems, which requires further studies and standardization of non-thermal atmospheric plasma treatments.

Intraspecific and Intrageneric Genomic Variation across Three Sedum Species (Crassulaceae): A Plastomic Perspective.

Sedum is the largest succulent genus in Crassulaceae. Because of predominant maternal inheritance, little recombination, and slow evolution, plastomes can serve as powerful super barcodes for inter- or intra-species phylogenetic analyses. While previous research has focused on plastomes between Sedum species, intra-species studies are scarce. Here, we sequenced plastomes from three Sedum species (Sedum alfredii, Sedum plumbizincicola, and Sedum japonicum) to understand their evolutionary relationships and plastome structural evolution. Our analyses revealed minimal size and GC content variation across species. However, gene distribution at IR boundaries, repeat structures, and codon usage patterns showed diversity at both inter-specific and intra-specific levels. Notably, an rps19 gene expansion and a bias toward A/T-ending codons were observed. Codon aversion motifs also varied, potentially serving as markers for future studies. Phylogenetic analyses confirmed the non-monophyly of Sedum and divided the Acre clade into two groups. Individuals from the same species clustered together, with strong support for the relationships between S. alfredii, S. tricarpum, and S. plumbizincicola. Additionally, S. japonicum clearly affiliates with the Acre clade. This study provides valuable insights into both intra-specific and intra-generic plastome variation in Sedum, as well as overall plastome evolution within the genus.

Molecular characterization of protein p50 of Dendrolimus punctatus cytoplasmic polyhedrosis virus.

Genome segment 7 of the 10-segmented RNA genomes of Dendrolimus punctatus cytoplasmic polyhedrosis virus (DpCPV) comprises 1502 nucleotides with one ORF of 1347 bp. This ORF was predicted to encode a protein of 448 amino acids with a molecular mass of 49,756 Da (p50). Antisera against both p50 and an antigen domain (AD) near the N-terminus of p50 specifically bound to a viral structural protein of ca. 33 kDa (V5), indicating that V5 was an N-terminal product of p50. Immunoblotting analysis with anti-p50 antibodies detected p50 and V5 molecules in the host midguts three days and five days post infection, respectively. The intracellular localization of p50 protein was examined by expressing truncations of p50 fused with GFP in recombinant baculovirus-infected Sf9 cells. The p50 protein was present in the cytoplasm of the cells, and the N-terminal portion (67-135 aa) of the protein played a key role in this localization.

Evaluation of the Probiotic Potential of Lactobacillus delbrueckii ssp. indicus WDS-7 Isolated from Chinese Traditional Fermented Buffalo Milk In Vitro.

The present study aimed to evaluate the probiotic potential of lactic acid bacteria (LAB) isolated from Chinese traditional fermented buffalo milk. Out of 22 isolates, 11 were putatively identified as LAB preliminarily. A total of six LAB strains displayed strong adhesion to HT-29 cells and all these strains showed preferable tolerance to artificially simulated gastrointestinal juices. WDS-4, WDS-7, and WDS-18 exhibited excellent antioxidant capacities, including DPPH radical, ABTS+ radical, and superoxide anion scavenging activities. Compared with the other two LAB strains, WDS-7 had a stronger inhibition effect on four pathogens. Based on the 16S rRNA gene sequencing and phylogenetic analysis, WDS-7 was identified as Lactobacillus delbrueckii ssp. indicus and selected to assess the potential and safety of probiotics further. The results revealed that WDS-7 strain had a strong capacity for acid production and good thermal stability. WDS-7 strain also possessed bile salt hydrolase (BSH) activity. Compared to LGG, WDS-7 was a greater biofilm producer on the plastic surface and exhibited a better EPS production ability (1.94 mg/ml as a glucose equivalent). WDS-7 was proved to be sensitive in the majority of tested antibiotics and absence of hemolytic activity. Moreover, no production of biogenic amines and ß-glucuronidase was observed in WDS-7. The findings of this work indicated that L. delbrueckii ssp. indicus WDS-7 fulfilled the probiotic criteria in vitro and could be exploited for further evaluation in vivo.

Applying Cold Atmospheric Plasma to Preserve the Postharvest Qualities of Winter Jujube (Ziziphus jujuba Mill. cv. Dongzao) During Cold Storage.

Winter jujube (Ziziphus jujuba Mill. cv. Dongzao) is a very popular horticultural fruit worldwide, which contains a high number of bioactive compounds. Nevertheless, jujube is perishable by microbial contamination and has a short shelf life under non-controlled conditions. Cold atmospheric plasma (CAP) presents a great potential for food sterilization, maintain postharvest quality, and prolonged storage time. Herein, this study investigated the potential effect of CAP with different exposure times (0, 5, 10, and 20 min) on the physicochemical and biochemical changes in jujube during 15-day storage at 4°C and 90% relative humidity (RH). The results showed that CAP treatment could obviously delay ripening, but displayed no effects on the speed of weight loss and moisture content. Meanwhile, the total native aerobic bacterial count in each jujube group was restrained during whole storage. However, CAP treatment showed a time-dependent manner to improve gene expression (PAL, 4CL, DFR, ANS, LAR, and ANR) related to phenolic biosynthesis. As compared to other groups, 20-min CAP treatment can keep or increase total phenolic content (TPC), maintain antioxidant activity, and reduce oxidative damage. Furthermore, the hydrogen peroxide (H2O2) and malondialdehyde (MDA) content in jujube during middle storage were visibly reduced by 20-min CAP treatment. All in all, our findings concluded that appropriate CAP exposure time can be a promising candidate for the postharvest preservation of jujube.

Glutathione-depletion reinforced enzyme catalytic activity for photothermal assisted bacterial killing by hollow mesoporous CuO.

The emergence and prevalence of drug-resistant bacteria caused by the overuse of antibiotics pose new challenges to the treatment of bacterial infections. In this work, hollow mesoporous CuO nanozymes (HM-CuO nanozymes) as excellent antibacterial agents were prepared by a template method. The synthesized HM-CuO nanozymes exhibit peroxidase-like catalytic activity, which can efficiently catalyze H2O2 to generate toxic reactive oxygen species (ROS), causing fatal damage to bacteria. Moreover, the hyperthermia of HM-CuO produced by photothermal therapy (PTT) not only effectively kills bacteria but also enhances the catalytic activity of nanozymes and produces more ROS. Moreover, the HM-CuO nanozymes have a glutathione (GSH)-depleting function to effectively consume GSH in bacteria and generate Cu(I) with higher catalytic effect, which can significantly improve the sterilization effect and produce a 100% inhibitory rate against E. coli and S. aureus. Overall, the HM-CuO nanozymes with strong peroxidase-like catalytic activity, excellent photothermal performance and GSH consumption ability offer a promising synergistic strategy for clinical bacterial infection.

Microstructure Evolution and Formation of Gradient Structures in Single Crystal Nickel-Based Superalloy by Surface Mechanical Creep-Feed Grinding Treatment.

Gradient structures have been created in single crystal nickel-based superalloys (SX alloys) via surface mechanical creep-feed grinding treatment (SMCGT). It has been found that these gradient structures are mainly composed of nano-sized grains, sub-micron-sized grains, dislocation structures, and the matrix material of single crystals along the depth from the treated surface. In addition, the evolution of such structures is found to be dominated by the dislocation movements which run through both γ channels and γ' precipitates, subdividing the two types of microstructures into various dislocation structures, and eventually introducing the refined grains into the surface layer. Furthermore, the evolution process of gradient structures primarily originates from the mechanical effect between abrasive grits and workpiece material, owing to the large grinding force (up to 529 N) and low grinding temperature (less than 150 °C) during the unique creep-feed grinding treatment in the present investigation. Due to the typical grain refinement, the hardness of the nanostructures exhibits the largest value of around 10 GPa in the surface layer, approximately 26% higher than that of the matrix material. This study further enhances the understanding of the microstructure-property relationship of SX alloys subjected to creep-feed grinding treatment and contributes to achievement of high-performance components.

Cold atmospheric plasma: A non-negligible strategy for viral RNA inactivation to prevent SARS-CoV-2 environmental transmission.

Cold atmospheric plasma (CAP), regarded as a powerful physics technology, displays antimicrobial, antitumor, and even antiviral properties, but the underlying mechanism is rarely studied. In this study, four CAP exposure doses (30, 60, 120, and 240 s) were applied to inactivate a severe acute respiratory syndrome coronavirus 2 like pseudovirus on a stainless steel disk, which comprised spike protein on its membrane and can express a green fluorescent protein. In order to unravel the potential effects of CAP irradiation on pseudovirus, infection assay, optical emission spectra analysis, transmission electron microscopy (TEM), sodium dodecyl sulfate polyacrylamide gel electrophoresis, ELISA, and qPCR experiments were carried out. As a result, our study indicated that CAP irradiation can significantly decrease the infectivity of pseudovirus in a dose dependent manner through destroying the cell membrane and further damaging viral RNA, with the molecular weight and conformation of spike receptor binding domain protein unchanged.

Modal analysis and moving performance of a single-mode linear ultrasonic motor.

A single-mode linear ultrasonic motor was developed in this study. On the stator, a group of four pieces of piezoelectric ceramics PZT8 were utilized to generate the ultrasonic vibration. A specially designed modal conversion horn with an oblique beam was applied to transfer the longitudinal vibration to an additional bending vibration. Modal analysis was conducted by finite element method to illustrate the elliptical vibration process. Then the output performance (e.g. output thrust and output velocity) of the motor was evaluated via a series of experiments. The results show that the simulated amplitudes of longitudinal vibration and bending vibration are 9.6 µm and 3.4 µm, respectively, which match well with the tested results. The output thrust increases with the increase of voltage. The largest output thrust is 10 N at the voltage of 600 Vp-p, and the biggest output velocity is 200 mm/s at the supplied frequency of 19.8 kHz and the driving angle of 45°. The output velocity also decreases with the increase of applied load.