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Cathelicidin-RC1, extracted from the bullfrog Rana catesbeiana , has been found to effectively combat gram-negative bacteria but has limited inhibitory effects on gram-positive bacteria. Additionally, the specific mechanism of cathelicidin-RC1's interaction with bacteria remains unclear. In this research, we present the expression analysis of a chimeric peptide composed of three repetitive units of cathelicidin-RC1 (3×cathelicidin-RC1) with a hemagglutinin (HA) and a 6×His tag attached at its C-terminus in Chlamydomonas reinhardtii , leading to the production of a chimeric peptide with a molecular mass of ∼16.2 kDa. The recombinant peptide, 3×cathelicidin-RC1-HA-6×His, demonstrates a wide range of antimicrobial activity, with minimum inhibitory concentration (MIC) values of approximately 20–30 µg/ml and 10–60 µg/ml against gram-positive and negative bacteria, respectively. The minimum bactericidal concentration (MBC) values of 3×cathelicidin-RC1-HA-6×His varies from 1× to 3×MIC. Furthermore, 3×cathelicidin-RC1-HA-6×His demonstrates excellent stability, pH stability, and resistance to digestion by certain proteases. It also exhibits low cytotoxicity and negligible hemolytic activity against rat erythrocytes. Scanning electron microscopy and propidium iodide analysis indicate that 3×cathelicidin-RC1-HA-6×His disrupts bacterial cell membranes, leading to inhibition of bacterial growth. Overall, our findings demonstrate that 3×cathelicidin-RC1-HA-6×His, produced in the heterologous expression host C. reinhardtii , effectively inhibits bacterial growth and holds great promise for potential application. [Display omitted] • A multimer termed 3×cathelicidin-RC1 was stably expressed in green algae. • 3×cathelicidin-RC1 has a broad spectrum of antibacterial activity. • 3×cathelicidin-RC1 was tolerant of temperature, pH, salt and certain proteinases. • 3×cathelicidin-RC1 showed a low toxicity and low hemolytic activity. • 3×cathelicidin-RC1 disrupted the integrity of the bacterial cell membrane. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Introduction: The co-existence of S. mutans and C. albicans is frequently detected in root caries and early child caries and is reported to be associated with recurrent caries. The aim of this study was to investigate the effects of potassium iodide (KI) in combination with toluidine blue O-mediated antimicrobial photodynamic therapy (aPDT) on S. mutans and C. albicans mixed-species biofilm, as well as the antibiofilm mechanisms involved. Methods: Mixed-species biofilm was constructed of S. mutans and C. albicans on dentin blocks. The antibiofilm efficacy, cytotoxicity and antibiofilm mechanism of KI in combination with aPDT were determined and evaluated. Results: KI+TBO-aPDT treatment caused reduction in microorganism counts, metabolic activity, and biofilm biomass of mixed-species biofilm without inducing cytotoxicity to hDPCs (human dental pulp cells). Observations such increased ROS (reactive oxygen species) levels, impaired cell membrane function, cell apoptosis and reduced expression in several genes seem to be artifacts of reduced growth and general killing by KI+TBO-aPDT treatment. Discussion: These data suggested that KI in combination with aPDT as an innovative approach to combat S. mutans and C. albicans biofilm, and thus as an optional treatment for caries. [ABSTRACT FROM AUTHOR]

Zeolite imidazolate frameworks (ZIFs) have been widely used in drug delivery and antibacterial applications due to their highly controllable structure and pore size. However, the relationship between the structure of ZIFs and their antibacterial efficacy has not been fully elucidated. In this study, three ZIFs with uniform sizes and specific morphologies were synthesized: cubic (Z-8), leaf-like (Z-L), and flower-like (FZ-L). Flow cytometry was employed to assess the effects of these materials on Bacillus subtilis and Escherichia coli at different concentrations and exposure times. Results showed that sharp-edged ZIFs possess enhanced antibacterial effects. Specifically, FZ-L exhibited the lowest minimum inhibitory concentration of 400 μg/mL and a minimum bactericidal concentration of 20 μg/mL, which can kill bacteria effectively and rapidly. Further study on the antibacterial mechanisms showed that these materials do not produce reactive oxygen species (ROS) themselves but induce ROS production in bacteria and accelerate bacterial death. Biocompatibility studies suggested that ZIFs have minimal toxicity to human cells, indicating their potential in biomedical applications. This research provides insights into the antibacterial mechanisms of ZIFs, which can support their development for antimicrobial use. [ABSTRACT FROM AUTHOR]

Oh-defensin, an antimicrobial peptide, extracted from the venom of Ornithoctonus hainana , potently inhibited fungi and Gram-negative bacteria but showed limited antibacterial potency against Gram-positive bacteria via an unknown mechanism. In this study, a recombinant peptide termed as 3×Oh-defensin-HA-6×His composed of three repeats of Oh-defensin followed by hemagglutinin (HA) and six histidine (6×His) double tags was expressed in Chlamydomonas reinhardtii. The bacteriostatic activity of 3×Oh-defensin-HA-6×His certified against both Gram-negative and Gram-positive bacteria was confirmed, with minimum inhibitory concentration (MIC) between 10 and 80 µg/mL. The minimum bactericidal concentration (MBC) was determined to range from 1× to 2×MIC. In addition, 3×Oh-defensin-HA-6×His exhibited resistance to temperature shocks, extreme pH, and proteinase digestion and it was biologically safe because it displayed low cytotoxicity and hemolysis. In addition, scanning electron microscopy (SEM) and propidium iodide (PI) staining revealed that 3×Oh-defensin-HA-6×His caused the destruction of the bacterial cell membrane, which effectively inhibited bacterial growth. In summary, our findings suggest that green algae-derived 3×Oh-defensin-HA-6×His holds significant promise as a potential alternative to conventional antibiotics in the future. [Display omitted] • A triple Oh-defensin (3×Oh-defensin-HA-6×His) was stably expressed in green algae. • 3×Oh-defensin-HA-6×His inhibits the growth of a broad-spectrum bacteria. • 3×Oh-defensin-HA-6×His is thermostable and resists on extreme pH and proteinase digestion. • 3×Oh-defensin-HA-6×His is biologically safe. • 3×Oh-defensin-HA-6×His inhibits bacterial growth by disrupting the bacterial cell membrane. [ABSTRACT FROM AUTHOR]

In this study, gas chromatography-mass spectrometry (GC-MS) was used to analyze the chemical components of the essential oil extracted from the fruits of Aipinia oxyhylla Miq. (AOEO) by steam distillation. To evaluate the antimicrobial activity of AOEO against Listeria monocytogenes, the inhibitory zone diameter, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by means of filter paper and micro-double dilution methods. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were performed to observe the effect of AOEO on bacterial morphology. The antibacterial mechanism was investigated by measuring the growth curve, the change of electrical conductivity, the leakage of intracellular macromolecules, the activity of superoxide dismutase (SOD) and the content of malondialdehyde (MDA). The results showed that a total of 45 chemical components were identified in AOEO, mainly including terpenes, aromatic hydrocarbons and oxygen-containing derivatives. Among them, valencene, nootkatone, 2,6,10,10-tetramethylbicyclo[7.2.0]undeca-1,6-diene, (2S,4aR,8aR)-4a,8-dimethyl-2-(prop-1-en-2-yl)-1,2,3,4,4a,5,6,8a-octahydronaphthalene, (2R,8R,8aS)-8,8a-dimethyl-2-(prop-1-en-2-yl)-1,2,3,7,8,8a-hexahydronaphthalene and p-cymene were predominant. AOEO significantly inhibited the growth of L. monocytogenes with an inhibitory zone diameter of 14.20 mm. The MIC and MBC were 0.195 and 0.781 mg/mL, respectively. The growth curve showed that the antimicrobial activity of AOEO was concentration-dependent. SEM and TEM showed that AOEO destroyed the morphological structure of L. monocytogenes and changed the permeability of the cell membrane, thereby causing the leakage of a large number of electrolytes and macromolecular contents (nucleic acids and proteins) out of the cells. The dynamic balance of the SOD system was also destroyed by the oil while inducing the generation of a large number of free radicals, thus resulting in increased levels of lipid oxidation and MDA content in the cells. Therefore, AOEO inhibited the growth of L. monocytogenes and causes cell apoptosis by causing a series of cellular changes. This could be due to the synergistic action of multiple components and multiple targets of AOEO. Terpenes, aromatic hydrocarbons and ketones were tentatively identified as the major antibacterial substances of AOEO. This study provides a scientific theoretical basis for the development and utilization of Aipinia oxyhylla Miq. as a natural bacteriostatic agent in the food industry.

Yang Chong,1,2 Dong Yu,1,2 Rui Han,3 Yanxu Li,2 Yali Gu,3 Zhaoyu Lu,1,2 Fengsong Nie,1,2 Lingli Wang,1 Hengmi Cui4 1Department of Traditional Chinese Medicine, The Affiliated Hospital of Yangzhou University, Yangzhou University, Yangzhou, Jiangsu, 225000, People’s Republic of China; 2Department of General Surgery, The Affiliated Hospital of Yangzhou University, Yangzhou University, Yangzhou, Jiangsu, 225000, People’s Republic of China; 3Institute of Translational Medicine, Medical College, Yangzhou University, Yangzhou, 225009, People’s Republic of China; 4Institute of Epigenetics and Epigenomics and College of Animal Science and Technology, Yangzhou University, Yangzhou, Jiangsu, 225009, People’s Republic of ChinaCorrespondence: Yang Chong, Department of Traditional Chinese Medicine, The Affiliated Hospital of Yangzhou University, Yangzhou University, Yangzhou, Jiangsu, 225000, People’s Republic of China, Email 092016@yzu.edu.cn Hengmi Cui, Institute of Epigenetics and Epigenomics and College of Animal Science and Technology, Yangzhou University, Yangzhou, Jiangsu, 225009, People’s Republic of China, Email hmcui@yzu.edu.cnPurpose: Incorporation of luvangetin in nanoemulsions for antimicrobial and therapeutic use in infected wound healing.Patients and Methods: Luvangetin nanoemulsions were prepared by high-speed shear method and characterized based on their appearance structure, average droplet size, polydispersity index (PDI), electric potential, storage stability. Optimized formulation of luvangetin nanoemulsion by Box-Behnken design (BBD). The antimicrobial activity and antimicrobial mechanism of luvangetin nanoemulsions against common hospital pathogens, ie, Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), were investigated using luvangetin nanoemulsions. The biosafety of luvangetin nanoemulsion was evaluated through cytotoxicity, apoptosis, and reactive oxygen species (ROS) assay experiments using human normal epidermal cells and endothelial cells. Finally, the effect of luvangetin nanoemulsion on healing of infected wounds was investigated in B6 mice.Results: Luvangetin nanoemulsion formulation consists of 2.5% sunflower seed oil, 10% emulsifier Span-20 and 7 minutes of shear time, and with good stability. Luvangetin nanoemulsion produces antibacterial activity against S. aureus and E. coli by disrupting the structure of bacterial cell membranes. Luvangetin nanoemulsion are biologically safe for HaCat and HUVEC. Luvangetin nanoemulsion showed good therapeutic effect on MRSA infected wounds in mice.Conclusion: For the first time, developed a new formulation called luvangetin nanoemulsion, which exhibited superior antibacterial effects against Gram-positive bacteria. Luvangetin nanoemulsion has a favorable effect in promoting infected wound healing. We have combined luvangetin, which has multiple activities, with nanoemulsions to provide a new topical fungicidal formulation, and have comprehensively evaluated its effectiveness and safety, opening up new possibilities for further applications of luvangetin. Keywords: luvangetin, nanoemulsion, antimicrobial mechanism, infected wound healing

Background: Plant-derived antimicrobials (PDAs) are considered a viable alternative to synthetic antimicrobial agents. Diverse antimicrobial mechanisms of PDAs significantly reduce the risk of developing antimicrobial resistance. Utilization of PDAs also offers economic and environmental advantages, as they can be derived from agricultural byproducts, such as olive pomace. Results: In this study, a green, water-based, ultrasound-assisted extraction (UAE) was deployed to obtain aqueous olive pomace extract (OPE) from dry olive pomace. Total phenolic content, extraction yield, chemical compositions, and antimicrobial activities of OPE were evaluated. In addition, the potential synergistic interaction between the phenolic components in OPE and the antimicrobial mechanisms underlying the synergistic interaction were characterized. The results show that ca. 25 mg GAE/g of extraction yields were achieved by the UAE of dry olive pomace. Based on the high-performance liquid chromatography (HPLC) analysis, diverse phenolic compounds such as gallic acid (GA), hydroxytyrosol (HT), and 4-hydroxyphenylacetic acid (4-HPA) were identified in OPE. OPE exhibited strong antimicrobial activities, and 0.2 mg GAE/mL of OPE achieved > 5 log reductions of Escherichia coli O157:H7 and Listeria innocua cells within 30 min of treatment. A 3D isobologram analysis demonstrated that OPE exhibited strong synergistic antimicrobial activities, compared to those of individual phenolic components (GA, HT, or 4-HPA), showing interaction index (γ) of 0.092 and 0.014 against E. coli O157:H7 and L. innocua, respectively (γ < 1: synergistic activity). Antimicrobial mechanism analyses revealed that phenolic components in OPE exerted strong synergistic activities through diverse modes of action, and increased levels of oxidative stress, membrane damage, and decreased levels of metabolic activities were observed in the OPE-treated bacterial cells. Conclusions: These findings demonstrate an approach for valorizing agricultural byproducts to develop plant byproduct-based antimicrobials with strong synergistic activities. Multiple modes of action of this byproduct extract may enable the control of diverse microbes in food and agriculture systems. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Chinese Institute of Food Science & Technology / Zhongguo Shipin Xuebao is the property of Journal of Chinese Institute of Food Science & Technology Periodical Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Synthetic polymer surfaces provide an excellent opportunity for developing materials with inherent antimicrobial and/or biocidal activity, therefore representing an answer to the increasing demand for antimicrobial active medical devices. So far, biologists and material scientists have identified a few features of bacterial cells that can be strategically exploited to make polymers inherently antimicrobial. One of these is represented by the introduction of cationic charges that act by killing or deactivating bacteria by interaction with the negatively charged parts of their cell envelope (lipopolysaccharides, peptidoglycan, and membrane lipids). Among the possible cationic functionalities, the antimicrobial activity of polymers with quaternary ammonium centers (QACs) has been widely used for both soluble macromolecules and non-soluble materials. Unfortunately, most information is still unknown on the biological mechanism of action of QACs, a fundamental requirement for designing polymers with higher antimicrobial efficiency and possibly very low toxicity. This mini-review focuses on surfaces based on synthetic polymers with inherently antimicrobial activity due to QACs. It will discuss their synthesis, their antimicrobial activity, and studies carried out so far on their mechanism of action. [ABSTRACT FROM AUTHOR]

Garlic has long been used as an antimicrobial spice and herbal remedy. The aim of this study was to isolate the antimicrobial agent in garlic water extract against Staphylococcus aureus (S. aureus) and investigate its antimicrobial mechanism. By an activity-guided separation, garlic lectin-derived peptides (GLDPs) with main molecular weight of around 12 kDa were extracted by liquid nitrogen grinding and identified with high bactericidal activity toward S. aureus, and the MIC was determined as 24.38 μg/mL. In-gel digestion-based proteomic analysis indicated that the peptide sequences were highly identical to the B strain of garlic protein lectin II. Structure analysis suggested that the secondary structure was strongly affected by lyophilization and thus resulted in the inactivation of GLDPs (P < 0.05). Mechanism study revealed that treatment of GLDPs resulted in cell membrane depolarization in a dose-dependent manner, and the disruptions of the cell wall and membrane integrities were observed under electric microscopies. GLDPs could successfully dock with cell wall component lipoteichoic acid (LTA) via van der Waals and conventional bonds in molecular docking analysis. These results suggested that GLDPs were responsible for the S. aureus targeting activity and might be promising candidates for antibiotic development against bacterial infection. [ABSTRACT FROM AUTHOR]

Endophytic fungi are extensive in plant tissues and involved in the defense against stress from harmful microbes. The interaction between pedicel endophytic fungi and nectar yeasts is critical for maintaining nectar homeostasis. This study used Camellia reticulata as the research subject. High-throughput sequencing revealed that the community composition of endophytic fungi in the pedicel is dominated by Ascomycota and Basidiomycota. Their abundance varies at different taxonomic levels, showing sample variability. In total, 27 endophytic fungal isolates were isolated and screened from the pedicel under laboratory conditions. They exhibited antagonistic effects against three nectar yeasts (Metschnikowia reukaufii, Cryptococcus laurentii, and Rhodotorula glutinis) and displayed morphological and physiological diversity. The isolates were classified into the phylum Ascomycota and further categorized into the genera Alternaria, Trichoderma, Fusarium, and Dactylaria. The endophytic fungus D23, which effectively antagonizes nectar yeasts, was identified as Alternaria alternata. This fungus produces various secondary metabolites, including antibiotics such as penicillin G, grandiomycin, and cephalosporin C. The metabolic pathways involved include the biosynthesis of plant secondary metabolites, phenylpropanoids, amino acids, nucleotides, and antibiotics. The endophytic fungal community in C. reticulata pedicel is rich and diverse, making it a valuable material for screening antagonistic strains. This study provides a theoretical basis for the antagonistic effects of endophytic fungal metabolites from the pedicel of C. reticulata against nectar yeasts, highlighting their significance in maintaining nectar stability and reproductive fitness in cross-pollinated plants.

IntroductionThe co-existence of S. mutans and C. albicans is frequently detected in root caries and early child caries and is reported to be associated with recurrent caries. The aim of this study was to investigate the effects of potassium iodide (KI) in combination with toluidine blue O-mediated antimicrobial photodynamic therapy (aPDT) on S. mutans and C. albicans mixed-species biofilm, as well as the antibiofilm mechanisms involved.MethodsMixed-species biofilm was constructed of S. mutans and C. albicans on dentin blocks. The antibiofilm efficacy, cytotoxicity and antibiofilm mechanism of KI in combination with aPDT were determined and evaluated.ResultsKI+TBO-aPDT treatment caused reduction in microorganism counts, metabolic activity, and biofilm biomass of mixed-species biofilm without inducing cytotoxicity to hDPCs (human dental pulp cells). Observations such increased ROS (reactive oxygen species) levels, impaired cell membrane function, cell apoptosis and reduced expression in several genes seem to be artifacts of reduced growth and general killing by KI+TBO-aPDT treatment.DiscussionThese data suggested that KI in combination with aPDT as an innovative approach to combat S. mutans and C. albicans biofilm, and thus as an optional treatment for caries.

This study investigated the effect of carvacrol stress on the physiological characteristics and transcriptome of Saccharomyces cerevisiae, a common spoilage yeast in fruit and vegetable products. The results showed that the minimum inhibitory concentration (MIC) of carvacrol on S. cerevisiae was 160 mg/mL. With the increase in temperature (20–40 ℃), the inhibitory effect of carvacrol (160 mg/mL) on yeast growth gradually increased. Environmental pH (3–4.5) had no significant impact on the inhibitory effect of carvacrol. However, the addition of fructose (20–80 g/L) significantly reduced the antifungal activity. Carvacrol treatment damaged the structure of the cell envelope of S. cerevisiae, increased the plasma membrane permeability and caused plasma membrane depolarization, resulting in leakage of intracellular substances, a decrease in mitochondrial membrane potential, an imbalance in intracellular Ca2＋ homeostasis, and a decrease in intracellular ATP content. The transcriptomic analysis revealed that carvacrol stress inhibited the biosynthesis of mitochondrial respiratory chain complexes, ATP synthase and mitochondrial ribosome (MR) proteins, which could block electron transport along the respiratory chain and interfere with life activities related to MR.

Copyright of Food & Fermentation Industries is the property of Food & Fermentation Industries and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Agricultural Science & Technology (1008-0864) is the property of Journal of Agricultural Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

BACKGROUND: Phytophthora capsici, a refractory and model oomycete plant pathogen, especially threatens multiple vegetable crops. A limited number of chemical pesticides play a vital role in controlling oomycete plant diseases. However, this approach often leads to excessive use of chemical agent, exacerbates environmental issues and more and more drug‐resistant strains of oomycete. Therefore, it is imperative to devise innovative solutions that can effectively address the infection of oomycete while maintaining high levels of environmental sustainability and low toxicity. RESULTS: In this study, g‐C3N4@ZnO heterostructure was synthesized and characterized. The g‐C3N4@ZnO showed higher toxicity on Phytophthora capsici than graphitic carbon nitride (g‐C3N4) nanosheets and zinc oxide (ZnO) nanoparticles in vitro and in vivo. Except the hyphal growth of Phytophthora capsici, their germination rate of spores, sporangium formation and number of spores were all suppressed by g‐C3N4@ZnO heterostructure. Furthermore, we found that this g‐C3N4@ZnO heterostructure has higher photocatalytic activity under visible light, which potentially enhanced the reactive oxygen species (ROS) mediated stress on Phytophthora capsici. Ultrastructural morphology, global changes of gene expression and weighted gene co‐expression network analysis all supported that the anti‐oomycete activity of g‐C3N4@ZnO was manifested in the destruction of membrane system and inhibition of multiple metabolisms of Phytophthora capsici under visible irradiation, which also could be attributed to the ROS and zinc ion (Zn2+) mediated stress. CONCLUSION: This works offers a novel oomycete disease management strategy by using g‐C3N4@ZnO, which were attributed to the ROS stress, destruction of membrane system and inhibition of multiple metabolisms. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Nanotechnology has been rapidly developing in the past decade, and metal nanomaterials have shown promising improvement in microbial control. Metal nanoparticles have been applied in medical settings for adequate disease spread control and to overcome the challenges of multidrug-resistant microorganisms. Recently, the demand for safe water supply has increased, requiring higher sanitation of the water treatment technology as well as being environmentally sustainable. However, the employed water disinfection technologies cannot meet the elevated demand due to limitations including chemical byproducts, immobility, energy consumption, etc. Metal nanomaterials are considered to be an alternative disinfection technology considering their high efficiency, mobility, and stability. A significant amount of research has been carried out on enhancing the antimicrobial efficiency of metal nanomaterials and determining the underlying antimicrobial mechanisms. This paper provides an overview of emerging metal nanomaterials development, including the synthesis method, material characteristics, disinfection performance, environmental factors, potential mechanism, limitations, and future opportunities in the water disinfection process. HIGHLIGHTS Antimicrobial mechanisms are governed by microbe–metal nanoparticles interactions.; Synthesis methods and material characteristics impact microbial control performance.; Demonstrations via experimental study and simulation support its applicability.; Nanoscale metal materials have multi-tasking ability versus conventional treatments.; Limitations of possible toxicity, cost, and manufacturing call for further research.;

Antibiotic abuses cause pathogen resistance to conventional antibiotics, threating public health globally. Antimicrobial peptides were considered as substitutes for antibiotic because of their broaden and rapid antibacterial activity. BmKbpp extracted from the Chinese scorpion Mesobuthus martensii Karsch inhibits the growth of gram-negative bacteria and fungi efficiently, while its efficacy for inhibiting the growth of the gram-positive Staphylococcus aureus was limited. Besides, how BmKbpp inhibits bacterial growth remains elusive thus far. In this study, a C-terminal hemagglutinin (HA) and 6×His (HA-6×His) tagged BmKbpp of three repeats (3×BmKbpp) was expressed in Chlamydomonas reinhardtii. The recombinant 3×BmKbpp-HA-6×His exhibited antibacterial activity against both gram-positive and gram-negative bacteria with a minimum inhibitory concentration between 20⁓200 µg/ml. The minimum bactericidal concentration ranged from 1 × MIC to 3 × MIC for 3×BmKbpp-HA-6×His. 3×BmKbpp-HA-6×His exhibited a good thermostability and resisted on pH shock and digestion of certain proteinases. It also displayed low cytotoxicity and hemolysis as tested on cell lines including HEK293, Vero, MDCK, and BHK-21. In addition, 3×BmKbpp-HA-6×His inhibits bacterial growth by effectively distorting bacterial cell membrane. Thus, C. reinhardtii -derived 3×BmKbpp-HA-6×His effectively inhibits bacterial growth, making it a promising antimicrobial peptide. [Display omitted] • A triple BmKbpp (3×BmKbpp) was stably expressed in Chlamydomonas reinhardtii. • 3×BmKbpp inhibits the growth of a wide spectrum of bacteria. • 3×BmKbpp was thermostable and tolerant of pH shock and certain proteinases. • 3×BmKbpp showed a low toxicity to mammalian and human cells. • 3×BmKbpp disrupted the bacterial cell membrane integrity. [ABSTRACT FROM AUTHOR]

Materials and methods: The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and hemolytic activity were determined by the microdilution method. The antimicrobial kinetics of MR-22 against E. coli were studied by growth curves and time-killing curves. The cytotoxicity of MR-22 was detected by the CCK-8 assay. The antimicrobial activity of MR-22 in salt, serum, heat and trypsin was determined by the microdilution method. The antimicrobial mechanism of MR-22 against drug-resistant E. coli was studied by Scanning Electron Microscope, laser confocal microscopy, and Flow Cytometry. The in vivo antibacterial activity of MR-22 was evaluated by the micemodel of peritonitis. Results and discussion: In this study, MR-22 is a new antimicrobial peptide with good activity that has demonstrated against MDR E. coli. The antimicrobial activity of MR-22 exhibited stability under conditions of high temperature, 10% FBS, and Ca2+. However, a decline of the activity was observed in the presence of Na+, serum, and trypsin. MR-22 had no significant cytotoxicity or hemolysis in vitro. SEM and fluorescent images revealed that MR-22 could disrupt the integrity of cell membrane. DCFH-DA indicated that MR-22 increased the content of reactive oxygen species, while it decreased the content of intracellular ATP. In mice model of peritonitis, MR-22 exhibited potent antibacterial activity in vivo. These results indicated that MR-22 is a potential drug candidate against drugresistant E. coli. [ABSTRACT FROM AUTHOR]

The marine peptide, American oyster defensin (AOD), is derived from Crassostrea virginica and exhibits a potent bactericidal effect. However, recombinant preparation has not been achieved due to the high charge and hydrophobicity. Although the traditional fusion tags such as Trx and SUMO shield the effects of target peptides on the host, their large molecular weight (12–20 kDa) leads to the yields lower than 20% of the fusion protein. In this study, a short and acidic fusion tag was employed with a compact structure of only 1 kDa. Following 72 h of induction in a 5 L fermenter, the supernatant exhibited a total protein concentration of 587 mg/L. The recombinant AOD was subsequently purified through affinity chromatography and enterokinase cleavage, resulting in the final yield of 216 mg/L and a purity exceeding 93%. The minimum inhibitory concentrations (MICs) of AOD against Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus galactis ranged from 4 to 8 μg/mL. Moreover, time-killing curves indicated that AOD achieved a bactericidal rate of 99.9% against the clinical strain S. epidermidis G-81 within 0.5 h at concentrations of 2× and 4× MIC. Additionally, the activity of AOD was unchanged after treatment with artificial gastric fluid and intestinal fluid for 4 h. Biocompatibility testing demonstrated that AOD, at a concentration of 128 μg/mL, exhibited a hemolysis rate of less than 0.5% and a cell survival rate of over 83%. Furthermore, AOD's in vivo therapeutic efficacy against mouse subcutaneous abscess revealed its capability to restrain bacterial proliferation and reduce bacterial load, surpassing that of antibiotic lincomycin. These findings indicate AOD's potential for clinical usage. [ABSTRACT FROM AUTHOR]

To counter the harmful impacts of agricultural chemicals on the environment and human health, there is an increasing demand for safe, eco-friendly, and potent plant-based biopesticides. In this study, we aimed to investigate the antimicrobial effects of ginger essential oil and selected volatile compounds (linalool, eugenol, citral, and cinnamaldehyde [CA]) against Fusarium oxysporum FOX-1. Minimum inhibitory concentrations (MICs) were determined using the mycelium growth inhibition method. The compound CA exhibited the most potent antifungal effect against F. oxysporum FOX-1 and was selected for further investigation. After treatment with CA at 1/2 MIC or MIC, the spore germination of F. oxysporum FOX-1 was significantly inhibited at 12 h. Furthermore, microscopic observation revealed that CA treatment resulted in the morphological degradation of F. oxysporum FOX-1. CA destroyed the cell membrane integrity of F. oxysporum FOX-1, increasing the relative conductivity and the leakage of intracellular protein, nucleic acids, and malondialdehyde, affecting the integrity and metabolism of the cell membrane. The effects were positively related to CA concentration. Additionally, in vivo experiments with rhizome sections showed that CA significantly reduced the pathogenicity of F. oxysporum FOX-1. Overall, these findings provide evidence for the potential of using ginger essential oil components as fungicides, offering a basis for future research to develop robust and eco-friendly plant-derived fungicides that serve as a sustainable means to reduce fungus-driven agricultural losses. [ABSTRACT FROM AUTHOR]

Since the Fourth Industrial Revolution, three-dimensional (3D) printing has become a game changer in manufacturing, particularly in bioengineering, integrating complex medical devices and tools with high precision, short operation times, and low cost. Antimicrobial materials are a promising alternative for combating the emergence of unforeseen illnesses and device-related infections. Natural antimicrobial materials, surface-treated biomaterials, and biomaterials incorporated with antimicrobial materials are extensively used to develop 3D-printed products. This review discusses the antimicrobial mechanisms of different materials by providing examples of the most commonly used antimicrobial materials in bioengineering and brief descriptions of their properties and biomedical applications. This review will help researchers to choose suitable antimicrobial agents for developing high-efficiency biomaterials for potential applications in medical devices, packaging materials, biomedical applications, and many more. [ABSTRACT FROM AUTHOR]

To explore how metal-binding antimicrobial peptide SIF4 kills foodborne Escherichia coli by targeting nucleic acid and protein in the cytoplasmic membrane without cytoplasmic membrane damage, the effect of SIF4 on intracellular nucleic acid biosynthesis was investigated, and fluorescence spectral analysis of the competition between SIF4 and ethidium bromide (EB) for binding to genomic DNA, ultraviolet (UV) spectral analysis of the interaction between SIF4 and genomic DNA, and the binding mode between SIF4 and genomic DNA were studied. Besides, the effect of SIF4 on intracellular protein biosynthesis was systematically evaluated. Results demonstrated that SIF4 could bind to E. coli genomic DNA through groove insertion and inhibit dose-dependently nucleic acid biosynthesis. Fluorescence spectral analysis showed that SIF4 could compete with EB for binding to genomic DNA through intercalation binding and electrostatic adsorption. UV spectroscopy showed that combination with SIF4 changed the molecular conformation of genomic DNA, but did not break its double strand structure. Circular dichroism (CD) spectroscopy showed that the base stacking force of genomic DNA was weakened, the double helix structure became loose, and the genomic DNA structure was changed from B to C configuration after combination with SIF4. In addition, SIF4 could significantly affect intracellular protein biosynthesis, and its inhibition effect was positively correlated with the treatment time and dose of SIF4. It is believed that SIF4 can enter the DNA groove through electrostatic adsorption or intercalation with genomic DNA, affecting DNA replication, RNA transcriptional biomass and protein translation to produce antimicrobial effect against Escherichia coli without cytoplasmic membrane damage. These results can provide support for the biocontrol of foodborne E. coli.

Foodborne pathogens pose a major challenge to food safety. Dihydroquercetin (DHQ) can be used as a food preservative; however, its antimicrobial mechanism is still unclear. This study found that DHQ had significant antimicrobial activity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Proteus vulgaris, Enterobacter aerogenes and Candida tropicalis (P < 0.05), the effect being most pronounced against E. coli. The antimicrobial mechanism against E. coli was investigated. Observation by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the DHQ-treated cells became distorted and exhibited phenomena such as adhesion, folding, plasmolysis, and the occurrence of vacuoles. DHQ resulted in a significant increase in the level of reactive oxygen species (ROS) inside the cell membrane as determined using a fluorescence probe. The determination of Annexin V-FITC/P kit showed that cell membrane permeability significantly increased with increasing DHQ concentration (P < 0.05) and cell membrane integrity was damaged. Cell membrane potential measurement by Rhodamine 123 staining revealed that DHQ caused cell membrane depolarization, leading to a significant reduction in membrane potential (P < 0.05). Moreover, DHQ caused intracellular Ca2+ leakage, which perturbed the growth, metabolism and functional activity of E. coli. DHQ interfered with the cell cycle of E. coli as determined using propidium iodide/ribonuclease (PI/RNase) staining buffer. These findings revealed that DHQ can inhibit E. coli growth mainly by acting on the cell membrane and consequently affecting the normal passage of cells.

This study aimed to systematically elaborate on the inhibitory mechanism of metal-binding antimicrobial peptide SIF4 on the respiratory and energy metabolism of Escherichia coli. By analyzing changes in the metabolic activity, individual and synergistic respiratory inhibition rate, cytoplasmic membrane ion channel ATPase and intracellular ATP level of E. coli after being treated with SIF4, the effects of SIF4 on the cell metabolic activity, respiratory metabolic pathway, cytoplasmic membrane ion channel ATPase and intracellular ATP biosynthesis were studied. Results showed that the metabolic activity of E. coli decreased significantly with increasing dose of SIF4 (P < 0.05), and decreased by 70.41% in the 2 × minimal inhibitory concentration (MIC) group compared with the control group. SIF4 had good inhibitory effect on the respiration of Escherichia coli, with an inhibition rate of (19.387 ± 0.168)% and (25.222 ± 0.326)% at MIC and 2 × MIC, respectively. The synergistic respiratory inhibition rate of SIF4 combined with iodoacetic acid was the lowest ((19.982 ± 0.133)%), indicating that SIF4 could exhibit high antimicrobial activity mainly by inhibiting the glycolysis pathway of E. coli. The activities of cytoplasmic membrane ion channel Na+K+-ATPase and Ca2+Mg2+-ATPase decreased after treatment with SIF4, and this effect was positively correlated with SIF4 dose and treatment time, but weaker than that of the positive control Triton X-100. As SIF4 dose and treatment time increased, the intracellular ATP concentration decreased significantly, and after 12 h, the intracellular ATP concentration in the 2 × MIC group was significantly lower than that in the control group but higher than that in the positive control group (P < 0.05). All results confirmed that SIF4 could exhibit high antimicrobial activity against E. coli by interfering with respiratory metabolism, weakening cytoplasmic membrane ion channel ATPase activity and inhibiting the biosynthesis of intracellular ATP, which can provide theoretical support for the biocontrol of foodborne E. coli.

Synthetic polymer surfaces provide an excellent opportunity for developing materials with inherent antimicrobial and/or biocidal activity, therefore representing an answer to the increasing demand for antimicrobial active medical devices. So far, biologists and material scientists have identified a few features of bacterial cells that can be strategically exploited to make polymers inherently antimicrobial. One of these is represented by the introduction of cationic charges that act by killing or deactivating bacteria by interaction with the negatively charged parts of their cell envelope (lipopolysaccharides, peptidoglycan, and membrane lipids). Among the possible cationic functionalities, the antimicrobial activity of polymers with quaternary ammonium centers (QACs) has been widely used for both soluble macromolecules and non-soluble materials. Unfortunately, most information is still unknown on the biological mechanism of action of QACs, a fundamental requirement for designing polymers with higher antimicrobial efficiency and possibly very low toxicity. This mini-review focuses on surfaces based on synthetic polymers with inherently antimicrobial activity due to QACs. It will discuss their synthesis, their antimicrobial activity, and studies carried out so far on their mechanism of action.

Penicillium expansum, a common spoilage organism in postharvest fruits, can cause fruit decay and deterioration and endanger human health. It is of great significance to investigate the antimicrobial mechanism of the antimicrobial peptide from Paenibacillus ehimensis on P. expansum spores. The antimicrobial activity of the antimicrobial peptide against P. expansum spores was determined by using the two-fold dilution method as well as measuring the time-killing curve. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to evaluate the effect of the antimicrobial peptide on the ultrastructure of P. expansum spores. The effects of the antimicrobial peptide on the cell membrane and reactive oxygen species (ROS) accumulation of P. expansum were analyzed by fluorescence probes. The results showed that the minimum inhibitory concentration (MIC) of the antimicrobial peptide against P. expansum spores was 3.5 AU/mL. The spore germination rate was significantly decreased by 28.30%, 84.57% and 100% by the antimicrobial peptide at concentrations of 0.5 MIC, 1 MIC and 2 MIC compared with the blank control (P < 0.05). After treatment with the antimicrobial peptide, the spores appeared seriously sunken, the intracellular contents were leaked out, and the morphology and structure were changed. The antimicrobial peptide damaged the cell wall of P. expansum, resulting in the leakage of alkaline phosphatase. The antimicrobial peptide depolarized the cell membrane potential in a dose-dependent manner, and increased the cell membrane permeability, leading to K+ leakage. The fluidity of the cell membrane was increased, which in turn resulted in a significant decrease in DPH fluorescence intensity (P < 0.05). The integrity of the cell membrane was damaged by the antimicrobial peptide, so the fluorescence intensity of SYTOX-Green and the contamination rate of PI were increased. Moreover, the antimicrobial peptide at 1 MIC and 2 MIC increased the fluorescence intensity of DCFH-DA significantly (P < 0.05) and resulted in ROS accumulation, which affected the physiology and metabolism of P. expansum spores. This study indicated that the target sites of the antimicrobial peptide against P. expansum spores were mainly the cell membrane and ROS metabolism.

This study aimed to investigate the inhibitory effects of three major flavonoids from the Hippophae rhamnoides subsp. yunnanensis berries on four pathogenic microorganisms. The antimicrobial activity of total flavonoids from Hippophae rhamnoides subsp. yunnanensis berries on Staphylococcus aureus, Escherichia coli, Bacillus subtilis and Candida albicans was firstly measured by filter paper method. Then, the total flavonoids compositions were identified by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and the main components were quantified by high performance liquid chromatography (HPLC). Finally, the Bradford method and the double dilution method were used to assess the antimicrobial effect of the three flavonoids. The results showed that the major flavonoid components of the Hippophae rhamnoides subsp. yunnanensis berries were isorhamnetin-3-O-glucoside-7-O-rhamnoside (Is-3-G-7-Rh), quercetin-3-O-rutinoside (Qu-3-R) and isorhamnetin-3-O-glucoside (Is-3-G), which with the contents of 38.43±0.85, 29.44±0.42 and 21.11±0.55 mg/g, respectively. The extract and its three main flavonoids had inhibitory effect on the four microorganisms. The inhibitory effects of Is-3-G-7-Rh and Is-3-G on the microorganisms were better than Qu-3-R and extract, and the results of protein detection showed that flavonoids induced antimicrobial death through intracellular protein efflux. This study can provide a scientific basis for the application of flavonoids in the berries of Hippophae rhamnoides for antimicrobial purposes.

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Bacterial antibiotic resistance, especially the emergence of multidrug-resistant (MDR) strains, urgently requires the development of effective treatment strategies. It is always of interest to delve into the mechanisms of resistance to current antibiotics and target them to promote the efficacy of existing antibiotics. In recent years, non-antibiotic compounds have played an important auxiliary role in improving the efficacy of antibiotics and promoting the treatment of drug-resistant bacteria. The combination of non-antibiotic compounds with antibiotics is considered a promising strategy against MDR bacteria. In this review, we first briefly summarize the main resistance mechanisms of current antibiotics. In addition, we propose several strategies to enhance antibiotic action based on resistance mechanisms. Then, the research progress of non-antibiotic compounds that can promote antibiotic-resistant bacteria through different mechanisms in recent years is also summarized. Finally, the development prospects and challenges of these non-antibiotic compounds in combination with antibiotics are discussed. [ABSTRACT FROM AUTHOR]

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To explore the mechanism of action of Bacillus velezensis against sweet cherry soft rot disease, the inhibitory effect of Bacillus velezensis KT against Rhizopus stolonifer LC-7 in vitro and in inoculated sweet cherry fruits, and the effect of B. velezensis KT on defense-related enzyme activities were investigated. Besides, the expression of genes related to secondary metabolite synthesis and biological control in B. velezensis KT during the interaction with R. stolonifer was also analyzed by transcriptomics. The results showed that the percentage inhibition of 1 × 109 CFU/mL B. velezensis KT suspension against mycelial growth of R. stolonifer LC-7 was 87.12%, and the percentage of spore germination and germ length of R. stolonifer LC-7 in the presence of B. velezensis KT were 21.54% and 11.45 μm, respectively. At 48 h after being treated with 1 × 109 CFU/mL B. velezensis KT suspension, the incidence of soft rot in cherry fruits was about 20% and was about 80% lower than that in the control group. B. velezensis KT suspension inhibited the activity of polyphenoloxidase (PPO) and lipoxidase (LOX), increased the activity of peroxidase (POD), phenylalanine ammonia lyase (PAL) chitinase (CHI) and β-1,3-glucanase (GLU), and improved disease resistance and antioxidant capacity in cherry fruits. It was observed by scanning electron microscopy that after co-cultured with B. velezensis KT, the morphology of the mycelia and spores of R. stolonifer LC-7 was distorted and malformed. Transcriptomic analysis showed that the expression of pksIJ in the biosynthetic gene cluster for antibiotic bacillaene and tuaAGE in the biosynthetic gene cluster for teichuronic acid were up-regulated, and the differentially expressed genes were mainly concentrated in ribonucleoprotein complex assembly, subunit assembly and ribosomal assembly during biological processes. The B. velezensis KT could directly inhibit R. stolonifer LC-7 probably through nutritional and spatial competition and secreting anti-bacterial substances and could also induce disease resistance in sweet cherry fruits. The results showed that B. velezensis KT had an obvious control effect on sweet cherry soft rot caused by R. stolonifer LC-7, making it a potential biocontrol agent.

The traditional synthesis of nano silver chloride involves chemical precipitation or physical methods. Due to the hazardous substances generated during the synthesis, it can cause environmental pollution. In this study, a green and facile method is described to biosynthesize nano-silver chloride with excellent antibacterial activity via in situ reduction of Ag + using the extract of Bacillus thuringiensis (Bt). Compared with previous reports, the minimal inhibition concentration (MIC) against Escherichia coli (E. coli) is 3.0 μg/mL, which is 2– to 800-fold higher than that of nano silver chloride. Subsequent in vitro studies involving agricultural bacteria such as Ralstonia solanacearum (R. solanacearum) revealed a 92.95% antibacterial rate when the concentration of nano-silver chloride was 2.0 μg/mL. Previous studies of antibacterial activity of nano-silver chloride focused more on the basic antibacterial properties without describing its antibacterial molecular mechanisms. The microscopic investigations and DNA damage experiments indicated that the nano-silver chloride adsorbed to the bacterial surface, leading to cell wall rupture, DNA damage, and cytoplasmic leakage. In addition, electron paramagnetic resonance (EPR) spectroscopy indicated the synthesis of reactive oxygen species (·OH, ·O2− and 1O2) in the bacteria. Our study provides evidence supporting the use of nano-silver chloride as an antibacterial agent in agriculture, and theoretical insight into the antibacterial mechanism thereof.

【Objective】By measuring a series of index changes of Pseudomonas syringae pv. Actinidiae (Psa) after treatment with benzothiazolinone aqueous emulsion, the antibacterial mechanism of benzothiazolinone aqueous emulsion against Psa was revealed, which would provide a theoretical basis for the control of kiwifruit ulcer disease with benzothiazolinone.【Method】Psa was treated with benzothiazolinone diluted 10 times (X10), benzothiazolinone stock solution (Y) and sterile water (CK). The enzymatic activities of catalase (CAT) and superoxide dismutase (SOD) were determined by using kits and the soluble protein content was determined by Coomassie Brilliant Blue staining. Changes in the cell membrane structure of Psa were observed by fluorescence microscopy and scanning electron microscopy and cell cycle assays were performed by flow cytometry.【Result】The study showed that Psa growth and reproduction were significantly inhibited by benzothiazolinone treatment, which shortened the logarithmic growth period of Psa, caused cell membrane rupture, cell contents leakage and increased cell death, and the final amount of mycobacteria was only 5.5% of the control. Psa had oxidative stress response to benzothiazolinone, and the enzyme activities of Psa were significantly increased after treatment, showing a trend of increasing first and then decreasing. After treatment of benzothiazolinone, CAT enzyme activity reached a peak of 118.795 U/mg at 10 h and SOD enzyme activity reached a peak of 1 060.452 U/mg at 4 h. Bacterial protein content of X10 and Y differed significantly at 12 h compared with the control, decreasing by 47.1% and 73.4%, respectively. With the increase of the concentration of benzothiazolinone, more G0G1 phase cells piled up and the percentage of cells increased from 30.27% in the control group to 45.23% in treatment group Y. The percentage of S phase cells decreased from 58.84% in the control group to 41.86% in treatment group Y. The G0G1 phase cells in treatment group Y were 56.8% higher than those in CK and 23.7% lower than those in CK in S phase.【Conclusion】Benzothiazolinone ruptures bacterial cell membranes, causes oxidative stress response in Psa, and inhibits Psa growth by inhibiting DNA synthesis in bacterial cells. It can effectively prevent and control bacterial ulcer disease of kiwifruit.

The overuse and misuse of traditional antimicrobial drugs have led to their weakened effectiveness and the emergence of pathogenic bacterial resistance. Consequently, there has been growing interest in alternative options such as antimicrobial peptides (AMPs) in the pharmaceutical industry. Microcin J25 (MccJ25) has gained significant attention for its potent inhibitory effect on a diverse range of pathogens. Its unique rotaxane structure provides exceptional stability against extreme thermal, pH, and protease degradation, including chymotrypsin, trypsin, and pepsin. Given its remarkable stability and diverse bioactivity, we aim to provide an overview of the physicochemical properties, the mechanism underlying its antimicrobial activity, and the critical functional residues of MccJ25. Additionally, we have summarized the latest strategies for the heterologous expression of MccJ25, and its potential medical use and other applications.

Staphylococcus aureus is a zoonotic opportunistic pathogen that represents a significant threat to public health. Previous studies have shown that tannic acid (TA) has an inhibitory effect on a variety of bacteria. In this study, the proteome and transcriptome of S. aureus were analyzed to comprehensively assess changes in genes and proteins induced by TA. Initial observations of morphological changes revealed that TA damaged the integrity of the cell membrane. Next, proteomic and genetic analyses showed that exposure to TA altered the expression levels of 651 differentially expressed proteins (DEPs, 283 upregulated and 368 downregulated) and 503 differentially expressed genes (DEGs, 191 upregulated and 312 downregulated). Analysis of the identified DEPs and DEGs suggested that TA damages the integrity of the cell envelope by decreasing the expression and protein abundance of enzymes involved in the synthesis of peptidoglycans, teichoic acids and fatty acids, such as murB, murQ, murG, fmhX and tagA. After treatment with TA, the assembly of ribosomes in S. aureus was severely impaired by significant reductions in available ribosome components, and thus protein synthesis was hindered. The levels of genes and proteins associated with amino acids and purine synthesis were remarkably decreased, which further reduced bacterial viability. In addition, ABC transporters, which are involved in amino acid and ion transport, were also badly affected. Our results reveal the molecular mechanisms underlying the effects of TA on S. aureus and provide a theoretical basis for the application of TA as an antibacterial chemotherapeutic agent. [ABSTRACT FROM AUTHOR]

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Plant flavonoids have attracted increasing attention as new antimicrobial agents or adjuvants. In our previous work, it was confirmed that the cell membrane is the major site of plant flavonoids acting on the Gram-positive bacteria, which likely involves the inhibition of the respiratory chain. Inspired by the similar structural and antioxidant characters of plant flavonoids to hydro-menaquinone (MKH2), we deduced that the quinone pool is probably a key target of plant flavonoids inhibiting Gram-positive bacteria. To verify this, twelve plant flavonoids with six structural subtypes were preliminarily selected, and their minimum inhibitory concentrations (MICs) against Gram-positive bacteria were predicted from the antimicrobial quantitative relationship of plant flavonoids to Gram-positive bacteria. The results showed they have different antimicrobial activities. After their MICs against Staphylococcus aureus were determined using the broth microdilution method, nine compounds with MICs ranging from 2 to 4096 μg/mL or more than 1024 μg/mL were eventually selected, and then their MICs against S. aureus were determined interfered with different concentrations of menaquinone−4 (MK−4) and the MKs extracted from S. aureus. The results showed that the greater the antibacterial activities of plant flavonoids were, the more greatly their antibacterial activities decreased along with the increase in the interfering concentrations of MK−4 (from 2 to 256 μg/mL) and the MK extract (from 4 to 512 μg/mL), while those with the MICs equal to or more than 512 μg/mL decreased a little or remained unchanged. In particular, under the interference of MK−4 (256 μg/mL) and the MK extract (512 μg/mL), the MICs of α-mangostin, a compound with the greatest inhibitory activity to S. aureus out of these twelve plant flavonoids, increased by 16 times and 8 to 16 times, respectively. Based on the above, it was proposed that the quinone pool is a key target of plant flavonoids inhibiting Gram-positive bacteria, and which likely involves multiple mechanisms including some enzyme and non-enzyme inhibitions. [ABSTRACT FROM AUTHOR]

Salmonoid cathelicidin (termed CATH_BRALE) is a fish-derived antimicrobial peptide (AMP) isolated from Brachymystax lenok. In this study, CATH_BRALE was expressed in Chlamydomonas reinhardtii as a format of three repeats (3×CATH_BRALE) attached with hemagglutinin (HA) and 6×His at its C-terminus, producing a recombinant peptide with a molecular weight of ∼18 kDa. The recombinant 3×CATH_BRALE-HA-6×His remains to be expressed stably in Chlamydomonas cells even after passaging continuously for five months and yields up to 0.21% of the total Chlamydomonas soluble proteins. 3×CATH_BRALE-HA-6×His showed broad-spectrum antibacterial activity against bacteria, with MIC values ranging from 40 to 50 µg/ml for Gram-negative bacteria and 30–40 µg/ml for Gram-positive bacteria. This recombinant peptide had strong thermostability and pH stability, and its antibacterial activity was rarely altered when temperature and pH are changed. It resisted to the digestion of several tested proteases to certain extents. Besides, 3×CATH_BRALE-HA-6×His is biologically safe as it did not hemolyze rat erythrocytes nor caused cytotoxicity on Vero, BHK21, HEK293, and MDBK cells. Its antibacterial action was achieved by penetrating the cell membrane to disrupt the membrane of the target bacterial cell. In sum, our data showed that C. reinhardtii can be used as a heterologous expression host to produce biologically active CATH_BRALE. [Display omitted] • A multimer termed 3 ×CATH_BRALE was stably expressed in Chlamydomonas reinhardtii. • C. reinhardtii-derived 3 ×CATH_BRALE showed a wide spectrum of antibacterial activity. • C. reinhardtii-derived 3 ×CATH_BRALE was tolerant of temperature, pH, and proteinases. • C. reinhardtii-derived 3 ×CATH_BRALE was not toxic to mammalian and human cells. • C. reinhardtii-derived 3 ×CATH_BRALE permeabilizes the bacterial cell membrane. [ABSTRACT FROM AUTHOR]

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Copyright of Journal of Henan University of Technology Natural Science Edition is the property of Henan University of Technology Journal Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Silver nanoparticles (AgNPs) and green synthesis have hegemony over their counterparts. This paper reviews- green synthesis mechanism, antimicrobial mechanism and, incorporation of AgNPs in textiles. Green synthesis is nontoxic, unlike chemical methods, cost-effective and precise, unlike physical techniques. In green synthesis, the reconversion of biomolecules from NADPH to NADP+releases electrons that reduce silver ions. Harmoniously, the functional groups of biomolecules act as polar-end to formulate steric stabilization. Green synthesized AgNPs are loaded on fabrics through different loading techniques such as pad-dry-cure, immersion, in situ, and others. This review also depicts the feasible mechanisms to explain the antimicrobial action of AgNPs. The antimicrobial activity of AgNPs is adequate for annihilating both gram-positive and gram-negative bacteria. The nanoparticle morphology depends on various constituents such as pH, temperature, concentration, and others. The acidic environment causes a larger nanoparticle size. Typically, the room temperature is enough for green synthesis. Whereas, high concentration of either plant extracts or metal precursors causes large nanoparticles. Hence, various shapes and sizes are possible by consolidating diverse concentrations of plants and metal precursors. Complicated connections may prevail amongst numerous concentrations, pH, temperature, and others with varying phytochemicals.

Bacillus amyloliquefaciens (B. amyloliquefaciens) is widely used as beneficial bacteria for biological control, and the main antimicrobial substances are lipopeptides. These lipopeptides have antimicrobial, anti-tumor, antiviral activities and other biological activities, and they are safe, broad-spectrum, efficient, non-toxic, and easily decomposed in the body. Therefore, B. amyloliquefaciens and its lipopeptide metabolites can be widely used in the biological control of crops, freshness and preservation of fruits and vegetables, as well as post-harvest microbial control, which have great prospects for development and application. This paper focuses on the types and biosynthesis of lipopeptides in B. amyloliquefaciens, the mechanism of microbial inhibition and their application prospects.