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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]

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]

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.

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.

In this study, Lactiplantibacillus plantarum SCA12, a producer of bacteriocins, derived from traditional Chinese fermented mustard greens was isolated. A novel L. plantarum SCA12-derived bacteriocin, LPsca12, was purified through a multi-step protocol involving macroporous adsorption resin, cation exchange, Sephadex G-25 column chromatography, and reverse-phase high-performance liquid chromatography (RP-HPLC). The molecular mass of LPsca12 was determined to be 1197.0 Da through matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis. The amino acid sequence of LPsca12 was characterized as GLFPSLVRGPR via liquid chromatography-tandem mass spectrometry (LC-MS/MS). Antimicrobial assessment was then carried out, identifying LPsca12 as a broad-spectrum bacteriocin active against both Gram-negative and Gram-positive bacteria, particularly Salmonella paratyphi A. It demonstrates excellent thermal stability (121 °C, 15 min) and maintains its antibacterial activity under acidic conditions (pH 2.0–6.5). Additionally, LPsca12 is sensitive to digestion by pepsin and trypsin. The antimicrobial action of LPsca12 involves compromising the cell membrane integrity, forming pores, and promoting leakage of intracellular contents, which dissipates both the membrane potential (ΔΨ) and cytoplasmic transmembrane pH gradient (ΔpH) of the target cells. These findings suggest that LPsca12 holds promise as a natural biopreservative in food processing. • A bacteriocin-producing Lactiplantibacillus plantarum SCA12 was isolated. • A novel L. plantarum SCA12-derived bacteriocin, LPsca12, was purified and identified. • LPsca12 has a broad spectrum of antibacterial activity, particularly against Salmonella paratyphi A. • LPsca12 exerts the antibacterial effect by destroying integrity of the cell membrane, dissipating the membrane potential (ΔΨ) of indicator cells and cytoplasmic transmembrane pH gradient (ΔpH). [ABSTRACT FROM AUTHOR]

Bacillus cereus is a typical spore-forming strain that can transform into dormant spores to resist unfavorable growth conditions. Among the microorganisms that cause spoilage of dairy products, B. cereus accounts for a large proportion. In this study, we evaluated the inhibitory activity of monolauroyl-galactosylglycerol (MLGG) on B. cereus spores and explored its inhibitory mechanism. The minimum inhibitory spore concentration (MISC) and the minimum sporicidal concentration (MSC) of MLGG against B. cereus spores were 0.313 mg/mL and 2.5 mg/mL, respectively. Scanning electron microscopy was used to observe the changes in spore morphology after MLGG treatment. It was found that low concentrations of MLGG caused irregular spore shape, with a few spores slightly ruptured and high concentrations of MLGG increased the degree of spore rupture, resulting in significant leakage of spore contents. By measuring the effect of MLGG on spore structure, it could be determined that MLGG damaged the coat of the spores and weakened the resistance of the spores, but did not affect the activity of cortical lyases. Therefore, spores could not resume growth even with the addition of exogenous lytic enzymes. After propidium iodide (PI) staining of the spores, flow cytometry analysis revealed that the positive area gradually increased, indicating that the permeability of the inner membrane of the spores was disrupted, leading to dipicolinic acid (DPA) release. The amount of DPA release was proportional to the MLGG concentration, and the growth rate of the spores decreased under hypertonic conditions. These findings indicated that MLGG inactivated spores primarily by damaging the inner membrane of the spores. • The inhibitory effect of MLGG on Bacillus cereus spores was concentration dependent. • Effect of MLGG on the structural layer of B. cereus spore was investigated. • MLGG inhibited B. cereus spore germination by damaging its inner membrane. • MLGG extended the shelf life of pasteurized milk contaminated by B. cereus cells and spores. [ABSTRACT FROM AUTHOR]

Fuzheng Touxie Jiedu Huayu Decoction (FTJHD) is a commonly used clinical formula that has been found effective in resisting multidrug resistance- Pseudomonas aeruginosa in previous in vivo and in vitro studies. To investigate the antimicrobial effects of FTJHD and its drug-containing serum alone or in combination with ceftazidime on difficult-to-treat multidrug resistance- P. aeruginosa (DTMDR- P. aeruginosa). The antibacterial effects of FTJHD and its drug-containing alone or in combination with ceftazidime against DTMDR- P. aeruginosa were examined by the tube dilution method and bacterial growth curves. The changes in the bacterial ultrastructure were examined by transmission electron microscopy. The biofilm formation ability of bacteria was examined by crystal violet staining and scanning electron microscopy. The expression of the MexAB-OprM efflux pump and quorum sensing system genes were validated through quantitative polymerase chain reaction. Molecular docking was used to evaluate the interaction between active components and the MexAB-OprM efflux pump. FTJHD-containing serums at 1-, 2-, 4-, and 8-fold concentrations reduced the minimal inhibitory concentration (MIC) of ceftazidime against DTMDR- P. aeruginosa from 128 μg/mL to 64 μg/mL. Sub-inhibitory concentrations of ceftazidime in combination with FTJHD and FTJHD-containing serum prolonged the lag period of bacterial growth and reduced bacterial numbers. Additionally, 1/2 MIC of ceftazidime combined with FTJHD-containing serum significantly inhibited the activity of the MexAB-OprM efflux pump and quorum sensing system, thus reducing biofilm formation while causing more severe damage to the bacteria. Molecular docking revealed a strong affinity of quercetin, baicalein, luteolin, kaempferol, and β-sitosterol for the efflux pump regulatory proteins OprM and MexR. FTJHD can exert synergistic anti-DTMDR- P. aeruginosa effects with ceftazidime by inhibiting biofilm formation mediated by the MexAB-OprM efflux pump and quorum sensing. Fig. 9. Mechanism of Fuzheng Touxie Jiedu Huayu Decoction (FTJHD) inhibiting DTMDR-P. aeruginosa resistance. [Display omitted] • Fuzheng Touxie Jiedu Huayu Decoction (FTJHD) has a prominent efficacy in drug-resistant bacterial pneumonia. • FTJHD can enhance the antibacterial effect of ceftazidime. • FTJHD can inhibit the MexAB-OprM efflux pump and quorum sensing system of Pseudomonas aeruginosa. • FTJHD can inhibit the biofilm formation of pseudomonas aeruginosa. • FTJHD has the potential to be used as an efflux pump inhibitor. [ABSTRACT FROM AUTHOR]

Shewanella putrefaciens and Listeria monocytogenes are concerned by scientists and consumers due to their ability to produce dense biofilms to contaminate and cause food spoilage. The object of this study was to investigate the antimicrobial and anti-biofilm activities of octyl gallate (OG) against the two food-related bacteria. Results showed that the antimicrobial activities of OG were in a dose-dependent manner and the minimum inhibitory concentration (MIC) of S. putrefaciens and L. monocytogenes were 0.2 mmol/L and 0.1 mmol/L, respectively. OG can rapidly penetrate the bacteria and produce reactive oxygen species (ROS). Then, OG and ROS can lead to membrane damage and cell rupture, causing DNA and protein leakage. Our data also strongly suggested that OG not only can inhibit biofilms formation, but also eradicate the performed biofilms. Furthermore, it was shown that OG, as an additive, has great potential in antimicrobial application to prolong the shelf life of large yellow croakers. These prove that OG can combat bacteria and eradicate biofilm against S. putrefaciens and L. monocytogenes. • Octyl gallate (OG) can lead to membrane disruption and then bacterial lysis. • The cellular functions were inhibited by OG with reactive oxygen species (ROS) generation. • OG not only can inhibit biofilms formation, but also eradicate the performed biofilms. • OG can be applied as an attractive antibacterial additive to prolong the shelf life of large yellow croakers. [ABSTRACT FROM AUTHOR]

Antimicrobial packaging films are an effective means to avoid food infections. PVA has good film-forming and mechanical properties, but its water resistance and antimicrobial properties are insufficient. In this study, a rod-shaped Ag-MOF with photocatalytic properties was synthesized as an antimicrobial agent by a hydrothermal method using citrate esterified PVA as a film-forming substrate. The MICs of Ag-MOF against Escherichia coli and Staphylococcus aureus were 16 μg/mL and 32 μg/mL, respectively, and it had good biocompatibility. Under blue light irradiation, Ag-MOF induced the production of ROS, which increased the inhibition rate by more than 83.78%. The antimicrobial mechanism experiments showed that it caused irreversible damage to the bacterial cell membrane through the synergistic effect of Ag+ and ROS. The best mechanical properties of the films were obtained at 3% citric acid content, with the water vapor transmission rate, water solubility and swelling rate reduced by 0.19 g·mm·m−2·h−1·kPa−1, 65.33% and 11.26%, respectively. The antimicrobial rate of the composite film could reach more than 98% by adding only 1 MIC of Ag-MOF. In conclusion, photocatalytic antimicrobial agents have great potential for application in food packaging. [Display omitted] • MOF structure acts as a reservoir of Ag. • Blue light-induced the production of reactive oxygen species. • Crosslinking of citric acid (tricarboxylic acid) with polyvinyl alcohol esterification. • CA3 film with high transparency and good water-blocking properties. • Synergistic antimicrobial effect of ROS, mechanical damage and Ag+. [ABSTRACT FROM AUTHOR]

The synergistic mechanisms of ultrasound combined plasma-activated water (US-PAW) against Listeria innocua were investigated with the intention of crayfish disinfection. US and PAW showed a significantly synergistic effect against L. innocua at 7 min. Specifically, no significant change was observed in the CK (sterile water) and US treatment groups as the duration of treatment increased. At 7 min, the reduction of L. innocua achieved by US-PAW treatment was 4.49 Log CFU/mL, which was significantly higher (p < 0.05) than the reduction for PAW treatment (2.46 Log CFU/mL). Furthermore, the Weibull model demonstrated superior efficacy in fitting the kinetic inactivation curves of L. innocua throughout the US, PAW, and US-PAW treatments. In addition, PAW disrupted the morphology of L. innocua and increased the electrical conductivity of the bacterial suspension, accelerated leakage of proteins and nucleic acids from cells and increased the intracellular reactive oxygen species content, which was further promoted by US-PAW. The molecular mechanisms underlying these phenotypic changes were investigated using untargeted metabolomics. The results indicated that US exacerbated the destruction of PAW on the nucleotide, glycerolipid, peptidoglycan and amino acids metabolism, further affecting the metabolism of various substances and energy in cells, ultimately leading to cell death. Besides, US-PAW showed significant antibacterial effects on L. innocua in crayfish with minor effects on the sensory characteristics. These findings provided theoretical support for the application of US-PAW in crayfish disinfection. [Display omitted] • US enhanced the inhibition rates of PAW against L. innocua from 26 % to 47 % at 7 min. • US mainly strengthened the nucleotide metabolic disorder of PAW on L. innocua. • US enhanced PAW disruption of the L. innocua cell membranes and morphology. • US-PAW had a positive impact on the sensory characteristics of crayfish. [ABSTRACT FROM AUTHOR]

Multidrug-resistant (MDR) Gram-negative bacteria infections have gradually become a more serious health problem recently, and antibacterial drugs are urgently needed to tackle MDR Gram-negative bacteria. Herein, we synthesized a series of quaternary ammonium salt derivatives of hyperbranched polylysine (HPL- Cm - n ) with different alkyl chain lengths ( m = 4, 8, 12, 16) and grafting ratios ( n = 5.8-21.0) of alkyl quaternary ammonium salts ( Cm ). HPL- Cm - n s exhibited excellent antibacterial activities against drug-sensitive E. coli and P. aeruginosa , and specifically, HPL-C12- n s were also highly active against MDR E. coli and P. aeruginosa . The cytotoxicity and hemolytic activity of HPL- Cm - n s increased with the increase in the alkyl chain length and the grafting ratio of Cm . The killing study proved that HPL-C12-9.5 had fast killing kinetics and was bactericidal toward both drug-sensitive and MDR E. coli . The mechanistic studies showed that, similar to hyperbranched polylysine (HPL), HPL-C12-9.5 killed bacteria by disrupting the cell membranes and causing leakage of the cytoplasmic contents. HPL-C12- n s might have potential as an antibacterial agent to combat MDR Gram-negative bacteria.

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., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Li, Huang, Du, Wang, Cai and Huang.)

Copper-based nanomaterials are effective alternatives to traditional pesticides due to their antibacterial properties. However, the high cost and low dispersity limit their application. In this study, we synthesized cost-effective, eco-friendly, and stable chitosan-copper hybrid nanoflowers (CS-Cu HNFs) through facile self-assembly to manage agricultural diseases caused by the fungal pathogen ( Rhizoctonia solani ). The results show that CS-Cu HNFs, which utilized chitosan and copper phosphate as primary scaffolds, were formed via a series of nucleation, aggregation, self-assembly, and anisotropic growth processes. 200 mg/L CS-Cu HNFs exhibited an excellent inhibitory effect on R. solani , which was 6.11 times that of CuO nanoparticles, despite CS-Cu HNFs containing only 45% of Cu as that in CuO nanoparticles. Additionally, CS-Cu HNFs significantly reduced R. solani infection in various crops and displayed broad-spectrum antibacterial activity. This research provides new insights into the preparation and application of organic-inorganic hybrid nanoflowers as nanopesticides.

Rhamnolipids, a major category of glycolipid biosurfactant, have recently gained enormous attention in medical field because of their relevance as effective antibacterial agents against a wide variety of pathogenic bacteria. Our previous studies have shown that rhamnolipids from an environmental isolate of Pseudomonas aeruginosa UKMP14T possess antibacterial, anti-adhesive and anti-biofilm activity against multidrug-resistant ESKAPE (Enterococcus faecium , Staphylococcus aureus , Klebsiella pneumoniae , Acinetobacter baumannii , Pseudomonas aeruginosa and Enterobacter sp.) pathogens. However, the mechanism of their antibacterial action remains unclear. Thus, this study aimed to elucidate the mechanism of the antibacterial action of P. aeruginosa UKMP14T rhamnolipids by studying the changes in cells of one of the ESKAPE pathogens, Acinetobacter baumannii , which is the most difficult strain to kill. Results revealed that rhamnolipid treatment rendered A. baumannii cells more hydrophobic as evaluated through contact angle measurements. It also induced the release of cellular proteins measuring 510 μg/mL at a rhamnolipid concentration of 1000 μg/mL. In addition, rhamnolipids were found to be bactericidal in their action as they could permeate the inner membranes, leading to a leak-out of nucleotides. More than 50 % of the cells were found to be killed upon 1000 μg/mL rhamnolipid treatment as observed through fluorescence microscopy. Other cellular changes such as irregular shape and size, membrane perturbations, clumping, shrinkage and physical damage were clearly visible in SEM, FESEM and laser micrographs. Furthermore, rhamnolipid treatment inhibited the levels of acyl-homoserine lactones (AHLs) in A. baumannii , which are vital for their biofilm formation and virulence. The obtained results indicate that P. aeruginosa UKMP14T rhamnolipids target outer and inner bacterial membranes through permeation, including physical damage to the cells, leading to cell leakage. Furthermore, AHL inhibition appears to be the mechanism behind their anti-biofilm action. All these observations can be correlated to rhamnolipids' antibacterial effect against A. baumannii. • Rhamnolipids are effective antibacterial agents. • Pseudomonas aeruginosa UKMP14T rhamnolipids are antibacterial against multidrug-resistant bacteria. • Rhamnolipids are bactericidal in their action against Acinetobacter baumannii. • Rhamnolipids damage the cellular membranes. [ABSTRACT FROM AUTHOR]

Bacillus cereus , a food-borne pathogen, threatens human health and food safety. The quest for biologically active substances from natural sources acting as antimicrobial agents for the replacement of antibiotics and chemical additives has received increasing attention. In this study, the antimicrobial mechanism of morusin against B. cereus was outlined, as well as its function as a food supplement to extend the shelf-life of skimmed milk was assessed. Our findings demonstrated that the minimum inhibitory concentration (MIC) value of morusin against B. cereus was 2.25 μg/mL, inhibiting biofilm formation and reducing intracellular ATP and membrane depolarization by disturbing the permeability of the B. cereus cytoplasmic membrane. Damage or collapse of B. cereus cell membranes produced by morusin was identified using the field gun scanning electron microscope (FEG-SEM). Transcriptomic assessment indicated that the two-component system of B. cereus (narG , narH , narI , phoP , phoR , motA) responded positively to morusin within an adverse environment. Moreover, several genes associated with cell membrane and cell wall generation (murA , murB , ddlB) and amino acid metabolism (argF , argH , BCN_RS02850) were significantly downregulated, potentially accelerating the death of B. cereus. In addition, metabolomic investigation suggested that morusin restricted pyruvate metabolism, cysteine and methionine metabolic pathways, and disturbed the intracellular amino acid metabolism of B. cereus. Ultimately, 4.5 μg/mL of morusin was determined to significantly inhibit the growth of B. cereus within skimmed milk. Overall, morusin can be utilized as a natural antimicrobial agent for regulating B. cereus contamination in skimmed milk. [Display omitted] • Morusin exhibited antibacterial activity against Bacillus cereus. • Morusin destroyed the cell membrane structure of Bacillus cereus. • The addition of 4.5 μg/mL morusin can extend the shelf life of skimmed milk. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes is a food-borne pathogen that seriously threatens human health. We analyzed the antibacterial activity and mechanism of δ-cadinene against L. monocytogenes. The effect of δ-cadinene on L. monocytogenes gene expression was investigated using RNA sequencing. δ-Cadinene inhibited L. monocytogenes growth at a minimum inhibitory concentration of 5 μL/mL and a minimum bactericidal concentration of 10 μL/mL. In addition, δ-cadinene suppressed biofilm formation, altered cell morphology, and damaged the cell membrane of L. monocytogenes , enhancing membrane permeability and affecting the membrane potential. Of note, "plasma membrane" and "membrane" were the most significantly enriched Gene Ontology terms. Sixteen differentially expressed genes were strongly correlated with biofilm formation, protein and nucleic acid leakage, and membrane potential. The growth of L. monocytogenes in milk was effectively controlled with 10 μL/mL δ-cadinene, especially at 4 °C. In conclusion, treatment with δ-cadinene could be a potential strategy for controlling the contamination of foods by L. monocytogenes. • The sesquiterpene δ-cadinene exerts antibacterial activity against Listeria monocytogenes. • δ-Cadinene suppresses L. monocytogenes biofilm formation. • δ-Cadinene disrupts L. monocytogenes cell membrane integrity and permeability. • RNA-sequencing reveals the antibacterial mechanism at the level of gene expression. • Paved the way for the application of δ-cadinene in food preservation. [ABSTRACT FROM AUTHOR]

Avian eggshells exhibit excellent antimicrobial properties. In this study, we conducted simulation experiments to explore the defense mechanisms of eggshell membranes with regards to their physical features. We developed a mathematical model for the movement of microorganisms and estimated their penetration ratio into eggshell membranes based on several factors, including membrane thickness, microbial size, directional drift, and attachment probability to membrane fibers. These results not only suggest that an eggshell membrane with multiple layers and low porosity indicates high antimicrobial performance, but also imply that the fibrous network structure of the membrane might contribute to effective defense. Our simulation results aligned with experimental findings, specifically in measuring the penetration time of Escherichia coli through the eggshell membrane. We briefly discuss the significance and limitations of this pilot study, as well as the potential for these results, to serve as a foundation for the development of antimicrobial materials. [ABSTRACT FROM AUTHOR]

Bacterial infection has always posed a severe threat to public health. Gold nanoparticles (Au NPs) exhibit exceptional biocompatibility and hold immense potential in biomedical applications. However, their antibacterial effectiveness is currently unsatisfactory. Herein, a chiral antibacterial agent with high stability was prepared by the modification of Au NPs with d-cysteine with the assistance of polyethylene glycol (PEG). The as-synthesized d-cysteine/PEG-Au NPs (D/P-Au NPs) exhibited a stronger (99.5-99.9%) and more stable (at least 14 days) antibacterial performance against Gram-negative ( Escherichia coli and Listeria monocytogenes ) and Gram-positive ( Salmonella enteritidis and Staphylococcus aureus ) bacteria, compared with other groups. The analysis of the antibacterial mechanism revealed that the D/P-Au NPs mainly affected the assembly of ribosomes, the biosynthesis of amino acids and proteins, as well as the DNA replication and mismatch repair, ultimately leading to bacterial death, which is significantly different from the mechanism of reactive oxygen species-activated metallic antibacterial NPs. In particular, the D/P-Au NPs were shown to effectively accelerate the healing of S. aureus -infected wounds in mice to a rate comparable to or slightly higher than that of vancomycin. This work provides a novel approach to effectively design chiral antibacterial agents for bacterial infection treatment.

N-chloro-N-fluorobenzenesulfonylamide (CFBSA), was a novel chlorinating reagent, which exhibits potential antibacterial activities. In this study, CFBSA was confirmed as a wide-broad antimicrobial and bactericidal drug against different gram-negative bacteria, gram-positive bacteria and fungi, while it was found to have low cytotoxicity for eukaryotic cells. In addition, microorganism morphology assay and oxidative stress test was used to determine the antimicrobial mechanisms of CFBSA. According to the results, CFBSA probably had a target on cell membrane and killed microorganism by disrupting its cell membrane. Then, CFBSA was first combined with poly(L-lactide-co-caprolactone) (PLCL)/SF via electrospinning and applied in wound dressings. The characterization of different PLCL/SF of CFBSA-loaded nanofibrous mats was investigated by SEM, water contact angle, Fourier transform infrared spectroscopy, cell compatibility and antimicrobial test. CFBSA-loaded PLCL/SF nanofibrous mats showed excellent antimicrobial activities. In order to balance of the biocompatibility and antibacterial efficiency, SP-2.5 was selected as the ideal loading concentration for further application of CFBSA-loaded PLCL/SF. In conclusion, the electrospun CFBSA-loaded PLCL/SF nanofibrous mat with its broad-spectrum antimicrobial and bactericidal activity and good biocompatibility showed enormous potential for wound dressing., (© 2024 IOP Publishing Ltd.)

To develop novel bacterial biofilm inhibiting agents, a series of 1,3,4-thiadiazole derivatives containing sulfonylpiperazine structures were designed, synthesized, and characterized using 1 H nuclear magnetic resonance ( 1 H NMR), 13 C nuclear magnetic resonance ( 13 C NMR), and high-resolution mass spectrometry. Meanwhile, their biological activities were evaluated, and the ensuing structure-activity relationships were discussed. The bioassay results showed the substantial antimicrobial efficacy exhibited by most of the compounds. Among them, compound A 24 demonstrated a strong efficacy with an EC 50 value of 7.8 μg/mL in vitro against the Xanthomonas oryzae pv. oryzicola (Xoc) pathogen, surpassing commercial agents thiodiazole copper (31.8 μg/mL) and bismerthiazol (43.3 μg/mL). Mechanistic investigations into its anti-Xoc properties revealed that compound A 24 operates by increasing the permeability of bacterial cell membranes, inhibiting biofilm formation and cell motility, and inducing morphological changes in bacterial cells. Importantly, in vivo tests showed its excellent protective and curative effects on rice bacterial leaf streak. Besides, molecular docking showed that the hydrophobic effect and hydrogen-bond interactions are key factors between the binding of A 24 and AvrRxo1-ORF1. Therefore, these results suggest the utilization of 1,3,4-thiadiazole derivatives containing sulfonylpiperazine structures as a bacterial biofilm inhibiting agent, warranting further exploration in the realm of agrochemical development., (© 2024 Wiley-VHCA AG, Zurich, Switzerland.)

Listeria monocytogenes is a foodborne bacterial pathogen that seriously threatens dairy product safety and human health, hence effective and available antibacterial agents are urgently needed. This study aims to investigate the antibacterial mechanism of a recombinant enterocin CHQS against L. monocytogenes and its antibacterial effect on pasteurized milk. The minimum inhibitory concentration (MIC) of CHQS was 0.5 μg/mL in both TSB medium and tenfold diluted pasteurized milk. The anti- L. monocytogenes rate of 2 h reached 99.94% with the treatment of the 2 MIC of CHQS in the diluted pasteurized milk. CHQS led to the massive release of proteins and nucleic acids and the significant increase in propidium iodide (PI) uptake, indicating that integrity and permeability of the cell membrane were destroyed. The cell membrane and structure of L. monocytogenes were severely disrupted by observing with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Intracellular reactive oxygen species (ROS) level was increased to 2.18-fold with the 2 MIC CHQS treatment. CHQS at sub-MICs inhibited the biofilm formation and motility of L. monocytogenes in a concentration-dependent manner. In MIC treatment group, the number of L. monocytogenes was 4.55 log 10 CFU/mL fewer than the control group and the bacterial abundance of L. monocytogenes remained a low level (0.22%) on the 12th day of storage at 4 °C in pasteurized milk. The study suggested the antibacterial mechanism of CHQS and its application potentiality in pasteurized milk. • The antibacterial mechanism of a recombinant enterocin CHQS against L. monocytogenes was investigated. • The antibacterial effect of CHQS on pasteurized milk was explored. • CHQS inhibited L. monocytogenes growth by disrupting the integrity and permeability of cell membranes. • CHQS can stimulate ROS generation and inhibit the motility and biofilm formation of L. monocytogenes. [ABSTRACT FROM AUTHOR]

By incorporating Zn into NiCo 2 O 4 , a rod-shaped Zn/NiCo 2 O 4 nanocomposite with an increased number of active sites on its surface was constructed in this study. The antimicrobial activity of this material against Escherichia coli was investigated, revealing a significant improvement compared to pure NiCo 2 O 4 under both dark conditions and light irradiation, with an increase in the antimicrobial rate from 45.71 % to 99.06 % and 51.48 %–88.13 % at a dosage of 0.1 mg/mL, respectively. This enhancement can be attributed to the increased formation of oxygen vacancies on the material surface after Zn doping. These vacancies lead to greater exposure of high-valence metal active sites and enhanced redox reactions. Additionally, introducing defects improves the energy level distribution, resulting in a stronger reduction ability at the conduction band position. Consequently, the generation of reactive oxygen species increases, enhancing both contact sterilization and photocatalytic sterilization. Furthermore, Zn/NiCo 2 O 4 demonstrated excellent cyclic stability, maintaining an antibacterial rate of up to 95.13 % after five cycles of antibacterial activity. In conclusion, the use of this material is not restricted to light conditions, and the addition of Zn greatly enhances its antibacterial effectiveness. This study demonstrates that Zn/NiCo 2 O 4 has significant potential for applications in the field of antibacterial materials. • Zinc-doped NiCo 2 O 4 materials showed significantly enhanced antibacterial activity against Escherichia coli. • Increased amount of nickel(III) and oxygen vacancies on the material surface from zinc doping improves reactivity. • In contrast to conventional catalytic oxidizing antimicrobials, the antimicrobial effect of this material is unaffected by light and has good cyclic stability. [ABSTRACT FROM AUTHOR]

Lactic acid bacteria (LAB) exopolysaccharide (EPS) has good water absorption, high viscosity, good stability, so it was widely used in probiotics fields. In this study, EPS-producing LAB strain Lactiplantibacillus plantarum HDL-03 was isolated and identified. Moreover, the HDL-03 EPS was used as a stabilizer and mixed with AgNO 3 to synthesize a novel nanoparticle AgNPs whose structure and properties were explored. The monosaccharide composition and molecular weight indicated that HDL-03 EPS was a heteropolysaccharide composed of mannose and glucose. Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) spectroscopy analysis and methylation results jointly proved it was a heteropolysaccharide containing 1,3-Manp and 1,6-Glcp. The X-Ray diffraction (XRD) results showed that this EPS has an amorphous structure, while the synthesized AgNPs have crystalline properties. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results indicated EPS had a smooth and dense sheet structure, while the surface of AgNPs became rougher and large holes appeared after synthesis. Zeta particle size analysis suggested that the particle size of AgNPs increased by 36.63 nm compared to HDL-03 EPS. FT-IR analysis exhibited that the position of the characteristic peaks of AgNPs changed. The OH moving from a wavelength of 3388.49 cm -1 to a wavelength of 3316.79 cm -1 and telescopic vibration peak changed from 1356.07 cm -1 to 1344.22 cm -1 . A plate inhibition test revealed the effect of different concentrations of EPS and AgNO 3 synthesized AgNPs on the diameter of inhibition circle produced by the indicator bacteria Escherichia coli and Staphylococcus aureus. Furthermore, AgNPs were applied to the indicator bacteria, which the minimum inhibitory concentration (MIC), time-inhibitory curve, and changes in extracellular conductivity, nucleic acids, proteins, ATP, and lactate dehydrogenase (LDH) levels were determined. The AgNPs inhibited the growth of E. coli and S. aureus and exhibited outstanding antimicrobial properties. With the increase of treatment time, the degree of cell membrane damage increased, the permeability enhanced, and the intracellular substances leaked. These results indicate that HDL-03 EPS has good potential for applications in the production of food packaging, antimicrobials, catheters, textiles and coatings., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

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-C 3 N 4 @ZnO heterostructure was synthesized and characterized. The g-C 3 N 4 @ZnO showed higher toxicity on Phytophthora capsici than graphitic carbon nitride (g-C 3 N 4 ) 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-C 3 N 4 @ZnO heterostructure. Furthermore, we found that this g-C 3 N 4 @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-C 3 N 4 @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 (Zn 2+ ) mediated stress., Conclusion: This works offers a novel oomycete disease management strategy by using g-C 3 N 4 @ZnO, which were attributed to the ROS stress, destruction of membrane system and inhibition of multiple metabolisms. © 2023 Society of Chemical Industry., (© 2023 Society of Chemical Industry.)

The increasing severity of problems posed by drug-resistant pathogens has compelled researchers to explore innovative approaches for infection prevention. Among these strategies, conjugation methods stand out for their convenience and high efficacy. In this study, multiple covalent conjugates were synthesized, incorporating the natural antimicrobial peptide epsilon-poly-l-lysine (EPL) and two commonly used β-lactam antibiotics: penicillin G or ampicillin. Enhanced antimicrobial efficacy against typical Gram-negative pathogens, along with faster kill kinetics compared to combination approaches, was demonstrated by the EPL-Ampicillin covalent conjugates. Their antimicrobial mechanism was also substantiated through SEM and fluorescence tests in this work, confirming the inheritance of membrane-disrupting properties from EPL. Furthermore, the excellent biocompatibility of the raw materials was reserved in the covalent conjugates. This simplified conjugation method holds promise for the development of infection therapeutic drugs and potentially restores the sensitivity of conventional antibiotics to drug-resistant pathogens by introducing membrane-disrupting mechanisms.

The increasing emergence of multidrug-resistant pathogens and development of biopreservatives in food industries has increased the demand of novel and safe antimicrobial agents. In this study, a marine bacterial strain Bacillus licheniformis M1 was isolated and exhibited obvious antimicrobial activities against foodborne pathogens, especially against methicillin-resistant Staphylococcus aureus . The antimicrobial agent was purified and identified as a novel antimicrobial peptide, which was designated as bacipeptin, and the corresponding mechanism was further investigated by electron microscopy observation and transcriptomic analysis with biochemical validation. The results showed that bacipeptin could reduce the virulence of methicillin-resistant Staphylococcus aureus and exerted its antimicrobial activity by interfering with histidine metabolism, inducing the accumulation of reactive oxygen species and down-regulating genes related to Na + /H + antiporter and the cell wall, thus causing damage to the cell wall and membrane. Overall, our study provides a novel natural product against foodborne pathogens and discloses the corresponding action mechanism.

As antibiotic-resistant bacteria and genes continue to emerge, the identification of effective alternatives to traditional antibiotics has become a pressing issue. Antimicrobial peptides are favored for their safety, low residue, and low resistance properties, and their unique antimicrobial mechanisms show significant potential in combating antibiotic resistance. However, the high production cost and weak activity of antimicrobial peptides limit their application. Moreover, traditional laboratory methods for identifying and designing new antimicrobial peptides are time-consuming and labor-intensive, hindering their development. Currently, novel technologies, such as artificial intelligence (AI) are being employed to develop and design new antimicrobial peptide resources, offering new opportunities for the advancement of antimicrobial peptides. This article summarizes the basic characteristics and antimicrobial mechanisms of antimicrobial peptides, as well as their advantages and limitations, and explores the application of AI in antimicrobial peptides prediction amd design. This highlights the crucial role of AI in enhancing the efficiency of antimicrobial peptide research and provides a reference for antimicrobial drug development. [Display omitted] • Antimicrobial peptides have the potential to replace antibiotics. • Antimicrobial peptides have multiple antimicrobial mechanisms. • Application of artificial intelligence improves antimicrobial peptides development. [ABSTRACT FROM AUTHOR]