The antibacterial activity and modes of LI-F type antimicrobial peptides against Bacillus cereus in vitro

Assessment of Bacillus cereus spoilage potential and the antibacterial mechanism of Larimichthys crocea-derived peptide SDH73 against Bacillus cereus

This study investigated the spoilage bacteria associated with Larimichthys crocea (L. crocea) and the potential inhibitory effects of a derived peptide. Spoilage bacteria were isolated and identified using traditional culture methods combined with 16S rDNA sequencing. The results identified Bacillus cereus (B. cereus) as the dominant spoilage bacterium in L. crocea. Ultra-high performance liquid chromatography-mass spectrometry was used to identify small peptides from L. crocea, and bioinformatics methods were employed to screen for peptides with potential inhibitory activity. Among the identified peptides, SDH73 (KRGMLENCILLSLFAK) exhibited significant antibacterial activity, with a minimum inhibitory concentration of 31.25 μg/mL and a minimum bactericidal concentration of 62.50 μg/mL. Through a combination of experimental studies and molecular dynamics (MD) simulations on the interaction between SDH73 and bacterial cell membranes, it was demonstrated that SDH73 disrupted the permeability and integrity of the B. cereus cell membrane, leading to internal structural damage. After penetrating the cell membrane, SDH73 bound to bacterial DNA by inserting it into base pairs, causing structural disruption. Additionally, SDH73 induced apoptosis-like programmed cell death in B. cereus. Furthermore, SDH73 effectively inhibited the growth of B. cereus in sterile fish meat. In conclusion, this study preliminarily revealed the spoilage potential of B. cereus in fish meat and investigated the antibacterial mechanism of the antimicrobial peptide SDH73. The findings provide a scientific basis for the development and application of SDH73 as a novel antimicrobial agent.

BCP4: A novel antimicrobial peptide with potent efficacy against Bacillus cereus in rice porridge

Bacillus cereus is a common foodborne pathogen that frequently contaminates rice products and produces cereulide toxins, presenting a significant risk to food safety and human health. In contrast, Bacillus subtilis is a promising source of antimicrobial peptides (AMPs). In this research, a novel AMP named BCP4 (KGKTLLQ) was discovered through the fermentation of shrimp waste with B. subtilis, which speculated that BCP4 might be generated through enzymatic hydrolysis catalyzed by endogenous enzymes naturally present in shrimp waste. BCP4 demonstrated potent antibacterial activity against B. cereus with a minimum bactericidal concentration (MBC) of 62.5 μg/mL and bacterial time-kill of 3 h. BCP4 surpassed the bactericidal efficiency of nisin (500 μg/mL), a commonly used AMP of microbial origin. BCP4 operates by causing damage to the bacterial cell wall and membrane, which allows the contents of the cell to flow out. BCP4 also penetrates the cell membrane and binds with DNA, effectively sterilizing the bacteria. Meanwhile, treatment of BCP4 with mammalian red blood cells revealed that it was nonhemolytic. Furthermore, the growth of B. cereus in rice porridge was significantly inhibited by BCP4 at a concentration of 62.5 μg/mL. This study provides a theoretical basis for using BCP4 to control B. cereus contamination.

Molecular farming for sustainable production of clinical-grade antimicrobial peptides

Antimicrobial peptides (AMPs) are emerging as next-generation therapeutics due to their broad-spectrum activity against drug-resistant bacterial strains and their ability to eradicate biofilms, modulate immune responses, exert anti-inflammatory effects and improve disease management. They are produced through solid-phase peptide synthesis or in bacterial or yeast cells. Molecular farming, i.e. the production of biologics in plants, offers a low-cost, non-toxic, scalable and simple alternative platform to produce AMPs at a sustainable cost. In this review, we discuss the advantages of molecular farming for producing clinical-grade AMPs, advances in expression and purification systems and the cost advantage for industrial-scale production. We further review how 'green' production is filling the sustainability gap, streamlining patent and regulatory approvals and enabling successful clinical translations that demonstrate the future potential of AMPs produced by molecular farming. Finally, we discuss the regulatory challenges that need to be addressed to fully realize the potential of molecular farming-based AMP production for therapeutics.

Recombinant production of antimicrobial peptides in plants

Classical plant breeding methods are limited in their ability to confer disease resistance on plants. However, in recent years, advancements in molecular breeding and biotechnological have provided new approaches to overcome these limitations and protect plants from disease. Antimicrobial peptides (AMPs) constitute promising agents that may be able to protect against infectious agents. Recently, peptides have been recombinantly produced in plants at scale and low cost. Because AMPs are less likely than conventional antimicrobials to elicit resistance of pathogenic bacteria, they open up exciting new avenues for agricultural applications. Here, we review recent advances in the design and production of bioactive recombinant AMPs that can effectively protect crop plants from diseases.

Development of a novel hybrid antimicrobial peptide for enhancing antimicrobial spectrum and potency against food-borne pathogens

AIMS

To address the increasingly serious challenge of the transmission of foodbrone pathogens in the food chain.

METHODS AND RESULTS

In this study, we employed rational design strategies, including truncation, amino acid substitution, and heterozygosity, to generate seven engineered peptides with α-helical structure, cationic property, and amphipathic characteristics based on the original Abhisin template. Among them, as the hybird antimicrobial peptide (AMP), AM exhibits exceptional stability, minimal toxicity, as well as broad-spectrum and potent antimicrobial activity against foodborne pathogens. Besides, it was observed that the electrostatic incorporation demonstrates by AM results in its primary targeting and disruption of the cell wall and membrane of Escherichia coli O157: H7 (EHEC) and methicillin-resistant Staphylococcus aureus (MRSA), resulting in membrane perforation and enhanced permeability. Additionally, AM effectively counteracts the deleterious effects of lipopolysaccharide, eradicating biofilms and ultimately inducing the demise of both food spoilage and pathogenic microorganisms.

CONCLUSIONS

The findings highlight the significant potential of AM as a highly promising candidate for a novel food preservative and its great importance in the design and optimization of AMP-related agents.

Rational design of Abhisin-like peptides enables generation of potent antimicrobial activity against pathogens

Infections caused by pathogens can be a significant challenge in wound healing, particularly when antimicrobial resistance is a factor. This can pose a serious threat to human health and well-being. In this scenario, it is imperative to explore novel antimicrobial agents to fight against multi-drug resistant (MDR) pathogenic bacteria. This study employed rational design strategies, including truncation, amino acid replacement, and heterozygosity, to obtain seven α-helical, cationic, and engineered peptides based on the original template of Abhisin. Among the analogs of Abhisin, AB7 displayed broad-spectrum and potent antimicrobial activity, superior targeting of membranes and DNA, and the ability to disrupt biofilms and anti-endotoxins in vitro. Additionally, we evaluated the anti-infection ability of AB7 using a murine skin wound model infected with methicillin-resistant Staphylococcus aureus (MRSA) and found that AB7 displayed negligible toxicity both in vitro and in vivo. Furthermore, AB7 exhibited desirable therapeutic efficacy by reducing bacterial burden and pro-inflammatory mediators, modulating cytokines, promoting wound healing, and enhancing angiogenesis. These results highlight the potential of AB7 as a promising candidate for a new antibiotic. KEY POINTS: • A α-helical, cationic, and engineered peptide AB7 was obtained based on Abhisin. • AB7 exhibited potent antimicrobial activity and multiple bactericidal actions. • AB7 effectively treated infected skin wounds in mice.

Antimicrobial Peptides: The Production of Novel Peptide-Based Therapeutics in Plant Systems

The increased prevalence of antibiotic resistance is alarming and has a significant impact on the economies of emerging and underdeveloped nations. The redundancy of antibiotic discovery platforms (ADPs) and injudicious use of conventional antibiotics has severely impacted millions, across the globe. Potent antimicrobials from biological sources have been extensively explored as a ray of hope to counter the growing menace of antibiotic resistance in the population. Antimicrobial peptides (AMPs) are gaining momentum as powerful antimicrobial therapies to combat drug-resistant bacterial strains. The tremendous therapeutic potential of natural and synthesized AMPs as novel and potent antimicrobials is highlighted by their unique mode of action, as exemplified by multiple research initiatives. Recent advances and developments in antimicrobial discovery and research have increased our understanding of the structure, characteristics, and function of AMPs; nevertheless, knowledge gaps still need to be addressed before these therapeutic options can be fully exploited. This thematic article provides a comprehensive insight into the potential of AMPs as potent arsenals to counter drug-resistant pathogens, a historical overview and recent advances, and their efficient production in plants, defining novel upcoming trends in drug discovery and research. The advances in synthetic biology and plant-based expression systems for AMP production have defined new paradigms in the efficient production of potent antimicrobials in plant systems, a prospective approach to countering drug-resistant pathogens.

Peptides Isolated from Amphibian Skin Secretions with Emphasis on Antimicrobial Peptides

The skin of amphibians is a tissue with biological functions, such as defense, respiration, and excretion. In recent years, researchers have discovered a large number of peptides in the skin secretions of amphibians, including antimicrobial peptides, antioxidant peptides, bradykinins, insulin-releasing peptides, and other peptides. This review focuses on the origin, primary structure, secondary structure, length, and functions of peptides secreted from amphibians' skin. We hope that this review will provide further information and promote the further study of amphibian skin secretions, in order to provide reference for expanding the research and application of amphibian bioactive peptides.

Antibacterial properties of cyclolinopeptides from flaxseed oil and their application on beef

The objective of this study was to investigate the antibacterial activity and potential mechanism of cyclolinopeptides, a type of cyclic hydrophobic peptides present in flaxseed oil. In this study, 1-Mso cyclolinopeptides B and 1-Mso, 3-Mso-cyclolinopeptides F from flaxseed oil exhibited excellent antibacterial activity against Listeria monocytogenes through destroying bacterial cell membrane. Our results indicated that cyclolinopeptides are one of the antibacterial components in flaxseed oil. Also, the application of cyclolinopeptides B and 1-Mso, 3-Mso-cyclolinopeptides F in inhibiting the microbial contamination of beef was investigated as well. Thus, our study highlights the promising potential of cyclolinopeptides to serve as food additives or food preservations due to their strong antibacterial activity against Listeria monocytogenes.

LC-ESI-QTOF/MS characterization of antimicrobial compounds with their action mode extracted from vine tea (Ampelopsis grossedentata) leaves

Vine tea (Ampelopsis grossedentata) is a tea plant cultivated south of the Chinese Yangtze River. It has anti-inflammatory properties and is used to normalize blood circulation and detoxification. The leaves of vine tea are the most abundant source of flavonoids, such as dihydromyricetin and myricetin. However, as the main bioactive flavonoid in vine tea, dihydromyricetin was the main focus of previous research. This study aimed to explore the antibacterial activities of vine tea against selected foodborne pathogens. The antimicrobial activity of vine tea extract was evaluated by the agar well diffusion method. Cell membrane integrity and bactericidal kinetics, along with physical damage to the cell membrane, were also observed. The extract was analyzed using a high-performance liquid chromatography-diode array detector (HPLC-DAD), and the results were confirmed using a modified version of a previously published method that combined liquid chromatography and electrospray-ionized quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF/MS). Cell membrane integrity and bactericidal kinetics were determined by releasing intracellular material in suspension and monitoring it at 260 nm using an ultraviolet (UV) spectrophotometer. A scanning electron microscope (SEM) was used to detect morphological alterations and physical damage to the cell membrane. Six compounds were isolated successfully: (1) myricetin (C15H10O8), (2) myricetin 3-O-rhamnoside (C21H20O12), (3) 5,7,8,3,4-pentahydroxyisoflavone (C15H10O7), (4) dihydroquercetin (C15H12O7), (5) 6,8-dihydroxykaempferol (C15H10O8), and (6) ellagic acid glucoside (C20H16O13). Among these bioactive compounds, C15H10O7 was found to have vigorous antimicrobial activity against Bacillus cereus (AS11846) and Staphylococcus aureus (CMCCB26003). A dose-dependent bactericidal kinetics with a higher degree of absorbance at optical density 260 (OD260) was observed when the bacterial suspension was incubated with C15H10O7 for 8 h. Furthermore, a scanning electron microscope study revealed physical damage to the cell membrane. In addition, the action mode of C15H10O7 was on the cell wall of the target microorganism. Together, these results suggest that C15H10O7 has vigorous antimicrobial activity and can be used as a potent antimicrobial agent in the food processing industry.

UPLC/Q-TOF MS Screening and Identification of Antibacterial Compounds in Forsythia suspensa (Thunb.) Vahl Leaves

Forsythia suspensa (Thunb.) Vahl (F. suspensa) is a traditional Chinese medical herb and only its fruit is currently used in clinical therapies. However, the discarded parts like leaves also contain a large number of active components. In this study, we used macroporous adsorption resin to enrich the effective components from F. suspensa leaves. The separated active compounds were then identified and quantified by ultra-performance liquid chromatography coupled with quadrupole time of flight mass spectrometry (UPLC/Q-TOF MS) and high-performance liquid chromatography Active components with antibacterial properties extracted from F. suspensa leaves were confirmed in vitro and the corresponding mechanisms were explored. In sum, a stable and effective method for extracting antibacterial active components from F. suspensa leaves was established in this study, which proved the practicability of F. suspensa leaves as traditional Chinese medicine and is conducive to the more comprehensive utilization of the plant.

Purification, molecular characterization of Lactocin 63 produced by Lactobacillus coryniformis FZU63 and its antimicrobial mode of action against Shewanella putrefaciens

Bacteriocins derived from lactic acid bacteria (LAB) are well recognized as promising food preservative due to high safety and potent antibacterial activity against foodborne pathogens and spoilage bacteria. In this study, an antimicrobial agent-producing strain FZU63 from Chinese sauerkraut was identified as Lactobacillus coryniformis based on physio-biochemical characterization and 16S rDNA sequence analysis. In addition, a bacteriocin was purified from the culture supernatant of L. coryniformis FZU63, and its molecular mass was determined as 1493.709 Da. Moreover, the amino acid sequence of the bacteriocin was predicted to be RQQPMTLDYRW-NH₂ using nanoliter/microliter liquid chromatography combined with triple quadrupole-linear ion trap tandem mass spectrometry and was named as Lactocin 63. Furthermore, Lactocin 63 displays potent antimicrobial activity against the tested Gram-positive and negative bacteria based on the results of determining MICs. Subsequently, the action mode of Lactocin 63 against Shewanella putrefaciens was investigated. The results demonstrated that Lactocin 63 targets and is adsorbed onto the bacterial cell wall and membrane and then disrupts cytoplasmic membrane, which is leading to leakage of cytoplasm according to the results of flow cytometry analysis and the observation of cellular ultra-structure using confocal laser microscopy and atomic force microscopy. Collectively, these results are helpful and providing the theoretical base for developing and applying LAB-derived bacteriocins as promising bio-preservatives to combat foodborne pathogens and spoilage bacteria in seafood industries.Key points• A bacteriocin-producing strain Lactobacillus coryniformis was isolated.• A novel bacteriocin produced by Lactobacillus coryniformis FZU63 was characterized.• Action mechanism of the bacteriocin against S. putrefaciens was elucidated in vitro.

Optimization of the Antimicrobial Effects of Surfactin against Bacillus cereus Spores

ABSTRACT

The purpose of this study was to establish a three-variable bactericidal model of temperature, time, and concentration to determine the optimal conditions for Bacillus cereus spore inactivation by surfactin. To obtain the binary regression equation of the inactivated spore model, a total of 17 simulations were performed using response surface methodology. The experimental results showed that the three factors each had a discernible but nonequal impact on the inactivation response value. Multiple regression analysis of experimental results using Design-Expert software yielded the following equation: Y = 1.47 + 0.39ξ1(temperature) + 0.38ξ2(time) + 0.39ξ3(concentration) - 0.20ξ1ξ2 + 0.22ξ1ξ2 - 0.12ξ2ξ3 - 0.23ξ12 - 0.11ξ22 - 0.40ξ32. Optimal inactivation of spores was achieved by treatment with surfactin at a concentration of 4 mg/mL for 40 h at 53°C, with the response value reaching 1.8. The spores were treated with surfactin under these conditions; the microstructural changes of spores were observed by use of scanning electron microscopy. We found that the structures of the outer wall of the spores were damaged, whereas the spores in the control sample showed no visible damage.

HIGHLIGHTS

Mini Review on Antimicrobial Peptides, Sources, Mechanism and Recent Applications

Antimicrobial peptides in recent years have gained increased interest among scientists, health professionals and the pharmaceutical companies owing to their therapeutic potential. These are low molecular weight proteins with broad range antimicrobial and immuno modulatory activities against infectious bacteria (Gram positive and Gram negative), viruses and fungi. Inability of micro-organisms to develop resistance against most of the antimicrobial peptide has made them as an efficient product which can greatly impact the new era of antimicrobials. In addition to this these peptides also demonstrates increased efficacy, high specificity, decreased drug interaction, low toxicity, biological diversity and direct attacking properties. Pharmaceutical industries are therefore conducting appropriate clinical trials to develop these peptides as potential therapeutic drugs. More than 60 peptide drugs have already reached the market and several hundreds of novel therapeutic peptides are in preclinical and clinical development. Rational designing can be used further to modify the chemical and physical properties of existing peptides. This mini review will discuss the sources, mechanism and recent therapeutic applications of antimicrobial peptides in treatment of infectious diseases.

Antibiofilm activity and modes of action of a novel β-sheet peptide against multidrug-resistant Salmonella enterica

S. enterica is an important foodborne pathogen worldwide. As some strains can form biofilms which may offer protection against antimicrobials, it is of interest to explore ways to prevent biofilm formation by S. enterica. In this study, we engineered a short β-sheet peptide WK2 (WKWKCTKSGCKWKW-NH₂) and examined its antimicrobial and anti-biofilm activities against various S. enterica strains, including the multidrug-resistant S. Typhimurium DT104. WK2 displayed bacteriostatic activity with a geometric mean (GM) minimum inhibitory concentration (MIC) of 4.17 μg/mL, and bactericidal activity, with a GM lethal concentration (LC) of 7.51 μg/mL. Crystal violet staining and fluorescence measurements demonstrated that WK2 inhibited S. Typhimurium DT104 biofilm formation at 0.5 μg/mL and killed the sessile cells in biofilms at 8 μg/mL. Real-time polymerase chain reaction (qPCR) and microscopic observation revealed that the anti-biofilm activity of WK2 likely arises through the formation of complexes with bacterial DNA, inhibition of surface organelle biosynthesis and interference with autoinducer-2 (AI-2)-mediated quorum sensing (QS). Therefore, WK2 is a promising antimicrobial agent for the prevention and control of biofilms produced by multidrug-resistant S. enterica.

Fabrication of KR-12 peptide-containing hyaluronic acid immobilized fibrous eggshell membrane effectively kills multi-drug-resistant bacteria, promotes angiogenesis and accelerates re-epithelialization

Background: Designing a wound dressing that effectively prevents multi-drug-resistant bacterial infection and promotes angiogenesis and re-epithelialization is of great significance for wound management. Methods and results: In this study, a biocompatible composite membrane comprising biomimetic polydopamine-modified eggshell membrane nano/microfibres coated with KR-12 antimicrobial peptide and hyaluronic acid (HA) was developed in an eco-friendly manner. The physicochemical properties of the composite membrane were thoroughly characterized, and the results showed that the surface hydrophilicity and water absorption ability of the composite membrane were improved after the successive conjugation of the HA and the KR-12 peptide. Furthermore, the in vitrobiological results revealed that the composite membrane had excellent antibacterial activity against Gram-positive Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA) and Gram-negative Escherichia coli, and it could prevent MRSA biofilm formation on its surface. Additionally, it promoted the proliferation of keratinocytes and human umbilical vein endothelial cells and increased the secretion of VEGF. Finally, an in vivo animal study indicated that the composite membrane could promote wound healing via accelerating angiogenesis and re-epithelialization, which were demonstrated by the enhanced expression of angiogenetic markers (CD31 and VEGF) and keratinocyte proliferation marker (PCNA), respectively. Conclusion: These results indicated that the composite membrane is a potential candidate of wound dressings.

Purification, Characterization, and Mode of Action of Plantaricin GZ1-27, a Novel Bacteriocin against Bacillus cereus

Bacillus cereus is an opportunistic pathogen that causes foodborne diseases. We isolated a novel bacteriocin, designated plantaricin GZ1-27, and elucidated its mode of action against B. cereus. Plantaricin GZ1-27 was purified using ammonium sulfate precipitation, gel-filtration chromatography, and RP-HPLC. MALDI-TOF/MS revealed that its molecular mass was 975 Da, and Q-TOF-MS/MS analysis predicted the amino acid sequence as VSGPAGPPGTH. Plantaricin GZ1-27 showed thermostability and pH stability. The antibacterial mechanism was investigated using flow cytometry, confocal laser-scanning microscopy, scanning and transmission electron microscopy, and RT-PCR, which revealed that GZ1-27 increased cell membrane permeability, triggered K⁺ leakage and pore formation, damaged cell membrane integrity, altered cell morphology and intracellular organization, and reduced the expression of genes related to cytotoxin production, peptidoglycan synthesis, and cell division. These results suggest that plantaricin GZ1-27 effectively inhibits B. cereus at both the cellular and the molecular levels and is a potential natural food preservative targeting B. cereus.