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The antimicrobial resistance crisis along with challenges of antimicrobial discovery revealed the vital necessity to develop new antibiotics. Many of the animal proline-rich antimicrobial peptides (PrAMPs) inhibit the process of bacterial translation. Genome projects allowed to identify immune-related genes encoding animal host defense peptides. Here, using genome mining approach, we discovered a family of proline-rich cathelicidins, named rumicidins. The genes encoding these peptides are widespread among ruminant mammals. Biochemical studies indicated that rumicidins effectively inhibited the elongation stage of bacterial translation. The cryo-EM structure of the Escherichia coli 70S ribosome in complex with one of the representatives of the family revealed that the binding site of rumicidins span the ribosomal A-site cleft and the nascent peptide exit tunnel interacting with its constriction point by the conservative Trp23-Phe24 dyad. Bacterial resistance to rumicidins is mediated by knockout of the SbmA transporter or modification of the MacAB-TolC efflux pump. A wide spectrum of antibacterial activity, a high efficacy in the animal infection model, and lack of adverse effects towards human cells in vitro make rumicidins promising molecular scaffolds for development of ribosome-targeting antibiotics. The antimicrobial resistance crisis calls for development of new classes of antibiotics. Here, authors use genome mining approach to discover a distinct family of ribosome-targeting proline rich antimicrobial peptides. [ABSTRACT FROM AUTHOR]

Antimicrobial peptides (AMPs) are promising cationic and amphipathic molecules to fight antibiotic resistance. To search for novel AMPs, we applied a computational strategy to identify peptide sequences within the organisms' proteome, including in-house developed software and artificial intelligence tools. After analyzing 150.450 proteins from eight proteomes of bacteria, plants, a protist, and a nematode, nine peptides were selected and modified to increase their antimicrobial potential. The 18 resulting peptides were validated by bioassays with four pathogenic bacterial species, one yeast species, and two cancer cell-lines. Fourteen of the 18 tested peptides were antimicrobial, with minimum inhibitory concentrations (MICs) values under 10 µM against at least three bacterial species; seven were active against Candida albicans with MICs values under 10 µM; six had a therapeutic index above 20; two peptides were active against A549 cells, and eight were active against MCF-7 cells under 30 µM. This study's most active antimicrobial peptides damage the bacterial cell membrane, including grooves, dents, membrane wrinkling, cell destruction, and leakage of cytoplasmic material. The results confirm that the proposed approach, which uses bioinformatic tools and rational modifications, is highly efficient and allows the discovery, with high accuracy, of potent AMPs encrypted in proteins. [ABSTRACT FROM AUTHOR]

The negative membrane potential within bacterial cells is crucial in various essential cellular processes. Sustaining a hyperpolarised membrane could offer a novel strategy to combat antimicrobial resistance. However, it remains uncertain which molecules are responsible for inducing hyperpolarization and what the underlying molecular mechanisms are. Here, we demonstrate that chemically diverse antimicrobial peptides (AMPs) trigger hyperpolarization of the bacterial cytosolic membrane when applied at subinhibitory concentrations. Specifically, these AMPs adopt a membrane-induced amphipathic structure and, thereby, generate hyperpolarization in Escherichia coli without damaging the cell membrane. These AMPs act as selective ionophores for K+ (over Na+) or Cl− (over H2PO4− and NO3−) ions, generating diffusion potential across the membrane. At lower dosages of AMPs, a quasi-steady-state membrane polarisation value is achieved. Our findings highlight the potential of AMPs as a valuable tool for chemically hyperpolarising bacteria, with implications for antimicrobial research and bacterial electrophysiology. Antimicrobial peptides with membrane-induced structure generate diffusion potential across the E. coli cytosolic membrane at subinhibitory concentrations. The differential ion permeability generates bacterial hyperpolarization. [ABSTRACT FROM AUTHOR]

This study aimed to increase the antifungal and insecticidal activities of NaD1, as an antimicrobial peptides (AMP), by improving its interaction with the fungal cell wall and chitin monomeric units in insect midguts. Hence, the chitin-binding domains (CBDs) of wheat germ agglutinin protein (WGA) were fused to either N- or C-terminus of NaD1 generating transgenic Nicotiana tabacum hairy roots (HRs). Molecular assessments confirmed the integration of NaD1 transgenes, their transcription and production of recombinant peptides in the HR lines. Total protein of (CBD)4-NaD1 and NaD1-(CBD)4 transgenic lines inhibited the growth of Pyricularia oryzae mycelium, suggesting that fusion of CBD to NaD1 can increase NaD1 half-life, leading to higher affinity toward cell wall chitin. Furthermore, feeding the third-instar larvae of Chilo suppressalis with both (CBD)4-NaD1 and NaD1-(CBD)4 extracts exhibited a higher mortality rate. Both NaD1-CBDs caused a significant decrease in trypsin (TRY) and chymotrypsin (CTR) activities in the larvae, while enhancing the activity of antioxidant enzymes CAT, POD, APX, and SOD. Therefore, feeding the larvae by total extract of NaD1-(CBD)4 and (CBD)4-NaD1 HR lines probably increased affinity to midgut chitin in C. suppressalis, enhancing insecticidal activities. Overall, the results indicate that recombinant peptides are effective in enhancing fungal and insect resistance. [ABSTRACT FROM AUTHOR]

Cysteine-rich peptides play an important role in the plant defense system. The objective of this study was in silico searching for the genes encoding antimicrobial and signaling peptides in the genome of the tall wheatgrass Thinopyrumelongatum (Host) D.R. Dewey (2n = 14, EE), a wild cereal that is highly resistant to pathogens and abiotic stress. Bioinformatic analysis provided information for the identification in the tall wheatgrass genome of 154 novel genes coding for antimicrobial and signaling peptide precursors belonging to nine families. A number of cysteine-rich peptide genes were found to contain introns. The structure of peptide precursors and the location of the peptide genes on the wheatgrass chromosomes were determined. The highest similarity of the wheatgrass peptide sequences with homologous peptides from plants of the genera Triticum and Aegilops was demonstrated, supporting the cytogenetic data on the relatedness between genome E and genome D, as well as the genomes close to it. The data obtained contribute to the characterization of the molecular components of the Th. elongatum immune system and will serve as the basis for further studies of the mechanisms of resistance, as well as for the scientifically based practical use of this species as the resistance donor in wheat breeding. [ABSTRACT FROM AUTHOR]

The linear undecapeptide BP52 was previously reported to have antibacterial activity against phytopathogenic bacteria species. Due to the structural similarities to naturally occurring cationic helical antimicrobial peptides, it was speculated that this peptide could potentially target microbial pathogens and cancer cells found in mammals. Consequently, this study aims to further investigate the structural and biological properties of this peptide. Our findings indicate that BP52 exhibits strong antimicrobial and anticancer activity while displaying relatively low levels of hemolytic activity. Hence, this study suggests that BP52 could be a potential lead compound for drug discovery against infectious diseases and cancer. Besides, new insights into the relationships between the structure and the multifunctional properties of antimicrobial peptides were also explored. [ABSTRACT FROM AUTHOR]

Antibiotic resistance has emerged as a global threat, rendering the existing conventional treatment strategies ineffective. In view of this, antimicrobial peptides (AMPs) have proven to be potent alternative therapeutic interventions with a wide range of applications in clinical health. AMPs are small peptides produced naturally as a part of the innate immune responses against a broad range of bacterial, fungal and viral pathogens. AMPs present a myriad of advantages over traditional antibiotics, including their ability to target multiple sites, reduced susceptibility to resistance development, and high efficacy at low doses. These peptides have demonstrated notable potential in inhibiting microbes resistant to traditional antibiotics, including the notorious ESKAPE pathogens, recognized as the primary culprits behind nosocomial infections. AMPs, with their multifaceted benefits, emerge as promising candidates in the ongoing efforts to combat the escalating challenges posed by antibiotic resistance. This in-depth review provides a detailed discussion on AMPs, encompassing their classification, mechanism of action, and diverse clinical applications. Focus has been laid on combating newly emerging drug-resistant organisms, emphasizing the significance of AMPs in mitigating this pressing challenge. The review also illuminates potential future strategies that may be implemented to improve AMP efficacy, such as structural modifications and using AMPs in combination with antibiotics and matrix-inhibiting compounds. [ABSTRACT FROM AUTHOR]

The potential of new genetically modified recombinant endolysins as antimicrobial agents against Gram-negative bacteria was investigated. A series of enzymes based on LysSi3 lysozyme-like muramidase was obtained by modifying its sequence with antimicrobial peptides of different families, and recombinant expression in E. coli was demonstrated. Modification of LysSi3 resulted in increased bacteriolytic activity against the model isolate of A. baumannii and a higher kinetics rate compared to the native enzyme. The cytotoxic properties of the newly engineered lysins were investigated with the HEK293 and HaCaT cell lines, and it was shown that modification of LysSi3 with antimicrobial peptides does not significantly increase the toxic properties in vitro. [ABSTRACT FROM AUTHOR]

Antimicrobial peptides (AMPs) are small peptides existing in nature as an important part of the innate immune system in various organisms. Notably, the AMPs exhibit inhibitory effects against a wide spectrum of pathogens, showcasing potential applications in different fields such as food, agriculture, medicine. This review explores the application of AMPs in the food industry, emphasizing their crucial role in enhancing the safety and shelf life of food and how they offer a viable substitute for chemical preservatives with their biocompatible and natural attributes. It provides an overview of the recent advancements, ranging from conventional approaches of using natural AMPs derived from bacteria or other sources to the biocomputational design and usage of synthetic AMPs for food preservation. Recent innovations such as structural modifications of AMPs to improve safety and suitability as food preservatives have been discussed. Furthermore, the active packaging and creative fabrication strategies such as nano-formulation, biopolymeric peptides and casting films, for optimizing the efficacy and stability of these peptides in food systems are summarized. The overall focus is on the spectrum of applications, with special attention to potential challenges in the usage of AMPs in the food industry and strategies for their mitigation. [ABSTRACT FROM AUTHOR]

The intestine is the principal digestive organ which is generally divided into three segments as the proximal intestine (PI), the mid intestine (MI), and the distal intestine (DI) in fish. In this study, the role of dietary vitamin D3 (VD3) in regulating the function and health of different intestinal segments was evaluated in grass carp (Ctenopharyngodon idella) fingerlings through the supplementation with the increasing levels of dietary VD3 (0, 500, 1000, 1500, 2000, and 2500 IU/kg). The results showed that VD3 supplementation (1000–2000 IU/kg) significantly enhanced the fish growth performance, and the correlation analysis suggested that this effect was positively correlated with intestinal somatic index (ISI) and intestinal length index (ILI) of MI and DI except PI. In support of this finding, dietary VD3 enhanced the activities of digestive and brush border enzymes in the fish mainly in MI and DI rather than PI. Furthermore, the intestinal microbiota analysis revealed that VD3 increased the abundance of intestinal flora at the genus level rather than the phylum level. Meanwhile, hematoxylin and eosin staining presented that VD3 supplementation reduced epithelial goblet cell hyperplasia and lamina propria edema compared with the VD3 deficiency group in the MI and DI. Further studies showed that feeding VD3 decreased malondialdehyde levels but increased total antioxidant capacity, glutathione levels, and total superoxidase activity in MI or DI but not PI, suggesting the antioxidant potential of VD3 in two intestinal segments. Moreover, in MI and DI but not PI, dietary VD3 suppressed pro-inflammatory cytokine (il1 β and tnf α ) but enhanced antimicrobial peptide (hepcidin and βdefensin) mRNA levels and increased the activities of immune-related enzymes (lysozyme and acid phosphatase), highlighting the ability to improve fish immunity. Corresponding to these effects, dietary VD3 was able to mediate NF-E2-related factor 2 (Nrf2) and NF-κB pathways in MI and DI. Finally, quadratic regression models based on weight gain (PWG), feed efficiency (PE), ISI, and ILI suggested that the appropriate VD3 requirements for grass carp fingerlings were 1233.70–1387.11 IU/kg. Taken together, our findings strengthened the potential of dietary VD3 in managing the functions and health of particular intestinal segments and provided valuable reference data for VD3 requirements of fingerling fish. [ABSTRACT FROM AUTHOR]

Pneumococcal infections caused by Streptococcus pneumoniae are a leading cause of morbidity and mortality globally, particularly among children. The ability of S. pneumoniae to form enduring biofilms makes treatment inherently difficult, and options are further limited by emerging antibiotic resistance. The discovery of new antibiotics, particularly those with antibiofilm activity, is therefore increasingly important. Antimicrobial proteins and peptides (AMPs) from marine invertebrates are recognised as promising pharmacological leads. This study determined the in vitro antibacterial activity of hemolymph and unique protein fractions from an Australian oyster (Saccostrea glomerata) against multi-drug-resistant S. pneumoniae. We developed a successful method for hemolymph extraction and separation into 16 fractions by preparative HPLC. The strongest activity was observed in fraction 7: at 42 µg/mL protein, this fraction was bactericidal to S. pneumoniae and inhibited biofilm formation. Proteomic analysis showed that fraction 7 contained relatively high abundance of carbonic anhydrase, cofilin, cystatin B–like, and gelsolin-like proteins, while surrounding fractions, which showed lower or no antibacterial activity, contained these proteins in lower abundance or not at all. This work supports traditional medicinal uses of oysters and contributes to further research and development of novel hemolymph/AMP-based treatments for pneumococcal infections. [ABSTRACT FROM AUTHOR]

Secretory leukocyte protease inhibitor (SLPI) functions as a protease inhibitor that modulates excessive proteolysis in the body, exhibits broad-spectrum antimicrobial activity, regulates inflammatory responses, and plays an important role in the innate immunity. The purpose of the study was to artificially synthesize a SLPI, an antimicrobial peptide, and investigate its effect on antimicrobial activity against Porphyromonas gingivalis and interleukin-6 (IL-6) production. SLPI protein with a molecular weight of approximately 13 kDa was artificially synthesized using a cell-free protein synthesis (CFPS) system and investigated by western blotting and enzyme-linked immunosorbent assay (ELISA). Disulfide bond isomerase in the protein synthesis mixture increased the amount of SLPI synthesized. The synthesized SLPI (sSLPI) protein was purified and its antimicrobial activity was investigated based on the growth of Porphyromonas gingivalis and bacterial adhesion to oral epithelial cells. The effect of sSLPI on IL-6 production in human periodontal ligament fibroblasts (HPLFs) was examined by ELISA. Our results showed that sSLPI significantly inhibited the growth of Porphyromonas gingivalis and bacterial adhesion to oral epithelial cells and further inhibited IL-6 production by HPLFs. These results suggested that SLPI artificially synthesized using the CFPS system may play a role in the prevention of periodontal diseases through its antimicrobial and anti-inflammatory effects. [ABSTRACT FROM AUTHOR]

Cyclotides are small disulfide-rich peptides (28–37 amino acids) with a wide range of biological activities. The Rubiaceae family is a good source for cyclotide production, but the quantity produced is not sufficient. Therefore, we aimed to enhance cyclotide production in Oldenlandia umbellata (Rubiaceae family) cell cultures using a fungal elicitation process. Aspergillus niger was used as an elicitor to enhance the cyclotides in this plant. After elicitation, proteins were extracted and analyzed using 2-D gel electrophoresis, followed by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry. The results of this study showed a 3.4-fold increase in protein spot intensity in fungal elicitor-treated cultures compared to untreated cultures. Mass spectrometric data showed two intense peaks in the monoisotopic protonated mass. Peptide sequencing of these peaks yielded two sequence hits that matched known cyclotide sequences in the CyBase database. The present study identified Varv-A and cycloviolacin O23-like peptides with antimicrobial properties, low cell permeability and solubility, and a lack of hemolytic, allergenic, toxic, and aggregation properties. Varv-A-like and cycloviolacin O23-like peptides are predicted to exhibit anticancer and antiviral properties, respectively. In conclusion, the cyclotides identified in this study may improve drug design and protein engineering, highlighting their therapeutic potential in the pharmaceutical industry.Key message: The production of antimicrobial varv-A and cycloviolacin O23-like peptides in O. umbellata cell cultures was significantly increased by 3.4 times using A. niger elicitation. [ABSTRACT FROM AUTHOR]

Identifying anti-inflammatory peptides (AIPs) and antimicrobial peptides (AMPs) is crucial for the discovery of innovative and effective peptide-based therapies targeting inflammation and microbial infections. However, accurate identification of AIPs and AMPs remains a computational challenge mainly due to limited utilization of peptide sequence information. Here, we propose PepNet, an interpretable neural network for predicting both AIPs and AMPs by applying a pre-trained protein language model to fully utilize the peptide sequence information. It first captures the information of residue arrangements and physicochemical properties using a residual dilated convolution block, and then seizes the function-related diverse information by introducing a residual Transformer block to characterize the residue representations generated by a pre-trained protein language model. After training and testing, PepNet demonstrates great superiority over other leading AIP and AMP predictors and shows strong interpretability of its learned peptide representations. A user-friendly web server for PepNet is freely available at http://liulab.top/PepNet/server. PepNet achieves accurate identification of both AIPs and AMPs by developing an interpretable neural network and applying a pre-trained protein language model. [ABSTRACT FROM AUTHOR]

The practice of preserving and adding value to food dates back to over 10,000 BCE, when unintentional microbial-driven chemical reactions imparted flavor and extended the shelf life of fermented foods. The process evolved, and with the urbanization of society, significant shifts in dietary habits emerged, accompanied by sporadic food poisoning incidents. The repercussions of the COVID-19 pandemic have intensified the search for antibiotic alternatives owing to the rise in antibiotic-resistant pathogens, emphasizing the exploration of probiotic-origin antimicrobial peptides to alleviate human microbiome collateral damage. Often termed 'molecular knives', these peptides outstand as potent antimicrobials due to their compatibility with innate microflora, amenability to bioengineering, target specificity, versatility and rapidity in molecular level mode of action. This review centres on bacteriocins sourced from lactic acid bacteria found in ethnic fermented foods, accentuating their desirable attributes, technological applications as nanobiotics and potential future applications in the modern context of ensuring food safety. [ABSTRACT FROM AUTHOR]

E50-52, a class IIa-peptidic bacteriocin produced by a strain of Enterococcus faecium, has broad-spectrum antimicrobial activity against various foodborne pathogens. However, effective utilization of the E50-52 has been limited by low production yields and challenges associated with separation and purification of this 39-amino acid antimicrobial peptide. In this study, we have successfully produced a biologically active recombinant form of E50-52 by fusing it with the 16-kDa catalytic domain of lysostaphin-class III bacteriocin (LssCAT), which resulted in high-yield production. Initially, the LssCAT-E50-52 chimeric protein was insoluble upon over-expression in Escherichia coli, but it became soluble using phosphate buffer (pH 7.4) supplemented with 8 M urea. Purification using immobilized-Ni2+ affinity chromatography under urea denaturing conditions resulted in consistent production a homogenous products (LssCAT-E50-52) with >95% purity. The purified protein was refolded using an optimized stepwise dialysis process. The resulting refolded LssCAT-E50-52 protein exhibited dose-dependent inhibitory activity against Helicobacter pylori, a Gram-negative, flagellated, helical bacterium that is associated with gastric cancer. Overall, the optimized protocol described in this study effectively produced large quantities of high-purity recombinant LssCAT-E50-52 protein, yielding approximately 100 mg per liter of culture. To the best of our knowledge, this is the first report on the impact of LssCAT-E50-52 on H. pylori. This finding could pave the way for further research into bactericidal mechanism and potential applications of this bacteriocin in biomedical industry. [ABSTRACT FROM AUTHOR]

Antibiotics are the super drugs that have revolutionized modern medicine by curing many infectious diseases caused by various microbes. They efficiently inhibit the growth and multiplication of the pathogenic microbes without causing adverse effects on the host. However, prescribing suboptimal antibiotic and overuse in agriculture and animal husbandry have led to the emergence of antimicrobial resistance, one of the most serious threats to global health at present. The efficacy of a new antibiotic is high when introduced; however, a small bacterial population attains resistance gradually and eventually survives. Understanding the mode of action of these miracle drugs, as well as their interaction with targets is very complex. However, it is necessary to fulfill the constant need for novel therapeutic alternatives to address the inevitable development of resistance. Therefore, considering the need of the hour, this article has been prepared to discuss the mode of action and recent advancements in the field of antibiotics. Efforts has also been made to highlight the current scenario of antimicrobial resistance and drug repurposing as a fast-track solution to combat the issue. [ABSTRACT FROM AUTHOR]

The biofilm formation by various pathogens causes chronic infections and poses severe threats to industry, healthcare, and society. They can form biofilm on surfaces of medical implants, heart valves, pacemakers, contact lenses, vascular grafts, urinary catheters, dialysis catheters, etc. These biofilms play a central role in bacterial persistence and antibiotic tolerance. Biofilm formation occurs in a series of steps, and any interference in these steps can prevent its formation. Therefore, the hunt to explore and develop effective anti-biofilm strategies became necessary to decrease the rate of biofilm-related infections. In this review, we highlighted and discussed the current therapeutic approaches to eradicate biofilm formation and combat drug resistance by anti-biofilm drugs, phytocompounds, antimicrobial peptides (AMPs), antimicrobial lipids (AMLs), matrix-degrading enzymes, nanoparticles, phagebiotics, surface coatings, photodynamic therapy (PDT), riboswitches, vaccines, and antibodies. The clinical validation of these findings will provide novel preventive and therapeutic strategies for biofilm-associated infections to the medical world. [ABSTRACT FROM AUTHOR]

The aquaculture industry is suffering from significant financial setbacks due to an increasing frequency of disease outbreaks, posing a threat to the sector's sustainability. Various bacterial, viral, parasitic, and fungal pathogens have led to massive mortalities in farmed fish worldwide. Throughout the years, the management of fish diseases has predominantly centered around the utilization of conventional antibiotics and chemicals. Nevertheless, their indiscriminate use has given rise to serious implications, including an increase in resistant pathogens, disruptions in the metabolic processes of fish, degradation of the aquatic environment, the presence of drug residues in aquatic products, and a potential threat to human health. Various effective bio-based and immunoprophylaxis alternative therapies have been developed to overcome these impediments. Recent alternative therapeutic approaches to fish diseases encompass a range of strategies, including phytotherapeutics, nanotherapeutics, probiotics, prebiotics, synbiotics, phage therapy, vaccination, quorum quenching, antimicrobial peptides, biosurfactants, bacteriocins, stem cells, and diagnostic-based therapy. Advancements in biotechnology have significantly enhanced the efficacy of these therapies. However, additional research is essential to refine the utilization of these therapeutic approaches. Critical concerns, such as efficacy, cost, risks, availability, and adverse effects on fish and the ecosystem, need to be addressed to establish guidelines for their sustainable application in aquaculture. This review will increase aquaculturists' awareness of recent therapies used in fish farming, their mechanisms, challenges, and impacts while promoting the sustainability of commercial aquaculture. [ABSTRACT FROM AUTHOR]

Background: One of the problems of diabetic patients is the formation of ulcers in the lower areas, especially the legs, and the treatment of these ulcers is very important. In wounds, grampositive and Gram-negative opportunistic and biofilm-forming bacteria accumulate, and these bacteria often become resistant to antibiotics over time. For this reason, researchers are looking for new alternatives to break the barrier of antibiotic resistance. Due to their unique properties and natural origin, antimicrobial peptides can be a suitable alternative to common antibiotics. Methods: In this research, several antimicrobial peptides of animal origin were investigated using docking and molecular dynamics techniques. Then, the antibacterial disk diffusion test was performed and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were measured. Results: According to the Insilico results, the melittin peptide, which is present in Apis mellifera bee venom, was selected as the best candidate for measuring the antibacterial effect on the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacterium Pseudomonas aeruginosa. Then, a wound dressing was prepared using Apis mellifera bee venom, and an antibacterial disk diffusion test and the minimum inhibitory concentration (MIC) and the minimum bactericidal concentrate (MBC) measurements were performed. The results of the invitro tests showed that compared with the antibiotic ciprofloxacin, the wound dressing containing melittin could effectively inhibit the target bacteria and create a non-growth halo with an acceptable diameter. Conclusion: According to the results of this research, wound dressing containing the antimicrobial peptide melittin can be a suitable option for treating diabetic foot ulcers. The inhibitory effect observed on Pseudomonas aeruginosa and Staphylococcus aureus bacteria can be generalized to all Gram-positive and Gram-negative bacteria present in diabetic foot ulcers. [ABSTRACT FROM AUTHOR]

Plant Snakin/GASA and defensin peptides are cysteine-rich molecules with a wide range of biological functions. They are included within the large family of plant antimicrobial peptides (AMPs), characterized by their structural stability, broad spectrum of activity, and diverse mechanisms of action. The Dilatata group of Paspalum includes five allotetraploids that share an equivalent genomic formula IIJJ. From RNA-seq data of seedling tissues, we performed an in silico characterization of the defensin and Snakin/GASA genes in these species and diploids with a II and JJ genome formula and studied the evolutionary consequences of polyploidy on the expression of the two AMPs families. A total of 107 defensins (distributed in eight groups) and 145 Snakin/GASA (grouped in three subfamilies) genes were identified. Deletions, duplications and/or gene silencing seem to have mediated the evolution of these genes in the allotetraploid species. In defensin genes, the IIJJ allopolyploids retained the I subgenome defensin copies in some of the identified groups supporting the closeness of their nuclear genome with the I subgenome species. In both AMPs families, orthologous genes in tetraploids exhibit higher similarity to each other than with diploids. This data supports the theory of a single origin for the allotetraploids. Several copies of both defensin and Snakin/GASA genes were detected in the five polyploids which could have arisen due to duplication events occurring independently during the diploidization processes in the allotetraploid taxa. [ABSTRACT FROM AUTHOR]

Purpose of Review: This review aims to elucidate the mechanisms employed by Host Defense Peptides (HDPs) in propagating their effector functions, associated bottlenecks complicating their therapeutic applications, and how these peptides can be optimized or modified as potential next-generation lead agents in targeted therapy in managing infectious diseases and cancer. Recent Findings: Emerging studies are affirming that due to dwindling therapeutic options, infectious diseases and cancers undoubtedly remain major threats to public health. This is mostly attributable to the toxicity and resistance of classical drugs in combating these health challenges, thus, novel bio-inspired treatment strategies are being sought. As the first line of defense in all organisms, the innate immune system produces many immune effector molecules including a group of biologically active endogenous peptides collectively known as Host Defense Peptides (HDPs), which can be further sub-classified into Antimicrobial Peptides (AMPs), or Anticancer Peptides (ACPs) based on their effector functions. These highly diverse, ubiquitous, and low-molecular-weight biomolecules are being identified and proposed as models for new drug/lead candidates. This is owing to their unique mechanism of action, sequence, and structural diversities which are integral to their downstream biological functions. Therefore, continuous efforts to elucidate the exploitability of these quintessential peptides in drug discovery research against these pathologies are worth exploring. Summary: The ubiquity, significant diversities, and neoteric novel biological activities of HDPs as one of the effectors of the innate immune system establish them as a unique and valuable therapeutic strategy for combating infectious diseases and cancer. They are especially becoming prominent in overcoming the limitations posed by conventional therapeutic agents in managing these diseases, making them promising candidates for future drug development. Furthermore, their diverse functions and numerous molecular targets will play a crucial role in their discovery as new therapeutics. [ABSTRACT FROM AUTHOR]

Background: Short cationic antimicrobial peptides (AMPs) have an excellent potential for treating various infections. Methods: This study focused on the de novo design of two peptides, LK3 (W(LK)3W-NH2) and LK4 (W(LK)4W-NH2), based on the most frequent and important amino acids in AMPs using in silico tools. The antibacterial activity of the designed peptides was evaluated under standard conditions, physiological NaCl concentration, and in the presence of serum (10% v/v). The antibiofilm and hemolytic activities of the peptides were assayed. Results: CAMPR4 algorithms predicted LK3 and LK4 as AMPs. Compared with LK3, the cationicity of LK4 was increased slightly, while its hydrophobicity was decreased a little. Both peptides had extended coil structures. The antibacterial activity of LK3 was better than that of LK4. The best minimum inhibitory concentration of LK3 (MIC: 64 µg/ml) was found against methicillin-resistant Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa under salt and no salt conditions. However, serum inhibited the antibacterial effect of the peptide. LK3 also exhibited 44.45% antibiofilm activity against P. aeruginosa at 4 × MIC concentration. The hemolytic activity of LK3 and LK4 peptides was lower than 10% up to 128 µg/ml. Among the two designed peptides, LK3 represented better selectivity against Gram-negative bacteria. Conclusions: In conclusion, LK3 with selective activity against Gram-negative bacteria, good salt stability, and low toxicity appears to be a good candidate for further design investigations to enhance its antibacterial activity. This study contributes to the development of AMPs active against antibiotic-resistant Gram-negative bacteria, a major global health concern. [ABSTRACT FROM AUTHOR]

Background: Despite the growing productivity of aquaculture, economic losses due to infectious diseases, environmental pollution, and human safety concerns related to antibiotic resistance are limiting its growth. Therefore, research is intensively focused on alternative strategies for controlling infectious diseases. Purpose: Antimicrobial peptides (AMPs) are short, usually cationic, amphipathic, germline-encoded endogenous peptides possessing molecular weight less than 13 kDa, which show an extended variety of different families of highly conserved peptides found widely throughout Nature, which play a crucial role in molecular and cellular host defense towards pathogens (bacteria, viruses, parasites, and fungi), tissue damage, and infection. Results: They emerge as a promising antibiotic alternative due to their unique and multidimensional properties, including their low potential for developing antimicrobial resistance, minimal cytotoxicity to mammalian cells, high selective cytotoxicity against bacteria, low residual flesh, and ability to modulate host immune responses. Also, their ability to act even in extremely high salt concentrations, makes them suitable potential targets for development as therapeutic antimicrobials. AMPs are induced by various elements, including dietary ingredients and specific molecules also known as pathogen-associated molecular patterns (PAMPs), which may activate downstream signals to initiate transcription of AMP genes. Fish are an excellent origin of the peptides, as they express all major AMP families, including defensins, cathelicidins, hepcidins, histone-derived peptides, and a fish-specific class, called piscidins. Given their increasing attention in research, this review investigates various fish AMPs, their biological activities, and mechanisms of action. Conclusion: The findings suggest that fish can serve as sources of unique peptides with a broad range of biological activities, thereby offering a novel class of antibiotics. [ABSTRACT FROM AUTHOR]

The emergence of antibiotic-resistant microbes raises a pressing demand for novel alternative treatments. One promising alternative is the antimicrobial peptides (AMPs), a class of innate immunity mediators within the therapeutic peptide realm. AMPs offer salient advantages such as high specificity, cost-effective synthesis, and reduced toxicity. Although some computational methodologies have been proposed to identify potential AMPs with the rapid development of artificial intelligence techniques, there is still ample room to improve their performance. This study proposes a predictive framework which ensembles deep learning and statistical learning methods to screen peptides with antimicrobial activity. We integrate multiple LightGBM classifiers and convolution neural networks which leverages various predicted sequential, structural and physicochemical properties from their residue sequences extracted by diverse machine learning paradigms. Comparative experiments exhibit that our method outperforms other state-of-the-art approaches on an independent test dataset, in terms of representative capability measures. Besides, we analyse the discrimination quality under different varieties of attribute information and it reveals that combination of multiple features could improve prediction. In addition, a case study is carried out to illustrate the exemplary favorable identification effect. We establish a web application at http://amp.denglab.org to provide convenient usage of our proposal and make the predictive framework, source code, and datasets publicly accessible at https://github.com/researchprotein/amp. [ABSTRACT FROM AUTHOR]

Development of potent and broad-spectrum antimicrobial peptides (AMPs) could help overcome the antimicrobial resistance crisis. We develop a peptide language-based deep generative framework (deepAMP) for identifying potent, broad-spectrum AMPs. Using deepAMP to reduce antimicrobial resistance and enhance the membrane-disrupting abilities of AMPs, we identify, synthesize, and experimentally test 18 T1-AMP (Tier 1) and 11 T2-AMP (Tier 2) candidates in a two-round design and by employing cross-optimization-validation. More than 90% of the designed AMPs show a better inhibition than penetratin in both Gram-positive (i.e., S. aureus) and Gram-negative bacteria (i.e., K. pneumoniae and P. aeruginosa). T2-9 shows the strongest antibacterial activity, comparable to FDA-approved antibiotics. We show that three AMPs (T1-2, T1-5 and T2-10) significantly reduce resistance to S. aureus compared to ciprofloxacin and are effective against skin wound infection in a female wound mouse model infected with P. aeruginosa. In summary, deepAMP expedites discovery of effective, broad-spectrum AMPs against drug-resistant bacteria. New approaches to develop antimicrobial agents are urgently needed. In this study, the authors develop a peptide language-based deep generative model to design broad-spectrum antimicrobial peptides against drug-resistant bacteria and validate promising candidates in a wound mouse model. [ABSTRACT FROM AUTHOR]

Infections by drug-resistant microorganisms are a threat to global health and antimicrobial peptides are considered to be a new hope for their treatment. Temporin-WY2 was identified from the cutaneous secretion of the Ranidae frog, Amolops wuyiensis. It presented with a potent anti-Gram-positive bacterial efficacy, but its activity against Gram-negative bacteria and cancer cell lines was unremarkable. Also, it produced a relatively high lytic effect on horse erythrocytes. For further improvement of its functions, a perfect amphipathic analogue, QUB-1426, and two lysine-clustered analogues, 6K-WY2 and 6K-1426, were synthesised and investigated. The modified peptides were found to be between 8- and 64-fold more potent against Gram-negative bacteria than the original peptide. Additionally, the 6K analogues showed a rapid killing rate. Also, their antiproliferation activities were more than 100-fold more potent than the parent peptide. All of the peptides that were examined demonstrated considerable biofilm inhibition activity. Moreover, QUB-1426, 6K-WY2 and 6K-1426, demonstrated in vivo antimicrobial activity against MRSA and E. coli in an insect larvae model. Despite observing a slight increase in the hemolytic activity and cytotoxicity of the modified peptides, they still demonstrated a improved therapeutic index. Overall, QUB-1426, 6K-WY2 and 6K-1426, with dual antimicrobial and anticancer functions, are proposed as putative drug candidates for the future. [ABSTRACT FROM AUTHOR]

The emergence of drug-resistant bacteria poses a significant challenge to modern medicine. In response, Artificial Intelligence (AI) and Machine Learning (ML) algorithms have emerged as powerful tools for combating antimicrobial resistance (AMR). This review aims to explore the role of AI/ML in AMR management, with a focus on identifying pathogens, understanding resistance patterns, predicting treatment outcomes, and discovering new antibiotic agents. Recent advancements in AI/ML have enabled the efficient analysis of large datasets, facilitating the reliable prediction of AMR trends and treatment responses with minimal human intervention. ML algorithms can analyze genomic data to identify genetic markers associated with antibiotic resistance, enabling the development of targeted treatment strategies. Additionally, AI/ML techniques show promise in optimizing drug administration and developing alternatives to traditional antibiotics. By analyzing patient data and clinical outcomes, these technologies can assist healthcare providers in diagnosing infections, evaluating their severity, and selecting appropriate antimicrobial therapies. While integration of AI/ML in clinical settings is still in its infancy, advancements in data quality and algorithm development suggest that widespread clinical adoption is forthcoming. In conclusion, AI/ML holds significant promise for improving AMR management and treatment outcome. [ABSTRACT FROM AUTHOR]

Antimicrobial peptides have gradually gained advantages over small molecule inhibitors for their multifunctional effects, synthesising accessibility and target specificity. The current study aims to determine an antimicrobial peptide to inhibit PknB, a serine/threonine protein kinase (STPK), by binding efficiently at the helically oriented hinge region. A library of 5626 antimicrobial peptides from publicly available repositories has been prepared and categorised based on the length. Molecular docking using ADCP helped to find the multiple conformations of the subjected peptides. For each peptide served as input the tool outputs 100 poses of the subjected peptide. To maintain an efficient binding for relatively a longer duration, only those peptides were chosen which were seen to bind constantly to the active site of the receptor protein over all the poses observed. Each peptide had different number of constituent amino acid residues; the peptides were classified based on the length into five groups. In each group the peptide length incremented upto four residues from the initial length form. Five peptides were selected for Molecular Dynamic simulation in Gromacs based on higher binding affinity. Post-dynamic analysis and the frame comparison inferred that neither the shorter nor the longer peptide but an intermediate length of 15 mer peptide bound well to the receptor. Residual substitution to the selected peptides was performed to enhance the targeted interaction. The new complexes considered were further analysed using the Elastic Network Model (ENM) for the functional site's intrinsic dynamic movement to estimate the new peptide's role. The study sheds light on prospects that besides the length of peptides, the combination of constituent residues equally plays a pivotal role in peptide-based inhibitor generation. The study envisages the challenges of fine-tuned peptide recovery and the scope of Machine Learning (ML) and Deep Learning (DL) algorithm development. As the study was primarily meant for generation of therapeutics for Tuberculosis (TB), the peptide proposed by this study demands meticulous invitro analysis prior to clinical applications. [ABSTRACT FROM AUTHOR]

Objective: Lantibiotics are a family of bacterial antimicrobial peptides synthesized by ribosomes, that undergo post-translational modification to form lanthionine (Lan) and methyllanthionine (MeLan) residues. Lantibiotics are currently considered promising agents for combating antibiotic-resistant bacterial infections. This paper presents a biotechnological method for obtaining two components of the lantibiotic lichenicidin from Bacillus licheniformis B-511, Lchα and Lchβ. Such a system has the potential to facilitate the production of not only lichenicidin, but also other lantibiotics, including two-component ones, and also to enable the study of their biosynthesis and the activity and substrate specificity of modifying enzymes. Methods: The developed system is based on heterologous coexpression of the genes of Lchα and Lchβ precursors with the genes of their corresponding modifying enzymes in the cytoplasm of Escherichia coli BL21(DE3). Subsequent steps included immobilized metal affinity chromatography of the His-tagged hybrid peptide under denaturing conditions, cyanogen bromide cleavage in acidic medium, and final purification using reverse-phase HPLC. Results and Discussion: The system was employed for the expression and purification of lantibiotics, resulting in the successful isolation of the β-component of lichenicidin in high yield (approximately 4 mg/L of culture). This purified beta component exhibited structural and functional characteristics comparable to its natural counterpart, which was purified from the natural producer. However, the yield of the mature α-component of lichenicidin in such a system was significantly lower. Conclusions: The work presents a biotechnological method for obtaining recombinant two-component lantibiotic lichenicidin, which has proven to be particularly effective in the case of Lchβ. The developed method can also be applied to the production of other promising lantibiotics and their further research. [ABSTRACT FROM AUTHOR]

Scorpion venoms have proven to be excellent sources of antimicrobial agents. However, although many of them have been functionally characterized, they remain underutilized as pharmacological agents, despite their evident therapeutic potential. In this review, we discuss the physicochemical properties of short scorpion venom antimicrobial peptides (ssAMPs). Being generally short (13–25 aa) and amidated, their proven antimicrobial activity is generally explained by parameters such as their net charge, the hydrophobic moment, or the degree of helicity. However, for a complete understanding of their biological activities, also considering the properties of the target membranes is of great relevance. Here, with an extensive analysis of the physicochemical, structural, and thermodynamic parameters associated with these biomolecules, we propose a theoretical framework for the rational design of new antimicrobial drugs. Through a comparison of these physicochemical properties with the bioactivity of ssAMPs in pathogenic bacteria such as Staphylococcus aureus or Acinetobacter baumannii, it is evident that in addition to the net charge, the hydrophobic moment, electrostatic energy, or intrinsic flexibility are determining parameters to understand their performance. Although the correlation between these parameters is very complex, the consensus of our analysis suggests that there is a delicate balance between them and that modifying one affects the rest. Understanding the contribution of lipid composition to their bioactivities is also underestimated, which suggests that for each peptide, there is a physiological context to consider for the rational design of new drugs. [ABSTRACT FROM AUTHOR]

Antimicrobial peptides (AMPs) are natural ribosomal synthesized small peptides and are crucial effectors in all living organisms. AMPs are diverse polypeptides with varying amino acid composition and structure that often exhibit broad-spectrum and fast-acting antibacterial properties. As a result, AMPs offer a great deal of promise for restorative application in medicine, agriculture, and the environment. The maritime, industrial, and healthcare sectors all suffer major losses as a result of biofouling. This article will review antimicrobial peptides (AMPs), their structure and major class of AMPs that are reported as anti-biofouling agents, evolutionary concept of AMP, mechanism of action of AMPs against biofilm formation, intracellular active AMPs, synthetic AMPs, promising AMP modifications reported and AMP databases to understand AMPs specificity and activity for rational designing. Therefore, this review will provide a comprehensive assessment of AMPs numerous functions as well as to detect their therapeutic potential and avoid industry losses incurred by biofilms. [ABSTRACT FROM AUTHOR]

NLRP6 plays a crucial role in maintaining intestinal homeostasis by regulating the interaction between the intestinal mucosa and the microbiota. However, the impact of NLRP6 deficiency on intestinal damage following hematopoietic stem cell transplantation (HSCT) remains poorly understood. In this study, we established a syngeneic HSCT mouse model using C57BL/6 mice as donors and NLRP6-/- or C57BL/6 mice as recipients. Our findings revealed that NLRP6 deficiency had minimal influence on peripheral blood cell counts and splenic immune cell proportions in transplanted mice. However, it exacerbated pathological changes in the small intestine on day 14 post-transplantation, accompanied by increased proportions of macrophages, dendritic cells, and neutrophils. Furthermore, the NLRP6 deficiency resulted in elevated expression of MPO and CD11b, while reducing the levels mature caspase-1 and mature IL-1β in the intestine. Moreover, the NLRP6 deficiency disturbed the expression of apoptosis-related molecules and decreased the tight junction protein occludin. Notably, recipient mice with NLRP6 deficiency exhibited lower mRNA expression levels of antimicrobial genes, such as Reg3γ and Pla2g2a. The short-term increase in inflammatory cell infiltration caused by NLRP6 deficiency was associated with intestinal damage, increased apoptosis, reduced expression of antimicrobial peptides, and impaired intestinal repair. Taken together, our findings demonstrate that the loss of NLRP6 exacerbates post-transplantation intestinal damage in recipient mice. [ABSTRACT FROM AUTHOR]

Colonisation of sessile bacterial species on biotic and abiotic surfaces is responsible for the development of various infections in humans. At present, biofilm-associated chronic infections have been a prime concern among the healthcare practitioners since they are impermeable to drugs, resulting in the development of antibiotic resistance or multi-drug resistance. For a few decades, a lot of research activity has been performed in the development of alternative therapeutics to combat biofilm-associated chronic infections. The presence of extracellular polymeric substance (EPS) prevents the permeation of most of the drugs rendering drug failures. The use of small molecules has been necessary to penetrate easily through the EPS and act on the targeted cells. In present days, the use of antimicrobial peptides (AMPs) has gained immense importance as alternative therapeutics since they exhibit a novel class of antibiotics exhibiting a wide spectrum of activity and possess a low rate of development of resistance. In the last few decades, a large number of AMPs have been identified from varied groups of organisms as effector molecules for innate immune system acting as an important line of defence. In this review, we will discuss the use of AMPs as effective agents to combat various biofilm-associated chronic infections. [ABSTRACT FROM AUTHOR]

Antimicrobial peptides (AMPs), including beta-defensin from fish, are a crucial class of peptide medicines. The focus of the current study is the molecular and functional attributes of CmDef, a 63-amino acid beta-defensin AMP from Malabar trevally, Carangoides malabaricus. This peptide demonstrated typical characteristics of AMPs, including hydrophobicity, amphipathic nature, and +2.8 net charge. The CmDef was recombinantly expressed and the recombinant peptide, rCmDef displayed a strong antimicrobial activity against bacterial fish pathogens with an MIC of 8 µM for V. proteolyticus and 32 µM for A. hydrophila. The E. tarda and V. harveyi showed an inhibition of 94% and 54%, respectively, at 32 µM concentration. No activity was observed against V. fluvialis and V. alginolyticus. The rCmDef has a multimode of action that exerts an antibacterial effect by membrane depolarization followed by membrane permeabilization and ROS production. rCmDef also exhibited anti-cancer activities in silico without causing hemolysis. The peptide demonstrated stability under various conditions, including different pH levels, temperatures, salts, and metal ions (KCl and CaCl2), and remained stable in the presence of proteases such as trypsin and proteinase K at concentrations up to 0.2 µg/100 µl. The strong antibacterial efficacy and non-cytotoxic nature suggest that rCmDef is a single-edged sword that can contribute significantly to aquaculture disease management. [ABSTRACT FROM AUTHOR]

Background: This systematic review aims to review and assess the importance and relationship between host defence antimicrobial peptides with type 2 diabetes mellitus (T2DM) complications and the correlation of their expression with hyperglycaemic status. Main body: The systematic search included three electronic databases (PMC, PubMed, and Google Scholar) that were searched from July to November 2023. After identifying and screening the research articles, eleven studies fulfilled the selection criteria and were included (six case–control and five cross-sectional studies). The Newcastle Ottawa Scale assessed the selected studies' quality. Most studies indicated a correlation between certain types of AMPs and diabetic complications. Conclusion: Hyperglycaemia in type 2 diabetes mellitus (T2DM) affects the expression of certain types of antimicrobial peptides (AMPs) which have a dual function (antibacterial and modulation of immune response) that may enhance inflammation which may correlate with the development of long-term complications, increased susceptibility to bacterial infection, and impaired wound healing. [ABSTRACT FROM AUTHOR]

Bacteriocins are antimicrobial peptides that are naturally produced by many bacteria. They hold great potential in the fight against antibiotic resistant bacteria, including ESKAPE pathogens. Engineered live biotherapeutic products (eLBPs) that secrete bacteriocins can be created to deliver targeted bacteriocin production. Here we develop a modular bacteriocin secretion platform that can be used to express and secrete multiple bacteriocins from non-pathogenic Escherichia coli host strains. As a proof of concept we create Enterocin A (EntA) and Enterocin B (EntB) secreting strains that show strong antimicrobial activity against Enterococcus faecalis and Enterococcus faecium in vitro, and characterise this activity in both solid culture and liquid co-culture. We then develop a Lotka-Volterra model that can be used to capture the interactions of these competitor strains. We show that simultaneous exposure to EntA and EntB can delay Enterococcus growth. Our system has the potential to be used as an eLBP to secrete additional bacteriocins for the targeted killing of pathogenic bacteria. Bacteriocins are antimicrobial peptides that are naturally produced by many bacteria. In this work, authors develop a bacteriocin secretion platform, and test, in a proof-of-concept study, antimicrobial efficacy against Enterococcus faecalis and Enterococcus faecium. [ABSTRACT FROM AUTHOR]

Natural antimicrobial peptides (AMPs) and enzymes (AMEs) are promising non-antibiotic candidates against antimicrobial resistance but suffer from low efficiency and poor stability. Here, we develop peptide nanozymes which mimic the mode of action of AMPs and AMEs through de novo design and peptide assembly. Through modelling a minimal building block of IHIHICI is proposed by combining critical amino acids in AMPs and AMEs and hydrophobic isoleucine to conduct assembly. Experimental validations reveal that IHIHICI assemble into helical β-sheet nanotubes with acetate modulation and perform phospholipase C-like and peroxidase-like activities with Ni coordination, demonstrating high thermostability and resistance to enzymatic degradation. The assembled nanotubes demonstrate cascade antifungal actions including outer mannan docking, wall disruption, lipid peroxidation and subsequent ferroptotic death, synergistically killing >90% Candida albicans within 10 min on disinfection pad. These findings demonstrate an effective de novo design strategy for developing materials with multi-antimicrobial mode of actions. Natural antimicrobial peptides and enzymes are good candidates for application but suffer from low stability. Here, the authors report on biomimetic self-assembling peptides which mimic both antimicrobial peptide and enzyme functionality, demonstrating application against fungal infection. [ABSTRACT FROM AUTHOR]

Wildlife harbour a diverse range of microorganisms that affect their health and development. Marsupials are born immunologically naïve and physiologically underdeveloped, with primary development occurring inside a pouch. Secretion of immunological compounds and antimicrobial peptides in the epithelial lining of the female's pouch, pouch young skin, and through the milk, are thought to boost the neonate's immune system and potentially alter the pouch skin microbiome. Here, using 16S rRNA amplicon sequencing, we characterised the Tasmanian devil pouch skin microbiome from 25 lactating and 30 non-lactating wild females to describe and compare across these reproductive stages. We found that the lactating pouch skin microbiome had significantly lower amplicon sequence variant richness and diversity than non-lactating pouches, however there was no overall dissimilarity in community structure between lactating and non-lactating pouches. The top five phyla were found to be consistent between both reproductive stages, with over 85% of the microbiome being comprised of Firmicutes, Proteobacteria, Fusobacteriota, Actinobacteriota, and Bacteroidota. The most abundant taxa remained consistent across all taxonomic ranks between lactating and non-lactating pouch types. This suggests that any potential immunological compounds or antimicrobial peptide secretions did not significantly influence the main community members. Of the more than 16,000 total identified amplicon sequence variants, 25 were recognised as differentially abundant between lactating and non-lactating pouches. It is proposed that the secretion of antimicrobial peptides in the pouch act to modulate these microbial communities. This study identifies candidate bacterial clades on which to test the activity of Tasmanian devil antimicrobial peptides and their role in pouch young protection, which in turn may lead to future therapeutic development for human diseases. [ABSTRACT FROM AUTHOR]

2K4L is a rationally designed analog of the short α-helical peptide temporin-1CEc, a natural peptide isolated and purified from the skin secretions of the Chinese brown frog Rana chensinensis by substituting amino acid residues. 2K4L displayed improved and broad-spectrum antibacterial activity than temporin-1CEc in vitro. Here, the antibacterial and anti-inflammatory activities of 2K4L in macrophages, C. elegans and mice were investigated. The results demonstrated that 2K4L could enter THP-1 cells to kill a multidrug-resistant Acinetobacter baumannii strain (MRAB 0227) and a sensitive A. baumannii strain (AB 22933), as well as reduce proinflammatory responses induced by MRAB 0227 by inhibiting NF-κB signaling pathway. Similarly, 2K4L exhibited strong bactericidal activity against A. baumannii uptake into C. elegans, extending the lifespan and healthspan of the nematodes. Meanwhile, 2K4L alleviated the oxidative stress response by inhibiting the expression of core genes in the p38 MAPK/PMK-1 signaling pathway and downregulating the phosphorylation level of p38, thereby protecting the nematodes from damage by A. baumannii. Finally, in an LPS-induced septic model, 2K4L enhanced the survival of septic mice and decreased the production of proinflammatory cytokines by inhibiting the signaling protein expression of the MAPK and NF-κB signaling pathways and protecting LPS-induced septic mice from a lethal inflammatory response. In conclusion, 2K4L ameliorated LPS-induced inflammation both in vitro and in vivo. [ABSTRACT FROM AUTHOR]

Colistin remains an important antibiotic for the therapeutic management of drug-resistant Klebsiella pneumoniae. Despite the numerous reports of colistin resistance in clinical strains, it remains unclear exactly when and how different mutational events arise resulting in reduced colistin susceptibility. Using a bioreactor model of infection, we modelled the emergence of colistin resistance in a susceptible isolate of K. pneumoniae. Genotypic, phenotypic and mathematical analyses of the antibiotic-challenged and un-challenged population indicates that after an initial decline, the population recovers within 24 h due to a small number of "founder cells" which have single point mutations mainly in the regulatory genes encoding crrB and pmrB that when mutated results in up to 100-fold reduction in colistin susceptibility. Our work underlines the rapid development of colistin resistance during treatment or exposure of susceptible K. pneumoniae infections having implications for the use of cationic antimicrobial peptides as a monotherapy. A combined microbiological and mathematical approach to study colistin resistance in antibiotic sensitive K. pneumoniae reveals a rapid emergence and selection of genetic variants generated by spontaneous mutations in key regulatory genes. [ABSTRACT FROM AUTHOR]

Antimicrobial peptides (AMPs) have garnered attention for their differential regulation in cancers like oral squamous cell carcinomas (OSCC), suggesting their potential as novel anti-cancer agents. These small cationic peptides play crucial roles in innate immunity, particularly in the oral cavity where they are produced by salivary glands and epithelium to combat microbial invasion. AMPs exhibit antimicrobial and anti-cancer activities, disrupting microbial cell membranes and inducing cytotoxicity in cancer cells by binding to exposed phosphatidylserine moieties. Certain AMPs also trigger the release of tumor antigens and damage-associated molecular patterns. With increasing resistance to conventional chemotherapy, AMPs present a promising avenue for the development of effective therapeutic agents in oncology. In addition to their direct cytotoxic effects on cancer cells, AMPs exhibit potential in activating adaptive immunity and functioning as tumor suppressor genes. This review explores the properties, mode of action, and potential interaction of AMPs and specific cancer cells, emphasizing their role in combating oral cancer and the need for further research in this area. [ABSTRACT FROM AUTHOR]

Among all health-related issues, the rising concerns about drug resistance led to the look for alternative pharmaceutical drugs that are effective against both infectious and noninfectious diseases. Antimicrobial peptides (AMPs) are small molecular peptides that play a crucial role in the innate immunity of various organisms. They have amphiphilic structure and net positive charge, allowing them to interact with membranes and hydrophobic surfaces, showing strong broad-spectrum activity against different microorganisms, including bacteria, fungi, and viruses. They also exhibit other host-beneficial activities, including immunomodulation, anti-inflammatory, tissue regeneration, etc. AMPs exhibit antimicrobial activity through wide mechanisms of action, particularly by focusing on intracellular targets to inhibit the synthesis of nucleic acids and proteins. These wide ranges of mechanisms of action of AMPs have contributed to the slow development of resistance against microorganisms. The increasing pathogen resistance is a major global public health threat, and AMPs are constantly being explored and developed as another treatment for viral diseases such as HIV infection and (COVID-19). This review analyzes the potential of AMPs to combat antimicrobial resistance developed by several antimicrobial-resistant (AMR) microorganisms against existing antibiotics. This review focuses on the highlights of the sources, synthesis, mode, and mechanism of action, the evaluation of several benefits, and the outline of various hurdles. The review has also included the possible solution to the limitations associated with the clinical applications of AMPs, along with its future perspectives and development needed in drug discovery against AMR pathogens. [ABSTRACT FROM AUTHOR]

Background: Infection remains a major cause of morbidity and mortality, regardless of advances in antimicrobial therapy and improved knowledge of microorganisms. With the major global threat posed by antimicrobial resistance, fast and accurate diagnosis of infections, and the reliable identification of intractable infection, are becoming more crucial for effective treatment and the application of antibiotic stewardship. Molecular imaging with the use of nuclear medicine allows early detection and localisation of infection and inflammatory processes, as well as accurate monitoring of treatment response. There has been a continuous search for more specific radiopharmaceuticals to be utilised for infection imaging. This review summarises the most prominent discoveries in specifically bacterial infection imaging agents over the last five years, since 2019. Main body: Some promising new radiopharmaceuticals evaluated in patient studies are reported here, including radiolabelled bacterial siderophores like [68Ga]Ga-DFO-B, radiolabelled antimicrobial peptide/peptide fragments like [68Ga]Ga-NOTA-UBI29-41, and agents that target bacterial synthesis pathways (folic acid and peptidoglycan) like [11C]para-aminobenzoic acid and D-methyl-[11C]-methionine, with clinical trials underway for [18F]fluorodeoxy-sorbitol, as well as for 11C- and 18F-labelled trimethoprim. Conclusion: It is evident that a great deal of effort has gone into the development of new radiopharmaceuticals for infection imaging over the last few years, with remarkable progress in preclinical investigations. However, translation to clinical trials, and eventually clinical Nuclear Medicine practice, is apparently slow. It is the authors' opinion that a more structured and harmonised preclinical setting and well-designed clinical investigations are the key to reliably evaluate the true potential of the newly proposed infection imaging agents. [ABSTRACT FROM AUTHOR]

Endogenous antimicrobial peptides (AMPs) play a key role in the host defense against pathogens. AMPs attack pathogens preferentially at the site of entry to prevent invasive infection. Mycobacterium tuberculosis (Mtb) enters its host via the airways. AMPs released into the airways are therefore likely candidates to contribute to the clearance of Mtb immediately after infection. Since lysozyme is detectable in airway secretions, we evaluated its antimicrobial activity against Mtb. We demonstrate that lysozyme inhibits the growth of extracellular Mtb, including isoniazid-resistant strains. Lysozyme also inhibited the growth of non-tuberculous mycobacteria. Even though lysozyme entered Mtb-infected human macrophages and co-localized with the pathogen we did not observe antimicrobial activity. This observation was unlikely related to the large size of lysozyme (14.74 kDa) because a smaller lysozyme-derived peptide also co-localized with Mtb without affecting the viability. To evaluate whether the activity of lysozyme against extracellular Mtb could be relevant in vivo, we incubated Mtb with fractions of human serum and screened for antimicrobial activity. After several rounds of sub-fractionation, we identified a highly active fraction-component as lysozyme by mass spectrometry. In summary, our results identify lysozyme as an antimycobacterial protein that is detectable as an active compound in human serum. Our results demonstrate that the activity of AMPs against extracellular bacilli does not predict efficacy against intracellular pathogens despite co-localization within the macrophage. Ongoing experiments are designed to unravel peptide modifications that occur in the intracellular space and interfere with the deleterious activity of lysozyme in the extracellular environment. [ABSTRACT FROM AUTHOR]

Respiratory syncytial virus is the major cause of acute lower respiratory tract infections in young children, causing extensive mortality and morbidity globally, with limited therapeutic or preventative options. Cathelicidins are innate immune antimicrobial host defence peptides and have antiviral activity against RSV. However, upper respiratory tract cathelicidin expression and the relationship with host and environment factors in early life, are unknown. Infant cohorts were analysed to characterise early life nasal cathelicidin levels, revealing low expression levels in the first week of life, with increased levels at 9 months which are comparable to 2-year-olds and healthy adults. No impact of prematurity on nasal cathelicidin expression was observed, nor were there effects of sex or birth mode, however, nasal cathelicidin expression was lower in the first week-of-life in winter births. Nasal cathelicidin levels were positively associated with specific inflammatory markers and demonstrated to be associated with microbial community composition. Importantly, levels of nasal cathelicidin expression were elevated in infants with mild RSV infection, but, in contrast, were not upregulated in infants hospitalised with severe RSV infection. These data suggest important relationships between nasal cathelicidin, upper airway microbiota, inflammation, and immunity against RSV infection, with interventional potential. [ABSTRACT FROM AUTHOR]

The semislug Megaustenia siamensis, commonly found in Thailand, is notable for its exceptional capacity to produce biological adhesives, enabling it to adhere to tree leaves even during heavy rainfall. In this study, we generated the first reference genome for M. siamensis using a combination of three sequencing technologies: Illumina's short-read, Pac-Bio's HIFI long-read, and Hi-C. The assembled genome size was 2593 billion base pairs (bp), containing 34,882 protein-coding genes. Our analysis revealed positive selection in pathways associated with the ubiquitin–proteasome system. Furthermore, RNA sequencing of foot and mantle tissues unveiled the primary constituents of the adhesive, including lectin-like proteins (C-lectin, H-lectin, and C1q) and matrilin-like proteins (VWA and EGF). Additionally, antimicrobial peptides were identified. The comprehensive M. siamensis genome and tissue-specific transcriptomic data provided here offer valuable resources for understanding its biology and exploring potential medical applications. [ABSTRACT FROM AUTHOR]

Antimicrobial resistance remains a significant global threat, driving up mortality rates worldwide. Ribosomally synthesized and post-translationally modified peptides have emerged as a promising source of novel peptide antibiotics due to their diverse chemical structures. Here, we report the discovery of new aminovinyl-(methyl)cysteine (Avi(Me)Cys)-containing peptide antibiotics through a synergistic approach combining biosynthetic rule-based omics mining and heterologous expression. We first bioinformatically identify 1172 RiPP biosynthetic gene clusters (BGCs) responsible for Avi(Me)Cys-containing peptides formation from a vast pool of over 50,000 bacterial genomes. Subsequently, we successfully establish the connection between three identified BGCs and the biosynthesis of five peptide antibiotics via biosynthetic rule-guided metabolic analysis. Notably, we discover a class V lanthipeptide, massatide A, which displays excellent activity against gram-positive pathogens, including drug-resistant clinical isolates like linezolid-resistant S. aureus and methicillin-resistant S. aureus, with a minimum inhibitory concentration of 0.25 μg/mL. The remarkable performance of massatide A in an animal infection model, coupled with a relatively low risk of resistance and favorable safety profile, positions it as a promising candidate for antibiotic development. Our study highlights the potential of Avi(Me)Cys-containing peptides in expanding the arsenal of antibiotics against multi-drug-resistant bacteria, offering promising drug leads in the ongoing battle against infectious diseases. This study reports the genomics- and metabolomics-guided discovery of aminovinyl-(methyl-)cysteine-containing peptides (ACyP). One of these peptides, massatide A, demonstrates excellent activity against drug-resistant gram-positive pathogens. [ABSTRACT FROM AUTHOR]

Objective: To date, polychaetes remain a poorly studied class of invertebrate animals in terms of the features of functioning of their immune system and, in particular, the biodiversity of antimicrobial peptides (AMPs). AMPs also known as host defense peptides play a key role in host protection from various pathogens and regulation of the species composition of symbiotic microbes. A study of the biosynthesis of AMPs in polychaetes resulted in the discovery of the so-called BRICHOS domain in the structure of the precursor proteins of a number of such peptides. The conserved structure of this domain makes possible the bioinformatic search for AMP precursors in polychaete transcriptomes. In this work, we found and studied a novel BRICHOS-related AMP from the lugworm Arenicola marina, representing a previously undiscovered in polychaetes a structural family of defensin-like peptides stabilized by four disulfide bonds. Methods: The peptide, designated as AmBRI-44a and containing 44 amino acid residues, was obtained by heterologous expression in Escherichia coli. The peptide secondary structure was investigated by CD spectroscopy in water and dodecylphosphocholine (DPC) micelles. The minimum inhibitory concentrations (MICs) against a wide range of bacterial pathogens were assessed using the two-fold serial dilutions method. Cytotoxicity of AmBRI-44a was studied in vitro on human erythrocytes or adherent cell line HEK293T using the hemoglobin release assay or the MTT test, respectively. The AMBRI-44a potential target was discovered by successive daily subculturing of the AmBRI-44a resistant strain followed by whole-genome sequencing. Results and Discussion: According to CD data, AmBRI-44a is a predominantly β-structured peptide. AmBRI-44a was shown to have a specific activity against a narrow spectrum of Gram-positive bacteria and pronounced cytotoxic effects on the eukaryotic cell line HEK293T. The proposed mechanism of the antibacterial action of this peptide is associated with the inhibition of bacterial cell wall biosynthesis, as indicated by the genetic and phenotypic analysis of selected AmBRI-44a-resistant bacteria Bacillus licheniformis B-511. Conclusions: The resulting data allow us to consider the discovered peptide AmBRI-44a as a candidate compound for the development of an antibiotic agent that could potentially be effective in the treatment of infectious diseases mediated by multidrug-resistant Gram-positive bacteria. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to: (1) investigate the expression patterns of antimicrobial peptides (AMPs), specifically psoriasin (S100A7) and calgranulin A and B (S100A8/A9), in patients with oral lichen planus (OLP) compared to healthy individuals; (2) evaluate the oral health-related quality of life (OHrQoL) in OLP patients versus healthy controls; (3) investigate the impact of clinical severity of OLP on OHrQoL; and (4) assess the influence of AMP expression on clinical severity and OHrQoL in OLP patients. Materials and methods: Oral mucosal biopsies (n = 38) were collected from healthy individuals (n = 17) and patients with OLP (n = 21). Levels of AMPs (S100A7, S100A8, S100A9) and pro-inflammatory cytokines interleukin-8 (IL-8) and tumor necrosis factor alpha (TNFα) were assessed by RT-qPCR. AMP protein localization was identified by indirect immunofluorescence analysis. OHrQoL was assessed using the OHIP-G14 questionnaire, and clinical severity was evaluated with the Oral Disease Severity Score (ODSS). Correlations between OLP manifestation, OHrQoL, and AMP expression were evaluated. Results: (1) S100A7 (p < 0.001), IL-8 (p < 0.001), and TNFα (p < 0.001) mRNA levels were significantly upregulated in OLP tissue compared to healthy tissue, while S100A8 (p < 0.001) and S100A9 (p < 0.001) mRNA levels were downregulated. Immunofluorescence staining revealed an enhanced expression of S100A7 and decreased protein expression of S100A9 in OLP tissue. (2) OLP patients (9.58 ± 8.32) reported significantly higher OHIP-G14 scores compared to healthy individuals (0.67 ± 0.87; p < 0.001), particularly in the categories “physical pain” (p < 0.001) and “psychological discomfort” (p = 0.025). (3,4) Clinical severity (25.21 ± 9.77) of OLP correlated positively with OHrQoL (ρ = 0.497) and psoriasin expression (ρ = 0.402). Conclusions: This study demonstrated differential expression patterns of AMPs in OLP and highlighted the correlation between the clinical manifestation of OLP and OHrQoL. Further research approaches should address the role of psoriasin in the risk of malignant transformation of OLP. Clinical relevance: Psoriasin is a putative biomarker to monitor disease severity including malignant transformation of OLP lesions. OHIP-G14 scores can be useful to monitor OHrQoL in OLP patients. [ABSTRACT FROM AUTHOR]