Structure-activity relationships of antibacterial peptides

Contribution of the infection ecosystem and biogeography to antibiotic failure in vivo

The acquisition of antibiotic resistance in bacteria, though a deeply concerning international issue, is reasonably well-understood at a mechanistic level. Less well-understood is why bacteria that are sensitive in vitro to well-established and widely-used antibiotics sometimes fail to respond to these agents in vivo. This is a particularly common problem in chronic, polymicrobial infection scenarios. Here, we discuss this in vitro-in vivo disconnect from the perspective of the bacterium, focusing in particular on how infection micro/macro-environment, biogeography, and the presence of co-habiting species affect the response to antibiotics. Using selected exemplars, we also consider interventions that might improve treatment outcomes, as well as ecologically 'eubiotic' approaches that have less of an impact on the patient's commensal microflora. In our view, the accrued data strongly suggest that we need a more comprehensive understanding of the in situ microbiology at infection sites.

The Wheel of Fortune: Helical Wheel Alanine Scanning of a Spider Venom Antimicrobial Peptide Reveals Residues Involved in Antimicrobial and Cytotoxic Activity

A preference for several amino acids is observed to occur at particular positions of cationic α-helical antimicrobial peptides (AMPs), which ensures the formation of amphipathic regions once they assume their correct secondary structure in membranes or membrane-mimicking environments and makes them active against pathogens. This study determined the effect of alanine mutations on the secondary structure and bioactivity of lyp1987 (GRLQAFLAKMKEIAAQTL-NH2), a cationic α-helical AMP obtained from the venom of Lycosa poonaensis which exhibits broad range activity against Gram-positive and Gram-negative bacteria with micromolar minimum inhibitory concentrations (MIC). CD spectroscopy revealed no significant difference in the secondary structure, with all alanine-substituted analogs exhibiting predominantly α-helical structure in buffered 2,2,2-trifluoroethanol solution. Alanine substitution at Glu12 and Thr17 increased the activity of lyp1987 against Gram-positive and -negative bacteria, while alanine substitution at Lys9 increased its selectivity against Gram-positive bacteria. Further investigation can be done to determine positions and substitutions that will give less cytotoxic analogs.

Detection strategies of infectious diseases via peptide-based electrochemical biosensors

Infectious diseases have threatened human life for as long as humankind has existed. One of the most crucial aspects of fighting against these infections is diagnosis to prevent disease spread. However, traditional diagnostic methods prove insufficient and time-consuming in the face of a pandemic. Therefore, studies focusing on detecting viruses causing these diseases have increased, with a particular emphasis on developing rapid, accurate, specific, user-friendly, and portable electrochemical biosensor systems. Peptides are used integral components in biosensor fabrication for several reasons, including various and adaptable synthesis protocols, long-term stability, and specificity. Here, we discuss peptide-based electrochemical biosensor systems that have been developed over the last decade for the detection of infectious diseases. In contrast to other reports on peptide-based biosensors, we have emphasized the following points i) the synthesis methods of peptides for biosensor applications, ii) biosensor fabrication approaches of peptide-based electrochemical biosensor systems, iii) the comparison of electrochemical biosensors with other peptide-based biosensor systems and the advantages and limitations of electrochemical biosensors, iv) the pros and cons of peptides compared to other biorecognition molecules in the detection of infectious diseases, v) different perspectives for future studies with the shortcomings of the systems developed in the past decade.

Phosphorylation as an Effective Tool to Improve Stability and Reduce Toxicity of Antimicrobial Peptides

Developing a straightforward and effective strategy to modify antimicrobial peptides (AMPs) is crucial in overcoming the challenges posed by their instability and toxicity. Phosphorylation can reduce toxicity and improve the stability of AMPs. Based on these, we designed a series of peptides and their corresponding phosphorylated forms. The results showed that all phosphorylated peptides displayed reduced toxicity and enhanced stability compared to their unphosphorylated counterparts. Among them, W3BipY8-P stood out as the most promising peptide, exhibiting similar antibacterial activity as its unphosphorylated analog W3BipY8 but with significantly reduced hemolytic activity (19-fold decrease), cytotoxicity (3.3-fold decrease), and an extended serum half-life 6.3 times longer than W3BipY8. W3BipY8-P exerted bactericidal effects by disrupting bacterial membranes. Notably, W3BipY8-P significantly prolonged the survival of bacteria-infected animals while its LD50 was 4.2 times higher than that of W3BipY8. These findings highlight phosphorylation as an effective strategy for improving the antimicrobial properties of AMPs.

Evolutionary trends indicate a coherent organization of sap operons

Human hosts possess a complex network of immune responses against microbial pathogens. The production of antimicrobial peptides (AMPs), which target the pathogen cell membranes and inhibit them from inhabiting the hosts, is one such mechanism. However, pathogens have evolved systems that encounter these host-produced AMPs. The Sap (sensitivity to antimicrobial peptides) transporter uptakes AMPs inside the microbial cell and proteolytically degrades them. The Sap transporters comprise five subunits encoded by genes in an operon. Despite its ubiquitous nature, its subunits are not found to be in tandem with many organisms. In this study, a total of 421 Sap transporters were analyzed for their operonic arrangement. Out of 421, a total of 352 operons were found to be in consensus arrangement, while the remaining 69 show a varying arrangement of genes. The analysis of the intergenic distance between the subunits of the sap operon suggests a signature pattern with sapAB (-4), sapBC (-14), sapCD (-1), and sapDF (-4 to 1). An evolutionary analysis of these operons favors the consensus arrangement of the Sap transporter systems, substantiating its prevalence in most of the Gram-negative pathogens. Overall, this study provides insight into bacterial evolution, favoring the maintenance of the genetic organization of essential pathogenicity factors.

Antibiofilm and antivirulence potentials of iodinated fmoc-phenylalanine against Staphylococcus aureus

Staphylococcus aureus poses significant risks to public health due to its ability to form biofilm and produce virulence factors, contributing to the increase in antibiotic resistance and treatment complications. This emphasizes the urgent need for novel antimicrobial controls. Based on the premise that halogenation improves antimicrobial efficacy, this study investigated the ability of halogenated phenylalanine to effectively inhibit S. aureus biofilm formation and virulence activities. Among 29 halogenated compounds, Fmoc-4-iodo-phenylalanine (Fmoc-Iodo-Phe) displayed the highest antibiofilm effect against S. aureus, achieving 94.3 % reduction at 50 μg/mL. Microscopic studies confirmed its ability to prevent and disrupt mature biofilms. At 10 μg/mL, Fmoc-Iodo-Phe markedly inhibited virulence factors, such as cell surface hydrophobicity, hemolysin and slime production. It showed low propensity for resistance development and effectively inhibited biofilms formed by methicillin-resistant S. aureus (MRSA) and S. epidermidis, but was inactive against Gram-negative bacteria. Gene expression analysis complemented by molecular docking suggest that Fmoc-Iodo-Phe could target the AgrA quorum sensing cascade due to strong interactions with key residues at its DNA binding sites. Notably, it was non-cytotoxic in Caenorhabditis elegans model and satisfied drug-likeliness criteria based on ADMET prediction. Therefore, our findings position Fmoc-Iodo-Phe as a promising antimicrobial candidate against S. aureus infections, underscoring its potential as an alternative to traditional antibiotics.

Bioactive Peptides from Fermented Foods: Production Approaches, Sources, and Potential Health Benefits

Microbial fermentation is a well-known strategy for enhancing the nutraceutical attributes of foods. Among the fermentation outcomes, bioactive peptides (BAPs), short chains of amino acids resulting from proteolytic activity, are emerging as promising components thanks to their bioactivities. Indeed, BAPs offer numerous health benefits, including antimicrobial, antioxidant, antihypertensive, and anti-inflammatory properties. This review focuses on the production of bioactive peptides during the fermentation process, emphasizing how different microbial strains and fermentation conditions influence the quantity and quality of these peptides. Furthermore, it examines the health benefits of BAPs from fermented foods, highlighting their potential in disease prevention and overall health promotion. Additionally, this review addresses the challenges and future directions in this field. This comprehensive overview underscores the promise of fermented foods as sustainable and potent sources of bioactive peptides, with significant implications for developing functional foods and nutraceuticals.

Effects of Secondary Amine and Molecular Weight on the Biological Activities of Cationic Amphipathic Antimicrobial Macromolecules

Cationic amphipathic antimicrobial agents inspired by antimicrobial peptides (AMPs) have shown potential in combating multidrug-resistant bacteria because of minimal resistance development. Here, this study focuses on the development of novel cationic amphipathic macromolecules in the form of dendrons and polymers with different molecular weights that employ secondary amine piperidine derivative as the cationic moiety. Generally, secondary amine compounds, especially at low molecular weights, have stronger bacteriostatic, bactericidal, and inner membrane disruption abilities than those of their primary amine counterparts. Low molecular weight D2 dendrons with two cationic centers and one hydrophobic dodecyl chain produce outstanding synergistic activity with the antibiotic rifampicin against Escherichia coli, where one-eighth of the standalone dose of D2 dendrons could reduce the concentration of rifampicin required by up to 4000-fold. The low molecular weight compounds are also less toxic and therefore have higher therapeutic index values compared to compounds with larger molecular weights. This study thus reveals key information that may inform the design of future synthetic AMPs and mimics, specifically, the design of low-molecular-weight compounds with secondary amine as the cationic center to achieve high antimicrobial potency and biocompatibility.

How Unnatural Amino Acids in Antimicrobial Peptides Change Interactions with Lipid Model Membranes

This study investigates the potential of antimicrobial peptides (AMPs) as alternatives to combat antibiotic resistance, with a focus on two AMPs containing unnatural amino acids (UAAs), E2-53R (16 AAs) and LE-54R (14 AAs). In both peptides, valine is replaced by norvaline (Nva), and tryptophan is replaced by 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic). Microbiological studies reveal their potent activity against both Gram-negative (G(-)) and Gram-positive (G(+)) bacteria without any toxicity to eukaryotic cells at test concentrations up to 32 μM. Circular dichroism (CD) spectroscopy indicates that these peptides maintain α-helical structures when interacting with G(-) and G(+) lipid model membranes (LMMs), a feature linked to their efficacy. X-ray diffuse scattering (XDS) demonstrates a softening of G(-), G(+) and eukaryotic (Euk33) LMMs and a nonmonotonic decrease in chain order as a potential determinant for bacterial membrane destabilization. Additionally, XDS finds a significant link between both peptides' interfacial location in G(-) and G(+) LMMs and their efficacy. Neutron reflectometry (NR) confirms the AMP locations determined using XDS. Lack of toxicity in eukaryotic cells may be related to their loss of α-helicity and their hydrocarbon location in Euk33 LMMs. Both AMPs with UAAs offer a novel strategy to wipe out antibiotic-resistant strains while maintaining human cells. These findings are compared with previously published data on E2-35, which consists of the natural amino acids arginine, tryptophan, and valine.

The antibacterial activity and mechanisms of Trp-containing peptides against multidrug-resistant Pseudomonas aeruginosa persisters

Bacterial persisters avoid antibiotic-mediated death by entering a dormant state and are considered a major cause of antibiotic treatment failure. Antimicrobial peptides (AMPs) with membrane-disrupting activity are promising drugs to eradicate persister cells. In this study, carbonyl cyanide m-chlorophenylhydrazone (CCCP), ciprofloxacin (CIP), and rifampicin (RFP) were applied to induce the formation of multidrug-resistant Pseudomonas aeruginosa (MRPA0108) persisters, and the antibacterial activity and mechanisms of I1W and L12W (two Trp-containing peptides designed in our lab) against MRPA0108 persisters were investigated. The results showed that I1W and L12W displayed potent antibacterial activity against MRPA0108 persisters. Both Trp-containing peptides disturbed the inner and outer membrane of MRPA0108 persisters. In addition, I1W and L12W revealed novel antibacterial mechanisms by decreasing the enzymatic activities of superoxide dismutase (SOD) and catalase (CAT), increasing reactive oxygen species (ROS) and malondialdehyde (MDA) levels, consequently leading to oxidative stress. The transcriptome profile of I1W-treated MRPA0108 persisters revealed that the genes involved in carbon metabolism, biosynthesis of amino acids, and the TCA cycle were downregulated, indicating that I1W interfered with metabolism and energy synthesis processes. Furthermore, both Trp-containing peptides displayed synergistic activities with antibiotic tobramycin and showed additive activities with cefepime or ciprofloxacin, which revealed a potential therapeutic strategy for the eradication of MRPA0108 persisters.

Genetically engineered long-acting Esculentin-2CHa(1-30) fusion protein with potential applicability for the treatment of NAFLD

Esculentin-2CHa(1-30) (‟ESC") has been reported as a potent anti-diabetic peptide with little toxicity. However, its very short plasma residence time severely limits the therapeutic efficacy. To address this issue, we genetically engineered a fusion protein of tandem trimeric ESC with an albumin binding domain (ABD) and a fusion partner, SUMO (named ‟SUMO-3×ESC-ABD"). The SUMO-3×ESC-ABD, successfully produced from E. coli, showed low cellular and hemolytic toxicity while displaying potent activities for the amelioration of hyperglycemia as well as non-alcoholic fatty liver disease (NAFLD) in vitro. In animal studies, the estimated plasma half-life of SUMO-3×ESC-ABD was markedly longer (427-fold) than that of the ESC peptide. In virtue of the extended plasma residence, the SUMO-3×ESC-ABD could produce significant anti-hyperglycemic effects that lasted for >2 days, while both the ESC or ESC-ABD peptides elicited little effects. Further, twice-weekly treatment for 10 weeks, the SUMO-3×ESC-ABD displayed significant improvement in blood glucose control with a reduction in body weight. Most importantly, a significant improvement in the conditions of NAFLD was observed in the SUMO-3×ESC-ABD-treated mice. Along the systemic effects (by improved glucose tolerance and body weight reduction), direct inhibition of the hepatocyte lipid uptake was suggested as the major mechanism of the anti-NAFLD effects. Overall, this study demonstrated the utility of the long-acting SUMO-3×ESC-ABD as a potent drug candidate for the treatment of NAFLD.

Growth factor-functionalized titanium implants for enhanced bone regeneration: A review

Titanium and titanium alloys are widely favored materials for orthopedic implants due to their exceptional mechanical properties and biological inertness. The additional benefit of sustained local release of bioactive substances further promotes bone tissue formation, thereby augmenting the osseointegration capacity of titanium implants and attracting increasing attention in bone tissue engineering. Among these bioactive substances, growth factors have shown remarkable osteogenic and angiogenic induction capabilities. Consequently, researchers have developed various physical, chemical, and biological loading techniques to incorporate growth factors into titanium implants, ensuring controlled release kinetics. In contrast to conventional treatment modalities, the localized release of growth factors from functionalized titanium implants not only enhances osseointegration but also reduces the risk of complications. This review provides a comprehensive examination of the types and mechanisms of growth factors, along with a detailed exploration of the methodologies used to load growth factors onto the surface of titanium implants. Moreover, it highlights recent advancements in the application of growth factors to the surface of titanium implants (Scheme 1). Finally, the review discusses current limitations and future prospects for growth factor-functionalized titanium implants. In summary, this paper presents cutting-edge design strategies aimed at enhancing the bone regenerative capacity of growth factor-functionalized titanium implants-a significant advancement in the field of enhanced bone regeneration.

Multifunctional host-defense peptides isolated from skin secretions of the banana tree dwelling frog Boana platanera (Hylidae; Hylinae)

Five host-defense peptides (figainin 2PL, hylin PL, raniseptin PL, plasticin PL, and peptide YL) were isolated from norepinephrine-stimulated skin secretions of the banana tree dwelling frog Boana platanera (Hylidae; Hylinae) collected in Trinidad. Raniseptin PL (GVFDTVKKIGKAVGKFALGVAKNYLNS.NH2) and figainin 2PL (FLGTVLKLGKAIAKTVVPMLTNAMQPKQ. NH2) showed potent and rapid bactericidal activity against a range of clinically relevant Gram-positive and Gram-negative ESKAPE + pathogens and Clostridioides difficile. The peptides also showed potent cytotoxic activity (LC50 values < 30 μM) against A549, MDA-MB-231 and HT29 human tumor-derived cell lines but appreciably lower hemolytic activity against mouse erythrocytes (LC50 = 262 ± 14 μM for raniseptin PL and 157 ± 16 μM for figainin 2PL). Hylin PL (FLGLIPALAGAIGNLIK.NH2) showed relatively weak activity against microorganisms but was more hemolytic. The glycine-leucine-rich peptide with structural similarity to the plasticins (GLLSTVGGLVGGLLNNLGL.NH2) and the non-cytotoxic peptide YL (YVPGVIESLL.NH2) lacked antimicrobial and cytotoxic activities. Hylin PL, raniseptinPL and peptide YL stimulated the rate of release of insulin from BRIN-BD11 clonal β-cells at concentrations ≥100 nM. Peptide YL was the most effective (2.3-fold increase compared with basal rate at 1 μM concentration) and may represent a template for the design of a new class of incretin-based anti-diabetic drugs.

Recent Advances in Marine-Derived Compounds as Potent Antibacterial and Antifungal Agents: A Comprehensive Review

The increase in antimicrobial resistance (AMR) in microorganisms is a significant global health concern. Various factors contribute to AMR, including alterations in cell membrane permeability, increased efflux pump activity, enzymatic modification or inactivation of antibiotics, target site changes, alternative metabolic pathways, and biofilm formation. Marine environments, with their extensive biodiversity, provide a valuable source of natural products with a wide range of biological activities. Marine-derived antimicrobial compounds show significant potential against drug-resistant bacteria and fungi. This review discusses the current knowledge on marine natural products such as microorganisms, sponges, tunicates and mollusks with antibacterial and antifungal properties effective against drug-resistant microorganisms and their ecological roles. These natural products are classified based on their chemical structures, such as alkaloids, amino acids, peptides, polyketides, naphthoquinones, terpenoids, and polysaccharides. Although still in preclinical studies, these agents demonstrate promising in vivo efficacy, suggesting that marine sources could be pivotal in developing new drugs to combat AMR, thereby fulfilling an essential medical need. This review highlights the ongoing importance of marine biodiversity exploration for discovering potential antimicrobial agents.

Self-assembling short peptide amphiphiles as versatile delivery agents: a new frontier in antibacterial research

Self-assembling short peptide amphiphiles, crafted through a minimalistic approach, spontaneously generate well-ordered nanostructures, facilitating the creation of precise nanostructured biomaterials for diverse biomedical applications. The seamless integration of bioactive metal ions and nanoparticles endows them with the potential to serve as pioneering materials in combating bacterial infections. Nanomanipulation of these molecules' binary structures enables effective penetration of membranes, forming structured nanoarchitectures with antibacterial properties. Through a comprehensive exploration, we attempt to reveal the innovative potential of short peptide amphiphiles, particularly in conjugation with metal cations and nanoparticles, offering insights for future research trajectories.

Screening of Short-Chain Antimicrobial Peptide LKARI with Broad-Spectrum Bactericidal Properties and Its Application in Promoting Wound Healing

Due to the extensive use of antibiotics, many highly resistant bacteria and extensively resistant bacteria have been produced. In recent years, the increase of drug-resistant bacteria and the resulting proliferation of drug-resistant bacteria have increased the incidence of hospital-acquired infections and caused great harm to human health. Antimicrobial peptides (AMPs) are considered to be an innovative antibiotic and belong to the latest advances in this field. We designed a polypeptide and verified its low minimum inhibitory concentration and broad-spectrum activity against Gram-positive bacteria, Gram-negative bacteria, and fungi in microbiology and pharmacology. Several experiments have confirmed that the screened antimicrobial peptides have significant antidrug resistance and also show significant therapeutic properties in the treatment of systemic bacterial infections. In addition, through our experimental research, it was proved that the antibacterial hydrogel composed of poly(vinyl alcohol), sodium alginate, and antimicrobial peptides had excellent antibacterial properties and showed good wound healing ability.

1,3,5-Triazine as Branching Connector for the Construction of Novel Antimicrobial Peptide Dendrimers: Synthesis and Biological Characterization

Peptides displaying antimicrobial properties are being regarded as useful tools to evade and combat antimicrobial resistance, a major public health challenge. Here we have addressed dendrimers, attractive molecules in pharmaceutical innovation and development displaying broad biological activity. Triazine-based dendrimers were fully synthesized in the solid phase, and their antimicrobial activity and some insights into their mechanisms of action were explored. Triazine is present in a large number of compounds with highly diverse biological targets with broad biological activities and could be an excellent branching unit to accommodate peptides. Our results show that the novel peptide dendrimers synthesized have remarkable antimicrobial activity against Gram-negative bacteria (E. coli and P. aeruginosa) and suggest that they may be useful in neutralizing the effect of efflux machinery on resistance.

CATH-2-derived antimicrobial peptide inhibits multidrug-resistant Escherichia coli infection in chickens

Avian colibacillosis (AC), caused by infection with Escherichia coli (E. coli), is a major threat to poultry health, food safety and public health, and results in high mortality and significant economic losses. Currently, new drugs are urgently needed to replace antibiotics due to the continuous emergence and increasing resistance of multidrug-resistant (MDR) strains of E. coli caused by the irrational use of antibiotics in agriculture and animal husbandry. In recent years, antimicrobial peptides (AMPs), which uniquely evolved to protect the host, have emerged as a leading alternative to antibiotics in clinical settings. CATH-2, a member of the antimicrobial cathelicidin peptide family, has been reported to have antibacterial activity. To enhance the antimicrobial potency and reduce the adverse effects on animals, we designed five novel AMPs, named C2-1, C2-2, C2-3, C2-4 and C2-5, based on chicken CATH-2, the secondary structures of these AMPs were consistently α-helical and had an altered net charge and hydrophobicity compared to those of the CATH-2 (1-15) sequences. Subsequently, the antimicrobial activities of CATH-2 (1-15) and five designed peptides against MDR E. coli were evaluated in vitro. Specifically, C2-2 showed excellent antimicrobial activity against either the ATCC standard strain or veterinary clinical isolates of MDR E. coli, with concentrations ranging from 2-8 μg/mL. Furthermore, C2-2 maintained its strong antibacterial efficacy under high temperature and saline conditions, demonstrating significant stability. Similarly, C2-2 retained a high level of safety with no significant hemolytic activity on chicken mature red blood cells or cytotoxicity on chicken kidney cells over the concentration range of 0-64 μg/mL. Moreover, the administration of C2-2 improved the survival rate and reduced the bacterial load in the heart, liver and spleen during MDR E. coli infection in chickens. Additionally, pathological damage to the heart, liver and intestine was prevented when MDR E. coli infected chickens were treated with C2-2. Together, our study showed that C2-2 may be a promising novel therapeutic agent for the treatment of MDR E. coli infections and AC.

Navigating Antibacterial Frontiers: A Panoramic Exploration of Antibacterial Landscapes, Resistance Mechanisms, and Emerging Therapeutic Strategies

The development of effective antibacterial solutions has become paramount in maintaining global health in this era of increasing bacterial threats and rampant antibiotic resistance. Traditional antibiotics have played a significant role in combating bacterial infections throughout history. However, the emergence of novel resistant strains necessitates constant innovation in antibacterial research. We have analyzed the data on antibacterials from the CAS Content Collection, the largest human-curated collection of published scientific knowledge, which has proven valuable for quantitative analysis of global scientific knowledge. Our analysis focuses on mining the CAS Content Collection data for recent publications (since 2012). This article aims to explore the intricate landscape of antibacterial research while reviewing the advancement from traditional antibiotics to novel and emerging antibacterial strategies. By delving into the resistance mechanisms, this paper highlights the need to find alternate strategies to address the growing concern.

Tapping the biosynthetic potential of marine Bacillus licheniformis LHG166, a prolific sulphated exopolysaccharide producer: structural insights, bio-prospecting its antioxidant, antifungal, antibacterial and anti-biofilm potency as a novel anti-infective lead

The escalating global threat of antimicrobial resistance necessitates prospecting uncharted microbial biodiversity for novel therapeutic leads. This study mines the promising chemical richness of Bacillus licheniformis LHG166, a prolific exopolysaccharide (EPSR2-7.22 g/L). It comprised 5 different monosaccharides with 48.11% uronic acid, 17.40% sulfate groups, and 6.09% N-acetyl glucosamine residues. EPSR2 displayed potent antioxidant activity in DPPH and ABTS+, TAC and FRAP assays. Of all the fungi tested, the yeast Candida albicans displayed the highest susceptibility and antibiofilm inhibition. The fungi Aspergillus niger and Penicillium glabrum showed moderate EPSR2 susceptibility. In contrast, the fungi Mucor circinelloides and Trichoderma harzianum were resistant. Among G+ve tested bacteria, Enterococcus faecalis was the most susceptible, while Salmonella typhi was the most sensitive to G-ve pathogens. Encouragingly, EPSR2 predominantly demonstrated bactericidal effects against both bacterial classes based on MBC/MIC of either 1 or 2 superior Gentamicin. At 75% of MBC, EPSR2 displayed the highest anti-biofilm activity of 88.30% against B. subtilis, while for G-ve antibiofilm inhibition, At 75% of MBC, EPSR2 displayed the highest anti-biofilm activity of 96.63% against Escherichia coli, Even at the lowest dose of 25% MBC, EPSR2 reduced biofilm formation by 84.13% in E. coli, 61.46% in B. subtilis. The microbial metabolite EPSR2 from Bacillus licheniformis LHG166 shows promise as an eco-friendly natural antibiotic alternative for treating infections and oxidative stress.

The antibiotic crisis: On the search for novel antibiotics and resistance mechanisms

In the relentless battle for human health, the proliferation of antibiotic-resistant bacteria has emerged as an impending catastrophe of unprecedented magnitude, potentially driving humanity towards the brink of an unparalleled healthcare crisis. The unyielding advance of antibiotic resistance looms as the foremost threat of the 21st century in clinical, agricultural and environmental arenas. Antibiotic resistance is projected to be the genesis of the next global pandemic, with grim estimations of tens of millions of lives lost annually by 2050. Amidst this impending calamity, our capacity to unearth novel antibiotics has languished, with the past four decades marred by a disheartening 'antibiotic discovery void'. With nearly 80% of our current antibiotics originating from natural or semi-synthetic sources, our responsibility is to cast our investigative nets into uncharted ecological niches teeming with microbial strife, the so-called 'microbial oases of interactions'. Within these oases of interactions, where microorganisms intensively compete for space and nutrients, a dynamic and ever-evolving microbial 'arms race' is constantly in place. Such a continuous cycle of adaptation and counter-adaptation is a fundamental aspect of microbial ecology and evolution, as well as the secrets to unique, undiscovered antibiotics, our last bastion against the relentless tide of resistance. In this context, it is imperative to invest in research to explore the competitive realms, like the plant rhizosphere, biological soil crusts, deep sea hydrothermal vents, marine snow and the most modern plastisphere, in which competitive interactions are at the base of the microorganisms' struggle for survival and dominance in their ecosystems: identify novel antibiotic by targeting microbial oases of interactions could represent a 'missing piece of the puzzle' in our fight against antibiotic resistance.

Characterization of heteropolysaccharides from Rhizoctonia solani AG1 IA cell wall and comparison of their effect on inducing plant defense

Rhizoctonia solani (R. solani) is an important pathogenic fungus that causes symptoms of sheath blight, and the polysaccharide-rich cell wall plays a major role in plant-pathogen interactions. However, the composition and structure of its cell wall polysaccharides are insufficiently understood, and its specific function in plant-pathogen interactions is unknown, which makes effective control of sheath blight difficult at present. Herein, five cell wall polysaccharides (WF-1, WF-2, CAF-1, HAF-1 and HAF 2-1) were sequentially extracted by boiling water, cold and hot alkali from R. solani AG1 IA. They were heteropolysaccharides containing mainly glucose, mannose and galactose and less fucose, with molecular weights above 1100 kDa. These five polysaccharides mainly composed of →4)-Glcp-(1→, →6)-Glcp-(1→, →4,6)-Glcp-(1→, →3,4)-Glcp-(1→, and Manp-(1→. Several polysaccharides, except WF-1, showed different induced resistance degrees on rice plant, with HAF 2-1 having the most significant effect. Further analysis using NMR confirmed that the backbone of HAF 2-1 mainly consisted of →4)-α-D-Glcp-(1→ and →6)-α-D-Glcp-(1→ with branches of →4,6)-D-Glcp-(1→. HAF 2-1 enhance the resistance of rice against R. solani through salicylic acid (SA)-mediated immune signaling pathway. This work improves our knowledge of the cell wall polysaccharides in plant pathogens and facilitates the study of pathogenic mechanisms and effective disease control.

Discovery and Characterization of MaK: A Novel Knottin Antimicrobial Peptide from Monochamus alternatus

Knottin-type antimicrobial peptides possess exceptional attributes, such as high efficacy, low vulnerability to drug resistance, minimal toxicity, and precise targeting of drug sites. These peptides play a crucial role in the innate immunity of insects, offering protection against bacteria, fungi, and parasites. Knottins have garnered considerable interest as promising contenders for drug development due to their ability to bridge the gap between small molecules and protein-based biopharmaceuticals, effectively addressing the therapeutic limitations of both modalities. This work presents the isolation and identification of a novel antimicrobial peptide derived from Monochamus alternatus. The cDNA encodes a 56-amino acid knottin propeptide, while the mature peptide comprises only 34 amino acids. We have labeled this knottin peptide as MaK. Using chemically synthesized MaK, we evaluated its hemolytic activity, thermal stability, antibacterial properties, and efficacy against nematodes. The results of this study indicate that MaK is an exceptionally effective knottin-type peptide. It demonstrates low toxicity, superior stability, potent antibacterial activity, and the ability to suppress pine wood nematodes. Consequently, these findings suggest that MaK has potential use in developing innovative therapeutic agents to prevent and manage pine wilt disease.

A novel fluorescent traceable carbon quantum dots with selective antibacterial activity against Porphyromonas gingivalis

Antibiotics can kill bacteria, but their continued use can easily lead to drug resistance, particularly the main pathogenic bacteria of periodontitis, Porphyromonas gingivalis. However, to avoid drug resistance, carbon quantum dots (CDs) have great potential as a bioactive material in antimicrobial therapy. Herein, we use ornidazole as raw material to prepare CDs of different sizes by microwave irradiation and screen CDs with fluorescence and bacteriostatic properties. The inhibition experiments and live/dead assays of P. gingivalis exhibited outstanding antibacterial effects. This research aimed to develop nano-level antibacterial active materials that also have fluorescence traceability. This study offers a different method for the development of multifunctional CDs, provides valuable strategies for the treatment of diseases associated with P. gingivalis, and predicts great application prospects in the field of biomedicine.

Weizmannia coagulans Extracellular Proteins Reduce Skin Acne by Inhibiting Pathogenic Bacteria and Regulating TLR2/TRAF6-Mediated NF-κB and MAPKs Signaling Pathways

As a probiotic, Weizmannia coagulans (W. coagulans) is often used in food and medicine to regulate intestinal flora and exert anti-inflammatory effects. In this study, the anti-acne efficacy and mechanism of extracellular proteins (YTCY-EPs) from W. coagulans YTCY strain are analyzed. The main components of YTCY-EPs, extracted and separated from the fermentation broth, are peptides ranging from 1.51 to 11.44 kDa, accounting for about 80%. Among the peptides identified by LC/MS-MS, YTCY_A-F possess the properties of antimicrobial peptides, while YTCY_1-4 possess antioxidative properties. These peptides have a strong effect on Cutibacterium acnes (C. acnes) and significantly inhibit Staphylococcus aureus. The inhibition rate of biofilm adhesion of YT-EPs to C. acnes reached 50% under the MIC. It was found that YTCY-EPs possess strong antioxidant and anti-inflammatory properties. It can effectively reduce active oxygen nearly 3 times and can reduce the downstream TLR2/NF-κB and MAPKs/AP-1 pathways by regulating the nuclear translocation of NF-κB and AP-1 in vitro. The transcriptional expression of inflammatory cytokines, inflammatory chemokines, and matrix metalloproteinase genes is also regulated, thereby slowing the recruitment of inflammatory cells and the development of inflammation, and increasing keratinocyte mobility. In addition, the expression levels of inflammatory factors and matrix metalloproteinases in the rabbit ears with acne problems that were tested with YTCY-EPs were significantly reduced, and it was obviously observed that the rabbit ear inflammation, acne, and keratinization problems were repaired. The results of this study prove that YTCY-EPs can be used as a potential anti-acne raw material in cosmetics.

Recent Advances in the Development of Biomimetic Materials

In this review, we focused on recent efforts in the design and development of materials with biomimetic properties. Innovative methods promise to emulate cell microenvironments and tissue functions, but many aspects regarding cellular communication, motility, and responsiveness remain to be explained. We photographed the state-of-the-art advancements in biomimetics, and discussed the complexity of a "bottom-up" artificial construction of living systems, with particular highlights on hydrogels, collagen-based composites, surface modifications, and three-dimensional (3D) bioprinting applications. Fast-paced 3D printing and artificial intelligence, nevertheless, collide with reality: How difficult can it be to build reproducible biomimetic materials at a real scale in line with the complexity of living systems? Nowadays, science is in urgent need of bioengineering technologies for the practical use of bioinspired and biomimetics for medicine and clinics.

Application and Development Prospect of Nanoscale Iron Based Metal-Organic Frameworks in Biomedicine

Metal-organic frameworks (MOFs) are coordination polymers that comprise metal ions/clusters and organic ligands. MOFs have been extensively employed in different fields (eg, gas adsorption, energy storage, chemical separation, catalysis, and sensing) for their versatility, high porosity, and adjustable geometry. To be specific, Fe2+/Fe3+ exhibits unique redox chemistry, photochemical and electrical properties, as well as catalytic activity. Fe-based MOFs have been widely investigated in numerous biomedical fields over the past few years. In this study, the key index requirements of Fe-MOF materials in the biomedical field are summarized, and a conclusion is drawn in terms of the latest application progress, development prospects, and future challenges of Fe-based MOFs as drug delivery systems, antibacterial therapeutics, biocatalysts, imaging agents, and biosensors in the biomedical field.

Tuning the Anthranilamide Peptidomimetic Design to Selectively Target Planktonic Bacteria and Biofilm

There is a pressing need to develop new antimicrobials to help combat the increase in antibiotic resistance that is occurring worldwide. In the current research, short amphiphilic antibacterial and antibiofilm agents were produced by tuning the hydrophobic and cationic groups of anthranilamide peptidomimetics. The attachment of a lysine cationic group at the tail position increased activity against E. coli by >16-fold (from >125 μM to 15.6 μM) and greatly reduced cytotoxicity against mammalian cells (from ≤20 μM to ≥150 μM). These compounds showed significant disruption of preformed biofilms of S. aureus at micromolar concentrations.