Fungi-derived lipopeptide antibiotics developed since 2000

Cytotoxic Peptaibols from Trichoderma strigosum

Five new lipopeptaibols (1-5) and eight new 19-residue peptaibols (8-15) along with two known lipopeptaibols, lipovelutibols C (6) and D (7) were isolated from Trichoderma strigosum. The planar structures of the newly discovered peptaibols (1-5, 8-15) were elucidated using 1D and 2D NMR, and UPLC-MS/MS data. The absolute configurations for new peptaibols (1-5, 8-15) were elucidated using the advanced Marfey's method and GITC (2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl isothiocyanate) derivatization. Through analysis of CD spectra, these peptabols were found to have right-handed helical conformations. While most of the new compounds were significantly more active than the positive control, 9, 10, 12, and 15 containing Ser and Leu at positions 10 and 11, respectively, were the most cytotoxic against MDA-MB-231, SNU449, SKOV3, DU145, and HCT116 cancer cell lines, and the 19-residue peptaibols were generally more potent than lipopeptaibols.

Production, characterization, and potential applications of lipopeptides in food systems: A comprehensive review

Lipopeptides are a class of lipid-peptide-conjugated compounds with differing structural features. This structural diversity is responsible for their diverse range of biological properties, including antimicrobial, antioxidant, and anti-inflammatory activities. Lipopeptides have been attracting the attention of food scientists due to their potential as food additives and preservatives. This review provides a comprehensive overview of lipopeptides, their production, structural characteristics, and functional properties. First, the classes, chemical features, structure-activity relationships, and sources of lipopeptides are summarized. Then, the gene expression and biosynthesis of lipopeptides in microbial cell factories and strategies to optimize lipopeptide production are discussed. In addition, the main methods of purification and characterization of lipopeptides have been described. Finally, some biological activities of the lipopeptides, especially those relevant to food systems along with their mechanism of action, are critically examined.

Strategies for improving fengycin production: a review

Fengycin is an important member of the lipopeptide family with a wide range of applications in the agricultural, food, medical and cosmetic industries. However, its commercial application is severely hindered by low productivity and high cost. Therefore, numerous studies have been devoted to improving the production of fengycin. We summarize these studies in this review with the aim of providing a reference and guidance for future researchers. This review begins with an overview of the synthesis mechanism of fengycin via the non-ribosomal peptide synthetases (NRPS), and then delves into the strategies for improving the fengycin production in recent years. These strategies mainly include fermentation optimization and metabolic engineering, and the metabolic engineering encompasses enhancement of precursor supply, application of regulatory factors, promoter engineering, and application of genome-engineering (genome shuffling and genome-scale metabolic network model). Finally, we conclude this review with a prospect of fengycin production.

A Fluorous Peptide Amphiphile with Potent Antimicrobial Activity for the Treatment of MRSA-induced Sepsis and Chronic Wound Infection

The rising prevalence of global antibiotic resistance evokes the urgent need for novel antimicrobial candidates. Cationic lipopeptides have attracted much attention due to their strong antimicrobial activity, broad-spectrum and low resistance tendency. Herein, a library of fluoro-lipopeptide amphiphiles was synthesized by tagging a series of cationic oligopeptides with a fluoroalkyl tail via a disulfide spacer. Among the lipopeptide candidates, R6F bearing six arginine moieties and a fluorous tag shows the highest antibacterial activity, and it exhibits an interesting fluorine effect as compared to the non-fluorinated lipopeptides. The high antibacterial activity of R6F is attributed to its excellent bacterial membrane permeability, which further disrupts the respiratory chain redox stress and cell wall biosynthesis of the bacteria. By co-assembling with lipid nanoparticles, R6F showed high therapeutic efficacy and minimal adverse effects in the treatment of MRSA-induced sepsis and chronic wound infection. This work provides a novel strategy to design highly potent antibacterial peptide amphiphiles for the treatment of drug-resistant bacterial infections.

Elucidating Daptomycin's Antibacterial Efficacy: Insights into the Tripartite Complex with Lipid II and Phospholipids in Bacterial Septum Membrane

This study elucidated the mechanism of formation of a tripartite complex containing daptomycin (Dap), lipid II, and phospholipid phosphatidylglycerol in the bacterial septum membrane, which was previously reported as the cause of the antibacterial action of Dap against gram-positive bacteria via molecular dynamics and enhanced sampling methods. Others have suggested that this transient complex ushers in the inhibition of cell wall synthesis by obstructing the downstream polymerization and cross-linking processes involving lipid II, which is absent in the presence of cardiolipin lipid in the membrane. In this work, we observed that the complex was stabilized by Ca2+-mediated electrostatic interactions between Dap and lipid head groups, hydrophobic interaction, hydrogen bonds, and salt bridges between the lipopeptide and lipids and was associated with Dap concentration-dependent membrane depolarization, thinning of the bilayer, and increased lipid tail disorder. Residues Orn6 and Kyn13, along with the DXDG motif, made simultaneous contact with constituent lipids, hence playing a crucial role in the formation of the complex. Incorporating cardiolipin into the membrane model led to its competitively displacing lipid II away from the Dap, reducing the lifetime of the complex and the nonexistence of lipid tail disorder and membrane depolarization. No evidence of water permeation inside the membrane hydrophobic interior was noted in all of the systems studied. Additionally, it was shown that using hydrophobic contacts between Dap and lipids as collective variables for enhanced sampling gave rise to a free energy barrier for the translocation of the lipopeptide. A better understanding of Dap's antibacterial mechanism, as studied through this work, will help develop lipopeptide-based antibiotics for rising Dap-resistant bacteria.

Screening inhibitors against the Ef-Tu of Fusobacterium nucleatum: a docking, ADMET and PBPK assessment study

The oral pathogen Fusobacterium nucleatum has recently been associated with an elevated risk of colorectal cancer (CRC), endometrial metastasis, chemoresistance, inflammation, metastasis, and DNA damage, along with several other diseases. This study aimed to explore the disruption of protein machinery of F. nucleatum via inhibition of elongation factor thermo unstable (Ef-Tu) protein, through natural products. No study on Ef-Tu inhibition by natural products or in Fusobacterium spp. exists till todate. Ef-Tu is an abundant specialized drug target in bacteria that varies from human Ef-Tu. Elfamycins target Ef-Tu and hence, Enacyloxin IIa was used to generate pharmacophore for virtual screening of three natural product libraries, Natural Product Activity and Species Source (NPASS) (n = 30000 molecules), Tibetan medicinal plant database (n = 54 molecules) and African medicinal plant database (n > 6000 molecules). Peptaibol Septocylindrin B (NPC141050), Hirtusneanoside, and ZINC95486259 were prioritized from these libraries as potential therapeutic candidates. ADMET profiling was done for safety assessment, physiological-based pharmacokinetic modeling in human and mouse for getting insight into drug interaction with body tissues and molecular dynamics was used to assess stability of the best hit NPC141050 (Septocylindrin B). Based on the promising results, we propose further in vitro, in vivo and pharmacokinetic testing on the lead Septocylindrin B, for possible translation into therapeutic interventions.

Improvement of lipopeptide production in Bacillus subtilis HNDF2-3 by overexpression of the sfp and comA genes

Bacillus subtilis HNDF2-3 can produce a variety of lipopeptide antibiotics with lower production. To improve its lipopeptide production, three genetically engineered strains were constructed. The results of real-time PCR showed that the highest transcriptional levels of the sfp gene in F2-3sfp, F2-3comA and F2-3sfp-comA were 29.01, 6.65 and 17.50 times of the original strain, respectively, while the highest transcriptional levels of the comA gene in F2-3comA and F2-3sfp-comA were 10.44 and 4.13 times of the original strain, respectively. The results of ELISA showed that the malonyl-CoA transacylase activity of F2-3comA was the highest, reaching 18.53 IU/L at 24 h, the data was 32.74% higher than that of the original strain. The highest total lipopeptide production of F2-3sfp, F2-3comA and F2-3sfp-comA induced by IPTG at optimal concentration were 33.51, 46.05 and 38.96% higher than that of the original strain, respectively. The results of HPLC showed that iturin A production of F2-3sfp-comA was the highest, which was 63.16% higher than that of the original strain. This study laid the foundation for further construction of genetically engineered strains with high lipopeptide production.

N-Arylation of Amino Acid Esters via an I2-Mediated Metal-Free Multicomponent Benzannulation Strategy

Herein, we present a novel method for the N-arylation of amino acid esters using α-bromoacetaldehyde acetal and acetoacetate via an I2-mediated metal-free benzannulation strategy, which disclosed the first synthetic application of N-arylation of amino acids using nonaromatic building blocks. The synthesized N-arylated amino acid derivatives were found to possess promising selective inhibition against human hepatocellular liver carcinoma cells, human melanoma cells, and human normal liver cells, with an IC50 value as low as 16.79 μg·mL-1.

Thirteen new peptaibols with antimicrobial activities from Trichoderma sp

From the fungus Trichoderma sp., we isolated seven novel 18-residue peptaibols, neoatroviridins E-K (1-7), and six new 14-residue peptaibols, harzianins NPDG J-O (8-13). Additionally, four previously characterized 18-residue peptaibols neoatroviridins A-D (14-17) were also identified. The structural configurations of the newly identified peptaibols (1-13) were determined by comprehensive nuclear magnetic resonance (NMR) and high-resolution electrospray ionization tandem mass spectrometry (HR-ESI-MS/MS) data. Their absolute configurations were further determined using Marfey's method. Notably, compounds 12 and 13 represent the first 14-residue peptaibols containing an acidic amino acid residue. In antimicrobial assessments, all 18-residue peptaibols (1-7, 14-17) exhibited moderate inhibitory activities against Staphylococcus aureus 209P, with minimum inhibitory concentration (MIC) values ranging from 8-32 μg·mL-1. Moreover, compound 9 exhibited moderate inhibitory effect on Candida albicans FIM709, with a MIC value of 16 μg·mL-1.

Peptaibiotics: Harnessing the potential of microbial secondary metabolites for mitigation of plant pathogens

Agricultural systems are in need of low-cost, safe antibiotics to protect crops from pests and diseases. Peptaibiotics, a family of linear, membrane-active, amphipathic polypeptides, have been shown to exhibit antibacterial, antifungal, and antiviral activity, and to be inducers of plant resistance against a wide range of phytopathogens. Peptaibiotics belong to the new generation of alternatives to agrochemicals, aligned with the United Nations Sustainable Development Goals and the One Health approach toward ensuring global food security and safety. Despite that, these fungi-derived, non-ribosomal peptides remain surprisingly understudied, especially in agriculture, where only a small number has been tested against a reduced number of phytopathogens. This lack of adoption stems from peptaibiotics' poor water solubility and the difficulty to synthesize and purify them in vitro, which compromises their delivery and inclusion in formulations. In this review, we offer a comprehensive analysis of peptaibiotics' classification, biosynthesis, relevance to plant protection, and mode of action against phytopathogens, along with the techniques enabling researchers to extract, purify, and elucidate their structure, and the databases holding such valuable data. It is also discussed how chemical synthesis and ionic liquids could increase their solubility, how genetic engineering and epigenetics could boost in vitro production, and how omics can reduce screenings' workload through in silico selection of the best candidates. These strategies could turn peptaibiotics into effective, ultra-specific, biodegradable tools for phytopathogen control.

Lipopeptides as tools in catalysis, supramolecular, materials and medicinal chemistry

Lipopeptides are amphiphilic peptides in which an aliphatic chain is attached to either the C or N terminus of peptides. Their self-assembly - into micelles, vesicles, nanotubes, fibres or nanobelts - leads to applications in nanotechnology, catalysis or medicinal chemistry. Self-organization of lipopeptides is dependent on both the length of the lipid tail and the amino acid sequence, in which the chirality of the peptide sequence can be transmitted into the supramolecular species. This Review describes the use of lipopeptides to design synthetic advanced dynamic supramolecular systems, nanostructured materials or self-responsive delivery systems in the area of medical biotechnology. We examine the influence of external stimuli, the ability of lipopeptide-derived structures to adapt over time and their application as medicinal agents with antibacterial, antifungal, antiviral or anticancer activities. Finally, we discuss the catalytic efficiency of lipopeptides, with the aim of building minimal synthetic enzymes, and recent efforts to incorporate metals into lipopeptide assemblies.

Enhancement of herbicolin A production by integrated fermentation optimization and strain engineering in Pantoea agglomerans ZJU23

BACKGROUND

The lipopeptide herbicolin A (HA) secreted by the biocontrol agent Pantoea agglomerans ZJU23 is a promising antifungal drug to combat fungal pathogens by targeting lipid rafts, both in agricultural and clinical settings. Improvement of HA production would be of great significance in promoting its commercialization. This study aims to enhance the HA production in ZJU23 by combining fermentation optimization and strain engineering.

RESULTS

Based on the results in the single-factor experiments, corn steep liquor, temperature and initial pH were identified as the significant affecting factors by the Plackett-Burman design. The fermentation medium and conditions were further optimized using the Box-Behnken response surface method, and the HA production of the wild type strain ZJU23 was improved from ~ 87 mg/mL in King's B medium to ~ 211 mg/mL in HA induction (HAI) medium. A transposon library was constructed in ZJU23 to screen for mutants with higher HA production, and two transcriptional repressors for HA biosynthesis, LrhA and PurR, were identified. Disruption of the LrhA gene led to increased mRNA expression of HA biosynthetic genes, and subsequently improved about twofold HA production. Finally, the HA production reached ~ 471 mg/mL in the ΔLrhA mutant under optimized fermentation conditions, which is about 5.4 times higher than before (~ 87 mg/mL). The bacterial suspension of the ΔLrhA mutant fermented in HAI medium significantly enhanced its biocontrol efficacy against gray mold disease and Fusarium crown rot of wheat, showing equivalent control efficacies as the chemical fungicides used in this study. Furthermore, HA was effective against fungicide resistant Botrytis cinerea. Increased HA production substantially improved the control efficacy against gray mold disease caused by a pyrimethanil resistant strain.

CONCLUSIONS

This study reveals that the transcriptional repressor LrhA negatively regulates HA biosynthesis and the defined HAI medium is suitable for HA production. These findings provide an extended basis for large-scale production of HA and promote biofungicide development based on ZJU23 and HA in the future.

A comprehensive review of microorganism-derived cyclic peptides: Bioactive functions and food safety applications

Cyclic peptides possess advanced structural characteristics of stability and play a vital role in medical treatment and agriculture. However, the biological functions of microorganism-derived cyclic peptides (MDCPs) and their applications in food industry were relatively absent. MDCPs are derived from extensive fermented food or soil. In this review, the synthesis approaches and structural characteristics are overviewed, while the interrelationship between bioactivities and functions is emphasized. This review summarizes the bioactivities of MDCPs from in vitro to in vivo, including antimicrobial activities, immune regulation, and antiviral cell activation. Their multiple functions as well as applications during food product processing, packaging, and storage are also comprehensively reviewed. Remarkably, some potential risks and cytotoxicity of MDCPs are also critically discussed. Moreover, future applications of MDCPs in the development of novel food additives and bioengineering materials are organized. Based on this review of native MDCPs, it is noteworthy that expected improvements of synthetic cyclic peptides in bioactive properties present potential valuable applications in future food, including artificial meat.

Self-Uptake Mechanism of Polymyxin-Based Lipopeptide against Gram-Negative Bacterial Membrane: Role of the First Adsorbed Lipopeptide

Research in the continuously increasing threat of polymyxin-resistant multidrug-resistant Pseudomonas aeruginosa, which causes severe infection in immunocompromised patients, has resulted in the development of several polymyxin-derived cyclic lipopeptides containing l-α-γ- diamino butyric acid-like FADDI-019 (F19). In this work, F19's insertion into a minimal model of the asymmetric outer membrane of the bacterium, which contained only penta-acylated lipid A (LipA) and lacked keto-d-octulosonic acid and O-antigens, in the top leaflet and phospholipids in the bottom leaflet, was studied. F19 exhibited all of the hallmarks of the self-uptake mechanism into the asymmetric bilayer. While a single monomer of the lipopeptide did not get partitioned into the inside of the bilayer, it competitively displaced Ca²⁺ from the membrane surface, observed as a decrease in Ca²⁺ coordination number with phosphate groups (1.89 vs 1.718), resulting in membrane destabilization. This resulted in an increment of the average defect size and the probability of interplay between lipid tails and hydrophobic residues of another F19. When more than one monomer was present in the system, the first monomer remained docked on the surface, while other monomers intercalated into the bilayer interior with their hydrophobic moieties "sleeved" by lipid acyl chains. The free energy barrier for partial insertion of the lipopeptide into a bilayer in the presence of surface-docked second F19 was recorded at ∼1.3 kcal/mol using two-dimensional (2D) well-tempered metadynamics, making it a low barrier process at 300 K. This study is an attempt to demonstrate the self-uptake mechanism of F19 during intercalation process into the bilayer interior, which may help in the design of better alternates for polymyxins to work against polymyxin resistance.

Discovery of a Cyclic Depsipeptide from Chaetomium mollipilium by the Genome Mining Approach

Genome mining and bioinformatics analyses allowed us to rationally find a candidate biosynthetic gene cluster for a new cyclic depsipeptide of Chaetomium mollipilium. A heterologous reconstitution of the identified biosynthetic pathway predictably afforded a new cyclic depsipeptide composed of l-leucine, l-tryptophan, and a polyketide moiety. Interestingly, the 10-membered macrocycle structure generated equilibrium to an unprecedented cyclol structure. This study demonstrates the advantage of a synthetic biology method in achieving rational access to new natural products.

Bacterial hitchhikers derive benefits from fungal housing

Fungi and bacteria are ubiquitous constituents of all microbiomes, yet mechanisms of microbial persistence in polymicrobial communities remain obscure. Here, we examined the hypothesis that specialized fungal survival structures, chlamydospores, induced by bacterial lipopeptides serve as bacterial reservoirs. We find that symbiotic and pathogenic gram-negative bacteria from non-endosymbiotic taxa enter and propagate in chlamydospores. Internalized bacteria have higher fitness than planktonic bacteria when challenged with abiotic stress. Further, tri-cultures of Ralstonia solanacearum, Pseudomonas aeruginosa, and Aspergillus flavus reveal the unprecedented finding that chlamydospores are colonized by endofungal bacterial communities. Our work identifies a previously unknown ecological role of chlamydospores, provides an expanded view of microbial niches, and presents significant implications for the persistence of pathogenic and beneficial bacteria.

Microbial Lipopeptide-Producing Strains and Their Metabolic Roles under Anaerobic Conditions

The lipopeptide produced by microorganisms is one of the representative biosurfactants and is characterized as a series of structural analogues of different families. Thirty-four families covering about 300 lipopeptide compounds have been reported in the last decades, and most of the reported lipopeptides produced by microorganisms were under aerobic conditions. The lipopeptide-producing strains under anaerobic conditions have attracted much attention from both the academic and industrial communities, due to the needs and the challenge of their applications in anaerobic environments, such as in oil reservoirs and in microbial enhanced oil recovery (MEOR). In this review, the fifty-eight reported bacterial strains, mostly isolated from oil reservoirs and dominated by the species Bacillus subtilis, producing lipopeptide biosurfactants, and the species Pseudomonas aeruginosa, producing glycolipid biosurfactants under anaerobic conditions were summarized. The metabolic pathway and the non-ribosomal peptide synthetases (NRPSs) of the strain Bacillus subtilis under anaerobic conditions were analyzed, which is expected to better understand the key mechanisms of the growth and production of lipopeptide biosurfactants of such kind of bacteria under anaerobic conditions, and to expand the industrial application of anaerobic biosurfactant-producing bacteria.

Longibramides A-E, Peptaibols Isolated from a Mushroom Derived Fungus Trichoderma longibrachiatum Rifai DMG-3-1-1

Five new peptaibols, longibramides A-E (1-5) with 11 amino acid residues, were isolated from a fungus Trichoderma longibrachiatum Rifai DMG-3-1-1, which was isolated from a mushroom Clitocybe nebularis (Batsch) P. Kumm collected from coniferous forest in the subboreal area of northeast China. The structures of longibramides A-E were determined by their spectroscopic data (NMR and MS-MS spectra), their absolute configurations were determined by X-ray diffractions and Marfey's analyses. The X-ray diffractions of longibramides A, B, and the similar CD spectra of A-E showed that they all had α-helix conformations. Longibramides B and E showed moderate cytotoxicities against BV2 and MCF-7 cells and also showed some inhibitory effects against methicillin-resistant Staphylococcus aureus MRSA T144. L-trans-Hyp was not commonly found in natural peptaibols, which was the 6^th or 10^th amino acid residue in longibramides C-E. The X-ray diffractions of longibramides A and B afforded the accuracy conformations of their secondary structures, which maybe help to interpret the structure-activity relationships of the family of peptaibols in the future.

The ecological roles of microbial lipopeptides: Where are we going?

Lipopeptides (LPs) are secondary metabolites produced by a diversity of bacteria and fungi. Their unique chemical structure comprises both a peptide and a lipid moiety. LPs are of major biotechnological interest owing to their emulsification, antitumor, immunomodulatory, and antimicrobial activities. To date, these versatile compounds have been applied across multiple industries, from pharmaceuticals through to food processing, cosmetics, agriculture, heavy metal, and hydrocarbon bioremediation. The variety of LP structures and the diversity of the environments from which LP-producing microorganisms have been isolated suggest important functions in their natural environment. However, our understanding of the ecological role of LPs is limited. In this review, the mode of action and the role of LPs in motility, antimicrobial activity, heavy metals removal and biofilm formation are addressed. We include discussion on the need to characterise LPs from a diversity of microorganisms, with a focus on taxa inhabiting 'extreme' environments. We introduce the use of computational target fishing and molecular dynamics simulations as powerful tools to investigate the process of interaction between LPs and cell membranes. Together, these advances will provide new understanding of the mechanism of action of novel LPs, providing greater insights into the roles of LPs in the natural environment.

Bacterial Resistance: Antibiotics of Last Generation used in Clinical Practice and the Arise of Natural Products as New Therapeutic Alternatives

Bacterial resistance to therapeutical drugs has been a serious issue over the last decades. In fact, the quick development of resistance mechanisms by the microorganisms has been fatal for millions of people around the world, turning into a public health issue. The major cause of the resistance mechanisms is the overuse of antimicrobials. European countries try to implement mechanisms to overcome antimicrobial resistance in the community through the rational use of antimicrobials. The scientific community has been exhaustively dedicated to the discovering of new, safer and efficient drugs, being the exploitation of natural resources, mainly plants and fungi, considered as a hot topic in the field of antimicrobial agents. Innumerous reports have already shown the promising capacity of natural products or molecules extracted from these natural resources, to act as bacteriostatic and bactericidal agents. More importantly, these natural agents present significantly lower harmful effects. Bearing that in mind, this review aims at giving a contribution to the knowledge about the synthetic antibiotics of the last generation. Moreover, it is intended to provide information about the last advances regarding the discovery of new antimicrobial agents. Thus, a compilation of the chemical characteristics, efficiency, harmful outcomes and resistance mechanisms developed by the microorganisms can be consulted in the following sections together with a critical discussion, in line with the recent approaches. Furthermore, modern strategies for the prospection of novel anti-infective compounds for tackling resistant bacteria have been considered as also a current synopsis of plants and mushrooms with relevant antimicrobial potentials.

Antimicrobial Peptides: a New Frontier in Antifungal Therapy

Invasive fungal infections in humans are generally associated with high mortality, making the choice of antifungal drug crucial for the outcome of the patient. The limited spectrum of antifungals available and the development of drug resistance represent the main concerns for the current antifungal treatments, requiring alternative strategies. Antimicrobial peptides (AMPs), expressed in several organisms and used as first-line defenses against microbial infections, have emerged as potential candidates for developing new antifungal therapies, characterized by negligible host toxicity and low resistance rates. Most of the current literature focuses on peptides with antibacterial activity, but there are fewer studies of their antifungal properties. This review focuses on AMPs with antifungal effects, including their in vitro and in vivo activities, with the biological repercussions on the fungal cells, when known. The classification of the peptides is based on their mode of action: although the majority of AMPs exert their activity through the interaction with membranes, other mechanisms have been identified, including cell wall inhibition and nucleic acid binding. In addition, antifungal compounds with unknown modes of action are also described. The elucidation of such mechanisms can be useful to identify novel drug targets and, possibly, to serve as the templates for the synthesis of new antimicrobial compounds with increased activity and reduced host toxicity.

Rezafungin-Mechanisms of Action, Susceptibility and Resistance: Similarities and Differences with the Other Echinocandins

Rezafungin (formerly CD101) is a new β-glucan synthase inhibitor that is chemically related with anidulafungin. It is considered the first molecule of the new generation of long-acting echinocandins. It has several advantages over the already approved by the Food and Drug Administration (FDA) echinocandins as it has better tissue penetration, better pharmacokinetic/phamacodynamic (PK/PD) pharmacometrics, and a good safety profile. It is much more stable in solution than the older echinocandins, making it more flexible in terms of dosing, storage, and manufacturing. These properties would allow rezafungin to be administered once-weekly (intravenous) and to be potentially administered topically and subcutaneously. In addition, higher dose regimens were tested with no evidence of toxic effect. This will eventually prevent (or reduce) the selection of resistant strains. Rezafungin also has several similarities with older echinocandins as they share the same in vitro behavior (very similar Minimum Inhibitory Concentration required to inhibit the growth of 50% of the isolates (MIC50) and half enzyme maximal inhibitory concentration 50% (IC50)) and spectrum, the same target, and the same mechanisms of resistance. The selection of FKS mutants occurred at similar frequency for rezafungin than for anidulafungin and caspofungin. In this review, rezafungin mechanism of action, target, mechanism of resistance, and in vitro data are described in a comparative manner with the already approved echinocandins.

Diversity of Linear Non-Ribosomal Peptide in Biocontrol Fungi

Biocontrol fungi (BFs) play a key role in regulation of pest populations. BFs produce multiple non-ribosomal peptides (NRPs) and other secondary metabolites that interact with pests, plants and microorganisms. NRPs-including linear and cyclic peptides (L-NRPs and C-NRPs)-are small peptides frequently containing special amino acids and other organic acids. They are biosynthesized in fungi through non-ribosomal peptide synthases (NRPSs). Compared with C-NRPs, L-NRPs have simpler structures, with only a linear chain and biosynthesis without cyclization. BFs mainly include entomopathogenic and mycoparasitic fungi, that are used to control insect pests and phytopathogens in fields, respectively. NRPs play an important role of in the interactions of BFs with insects or phytopathogens. On the other hand, the residues of NRPs may contaminate food through BFs activities in the environment. In recent decades, C-NRPs in BFs have been thoroughly reviewed. However, L-NRPs are rarely investigated. In order to better understand the species and potential problems of L-NRPs in BFs, this review lists the L-NRPs from entomopathogenic and mycoparasitic fungi, summarizes their sources, structures, activities and biosynthesis, and details risks and utilization prospects.

Antimalarial Agents as Therapeutic Tools Against Toxoplasmosis-A Short Bridge between Two Distant Illnesses

Toxoplasmosis is an infectious disease with paramount impact worldwide, affecting many vulnerable populations and representing a significant matter of concern. Current therapies used against toxoplasmosis are based essentially on old chemotypes, which fail in providing a definitive cure for the disease, placing the most sensitive populations at risk for irreversible damage in vital organs, culminating in death in the most serious cases. Antimalarial drugs have been shown to possess key features for drug repurposing, finding application in the treatment of other parasite-borne illnesses, including toxoplasmosis. Antimalarials provide the most effective therapeutic solutions against toxoplasmosis and make up for the majority of currently available antitoxoplasmic drugs. Additionally, other antiplasmodial drugs have been scrutinized and many promising candidates have emanated in recent developments. Available data demonstrate that it is worthwhile to explore the activity of classical and most recent antimalarial chemotypes, such as quinolines, endoperoxides, pyrazolo[1,5-a]pyrimidines, and nature-derived peptide-based parasiticidal agents, in the context of toxoplasmosis chemotherapy, in the quest for encountering more effective and safer tools for toxoplasmosis control or eradication.

Lesson from Ecotoxicity: Revisiting the Microbial Lipopeptides for the Management of Emerging Diseases for Crop Protection

Microorganisms area treasure in terms of theproduction of various bioactive compounds which are being explored in different arenas of applied sciences. In agriculture, microbes and their bioactive compounds are being utilized in growth promotion and health promotion withnutrient fortification and its acquisition. Exhaustive explorations are unraveling the vast diversity of microbialcompounds with their potential usage in solving multiferous problems incrop production. Lipopeptides are one of such microbial compounds which havestrong antimicrobial properties against different plant pathogens. These compounds are reported to be produced by bacteria, cyanobacteria, fungi, and few other microorganisms; however, genus Bacillus alone produces a majority of diverse lipopeptides. Lipopeptides are low molecular weight compounds which havemultiple industrial roles apart from being usedas biosurfactants and antimicrobials. In plant protection, lipopeptides have wide prospects owing totheirpore-forming ability in pathogens, siderophore activity, biofilm inhibition, and dislodging activity, preventing colonization bypathogens, antiviral activity, etc. Microbes with lipopeptides that haveall these actions are good biocontrol agents. Exploring these antimicrobial compounds could widen the vistasof biological pest control for existing and emerging plant pathogens. The broader diversity and strong antimicrobial behavior of lipopeptides could be a boon for dealing withcomplex pathosystems and controlling diseases of greater economic importance. Understanding which and how these compounds modulate the synthesis and production of defense-related biomolecules in the plants is a key question—the answer of whichneeds in-depth investigation. The present reviewprovides a comprehensive picture of important lipopeptides produced by plant microbiome, their isolation, characterization, mechanisms of disease control, behavior against phytopathogens to understand different aspects of antagonism, and potential prospects for future explorations as antimicrobial agents. Understanding and exploring the antimicrobial lipopeptides from bacteria and fungi could also open upan entire new arena of biopesticides for effective control of devastating plant diseases.

Droplet probe: coupling chromatography to the in situ evaluation of the chemistry of nature

Covering: up to 2019The chemistry of nature can be beautiful, inspiring, beneficial and poisonous, depending on perspective. Since the isolation of the first secondary metabolites roughly two centuries ago, much of the chemical research on natural products has been both reductionist and static. Typically, compounds were isolated and characterized from the extract of an entire organism from a single time point. While there could be subtexts to that approach, the general premise has been to determine the chemistry with very little in the way of tools to differentiate spatial and/or temporal changes in secondary metabolite profiles. However, the past decade has seen exponential advances in our ability to observe, measure, and visualize the chemistry of nature in situ. Many of those techniques have been reviewed in this journal, and most are tapping into the power of mass spectrometry to analyze a plethora of sample types. In nearly all of the other techniques used to study chemistry in situ, the element of chromatography has been eliminated, instead using various ionization sources to coax ions of the secondary metabolites directly into the mass spectrometer as a mixture. Much of that science has been driven by the great advances in ambient ionization techniques used with a suite of mass spectrometry platforms, including the alphabet soup from DESI to LAESI to MALDI. This review discusses the one in situ analysis technique that incorporates chromatography, being the droplet-liquid microjunction-surface sampling probe, which is more easily termed "droplet probe". In addition to comparing and contrasting the droplet probe with other techniques, we provide perspective on why scientists, particularly those steeped in natural products chemistry training, may want to include chromatography in in situ analyses. Moreover, we provide justification for droplet sampling, especially for samples with delicate and/or non-uniform topographies. Furthermore, while the droplet probe has been used the most in the analysis of fungal cultures, we digest a variety of other applications, ranging from cyanobacteria, to plant parts, and even delicate documents, such as herbarium specimens.

Role of Lipid Composition, Physicochemical Interactions, and Membrane Mechanics in the Molecular Actions of Microbial Cyclic Lipopeptides

Several experimental and theoretical studies have extensively investigated the effects of a large diversity of antimicrobial peptides (AMPs) on model lipid bilayers and living cells. Many of these peptides disturb cells by forming pores in the plasma membrane that eventually lead to the cell death. The complexity of these peptide-lipid interactions is mainly related to electrostatic, hydrophobic and topological issues of these counterparts. Diverse studies have shed some light on how AMPs act on lipid bilayers composed by different phospholipids, and how mechanical properties of membranes could affect the antimicrobial effects of such compounds. On the other hand, cyclic lipopeptides (cLPs), an important class of microbial secondary metabolites, have received comparatively less attention. Due to their amphipathic structures, cLPs exhibit interesting biological activities including interactions with biofilms, anti-bacterial, anti-fungal, antiviral, and anti-tumoral properties, which deserve more investigation. Understanding how physicochemical properties of lipid bilayers contribute and determining the antagonistic activity of these secondary metabolites over a broad spectrum of microbial pathogens could establish a framework to design and select effective strategies of biological control. This implies unravelling-at the biophysical level-the complex interactions established between cLPs and lipid bilayers. This review presents, in a systematic manner, the diversity of lipidated antibiotics produced by different microorganisms, with a critical analysis of the perturbing actions that have been reported in the literature for this specific set of membrane-active lipopeptides during their interactions with model membranes and in vivo. With an overview on the mechanical properties of lipid bilayers that can be experimentally determined, we also discuss which parameters are relevant in the understanding of those perturbation effects. Finally, we expose in brief, how this knowledge can help to design novel strategies to use these biosurfactants in the agronomic and pharmaceutical industries.