Antifungal Cyclic Lipopeptide Research Articles

Fungal membrane determinants affecting sensitivity to antifungal cyclic lipopeptides from Bacillus spp.

Bacillus spp. produce numerous antimicrobial metabolites. Among these metabolites, cyclic lipopeptides (CLP) including fengycins, iturins, and surfactins are known to have varying antifungal activity against phytopathogenic fungi. The differential activities of CLP have been attributed to diverse mechanisms of action on fungal membranes. However, the precise biochemical determinants driving their antifungal modes of action have not been conclusively identified. In this study, three plant pathogenic fungi of varying lipopeptide sensitivities, Alternaria solani, Cladosporium cucumerinum, and Fusarium sambucinum, were studied to determine how their cell membrane lipid compositions may confer sensitivity and/or tolerance to fengycin, iturin, and surfactin. Results indicated that sensitivity to all three lipopeptides correlated with lower ergosterol content and elevated phospholipid fatty acid unsaturation. Fungal sensitivity to surfactin was also notably different than fengycin and iturin, as surfactin was influenced more by lower phosphatidylethanolamine amounts, higher levels of phosphatidylinositol, and less by phospholipid fatty acyl chain length. Results from this study provide insight into the fungal membrane composition of A. solani, F. sambucinum, and C. cucumerinum and the specific membrane characteristics influencing the antifungal effectiveness of fengycin, iturin, and surfactin. Understanding of these determinants should enable more accurate prediction of sensitivity-tolerance outcomes for other fungal species exposed to these important CLP.

P068 Inhibition of Candida glabrata biofilm using the combination of a novel antifungal cyclic lipopeptide and azole: An in vitro synergistic approach

Poster session 1, September 21, 2022, 12:30 PM - 1:30 PMThe general feature of the biofilm is a densely packed microbial community with an extracellular matrix composed of polysaccharides and proteins. Candida glabrata was reported as the most biofilm-forming species responsible for causing virulent Candida infections among Candida non-albicans (CNA). Candida glabrata is the most azole-resistant species of all Candida species. The early and maturing biofilms enable the Candida cells to overcome the effects of azoles and exhibit higher drug resistance. Since simple azole mono-therapy rarely eradicates recalcitrant Candida biofilms, removal of the infected device becomes necessary for curing the infection.ObjectiveThe objective was to assess the biofilm inhibition effect of antifungal cyclic lipopeptide which has been purified by a multi-step process from the cell-free supernatant of Bacillus subtilis, and to analyze the synergistic activity of the purified lipopeptide lead compound designated as AF4 with the standard antifungal fluconazole using different concentrations.MethodsBriefly, cell-free supernatant was extracted using a solvent mixture and silica gel-based adsorption chromatography. The potential antifungal cyclic lipopeptide variant AF4 was extracted from the soil isolate B. subtilis by a multi-step purification process that involves reversed-phase HPLC and exhibited a wide-spectrum of anti-Candida activity. The XTT reduction assay was used for metabolically active cells after treatment with a combination of drugs, and crystal violet (CV) assay was performed to quantify the cell biomass. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were used to analyze the biofilm morphology and architecture of the AF4 lipopeptide at (2xMIC) and fluconazole (8x-16xMIC)-treated biofilms. For confocal microscopy-based biofilm visualization, a combination of two different dyes was used. Extracellular polymeric substances were stained by concanavalin A-Alexa Fluor 488 conjugate and, the FUN- 1 fluorescent dye was used for staining the live biofilm-forming Candida cells. After capturing the Z-stack images in CLSM, the biomass (μm3/μm2), average thickness (μm), and roughness of the biofilm were analyzed by Comstat 2.1 software.ResultsThe AFST analysis showed that the MIC of the lead antifungal lipopeptide was 8 μg/mL against the C. glabrata planktonic cells. Adding the antifungal compound at higher MICs such as by 2-folds exhibited strong antibiofilm effect that significantly enhanced the synergistic antifungal activity of the fluconazole against C. glabrata biofilm formation. Synergistic effect of fluconazole at 8x-16xMIC with 2xMIC of the lead compound AF4 on C. glabrata 24 h maturing biofilm had increased significantly as revealed by the XTT and CV assays. The results confirmed ˃ 50% inhibition of the biofilm in both 6 h developmental and 24 h maturing biofilms in 8xMIC fluconazole plus 2xMIC AF4 while compared with fluconazole alone at the same concentration. The results from the XTT and, CV assays and SEM and CLSM (Fig. 1) suggest that the combinatorial treatments of the lead antifungal lipopeptide and fluconazole at varying concentrations have the potential of eradicating or nearly eradicating the maturing biofilm of CAN.ConclusionsThe combinatorial study was found effective in combating the biofilm formation. A correlation between metabolic activity and antifungal resistance in maturing biofilms has been found.

Chemical diversity and cellular effects of antifungal cyclic lipopeptides from cyanobacteria.

Cyanobacteria produce a variety of chemically diverse cyclic lipopeptides with potent antifungal activities. These cyclic lipopeptides have an amphipathic structure comprised of a polar peptide cycle and hydrophobic fatty acid side chain. Many have antibiotic activity against a range of human and plant fungal pathogens. This review article aims to summarize the present knowledge on the chemical diversity and cellular effects of cyanobacterial cyclic lipopeptides that display antifungal activity. Cyclic antifungal lipopeptides from cyanobacteria commonly fall into four structural classes; hassallidins, puwainaphycins, laxaphycins, and anabaenolysins. Many of these antifungal cyclic lipopeptides act through cholesterol and ergosterol-dependent disruption of membranes. In many cases, the cyclic lipopeptides also exert cytotoxicity in human cells, and a more extensive examination of their biological activity and structure-activity relationship is warranted. The hassallidin, puwainaphycin, laxaphycin, and anabaenolysin structural classes are unified through shared complex biosynthetic pathways that encode a variety of unusual lipoinitiation mechanisms and branched biosynthesis that promote their chemical diversity. However, the biosynthetic origins of some cyanobacterial cyclic lipopeptides and the mechanisms, which drive their structural diversification in general, remain poorly understood. The strong functional convergence of differently organized chemical structures suggests that the production of lipopeptide confers benefits for their producer. Whether these benefits originate from their antifungal activity or some other physiological function remains to be answered in the future. However, it is clear that cyanobacteria encode a wealth of new cyclic lipopeptides with novel biotechnological and therapeutic applications.

Host nutrition-based approach for biotechnological production of the antifungal cyclic lipopeptide jagaricin

In today’s, society multi-resistant pathogens have become an emerging threat, which makes the search for novel anti-infectives more urgent than ever. A promising class of substances are cyclic lipopeptides like the antifungal jagaricin. Jagaricin is formed by the bacterial mushroom pathogen Janthinobacterium agaricidamnosum. It has shown antifungal activity against human pathogenic fungi like Candida albicans and Aspergillus fumigatus. In addition, jagaricin is nearly non-toxic for plants, which makes it a promising agent for agricultural applications. Cyclic lipopeptides formed by microorganisms originate from their secondary metabolism. This makes it very challenging to determine the inducing factor for product formation, especially for unknown microbial systems like J. agaricidamnosum. In the presented study, a biotechnological process for jagaricin formation was developed, investigating impact factors like the medium, oxygen availability, and phosphate. For this reason, experiments were conducted on microtiter plate, shake flask, and stirred tank bioreactor level. Ultimately, a final maximum jagaricin concentration of 251 mg L−1 (15.5 mgJagaricin∙gCDW−1) could be achieved, which is an increase of approximately 458 % in comparison to previous results in standard glucose medium. This concentration allows the production of significantly higher amounts of jagaricin and enables further experiments to investigate the potential of this substance.

Process development for the antifungal cyclic lipopeptide jagaricin

Process development for the antifungal cyclic lipopeptide jagaricin

1,3-Thiazine, 1,2,3,4-Dithiadiazole, and Thiohydrazide Derivatives Affect Lipid Bilayer Properties and Ion-Permeable Pores Induced by Antifungals.

Over the past decade, thiazines, thiadiazoles, and thiohydrazides have attracted increasing attention due to their sedative, antimicrobial, antiviral, antifungal, and antitumor activities. The clinical efficacy of such drugs, as well as the possibility of developing resistance to antimicrobials, will depend on addressing a number of fundamental problems, including the role of membrane lipids during their interaction with plasma membranes. The effects of the eight 1,3- thiazine-, 1,2,3,4- dithiadiazole-, and thiohydrazide-related compounds on the physical properties of model lipid membranes and the effects on reconstituted ion channels induced by the polyene macrolide antimycotic nystatin and antifungal cyclic lipopeptides syringomycin E and fengycin were observed. We found that among the tested agents, the fluorine-containing compound N′-(3,5-difluorophenyl)-benzenecarbothiohydrazide (C6) was the most effective at increasing the electric barrier for anion permeation into the hydrophobic region of the membrane and reducing the conductance of anion-permeable syringomycin pores. A decrease in the membrane boundary potential with C6 adsorption also facilitated the immersion of positively charged syringomycin molecules into the lipid bilayer and increases the pore-forming ability of the lipopeptide. Using differential scanning microcalorimetry, we showed that C6 led to disordering of membrane lipids, possibly by potentiating positive curvature stress. Therefore, we used C6 as an agonist of antifungals forming the pores that are sensitive to membrane curvature stress and lipid packing, i.e., nystatin and fengycin. The dramatic increase in transmembrane current induced by syringomycin E, nystatin, and fengycin upon C6 treatment suggests its potential in combination therapy for treating invasive fungal infections.

Improved Production of Two Anti-Candida Lipopeptide Homologues Co- Produced by the Wild-Type Bacillus subtilis RLID 12.1 under Optimized Conditions.

Antifungal cyclic lipopeptides, bioactive metabolites produced by many species of the genus Bacillus, are promising alternatives to synthetic fungicides and antibiotics for the biocontrol of human pathogenic fungi. In a previous study, the co- production of five antifungal lipopeptides homologues (designated as AF1, AF2, AF3, AF4 and AF5) by the producer strain Bacillus subtilis RLID 12.1 using unoptimized medium was reported; though the two homologues AF3 and AF5 differed by 14 Da and in fatty acid chain length were found effective in antifungal action, the production/ yield rate of these two lipopeptides determined by High-Performance Liquid Chromatography was less in the unoptimized media. In this study, the production/yield enhancement of the two compounds AF3 and AF5 was specifically targeted. Following the statistical optimization (Plackett-Burman and Box-Behnken designs) of media formulation, temperature and growth conditions, the production of AF3 and AF5 was improved by about 25.8- and 7.4-folds, respectively under static conditions. To boost the production of these two homologous lipopeptides in the optimized media, heat-inactivated Candida albicans cells were used as a supplement resulting in 34- and 14-fold increase of AF3 and AF5, respectively. Four clinical Candida auris isolates had AF3 and AF5 MICs (100 % inhibition) ranging between 4 and 16 μg/ml indicating the lipopeptide's clinical potential. To determine the in vitro pharmacodynamic potential of AF3 and AF5, time-kill assays were conducted which showed that AF3 (at 4X and 8X concentrations) at 48h exhibited mean log reductions of 2.31 and 3.14 CFU/ml of C. albicans SC 5314, respectively whereas AF5 at 8X concentration showed a mean log reduction of 2.14 CFU/ml. With the increasing threat of multidrug-resistant yeasts and fungi, these antifungal lipopeptides produced by optimized method promise to aid in the development of novel antifungal that targets disease-causing fungi with improved efficacy.

Structural characterization of Kannurin isoforms and evaluation of the role of \u03b2-hydroxy fatty acid tail length in functional specificity

The novel anti-fungal cyclic lipopeptide ‘Kannurin’ and its three structural variants produced by Bacillus cereus AK1 were previously reported from our laboratory. The present study reports unexplored structural variants of Kannurin those have functional benefits. Due to the difference in β-hydroxy fatty acid tail length, they are designated here as Kannurin A (m/z 994.67 ± 0.015), B (m/z 1008.68 ± 0.017), C (m/z 1022.69 ± 0.021), D (m/z 1036.70 ± 0.01), CL (m/z 1040.71 ± 0.02) and DL (m/z 1054.72 ± 0.01). The isoform A (m/z 994.67 ± 0.015) is the shortest cyclic form of Kannurin identified so far. In addition, CL (m/z 1040.71 ± 0.02) and DL (m/z 1054.72 ± 0.01) are the rare natural linear forms. The results of the antimicrobial assays deduced that the difference in lipid tail length of the isoforms contributes tremendous differences in their antimicrobial properties. The isoforms with short lipid tails (A and B) are more selective and potent towards bacteria, whereas the isoforms with long lipid tails (C and D) are more potent against fungi. The molecular dynamics studies and electron microscopic observations supported with circular dichroic spectroscopy analysis showed the structural confirmation and formation of aggregates of Kannurin in solution. The molecular dynamics simulation studies revealed that a single molecule of Kannurin makes enormous intra-molecular interactions and structural re-arrangements to attain stable lowest energy state in solution. When they reach a particular concentration (CMC) especially in aqueous environment, tends to form structural aggregates called ‘micelles’. With the structural information and activity relationship described in this study, it is trying to point out the sensitive structural entities that can be modified to improve the efficacy and target specificities of lipopeptide class of antibiotics.

Establishment of a rapeseed meal fermentation model for iturin A production by Bacillus amyloliquefaciens CX-20.

SummaryIturin A is an important broad‐spectrum antifungal cyclic lipopeptide used as an ideal potential biological control agent. However, its application is limited mainly due to the producer strains’ low productivity and the high production costs. Here, a potentially industrial strain Bacillus amyloliquefaciens CX‐20 was proved to use low‐cost rapeseed meal (RSM) as the sole source of all nutrients except the carbon source for the high productivity of iturin A. A fermentation model was first established to analyse the specific roles of different RSM components on iturin A production. Proteins and minerals in RSM were confirmed to play positive role, whereas fibre had negative effect. And the maximal concentration of iturin A was predicted to be more than 1.64 g l−1 by the established evaluation model. Moreover, submerged fermentation of B. amyloliquefaciens CX‐20 demonstrated a strong ability to hydrolyse RSM and release water‐soluble nutrients. This fermentation broth, a mixture of Bacillus, iturin A and RSM hydrolysate, could simultaneously combat clubroot disease and promote the growth of Brassica napus. In conclusion, this study provides a promising strategy to achieve full utilization of RSM for the production of a combination of value‐added biological control agent and biofertilizer.

Molecular Docking and Dynamics Simulation of Protein β-Tubulin and Antifungal Cyclic Lipopeptides.

To elucidate interactions between the antifungal cyclic lipopeptides iturin A, fengycin, and surfactin produced by Bacillus bacteria and the microtubular protein β-tubulin in plant pathogenic fungi (Fusarium oxysporum, Colletrotrichum gloeosporioides, Alternaria alternata, and Fusarium solani) in molecular docking and molecular dynamics simulations, we retrieved the structure of tubulin co-crystallized with taxol from the Protein Data Bank (PDB) (ID: 1JFF) and the structure of the cyclic lipopeptides from PubChem (Compound CID: 102287549, 100977820, 10129764). Similarity and homology analyses of the retrieved β-tubulin structure with those of the fungi showed that the conserved domains shared 84% similarity, and the root mean square deviation (RMSD) was less than 2 Å. In the molecular docking studies, within the binding pocket, residues Pro274, Thr276, and Glu27 of β-tubulin were responsible for the interaction with the cyclic lipopeptides. In the molecular dynamics analysis, two groups of ligands were formed based on the number of poses analyzed with respect to the RMSD. Group 1 was made up of 10, 100, and 500 poses with distances 0.080 to 0.092 nm and RMSDs of 0.10 to 0.15 nm. For group 2, consisting of 1000 poses, the initial and final distance was 0.1 nm and the RMSDs were in the range of 0.10 to 0.30 nm. These results suggest that iturin A and fengycin bind with higher affinity than surfactin to β-tubulin. These two lipopeptides may be used as lead compounds to develop new antifungal agents or employed directly as biorational products to control plant pathogenic fungi.

The first report of antifungal lipopeptide production by a Bacillus subtilis subsp. inaquosorum strain

A strain of bacteria in the Bacillus subtilis species complex was isolated from a building’s air vent in the Washington DC area, USA, and produced strong antifungal activity with in vitro assays. This strain, designated (HU Biol-II), showed pronounced inhibitory effects on mycelial growth of a wide spectrum of fungi. The objectives of this study were to use genome sequencing to confirm the taxonomy of HU Biol-II, evaluate its antifungal activity and implement genome mining and HPLC-MS/MS to characterize the bioactive secondary metabolites. The strain, as determined by multilocus sequence alignment analysis, was identified as a member of Bacillus subtilis subsp. inaquosorum clade. Core genome phylogeny showed that the isolate is most closely related to B. subtilis subsp. inaquosorum strain DE111, a commercially produced human probiotic. The investigation identified eight bioactive metabolite clusters in the genome. HPLC MS/MS was able to confirm the production of seven of the metabolites. This study is the first to report the production of two antifungal cyclic lipopeptides (bacillomycin F and fengycin) from a member of B. subtilis subsp. inaquosorum. The strain also produced the antibacterial aurantinin B, which confirms the biosynthetic cluster responsible for its production. Comparative genomics and metabolomics demonstrated the commercial probiotic strain DE111 produced the same metabolites, with the exception of aurantinin B. These findings are the first description of the secondary metabolites produced by a strain of B. subtilis subsp. inaquosorum.

Ion Channels Induced by Antimicrobial Agents in Model Lipid Membranes are Modulated by Plant Polyphenols Through Surrounding Lipid Media.

The potential therapeutic applications of plant polyphenols in various neurological, cardiovascular, metabolic and malignant disorders determine the relevance of studying the molecular mechanisms of their action on the cell membranes. Here, the quantitative changes in the physical parameters of model bilayer lipid membranes upon the adsorption of plant polyphenols were evaluated. It was shown that butein and naringenin significantly decreased the intrinsic dipole potential of cholesterol-free and cholesterol-enriched membranes. Cardamonin, 4'-hydroxychalcone, licochalcone A and liquiritigenin demonstrated the average efficiency, while resveratrol did not characterized by the ability to modulate the bilayer electrostatics. At the same time, the tested polyphenols affected melting of phospholipids with saturated acyl chains. The effects were attributed to the lipid disordering and a promotion of the positive curvature stress. According to DSC data and results of measurements of the threshold voltages that cause bilayer breakdown licochalcone A is the most effective agent. Furthermore, the role of the polyphenol induced changes in the electric and elastic properties of lipid host in the regulation of reconstituted ion channels was examined. The ability of the tested polyphenols to decrease the conductance of single ion channels produced by the antifungal cyclic lipopeptide syringomycin E was in agreement with their effects on the dipole potential of the lipid bilayers. The greatest effect of licochalcone A on the steady-state membrane conductance induced by the antifungal polyene macrolide antibiotic nystatin correlated with its greatest efficacy to induce the positive curvature stress. We also found that butein and naringenin bind specifically to a single pore formed by α-hemolysin from Staphylococcus aureus.

A Novel Variant of Narrow-Spectrum Antifungal Bacterial Lipopeptides That Strongly Inhibit Ganoderma boninense.

Bacterial antifungal cyclic lipopeptides (ACLs) have become a promising alternative to synthetic fungicide to control pathogenic fungi. Bacillus sp. is known to produce three families of ACL, namely iturin, surfactin, and fengycin. In this paper, we characterized the ACLs produced by B. methylotrophicus HC51 (referred as HC51) mainly regarding its composition and effectivity against fungal plant pathogen. HC51 culture was tested against various pathogenic fungi and the ACLs were extracted and analyzed using liquid chromatography-electrospray ionization mass spectrometry. HC51 showed strong antifungal activity against the plant pathogens Ganoderma sp. and Fusarium sp. Cell-free methanol extract of HC51 contains iturin A and various variants of fengycin. C16 fengycin A was present in four fractions which indicates it as a major component of ACL from HC51. Five variants of fengycin were detected, four of which had been previously reported. We found a novel C17 fengycin F that is characterized by a substitution of L-ornithine into lysine. Considering that L-ornithine is an important building block of fengycin, this substitution suggests the possibility of an alternative pathway for fengycin biosynthesis.

Cyclic lipopeptide iturin A structure-dependently induces defense response in Arabidopsis plants by activating SA and JA signaling pathways

Iturin A is the most well studied antifungal cyclic lipopeptide produced by Bacillus species that are frequently utilized as biological control agents. Iturin A not only shows strong antifungal activity against phytopathogens but also induces defense response in plants, thereby reducing plant disease severity. Here we report the defense signaling pathways triggered by iturin A in Arabidopsis salicylic acid (SA) or jasmonic acid (JA)-insensitive mutants. Iturin A activated the transcription of defense genes PR1 and PDF1.2 through the SA and JA signaling pathways, respectively. The role of iturin A as an elicitor was dependent on the cyclization of the seven amino acids and/or the β-hydroxy fatty acid chain. The iturin A derivative peptide, NH2-(L-Asn)-(D-Tyr)-(D-Asn)-(L-Gln)-(L-Pro)-(D-Asn)-(L-Ser)-COOH, completely suppressed PR1 and PDF1.2 gene expression in wild Arabidopsis plants. The identification of target molecules binding to iturin A and its derivative peptide is expected to shed new light on defense response in plants through the SA and JA signaling pathways.

Both extracellular chitinase and a new cyclic lipopeptide, chromobactomycin, contribute to the biocontrol activity of Chromobacterium sp. C61

Chromobacterium sp. strain C61 displays antifungal activities in vitro and has been used successfully for the biocontrol of plant diseases under field conditions. In this study, the roles of extracellular chitinase and an antifungal compound produced by strain C61 were investigated to elucidate their contributions to biological control activity. The bacterium possessed a locus chi54 encoding an extracellular chitinase, and mutation of chi54 eliminated chitinase production. Production of the extracellular enzyme and expression of the chi54 transcript were increased in the wild-type strain when chitin was added to the culture medium. In vitro assays showed that purified chitinase inhibited spore germination of multiple pathogens. However, the in planta biocontrol activity of filtrates of cultures grown in the presence of chitin was lower than that of filtrates grown without chitin, indicating that correlation between chitinase and biocontrol activity was lacking. The analysis of C61 culture filtrates revealed an antifungal cyclic lipopeptide, chromobactomycin, whose structure contained a unique nonameric peptide ring. The purified chromobactomycin inhibited the growth of several phytopathogenic fungi in vitro, and plant application significantly reduced disease severity for several pathogens. Furthermore, the production of chromobactomycin was reduced in cultures amended with chitin. These data suggest that the production of both the extracellular chitinase Chi54 and the newly identified antibiotic chromobactomycin can contribute, in an interconnected way, to the suppression of plant disease by Chromobacterium sp. strain C61.

Total synthesis and structure–activity relationships of caspofungin-like macrocyclic antifungal lipopeptides

The echinocandins represent a well-known class of macrocyclic antifungal lipopeptides that can be used for treatment of invasive fungal infections. Due to their complex chemical structures and synthetic difficulties, the structure–activity relationships (SARs) of them are still limited. A total synthetic approach was developed to synthesize structurally diverse caspofungin-like antifungal cyclic lipopeptides, allowing for systemically investigating their SARs. Most of the designed cyclic lipopeptides showed potent antifungal activities with broad spectrum. In particular, several compounds (e.g., 30a, 30e–h, 31a–d, 32c, and 33a,b) were more active in vitro against Candida albicans or Aspergillus fumigatus than caspofungin. The findings in this work indicated that the ‘left’ tripeptide segment of cyclic lipopeptide scaffold might be suitable for a hydrophilic structural motif, whereas the ‘right’ lipotripeptide segment was preferred as a hydrophobic core. The alkoxy-naphthoyl was found to be optimal side chain and alkyl length could affect the SARs of alkoxy-aroyl side chains.

ESI LC-MS and MS/MS Characterization of Antifungal Cyclic Lipopeptides Produced by Bacillus subtilis XF-1

Bacillus subtilis XF-1 (CGMCC No. 2357), a patent strain with good effects for controlling the clubroot of crucifer and many pathogenic fungi, was predicted to produce cyclic lipopeptide (CLP) antibiotics based on its genomic analysis. In this study, the CLPs were purified and determined with the following protocol: the supernatant of XF-1 cultivating mixture was firstly precipitated, then the precipitants were extracted with methanol and further separated by Sephadex LH-20 chromatography to test its antifungal activities. Fungi-inhibiting fractions were further characterized with LC/ESI-MS and LC/ESI-MS/MS. The results show that four molecular ion peaks [M+H]⁺ (m/z 1,464, 1,478, 1,492 and 1,506) from fungi suppression fraction were identified as fengycin A with fatty acid of C₁₆–C₁₉, fengycin B (C₁₄–C₁₇), fengycin C (C₁₅–C₁₈), fengycin D (C₁₅–C₁₈) and fengycin S (C₁₅–C₁₈). Fengycin C (C₁₅ and C₁₈), fengycin D (C₁₅, C₁₆ and C₁₈) and fengycin S (C₁₅, C₁₆ and C₁₈) were reported for the first time. The diversity of the fengycins that exist in this strain will help the elucidation of their biocontrol mechanisms.

A New Antifungal Cyclic Lipopeptide from Bacillus marinus B‐9987

AbstractA new cyclic lipopeptide, marihysin A (1), along with the three known cyclodipeptides cyclo(Ala‐Ile) (2), cyclo(Ala‐Leu) (3), and cyclo(Ala‐Tyr) (4), was isolated from the fermentation broth of the marine microorganism Bacillus marinus B‐9987 isolated from the tissues of rhizophere of Suaeda salsa in the intertidal zone of the Bohai Bay of P. R. China. Marihysin A (1) was established to be cyclo(Pro‐Gln‐Asn1‐Ser‐Asn2‐Tyr‐Asn3‐β‐aminotetradecanoic acid) by spectroscopic analysis, and it exhibits broad‐spectrum but low activity against plant pathogens as determined by antifungal bioassay.

Burkholdines 1097 and 1229, Potent Antifungal Peptides from Burkholderia ambifaria 2.2N

Potent antifungal cyclic lipopeptides, burkholdines (Bk), were isolated from a culture of Burkholderia ambifaria 2.2N. Bk-1229 (1) and Bk-1097 (2) are octapeptides comprised of nonproteinogenic amino acids, including beta-hydroxytyrosine, beta-hydroxyasparagine, and a new fatty acyl amino acid. 1 and 2 are fungicidal against a panel of fungi with potencies 2-60-fold better than amphotericin B control.

Two New Antifungal Cyclic Lipopeptides from Bacillus marinus B-9987

Two new cyclic lipopeptides maribasins A (1) and B (2) were isolated from the fermentation broth of the marine microorganism Bacillus marinus B-9987 isolated from Suaeda salsa in Bohai coastline of P. R. China. Both structures were established to be cyclo (D-Pro-L-Gln-L-Asn-L-Ser-D-Asn¹-D-Tyr-D-Asn²-D-β-aminoisopentadecanoic acid) (1) and cyclo (D-Pro-L-Gln-L-Asn-L-Ser-D-Asn¹-D-Tyr-D-Asn²-D-β-aminoanteisopentadecanoic acid) (2) by spectroscopic analysis and exhibited broad-spectrum activity against phytopathogens by the antifungal bioassay.