A new member of the fusaricidin family - structure elucidation and synthesis of fusaricidin E

Origin and characterization of cyclodepsipeptides: Comprehensive structural approaches with focus on mass spectrometry analysis of alkali-cationized molecular species

Cyclodepsipeptides (CDPs) represent a huge family of chemically and structurally diverse molecules with a wide ability for molecular interactions. CDPs are cyclic peptide-related natural products made up of both proteinogenic and nonproteinogenic amino acids linked by amide and ester bonds. The combined use of different analytical methods is required to accurately determine their integral structures including stereochemistry, thus allowing deeper insights into their often-intriguing bioactivities and their possible usefulness. Our goal is to present the various methods developed to accurately characterize CDPs. Presently, Marfey's method and NMR (nuclear magnetic resonance) are still considered the best for characterizing CDP configuration. Nevertheless, electrospray-high resolution tandem mass spectrometry (ESI-HRMS/MS) is of great value for efficiently resolving CDP's composition and sequences. For instance, recent data shows that the fragmentation of cationized CDPs (e.g., [M + Li]+ and [M + Na]+) leads to selective cleavage of ester bonds and specific cationized product ions (b series) useful to get unprecedented sequence information. Thus, after a brief presentation of their structure, biological functions, and biosynthesis, we also provide a historic overview of these various analytical approaches as well as their advantages and limitations with a special emphasis on the emergence of methods based on HRMS/MS through recent fundamental works and applications.

Structure modification of an antibiotic: by engineering the fusaricidin bio-synthetase A in Paenibacillus polymyxa

Fusaricidin, a lipopeptide antibiotic, is specifically produced by Paenibacillus polymyxa strains, which could strongly inhibit Fusarium species fungi. Fusaricidin bio-synthetase A (FusA) is composed of six modules and is essential for synthesizing the peptide moiety of fusaricidin. In this study, we confirmed the FusA of Paenibacillus polymyxa strain WLY78 involved in producing Fusaricidin LI-F07a. We constructed six engineered strains by deletion of each module within FusA from the genome of strain WLY78. One of the engineered strains is able to produce a novel compound that exhibits better antifungal activity than that of fusaricidin LI-F07a. This new compound, known as fusaricidin [ΔAla6] LI-F07a, has a molecular weight of 858. Our findings reveal that it exhibits a remarkable 1-fold increase in antifungal activity compared to previous fusaricidin, and the fermentation yield reaches ~55 mg/L. This research holds promising implications for plant protection against infections caused by Fusarium and Botrytis pathogen infection.

The Potential Biocontrol Agent Paenibacillus polymyxa TP3 Produces Fusaricidin-Type Compounds Involved in the Antagonism Against Gray Mold Pathogen Botrytis cinerea

Paenibacillus polymyxa is a beneficial bacterium for plant health. P. polymyxa TP3 exhibits antagonistic activity toward Botrytis cinerea and alleviates gray mold symptoms on the leaves of strawberry plants. Moreover, suppression of gray mold on the flowers and fruits of strawberry plants in field trials, including vegetative cells and endospores, was demonstrated, indicating the potential of strain TP3 as a biological control agent. To examine the anti-B. cinerea compounds produced by P. polymyxa TP3, we performed matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and fusaricidin-corresponding mass spectra were detected. Moreover, fusaricidin-related signals appeared in imaging mass spectrometry of TP3 when confronted with B. cinerea. By using liquid chromatography mass spectrometry-based molecular networking approach, we identified several fusaricidins including a new variant of mass/charge ratio 917.5455 with serine in the first position of the hexapeptide. Via advanced mass spectrometry and network analysis, fusaricidin-type compounds produced by P. polymyxa TP3 were efficiently disclosed and were presumed to play roles in the antagonism against gray mold pathogen B. cinerea.

Fusaricidin Biosynthesis Is Controlled via a KinB-Spo0A-AbrB Signal Pathway in Paenibacillus polymyxa WLY78

Fusaricidins produced by Paenibacillus polymyxa are important lipopeptide antibiotics against fungi. The fusGFEDCBA (fusaricidin biosynthesis) operon is responsible for synthesis of fusaricidins. However, the regulation mechanisms of fusaricidin biosynthesis remain to be fully clarified. In this study, we revealed that fusaricidin production is controlled by a complex regulatory network including KinB-Spo0A-AbrB. Evidence suggested that the regulator AbrB represses the transcription of the fus gene cluster by direct binding to the fus promoter, in which the sequences (5'-AATTTTAAAATAAATTTTGTGATTT-3') located from -136 to -112 bp relative to the transcription start site is required for this repression. Spo0A binds to the abrB promoter that contains the Spo0A-binding sequences (5'-TGTCGAA-3', 0A box) and in turn prevents the further transcription of abrB. The decreasing concentration of AbrB allows for the derepression of the fus promoter repressed by AbrB. The genome of P. polymyxa WLY78 contains two orthologs (named Kin1508 and Kin4833) of Bacillus subtilis KinB, but only Kin4833 activates sporulation and fusaricidin production, indicating that this kinase may be involved in phosphorylating Spo0A to initiate sporulation and regulate the abrB transcription. Our results reveal that Kin4833 (KinB), Spo0A, and AbrB are involved in regulation of fusaricidin production and a signaling mechanism that links fusaricidin production and sporulation.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

The chemistry and biology of guanidine secondary metabolites

Covering: 2017-2019Guanidine natural products isolated from microorganisms, marine invertebrates and terrestrial plants, amphibians and spiders, represented by non-ribosomal peptides, guanidine-bearing polyketides, alkaloids, terpenoids and shikimic acid derived, are the subject of this review. The topics include the discovery of new metabolites, total synthesis of natural guanidine compounds, biological activity and mechanism-of-action, biosynthesis and ecological functions.

Mining the Yucatan Coastal Microbiome for the Identification of Non-Ribosomal Peptides Synthetase (NRPS) Genes

Prokaryotes represent a source of both biotechnological and pharmaceutical molecules of importance, such as nonribosomal peptides (NRPs). NRPs are secondary metabolites which their synthesis is independent of ribosomes. Traditionally, obtaining NRPs had focused on organisms from terrestrial environments, but in recent years marine and coastal environments have emerged as an important source for the search and obtaining of nonribosomal compounds. In this study, we carried out a metataxonomic analysis of sediment of the coast of Yucatan in order to evaluate the potential of the microbial communities to contain bacteria involved in the synthesis of NRPs in two sites: one contaminated and the other conserved. As well as a metatranscriptomic analysis to discover nonribosomal peptide synthetases (NRPSs) genes. We found that the phyla with the highest representation of NRPs producing organisms were the Proteobacteria and Firmicutes present in the sediments of the conserved site. Similarly, the metatranscriptomic analysis showed that 52% of the sequences identified as catalytic domains of NRPSs were found in the conserved site sample, mostly (82%) belonging to Proteobacteria and Firmicutes; while the representation of Actinobacteria traditionally described as the major producers of secondary metabolites was low. It is important to highlight the prediction of metabolic pathways for siderophores production, as well as the identification of NRPS's condensation domain in organisms of the Archaea domain. Because this opens the possibility to the search for new nonribosomal structures in these organisms. This is the first mining study using high throughput sequencing technologies conducted in the sediments of the Yucatan coast to search for bacteria producing NRPs, and genes that encode NRPSs enzymes.

Structure elucidation of bacterial nonribosomal lipopeptides

We provide a summary of the tools, which allow elucidate the structures of nonribosomal lipopetides.

Fusaricidin Produced by Paenibacillus polymyxa WLY78 Induces Systemic Resistance against Fusarium Wilt of Cucumber

Cucumber is an important vegetable crop in China. Fusarium wilt is a soil-borne disease that can significantly reduce cucumber yields. Paenibacillus polymyxa WLY78 can strongly inhibit Fusarium oxysporum f. sp. Cucumerium, which causes Fusarium wilt disease. In this study, we screened the genome of WLY78 and found eight potential antibiotic biosynthesis gene clusters. Mutation analysis showed that among the eight clusters, the fusaricidin synthesis (fus) gene cluster is involved in inhibiting the Fusarium genus, Verticillium albo-atrum, Monilia persoon, Alternaria mali, Botrytis cinereal, and Aspergillus niger. Further mutation analysis revealed that with the exception of fusTE, the seven genes fusG, fusF, fusE, fusD, fusC, fusB, and fusA within the fus cluster were all involved in inhibiting fungi. This is the first time that demonstrated that fusTE was not essential. We first report the inhibitory mode of fusaricidin to inhibit spore germination and disrupt hyphal membranes. A biocontrol assay demonstrated that fusaricidin played a major role in controlling Fusarium wilt disease. Additionally, qRT-PCR demonstrated that fusaricidin could induce systemic resistance via salicylic acid (SA) signal against Fusarium wilt of cucumber. WLY78 is the first reported strain to both produce fusaricidin and fix nitrogen. Therefore, our results demonstrate that WLY78 will have great potential as a biocontrol agent in agriculture.