Bioprospecting and biodiversity investigations of endophytic fungi isolated from Juniperus communis

Endophytes are a group of highly diverse microorganisms that reside within plant tissues without causing obvious symptoms on the host. In our study, Juniperus communis samples were collected from Hungary and used for the isolation of endophytic fungal strains. From 240 plant samples, 76 fungal isolates were recovered and subcultured for homogeneity. The isolates were identifi ed using molecular taxonomical tools at the genus level and their biodiversity parameters were determined. The taxonomic diversity of the isolates was remarkably high, and the most abundant genera were Fusarium, Alternaria and Trichoderma. The secondary metabolites produced by the isolated endophytic fungi were extracted both from their mycelia and their ferment broth and their antimicrobial activities were tested against bacteria, yeasts, and fi lamentous fungi. In the antimicrobial tests, a total of 58 strains showed antimicrobial activity against at least one test organism. Altogether, 6.67% of the isolates have antibacterial eff ects with wide spectrum, and 10 strains showed remarkably high inhibitory percentage against yeast, while the extracts of 11 isolates proved to be active against fi lamentous fungi

Effects of Different Cultivation Parameters on the Production of Surfactin Variants by a Bacillus subtilis Strain

Surfactins are lipopeptide-type biosurfactants produced mainly by Bacillus species, consisting of a peptide loop of seven amino acids and a hydrophobic fatty acid chain (C12–C16). These molecules have been proven to exhibit various biological activities; thus, their therapeutic and environmental applications are considered. Within the surfactin lipopeptide family, there is a wide spectrum of different homologues and isomers; to date, more than 30 variants have been described. Since the newest members of these lipopeptides were described recently, there is no information that is available on their characteristic features, e.g., the dependence of their production from different cultivation parameters. This study examined the effects of both the different carbon sources and various metal ions on the surfactin production of a selected B. subtilis strain. Among the applied carbon sources, fructose and xylose had the highest impacts on the ratio of the different variants, regarding both the peptide sequences and the lengths of the fatty acids. Furthermore, the application of metal ions Mn2+, Cu2+ and Ni2+ in the media completely changed the surfactin variant compositions of the fermenting broths leading to the appearance of methyl esterified surfactin forms, and resulted in the appearance of novel surfactin variants with fatty acid chains containing no more than 11 carbon atoms

Host metabolite producing endophytic fungi isolated from Hypericum perforatum

In the present study, endophytic fungi have been isolated from various parts of the medicinal herb Hypericum perforatum (St. John’s Wort), which is known as a source of medically important metabolites. The isolated strains were cultured in liquid media and their ability to synthesize hypericin, the secondary metabolite of the host and its suspected precursor, emodin was tested analyzing the extracts of the fermentation broth and the mycelia. The HPLC-UV analysis of the chloroform/methanol extracts of the mycelia revealed that three isolates were able to produce emodin (SZMC 23771, 19.9 ng/mg; SZMC 23772, 20.8 ng/mg; SZMC 23769, 427.9 ng/mg) and one of them also could synthesize hypericin (SZMC 23769, 320.4 ng/mg). These results were also confirmed via UHPLC-HRMS technique both in full scan and MS/MS mode. The strains producing only emodin belong to the section Alternata of the genus Alternaria, while the isolate producing both metabolites was identified as Epicoccum nigrum. The mycelial extracts of E. nigrum and the Alternaria sp. SZMC 23772 showed higher inhibitory activities in the antimicrobial tests against the six selected bacteria compared to the hypericin and emodin standards in the applied concentration (100 μg/mL), while in case of the Alternaria sp. SZMC 23771 lower inhibition activities were observed on Staphylococcus aureus and Streptomyces albus than the pure compounds.</div

MIBiG 3.0 : a community-driven effort to annotate experimentally validated biosynthetic gene clusters

With an ever-increasing amount of (meta)genomic data being deposited in sequence databases, (meta)genome mining for natural product biosynthetic pathways occupies a critical role in the discovery of novel pharmaceutical drugs, crop protection agents and biomaterials. The genes that encode these pathways are often organised into biosynthetic gene clusters (BGCs). In 2015, we defined the Minimum Information about a Biosynthetic Gene cluster (MIBiG): a standardised data format that describes the minimally required information to uniquely characterise a BGC. We simultaneously constructed an accompanying online database of BGCs, which has since been widely used by the community as a reference dataset for BGCs and was expanded to 2021 entries in 2019 (MIBiG 2.0). Here, we describe MIBiG 3.0, a database update comprising large-scale validation and re-annotation of existing entries and 661 new entries. Particular attention was paid to the annotation of compound structures and biological activities, as well as protein domain selectivities. Together, these new features keep the database up-to-date, and will provide new opportunities for the scientific community to use its freely available data, e.g. for the training of new machine learning models to predict sequence-structure-function relationships for diverse natural products. MIBiG 3.0 is accessible online at https://mibig.secondarymetabolites.org/

Revealing of biodiversity and antimicrobial effects of Artemisia asiatica endophytes

Endophytic fungi produce a plethora of secondary metabolites, which may open new avenues to study their applicability in pharmaceuticals. Therefore, the present study focuses on the fungal endophytic community of Artemisia asiatica. During our work, fungal endophytes were isolated from a medicinal plant, A. asiatica. The culturable endophytic fungi were identifi ed using molecular techniques and biodiversity, richness and tissue specifi city were examined. As these microorganisms have been generally identifi ed as an abundant reservoir of novel antimicrobial compounds, the antimicrobial (i.e. antibacterial and antifungal) activities of the metabolites produced by the isolated fungi were studied. Numerous extracts containing the endophytic metabolites proved to be active against the applied test microorganisms including Gram-positive and Gramnegative bacteria, as well as yeasts and fi lamentous fungi, which can be examined in detail in the future and, based on the the chemical nature of these active metabolites, allow to discover novel bioactive metabolites

Characterization of the Plant Growth-Promoting Activities of Endophytic Fungi Isolated from Sophora flavescens

Endophytic fungi in symbiotic association with their host plant are well known to improve plant growth and reduce the adverse effects of both biotic and abiotic stresses. Therefore, fungal endophytes are beginning to receive increased attention in an effort to find growth-promoting strains that could be applied to enhance crop yield and quality. In our study, the plant growth-promoting activities of endophytic fungi isolated from various parts of Sophora flavescens (a medicinally important plant in Mongolia and China) have been revealed and investigated. Fungal isolates were identified using molecular taxonomical methods, while their plant growth-promoting abilities were evaluated in plate assays. Altogether, 15 strains were isolated, representing the genera Alternaria, Didymella, Fusarium and Xylogone. Five of the isolates possessed phosphate solubilization activities and twelve secreted siderophores, while all of them were able to produce indoleacetic acid (IAA) in the presence or absence of tryptophan. The endogenous and exogenous accumulation of IAA were also monitored in liquid cultures using the HPLC-MS/MS technique to refine the plate assay results. Furthermore, for the highest IAA producer fungi, the effects of their extracts were also examined in plant bioassays. In these tests, the primary root lengths of the model Arabidopsis thaliana were increased in several cases, while the biomasses were significantly lower than the control IAA treatment. Significant alterations have also been detected in the photosynthetic pigment (chlorophyll-a, -b and carotenoids) content due to the fungal extract treatments, but these changes did not show any specific trends