The genus Simplicillium and Emericellopsis: A review of phytochemistry and pharmacology

Marine-Fungus-Derived Natural Compound 4-Hydroxyphenylacetic Acid Induces Autophagy to Exert Antithrombotic Effects in Zebrafish

Marine natural products are important sources of novel drugs. In this study, we isolated 4-hydroxyphenylacetic acid (HPA) from the marine-derived fungus Emericellopsis maritima Y39-2. The antithrombotic activity and mechanism of HPA were reported for the first time. Using a zebrafish model, we found that HPA had a strong antithrombotic activity because it can significantly increase cardiac erythrocytes, blood flow velocity, and heart rate, reduce caudal thrombus, and reverse the inflammatory response caused by Arachidonic Acid (AA). Further transcriptome analysis and qRT-PCR validation demonstrated that HPA may regulate autophagy by inhibiting the PI3K/AKT/mTOR signaling pathway to exert antithrombotic effects.

New Antibacterial Peptaibiotics against Plant and Fish Pathogens from the Deep-Sea-Derived Fungus Simplicillium obclavatum EIODSF 020

Bacterial diseases could severely harm agricultural production. To develop new antibacterial agents, the secondary metabolites of a deep-sea-derived fungus Simplicillium obclavatum EIODSF 020 with antibacterial activities against plant and fish pathogens were investigated by a bioassay-guided approach, which led to the isolation of 11 new peptaibiotics, simplicpeptaibs A-K (1-11). They contain 16-19 residues, including β-alanine, tyrosine, or tyrosine O-sulfate, that were rarely present in peptaibiotics. Their structures were elucidated by spectroscopic analyses (NMR, HRMS, HRMS2, and ECD) and Marfey's method. The primary and secondary structures of novel sulfated peptaibiotic 9 were reconfirmed by single-crystal X-ray diffraction analysis. Genome sequencing of S. obclavatum EIODSF 020 allowed the detection of a gene cluster encoding two individual NRPSs (totally containing 19 modules) that was closely related to simplicpeptaib biosynthesis. Antibacterial investigations of 1-11 together with the previously isolated linear and cyclic peptides from this strain suggested the antibacterial property of this fungus was attributed to the peptaibiotics and cyclic lipopeptides. Among them, compounds 4, 6, 7, and 9 showed significant activity against the tobacco pathogen Ralstonia solanacearum or tilapia pathogens Streptococcus iniae and Streptococcus agalactiae. The antibacterial activity of 6 against R. solanacearum could be enhanced by the addition of 1% NaCl. The structure-bioactivity relationship of simplicpeptaibs was discussed.

Update on fungal lipid biosynthesis inhibitors as antifungal agents

Fungal diseases today represent a world-wide problem. Poor hygiene and decreased immunity are the main reasons behind the manifestation of this disease. After COVID-19, an increase in the rate of fungal infection has been observed in different countries. Different classes of antifungal agents, such as polyenes, azoles, echinocandins, and anti-metabolites, as well as their combinations, are currently employed to treat fungal diseases; these drugs are effective but can cause some side effects and toxicities. Therefore, the identification and development of newer antifungal agents is a current need. The fungal cell comprises many lipids, such as ergosterol, phospholipids, and sphingolipids. Ergosterol is a sterol lipid that is only found in fungal cells. Various pathways synthesize all these lipids, and the activities of multiple enzymes govern these pathways. Inhibiting these enzymes will ultimately impede the lipid synthesis pathway, and this phenomenon could be a potential antifungal therapy. This review will discuss various lipid synthesis pathways and multiple antifungal agents identified as having fungal lipid synthesis inhibition activity. This review will identify novel compounds that can inhibit fungal lipid synthesis, permitting researchers to direct further deep pharmacological investigation and help develop drug delivery systems for such compounds.

Biocrust reduces the soil erodibility of coral calcareous sand by regulating microbial community and extracellular polymeric substances on tropical coral island, South China Sea

Tropical coral islands assume a pivotal role in the conservation of oceanic ecosystem biodiversity. However, their distinctive environmental attributes and limited vegetation render them highly susceptible to soil erosion. The biological soil crust (biocrust), owing to its significant ecological role in soil stabilization and erosion prevention, is deemed an effective means of mitigating soil erosion on coral island. However, existing research on the mechanisms through which biocrusts resist soil erosion has predominantly concentrated on arid and semi-arid regions. Consequently, this study will specifically delve into elucidating the erosion-resistant mechanisms of biocrusts in tropical coral island environments, South China Sea. Specifically, we collected 16 samples of biocrusts and bare soil from Meiji Island. High-throughput amplicon sequencing was executed to analyze the microbial community, including bacteria, fungi, and archaea. Additionally, quantitative PCR was utilized to assess the abundance of the bacterial 16S rRNA, fungal ITS, archaeal 16S rRNA, and cyanobacterial 16S rRNA genes within these samples. Physicochemical measurements and assessments of extracellular polymeric substances (EPSs) were conducted to characterize the soil properties. The study reported a significantly decreased soil erodibility factor after biocrust formation. Compared to bare soil, soil erodibility factor decreased from 0.280 to 0.190 t h MJ-1 mm-1 in the biocrusts. Mechanistically, we measured the microbial EPS contents and revealed a negative correlation between EPS and soil erodibility factor. Consistent with increased EPS, the abundance of bacteria, fungi, archaea, and cyanobacteria were also detected significantly increased with biocrust formation. Correlation analysis detected Cyanobacteria, Chloroflexi, Deinococcota, and Crenarchaeota as potential microbials promoting EPSs and reducing soil erosion. Together, our study presents the evidence that biocrust from tropical coral island in the South China Sea promotes resistance to soil erosion, pinpointing key EPSs-producing microbials against soil erosion. The findings would provide insights for island soil restoration.

Antibacterial metabolites from an unexplored strain of marine fungi Emericellopsis minima and determination of the probable mode of action against Staphylococcus aureus and methicillin-resistant S. aureus

Increasing prevalence of drug resistance has led researchers to focus on discovering new antibacterial agents derived from the marine biome. Although ample studies have investigated marine fungi for their bioactive metabolites with hopeful prospects in drug discovery. The present study was aimed to isolate/ identify potential antimethicillin-resistant Staphylococcus aureus compounds producing marine fungal strain from the Indian marine environment. The effective anti-MRSA compound was produced by a marine fungal strain designated as D6. The D6 strain exhibited 99% similarity to Emericellopsis minima based on 18S rRNA gene analysis. The culture conditions of E. minima D6 were optimized using nutritional and environmental parameters for enhanced anti-MRSA compound production. The agar well diffusion assay was used to determine the inhibition zone diameter of the crude extract against S. aureus and methicillin-resistant S. aureus, whereas the broth microdilution method was used to determine their minimum inhibitory concentration (MIC) active fraction. MIC values of the ethyl acetate fraction ranged from 0.8 to 1 mg/mL. SEM analysis revealed that the ethyl acetate fraction induces deep craters in methicillin-resistant S. aureus. Further, GC-MS analysis confirmed the occurrence of a total of 15 major compounds in active ethyl acetate fraction. Some of the major antibacterial compounds included cyclopentanol, isothiazole, benzoic acid, pyrrolo[1,2-a] pyrazine-1,4-dione, and hexahydro. These findings suggest that the marine fungi of E. minima can be a valuable candidate for prospecting antibiotics and an alternative complementary strategy for drug-resistant bacterial infections.

Genomic and Metabolomic Analyses of the Marine Fungus Emericellopsis cladophorae: Insights into Saltwater Adaptability Mechanisms and Its Biosynthetic Potential

The genus Emericellopsis is found in terrestrial, but mainly in marine, environments with a worldwide distribution. Although Emericellopsis has been recognized as an important source of bioactive compounds, the range of metabolites expressed by the species of this genus, as well as the genes involved in their production are still poorly known. Untargeted metabolomics, using UPLC- QToF–MS/MS, and genome sequencing (Illumina HiSeq) was performed to unlock E. cladophorae MUM 19.33 chemical diversity. The genome of E. cladophorae is 26.9 Mb and encodes 8572 genes. A large set of genes encoding carbohydrate-active enzymes (CAZymes), secreted proteins, transporters, and secondary metabolite biosynthetic gene clusters were identified. Our analysis also revealed genomic signatures that may reflect a certain fungal adaptability to the marine environment, such as genes encoding for (1) the high-osmolarity glycerol pathway; (2) osmolytes’ biosynthetic processes; (3) ion transport systems, and (4) CAZymes classes allowing the utilization of marine polysaccharides. The fungal crude extract library constructed revealed a promising source of antifungal (e.g., 9,12,13-Trihydroxyoctadec-10-enoic acid, hymeglusin), antibacterial (e.g., NovobiocinA), anticancer (e.g., daunomycinone, isoreserpin, flavopiridol), and anti-inflammatory (e.g., 2’-O-Galloylhyperin) metabolites. We also detected unknown compounds with no structural match in the databases used. The metabolites’ profiles of E. cladophorae MUM 19.33 fermentations were salt dependent. The results of this study contribute to unravel aspects of the biology and ecology of this marine fungus. The genome and metabolome data are relevant for future biotechnological exploitation of the species.