Antifungal Activity and Action Mechanisms of 2,4-Di-tert-butylphenol against Ustilaginoidea virens

Antifungal Activity and Potential Mechanisms of Two Bafilomycin Analogues Isolated from Streptomyces sp. NEAU-Y11 against Colletotrichum orbiculare

Cucumber anthracnose, caused by Colletotrichum orbiculare, severely affects the cucumber yield and quality. In this study, two active compounds, bafilomycin C1 and JBIR-100, were isolated from strain NEAU-Y11 and exhibited strong antifungal activity against C. orbiculare, with EC50 values of 0.0491 and 0.1042 μg/mL, respectively, significantly lower than those of the commercial fungicide (4.42 μg/mL). Pot experiments demonstrated effective control of cucumber anthracnose at 0.2 μg/mL for bafilomycin C1 and 0.4 μg/mL for JBIR-100, with efficacies reaching 78.5 and 67.7%, respectively. Microscopy and biochemical analyses indicated that both compounds disrupted the fungal cell wall, membrane, and redox homeostasis, leading to cell death. Transcriptome analysis further revealed the effects of bafilomycin C1's on amino acid metabolism, cell structure, redox homeostasis, and DNA double-strand break repair. These findings suggest that bafilomycin C1 and JBIR-100 are promising candidates for use as agrochemical fungicides to control C. orbiculares and may serve as a basis for developing next-generation antifungal agents.

Dynamic changes in microbial communities and volatile compounds in kombucha fermentation using Flos sophorae and Elm fruits, compared to black and green tea

The dynamic changes in physicochemical properties, microbial communities, and volatile compounds in kombucha made from Flos sophorae (FLSK) and Elm fruit (EFK) were compared to those of black tea (BTK) and green tea (GTK) over a 12-day fermentation period. The results revealed that overall flavonoid and polyphenol content, as well as antioxidant activity, increased initially and then decreased, accompanied by a steady reduction in pH within the fermentation broths investigated. Notably, the GTK exhibited stronger antioxidant activity than the other fermentation broths. Furthermore, 16S rRNA gene sequencing revealed that Komagataeibacter rhaeticus, Komagataeibacter saccharivorans, and Acidovorax wautersii were the dominating microbial species in the fermentation broths under this study. Komagataeibacter rhaeticus initially reduced and then increased throughout the FLSK fermentation, whereas Komagataeibacter saccharivorans increased from day 0 to day 6, and remain stable by day 12 during the EFK fermentation. Comparative analysis revealed that Komagataeibacter rhaeticus was more abundant in the FLSK and GTK than in the EFK and BTK, whereas Komagataeibacter saccharivorans showed a higher abundance in the EFK relative to the other fermentation broths. Gas chromatography-mass spectrometry identified acetic acid, linalool, ethanol, and ethyl acetate as the major volatile chemicals that rose significantly in fermentation mixtures of the examined substrates. The FLSK had a much higher linalool concentration than the other fermentation broths, although the EFK and GTK had higher ethanol content. Correlation study found that Komagataeibacter rhaeticus was negatively related with alcohol compounds, but Komagataeibacter saccharivorans was positively associated with a diverse spectrum of acids, alcohols, and esters. The study found changes in bioactive chemicals as well as interactions between bacterial populations and volatile compounds throughout fermentation in the substrates investigated.

Baseline Sensitivity and Toxicity Mechanisms of Prochloraz to Alternaria alternata Strains Associated with Maize Leaf Blight in Heilongjiang Province in China

Alternaria species are fungal pathogens that can infect maize, causing leaf blight disease and significant economic losses. This study aimed to determine the baseline sensitivity to prochloraz of A. alternata isolates obtained from diseased maize leaves collected from Heilongjiang Province by assessing the half-maximal effective concentration (EC50) values. The EC50 values of prochloraz ranged from 0.0550 to 2.3258 μg/ml, with an average of 0.9995 ± 0.5192 μg/ml. At EC50 (1.2495 μg/ml) and 2EC50 (2.4990 μg/ml), prochloraz increased the number of mycelial offshoots, disrupted the cell membrane integrity of conidia and mycelia, and resulted in a reduced ergosterol content in the mycelia. Prochloraz significantly affected the mycelial cell membrane permeability and increased the malondialdehyde content and superoxide dismutase activity. No cross-resistance was detected between prochloraz and other fungicides. These data demonstrate that prochloraz is a promising fungicide for managing maize leaf blight caused by A. alternata and provide novel insights into understanding the mechanism of prochloraz toxicity against A. alternata isolates.

Magnolol from Magnolia officinalis inhibits Neopestalotiopsis ellipsospora by damaging the cell membrane

Tea gray blight disease is a significant threat to the tea industry. In this study, a biological activity approach was utilized to investigate the efficacy of green fungicides from Magnolia officinalis stem bark against Neopestalotiopsis ellipsospora. The active compounds were isolated and purified, and their structures were elucidated. In vitro and in vivo activity screenings revealed that the n-hexane extract, which contained magnolol and honokiol, exhibited strong activity against N. ellipsospora, showing complete inhibition at 100 mg/L. The EC50 values of magnolol and honokiol were 5.11 and 6.09 mg/L, respectively. Mechanistically, magnolol was found to disrupt N. ellipsospora invasion by damaging the cell membrane, increasing permeability, and causing leakage of intracellular substances. Transcriptome analysis revealed that magnolol treatment downregulates membrane-related genes and leads to the enrichment of lipid metabolism pathway genes. This study revealed that magnolol inhibits N. ellipsospora growth by affecting lipid metabolism and compromising cell membrane integrity.

A Novel Preservative Film with a Pleated Surface Structure and Dual Bioactivity Properties for Application in Strawberry Preservation due to Its Efficient Apoptosis of Pathogenic Fungal Cells

Botrytis cinerea (B. cinerea) and Colletotrichum gloeosporioides (C. gloeosporioides) were isolated from the decaying strawberry tissue. The antifungal properties of Monarda didyma essential oil (MEO) and its nanoemulsion were confirmed, demonstrating complete inhibition of the pathogens at concentrations of 0.45 μL/mL (0.37 mg/mL) and 10 μL/mL, respectively. Thymol, a primary component of MEO, was determined as an antimicrobial agent with IC50 values of 34.51 (B. cinerea) and 53.40 (C. gloeosporioides) μg/mL. Hippophae rhamnoides oil (HEO) was confirmed as a potent antioxidant, leading to the development of a thymol-HEO-chitosan film designed to act as an antistaling agent. The disease index and weight loss rate can be reduced by 90 and 60%, respectively, with nutrients also being well-preserved, offering an innovative approach to preservative development. Studies on the antifungal mechanism revealed that thymol could bind to FKS1 to disrupt the cell wall, causing the collapse of mitochondrial membrane potential and a burst of reactive oxygen species.

In-silico and in-vitro evaluation of antifungal bioactive compounds from Streptomyces sp. strain 130 against Aspergillus flavus

Streptomyces spp. are considered excellent reservoirs of natural bioactive compounds. The study evaluated the bioactive potential of secondary metabolites from Streptomyces sp. strain 130 through PKS-I and NRPS gene-clusters screening. GC-MS analysis was done for metabolic profiling of bioactive compounds from strain 130 in the next set of experiments. Identified antifungal compounds underwent ADMET analyses to screen their toxicity. All compounds' molecular docking was done with the structural gene products of the aflatoxin biosynthetic pathway of Aspergillus flavus. MD simulations were utilized to evaluate the stability of protein-ligand complexes under physiological conditions. Based on the in-silico studies, compound 2,4-di-tert butyl-phenol (DTBP) was selected for in-vitro studies against Aspergillus flavus. Simultaneously, bioactive compounds were extracted from strain 130 in two different solvents (ethyl-acetate and methanol) and used for similar assays. The MIC value of DTBP was found to be 314 µg/mL, whereas in ethyl-acetate extract and methanol-extract, it was 250 and 350 µg/mL, respectively. A mycelium growth assay was done to analyze the effect of compounds/extracts on the mycelium formation of Aspergillus flavus. In agar diffusion assay, zone of inhibitions in DTBP, ethyl-acetate extract, and methanol extract were observed with diameters of 11.3, 13.3, and 7.6 mm, respectively. In the growth curve assay, treated samples have delayed the growth of fungi, which signified that the compounds have a fungistatic nature. Spot assay has determined the fungal sensitivity to a sub-minimum inhibitory concentration of antifungal compounds. The study's results suggested that DTBP can be exploited for antifungal-drug development.