The potential biological activities of Aspergillus luchuensis-aided green synthesis of silver nanoparticles.

Biosynthetic metals have attracted global attention because of their safety, affordability, and environmental friendliness. As a consequence, the cell-free filtrate (CFF) of Dill leaf-derived endophytic fungus Aspergillus luchuensis was employed for the extracellularly synthesis silver nanoparticles (AgNPs). A reddish-brown color shift confirmed that AgNPs were successfully produced. The obtained AgNPs were characterized by UV-Vis (ultraviolet-visible spectroscopy), Transmission electron microscopy (TEM), FTIR, EDX, and zeta potential. Results demonstrated the creation of crystalline AgNPs with a spherical shape at 427.81 nm in the UV-Vis spectrum, and size ranged from 16 to 18 nm as observed by TEM. Additionally, the biogenic AgNPs had a promising antibacterial activity versus multidrug-resistant bacteria, notably, S. aureus, E. coli, and S. typhi. The highest growth reduction was recorded in the case of E. coli. Furthermore, the biosynthesized AgNPs demonstrated potent antifungal potential versus a variety of harmful fungi. The maximum growth inhibition was evaluated from A. brasinsilles, followed by C. albicans as compared to cell-free extract and AgNO3. In addition, data revealed that AgNPs possess powerful antioxidant activity, and their ability to scavenge radicals increased from 33.0 to 85.1% with an increment in their concentration from 3.9 to 1,000 µg/mL. Furthermore, data showed that AgNPs displayed high catalytic activity of safranin under light irradiation. The maximum decolorization percentage (100%) was observed after 6 h. Besides, the biosynthesized AgNPs showed high insecticidal potential against 3rd larval instar of Culex pipiens. Taken together, data suggested that endophytic fungus, A. luchuensis, is an attractive candidate as an environmentally sustainable and friendly fungal nanofactory.

Evaluation of the efficacy of ozonated olive oil for controlling the growth of Alternaria alternata and its toxins.

Toxigenic fungi infect fruits and vegetables either during harvest or storage and create mycotoxins as secondary metabolites, which pose a serious threat to human and animal health throughout the food chain. Therefore, the objective of this study was to determine the inhibitory effect of OZO against the growth and spore germination of the Alternaria alternata fungal strain. Additionally, evaluation of the synthesis inhibition of Alternaria toxins (ATs), among which are alternariol (AOH), alternariol-9-methyl ether (AME), and tenuazonic acid (TeA) in the potato dextrose broth (PDB) medium and orange fruit after harvest. The results indicated that the inhibition zone was 29.0 ± 1.2 mm at 20 mg/L of OZO. The MIC and MFC values were recorded at 0.186 and 1.57 mg/mL, respectively. In this regard, OZO prevented conidia germination at 98.8% with the treatment of 5 mg/mL. OZO at 20 mg/mL was efficacious in producing a high loss in ATs production in the PDB medium, reaching 73.4, 76, and 67.1% for AOH, AME, and TeA, respectively. In addition, OZO prevents the biosynthesis of AOH and AME during the storage of orange fruits compared with the positive control sample. In contrast, 20 mg/mL reduced TeA accumulation and the appearance of Alternaria brown spot (ABS) in orange. To the best of our knowledge, this is the first report that studies OZO to control ATs in vitro in orange fruits.

GC-MS Analysis, Antibacterial, and Anticancer Activities of Hibiscus sabdariffa L. Methanolic Extract: In Vitro and In Silico Studies.

The emergence of bacteria that are resistant to several antibiotics has represented a serious hazard to human health globally. Bioactive metabolites from medicinal plants have a wide spectrum of therapeutic possibilities against resistant bacteria. Therefore, this study was performed to investigate the antibacterial efficacy of various extracts of three medicinal plants as Salvia officinalis L., Ziziphus spina-christi L., and Hibiscus sabdariffa L. against pathogenic Gram-negative Enterobacter cloacae (ATCC13047), Pseudomonas aeruginosa (RCMB008001), Escherichia coli (RCMB004001), and Gram-positive Staphylococcus aureus (ATCC 25923), bacteria using the agar-well diffusion method. Results revealed that, out of the three examined plant extracts, the methanol extract of H. sabdariffa L. was the most effective against all tested bacteria. The highest growth inhibition (39.6 ± 0.20 mm) was recorded against E. coli. Additionally, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of the methanol extract of H. sabdariffa were detected in the case of all tested bacteria. Moreover, an antibiotic susceptibility test revealed that all tested bacteria showed multidrug resistance (MDR). While 50% of tested bacteria were sensitive and 50% were intermediately sensitive to piperacillin/tazobactam (TZP) based on the inhibition zone but still less than the extract. Synergistic assay demonstrated the promising role of using a combination of H. sabdariffa L. and (TZP) against tested bacteria. A surface investigation using a scanning electron microscope of the E. coli treated with TZP, extract, or a combination of the two revealed extremely considerable bacterial cell death. In addition, H. sabdariffa L. has a promising anticancer role versus Caco-2 cells with IC50 of 17.51 ± 0.07 µg/mL and minimal cytotoxicity upon testing versus Vero cells with CC50 of 165.24 ± 0.89 µg/mL. Flow cytometric analysis confirmed that H. sabdariffa extract significantly increased the apoptotic rate of Caco-2-treated cells compared to the untreated group. Furthermore, GC-MS analysis confirmed the existence of various bioactive components in the methanol hibiscus extract. Utilizing molecular docking with the MOE-Dock tool, binding interactions between n-Hexadecanoic acid, hexadecanoic acid-methyl ester, and oleic acid, 3-hydroxypropyl ester were evaluated against the target crystal structures of E. coli (MenB) (PDB ID:3T88) and the structure of cyclophilin of a colon cancer cell line (PDB ID: 2HQ6). The observed results provide insight into how molecular modeling methods might inhibit the tested substances, which may have applications in the treatment of E. coli and colon cancer. Thus, H. sabdariffa methanol extract is a promising candidate to be further investigated for developing alternative natural therapies for infection treatment.

Trichoderma asperellum empowers tomato plants and suppresses Fusarium oxysporum through priming responses.

Plant-associated microbes play crucial roles in plant health and promote growth under stress. Tomato (Solanum lycopersicum) is one of the strategic crops grown throughout Egypt and is a widely grown vegetable worldwide. However, plant disease severely affects tomato production. The post-harvest disease (Fusarium wilt disease) affects food security globally, especially in the tomato fields. Thus, an alternative effective and economical biological treatment to the disease was recently established using Trichoderma asperellum. However, the role of rhizosphere microbiota in the resistance of tomato plants against soil-borne Fusarium wilt disease (FWD) remains unclear. In the current study, a dual culture assay of T. asperellum against various phytopathogens (e.g., Fusarium oxysporum, F. solani, Alternaria alternata, Rhizoctonia solani, and F. graminerarum) was performed in vitro. Interestingly, T. asperellum exhibited the highest mycelial inhibition rate (53.24%) against F. oxysporum. In addition, 30% free cell filtrate of T. asperellum inhibited F. oxysporum by 59.39%. Various underlying mechanisms were studied to explore the antifungal activity against F. oxysporum, such as chitinase activity, analysis of bioactive compounds by gas chromatography-mass spectrometry (GC-MS), and assessment of fungal secondary metabolites against F. oxysporum mycotoxins in tomato fruits. Additionally, the plant growth-promoting traits of T. asperellum were studied (e.g., IAA production, Phosphate solubilization), and the impact on tomato seeds germination. Scanning electron microscopy, plant root sections, and confocal microscopy were used to show the mobility of the fungal endophyte activity to promote tomato root growth compared with untreated tomato root. T. asperellum enhanced the growth of tomato seeds and controlled the wilt disease caused by the phytopathogen F. oxysporum by enhancing the number of leaves as well as shoot and root length (cm) and fresh and dry weights (g). Furthermore, Trichoderma extract protects tomato fruits from post-harvest infection by F. oxysporum. Taking together, T. asperellum represents a safe and effective controlling agent against Fusarium infection of tomato plants.

Promising Endophytic Alternaria alternata from Leaves of Ziziphus spina-christi: Phytochemical Analyses, Antimicrobial and Antioxidant Activities.

Fungal endophytes are considered one of the most important reservoirs of bioactive compounds which defeat resistant microbes. In our study, endophytic Alternaria alternata was isolated from Ziziphus spina-christi and identified morphologically and genetically with accession number OM 331,682. Preliminary phytochemical screening of ethyl acetate (EA) crude extract of A. alternata revealed that this extract contains alkaloids, tannins, flavonoids, glycosides, phenols, and terpenoids. Moreover, the extract was analyzed using gas chromatography-mass spectrometry (GC-MS) which verified the presence of numerous bioactive compounds. Antimicrobial results illustrated that EA crude extract exhibited promising antimicrobial activity against Gram-negative bacteria (Escherichia coli ATCC 11229, Proteus vulgaris RCMB 004, Pseudomonas aeruginosa ATCC 27853, and Klebsiella pneumonia RCMB 003), Gram-positive bacteria (Bacillus subtilis RCMB 015, Staphylococcus aureus ATCC 25923, and Staphylococcus epidermidis ATCC 14990), and unicellular fungi (Candida albicans ATCC 90028). Ultrastructure study of treated K. pneumonia showed remarkably elucidated destruction of the cell wall and cell membrane and leakage of cytoplasmic materials. Furthermore, the extract has potential antioxidant activity where IC50 was 409 µg/mL. Moreover, this extract did not show any toxicity on Vero normal cell line. These findings confirmed that the endophytic A. alternata from Z. spina-christi is a promising source of bioactive compounds which can be used in different biological applications.

Drought Stress Triggers Shifts in the Root Microbial Community and Alters Functional Categories in the Microbial Gene Pool.

Drought is a major threat to crop productivity and causes decreased plant growth, poor yields, and crop failure. Nevertheless, the frequency of droughts is expected to increase in the coming decades. The microbial communities associated with crop plants can influence how plants respond to various stresses; hence, microbiome manipulation is fast becoming an effective strategy for improving the stress tolerance of plants. The effect of drought stress on the root microbiome of perennial woody plants is currently poorly understood. Using Populus trees as a model ecosystem, we found that the diversity of the root microbial community decreased during drought treatment and that compositional shifts in microbes during drought stress were driven by the relative abundances of a large number of dominant phyla, including Actinobacteria, Firmicutes, and Proteobacteria. A subset of microbes, including Streptomyces rochei, Bacillus arbutinivorans, B. endophyticus, B. megaterium, Aspergillus terreus, Penicillium raperi, Trichoderma ghanense, Gongronella butleri, and Rhizopus stolonifer, was isolated from the drought-treated poplar rhizosphere soils, which have potentially beneficial to plant fitness. Further controlled inoculation experiments showed that the isolated bacterial and fungal isolates positively impacted plant growth and drought tolerance. Collectively, our results demonstrate the impact of drought on root microbiome structure and provide a novel example of manipulating root microbiomes to improve plant tolerance.