A novel Aureobasidium pullulans isolate for the biological control of Penicillium commune in potato decay and its optimization for enhanced antifungal activity using the Taguchi method.

Isolation and characterization of an algicolous endophytic Mucor circinelloides from macroalga Colpomenia sinuosa as a promising source of bioactive metabolites for dermocosmetic applications

Marine endophytic fungi have arisen as a prospective source of bioactive secondary metabolites with potential cosmeceutical and pharmaceutical applications. In this study, four endophytic fungal isolates were obtained from Egyptian marine algae Colpomenia sinuosa. Preliminary screening for antibacterial activity against Staphylococcus epidermidis indicated that the isolate EF2 was the most active, exhibiting an inhibition percentage of 40.67%, and therefore was selected for optimization by the Plackett–Burman experiment and response surface methodology. This optimization significantly improved the inhibitory activity from 40.67% to 94.4%. The optimized crude extract of isolate EF2 exhibited strong antioxidant activity with the DPPH assay and significant anti-inflammatory activity by cyclooxygenase-2 (COX-2) enzyme inhibition. Furthermore, it demonstrated pronounced tyrosinase inhibitory activity, suggesting its potential role in melanin biosynthesis regulation. The isolate was molecularly identified as Mucor circinelloides AUMC 16435 with accession number PP837661. Cytotoxicity assessment revealed selective activity against carcinoma cells with relatively low toxicity toward normal fibroblasts, indicating a favorable safety profile. GC–MS analysis of EF2 isolate crude extract (Mucor circinelloides AUMC 16435) demonstrated several bioactive constituents, with 3-methoxy-2, 4, 6-trimethyl-cyclohex-2-enone and 2-fluoro-3-trifluoromethylbenzoicacid-3-hexadecyl ester as the predominant compounds. Molecular docking studies further confirmed favorable binding interactions of the compounds within the tyrosinase active site, with energies of binding -6.1 and -5.9 kcal/mol, respectively. Overall, this study reports the first isolation of M. circinelloides from Egyptian C. sinuosa and highlights its potential as a promising source of bioactive metabolites with enhanced antibacterial activity and multifunctional properties suitable for pharmaceutical and dermocosmetic applications.

Isolation and in vitro Evaluation of Antagonistic Bacterial Endophytes from Eleusine coracana (L.) Gaertn. against Magnaporthe oryzae

Findings identify finger millet-associated endophytes, particularly isolate AN6, as promising candidates for the biological management of rice blast disease, and require further greenhouse and field evaluations to confirm their efficacy under natural conditions.

Isolation and Characterization of Endophytic bacteria from Wedelia chinensis with Potent Biocontrol and Plant Growth-Promoting Activities

Endophytic bacteria represent a promising, sustainable alternative to synthetic agrochemicals for plant disease management by actively antagonizing phytopathogens and stimulating host immune responses. Despite its traditional use as an antimicrobial remedy, Wedelia chinensis remains underexplored as a source of beneficial endophytes. This study aimed to isolate and screen endophytic bacteria from W. chinensis for their antifungal activity against Fusarium oxysporum. Among 14 endophytic isolates, Bacillus subtilis LS1-5 showed the strongest antifungal activity by dual culture assay. Its cell-free culture filtrate effectively inhibited fungal spore germination by 91.3% at a 20% concentration. Crucially, B. subtilis LS1-5 produced several extracellular enzymes, including cellulase, amylase, chitinase, pectinase, gelatinase, lipase, and protease. Furthermore, the LS1-5 strain exhibited a broad array of plant growth-promoting and environmental resilience traits. Notably, it synthesized indole-3-acetic acid (IAA) at 2.11 ± 0.27 µg/mL in an LB medium without L-tryptophan, significantly promoted a 34.19% increase in root elongation, and demonstrated remarkable tolerance to extreme conditions, including high salinity (11% NaCl) and broad pH levels ranging from 6 to 12. Additionally, volatile organic compounds (VOCs) emitted by LS1-5 significantly inhibited the severe bacterial pathogens Xanthomonas oryzae (45.83%) and Xanthomonas citri (47.99%). These findings highlight B. subtilis LS1-5 as a highly effective candidate for biological control and sustainable agricultural applications.

Antifungal Surfactin-Producing Bacillus subtilis MGM123 Suppresses Fusarium sambucinum and Primes Growth, Yield, and Defence Responses in Potato

Serratia liquefaciens and Bacillus velezensis for Biocontrol of Quinoa Leaf Spot: Bioactive Metabolites Inducing Hyphal Deformation and Plant Growth Promotion

Quinoa leaf spot is an important fungal disease that limits quinoa yield and quality. This study aimed to evaluate the pathogenicity of isolates associated with quinoa leaf spot in Qinghai, China, and to screen multifunctional biocontrol bacteria with potential for further development. Pathogenicity assays conducted on healthy quinoa leaves showed that isolates Alternaria alternata AF15 and A. tenuissima AF18 induced typical leaf spot symptoms. The corresponding fungi were successfully re-isolated from the resulting lesions, confirming the pathogenicity of both isolates. Two highly effective biocontrol bacteria, Serratia liquefaciens CB82 and Bacillus velezensis CB316, were subsequently selected through dual-culture assays. Their maximum inhibition rates against the two fungal pathogens reached 56.00% and 57.00%, respectively. Both biocontrol strains exhibited broad adaptability to different temperatures, pH, and NaCl conditions, produced protease, amylase, and cellulase, and showed phosphate-solubilizing activity. Metabolite extraction and fractionation revealed that the antifungal substances were predominantly enriched in the n-butanol fractions, which caused severe shrinkage, surface roughening, breakage, and deformation of the pathogen hyphae. In addition, both strains exhibited strong biofilm-forming capacity and successfully colonized quinoa leaves. Their culturable populations peaked on day 3 after inoculation, reaching 5.58 × 107 and 6.06 × 107 CFU/mL, respectively. In seed germination pouch assays, the bacterial suspensions promoted quinoa root elongation, whereas the fermentation broths increased seedling biomass accumulation in pot experiments. Overall, this study confirmed the pathogenicity of fungal isolates associated with quinoa leaf spot in Qinghai, China, identified two promising biocontrol bacterial strains, and preliminarily characterized their antifungal substances. These findings provide valuable microbial resources and a research basis for the future development of biological control strategies against quinoa leaf spot.

Harnessing an endophytic Bacillus strain closely related to Bacillus velezensis for biocontrol of twig blight in bayberry caused by Pestalotiopsis versicolor.

BACKGROUND Twig blight disease caused by Pestalotiopsis versicolor threatens bayberry (Myrica rubra) cultivation in China, prompting extensive reliance on chemical fungicides with limited long-term efficacy. This study investigated the potential of endophytic bacteria isolated from bayberry leaves as sustainable biocontrol agents against this pathogenic fungus. RESULTS An endophytic bacterium designated strain Bay9 was isolated from healthy bayberry leaves and identified as a Bacillus sp. closely related to Bacillus velezensis based on 16 S rRNA gene sequence analysis. Bay9 exhibited strong antifungal activity against P. versicolor in vitro and showed disease-suppressive effects under semi-controlled greenhouse conditions. On potato dextrose agar (PDA) and in potato dextrose broth (PDB), inhibition rates reached 74.44% and 87.65%, respectively, accompanied by severe ultrastructural damage to fungal hyphae observed by electron microscopy. Cell-free supernatants (CFSs) of Bay9 exhibited concentration-dependent antifungal activity, with inhibition rates of 15.77%, 34.99%, 66.74%, and 98.82% at concentrations of 2.5%, 5%, 10%, and 20% (v/v), respectively. CFSs at EC50 and EC90 concentrations (7.30% and 17.43%, respectively) significantly reduced spore production and germination, induced leakage of intracellular nucleic acids and proteins consistent with membrane perturbation and leakage, but not direct evidence of a defined molecular mechanism and substantially reduced colony formation. In detached leaf assays, EC50 and EC90 treatments reduced lesion development by 65.31% and 94.58%, respectively. Under semi-controlled greenhouse conditions, Bay9 treatment significantly reduced disease incidence (from 97% to 49.33%) and disease severity index (from 82.19% to 38.69%) compared with pathogen-inoculated plants (p < 0.05), without causing phytotoxic effects on bayberry saplings. CONCLUSIONS Bay9 exhibited strong antifungal activity associated with multiple putative mechanisms, potentially involving siderophore production, hydrolytic enzyme activities (protease, amylase, and lipase), and lipopeptide-related metabolites, as suggested by biochemical assays and MALDI-TOF-MS-based tentative identification of surfactin-, iturin-, and fengycin-like compounds. Collectively, these findings suggest that Bay9 has potential as a biocontrol agent against P. versicolor under laboratory, detached-leaf, and semi-controlled greenhouse conditions. However, further studies are required to elucidate the underlying molecular mechanisms and to validate its efficacy under field conditions before practical application can be recommended.