Bioprospecting secondary metabolites from Streptomyces sp. HPM-9-01/B9-A from South Kalimantan as a potential antibiotic candidate

Actinomadura sp. 101_SQ a moderate halotolerant isolated from salt lake in east of Algeria: A potential source of antibacterial substances

Comparative Metabolite Profiling and Bioactivity Evaluation of Pneumatophore-Derived Aspergillus Strains From Three Geographically Distinct Mangrove Ecosystems of India: Isolation of a New Dahejpyrone Derivative

Genomic and Metabolomic Profiling of Streptomyces anulatus 89: Molecular Phylogeny and Biosynthesis of Antitumor Antibiotics

The investigated crude extract exhibited pronounced antitumor activity, making it a promising candidate for further studies, and the underlying hypothesis suggested that strains with broad adaptive potential may serve as promising producers of natural products with antitumor properties.

Endophytic Paenibacillus lactis PEL6 from Mitrephora heyneana as a Source of Anti-Staphylococcus aureus Metabolites: In Vitro and In Silico Evaluation

Endophytic bacteria from medicinal plants are increasingly recognised as sources of antimicrobial metabolites. However, the endophytic bacterial community of Mitrephora heyneana remains poorly explored. In the present study, endophytic bacteria were isolated from the leaves of M. heyneana, collected from the Western Ghats of Tamil Nadu, India. Among seven isolates, the plant endophyte strain from leaf 6th strain (PEL6) was identified as Paenibacillus lactis through 16S rRNA gene sequencing. The ethyl acetate extract of PEL6 (EAE-PEL6) was subjected to gas chromatography–mass spectrometry (GC-MS) analysis, which putatively identified 32 metabolites based on GC-MS library matching, including pyrrolo [1,2-a] pyrazine-1,4-dione derivatives and triazole compounds as major constituents. The EAE-PEL6 demonstrated significant in vitro antibacterial activity against Staphylococcus aureus. In silico ADMET (absorption, distribution, metabolism, excretion, and toxicity), profiling predicted drug-likeness and pharmacokinetic properties of selected candidate compounds. Molecular docking suggested favourable binding of selected metabolites to S. aureus target proteins; however, these interactions require experimental validation. Density Functional Theory calculations indicated that CID 70504 had the lowest Highest Occupied Molecular Orbital (HOMO)–Lowest Unoccupied Molecular Orbital (LUMO) energy gap, reflecting higher electronic reactivity. Molecular electrostatic potential mapping further supported its enhanced binding propensity. Molecular dynamics simulations suggested structural stability, with Root Mean Square Deviation, Solvent Accessible Surface Area, radius of gyration, and hydrogen-bond analyses indicating stable interactions throughout the 100 ns trajectory. Overall, this study identifies P. lactis PEL6 as a promising endophytic source of anti-S. aureus metabolites and provides candidates for future purification, structural confirmation, and biological validation.

A NEW Streptomyces STRAIN AHA8 FROM DESERT SOIL: ISOLATION, TAXONOMIC IDENTIFICATION, AND ANTAGONISTIC PROPERTIES

Actinobacteria from extreme environments represent a valuable source of novel bioactive secondary metabolites with potential antimicrobial applications. The aim of this study was to isolate, identify, and evaluate the antimicrobial potential of a newly isolated strain of actinobacteria. AHA8 strain, was isolated from an Algerian desert soil sample in the Ahaggar region (Tamanrasset) by the dilution-agar plating method using a chitin-vitamins B medium supplemented with nalidixic acid and actidione. Morphological characterization indicated that this strain belonged to the genus Streptomyces. Phylogenetic analysis based on the 16S rRNA gene showed that the strain is closely related to Streptomyces djakartensis NBRC 15409T (99.57% sequence similarity). Strain AHA8 showed very strong activity against pathogenic staphylococci, including Staphylococcus aureus (MRSA 639c), as well as against other Gram-positive bacteria: Bacillus subtilis (ATCC 663) and Listeria monocytogenes (ATCC 13932). Additionally, the strain exhibited a moderate activity against mycotoxigenic and phytopathogenic fungi, including Aspergillus carbonarius (M333), A. westerdijkiae (ATCC 3174), Fusarium culmorum (Fc), and Umbelopsis ramanniana (NRRL 1829). Almost the same results were observed for Gram-negative bacteria and the pathogenic yeast Candida albicans (M3). Therefore, four solvents (n-hexane, dichloromethane, ethyl acetate, and n-butanol) were used to extract the bioactive secondary metabolites produced by the AHA8 culture on a synthetic starch medium. The highest antibacterial activity was obtained with the butanolic and ethyl acetate extracts. These findings demonstrate that the desert-derived strain AHA8 represents a promising source of antimicrobial secondary metabolites and supports further studies aimed at the purification and characterization of its bioactive compounds.

Marine-Derived Cladosporium sp. MBLC9-138 as a Source of Mycophenolic Acid with Preliminary Antibacterial Activity

Marine-derived fungi are important reservoirs of bioactive secondary metabolites, yet the diversity of fungal producers of mycophenolic acid (MPA) remains incompletely explored. In this study, 304 fungal strains were isolated from marine sediments collected from three coastal regions of Vietnam and screened for MPA production using thin-layer chromatography, high-performance liquid chromatography, and LC-MS confirmation. Twenty-five isolates (8.22%) were identified as MPA producers and were preliminarily assigned to the fungal genera Penicillium, Aspergillus, and Cladosporium, with two isolates remaining unidentified, based on morphological characteristics. Strain MBLC9-138 was selected for detailed characterization because it represented a non-Penicillium MPA-producing isolate assigned to Cladosporium. Morphological observations and multilocus sequence analyses based on internal transcribed spacer region (ITS), actin gene (ACT), and beta-tubulin gene (TUB/TUB2) supported its identification as Cladosporium sp. MBLC9-138. HPLC analysis showed that this strain produced 463.25 mg/L MPA after 5 days of cultivation in NaCl-supplemented potato dextrose broth, while the maximum yield reached 632.03 ± 2.39 mg/L at 168 ± 12 h during the late exponential to early stationary phase. The purified MPA extract inhibited Bacillus cereus ATCC 11778, Escherichia coli ATCC 25922, and Staphylococcus aureus ATCC 33591, with MIC values of 16, 32, and 64 µg/mL, respectively. These findings identify Cladosporium sp. MBLC9-138 as a previously underreported marine fungal source of MPA, expand the known taxonomic range of MPA-producing fungi, and support further strain optimization, metabolite purification, and antibacterial characterization.