Integrated experimental and computational characterization of bioactive metabolites from Streptomyces paradoxus GH53 with antimicrobial, antioxidant, and antitumor activities

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.

Extracellular Polysaccharide From Marine Streptomyces sp. KAR3: Structural Characterization, Antibacterial, and Anticancer Potential.

Marine environments are an abundant source of sustainable polymers with considerable biomedical potential. In this study, a marine Streptomyces sp. strain KAR3 was isolated from the Gulf of Mannar. Extracellular polysaccharide (EPS) was isolated, characterized, and evaluated for its antibacterial, antibiofilm, and anticancer activity against MDA-MB-231 cells. Strain identification using biochemical characterization and 16S rRNA gene sequencing (Accession: PP330035) showed 100% similarity to Streptomyces geysiriensis, and phylogenetic analysis supported its affiliation with the S. geysiriensis clad. S. geysiriensis strain KAR3 produced 4.4 g/L of EPS in the media after 7 days. EPS production was optimized in several culture media and structurally characterized by UV spectroscopy, Fourier transform infrared (FTIR), 1H and 13C nuclear magnetic resonance (NMR), and GC-MS. FTIR analysis revealed C-H and C = O stretching and glycosidic linkages. 1H and 13C NMR shifts aligned with sugar moieties, indicating the EPS is a complex polysaccharide. GC-MS showed glucose as the major monosaccharide in the EPS. The isolated EPS exhibited dose-dependent inhibition, with the largest zone of inhibition observed at 100 µg/mL. The EPS exhibited notable antibacterial and biofilm inhibitory activity against Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli, and Enterococcus faecalis in a concentration-dependent manner. The minimum inhibitory concentration (MIC) calculated for the most susceptible strains was at 100 µg/mL. The IC50 value of EPS was found to be 25.44 µg/mL, indicating a strong cytotoxic effect against MDA-MB-231 cancer cells. Together, these findings demonstrate the broad-spectrum antibacterial and anticancer activity of marine EPS from S. geysiriensis and its potential as a natural source in the search for new antimicrobial compounds.

Screening of Actinomycetes from Rhizosphere Soils for L-glutaminase Production

The integrated experimental and in silico approach highlights soil-derived actinomycetes as versatile and sustainable bioresources with significant pharmaceutical and biotechnological potential, emphasizing their role in combating antimicrobial resistance and enabling the rational development of novel therapeutic and industrial products.

Streptomyces griseoincarnatus AR2 from the cold desert as a biofactory for secondary metabolites with multifaceted bioactivities, confirmed by in vitro and in silico approaches

Isolation and characterization of an endophytic Streptomyces sp. YBRX0 from Croton tonkinensis and assessment of its bioactive potential

The rise of antimicrobial resistance and emerging infectious diseases necessitates the discovery of novel antibacterial agents. Endophytic actinomycetes, especially Streptomyces species colonizing medicinal plant tissues, constitute a reservoir of structurally diverse bioactive metabolites that remains insufficiently characterized. This study reports the isolation and comprehensive characterization of an endophytic actinomycete, designated strain YBRX0, recovered from the root tissues of the Vietnamese medicinal plant Croton tonkinensis Gagnep. Strain identity was established through an integrated approach combining colony morphology, scanning electron microscopy, physiological and biochemical profiling, and 16S rRNA gene phylogenetic analysis. Bioactivity screening of the ethyl acetate fermentation extract employed agar well diffusion to assess antibacterial spectrum, with inhibitory potency quantified by broth microdilution. Antioxidant capacity was measured via DPPH radical scavenging, and secondary metabolite composition was profiled by GC–MS. The integrated characterization placed strain YBRX0 unambiguously within the genus. At 1 mg/mL, the ethyl acetate extract demonstrated broad-spectrum activity against both Gram-positive and Gram-negative pathogens, with MIC values ranging from 8 to 16 μg/mL. Antioxidant screening yielded an IC₅₀ of 197.26 ± 8.87 μg/mL. GC–MS tentatively identified Pyrrolopyrazine diketopiperazines and Benzeneacetamide as principal constituents. Collectively, these findings indicate that the crude extract of Streptomyces sp. YBRX0 exhibited notable antibacterial activity despite being an unfractionated mixture, supporting its potential as a promising source of bioactive metabolites for further bioprospecting and compound isolation efforts targeting drug-resistant pathogens.

A Marine Derived Carotenoid from Planococcus Maritimus KA01 with Promising Bioactivity

Marine ecosystems are recognized as rich reservoirs of bioactive pigment-producing microorganisms with potential industrial applications. In this study, an orange-pigmented bacterium was isolated from marine sediment collected from Colachel, Tamil Nadu, India, and identified as Planococcus maritimus KA01 through 16S rRNA sequencing and phylogenetic analysis. Optimization of culture conditions showed that maximum carotenoid production occurred at 25 °C, pH 7, after 96 h of incubation, with 1.0% NaCl, glucose as the carbon source, and under shaking conditions. Methanol showed the highest efficiency solvent for pigment extraction. Spectral characterization via UV-Vis, FTIR, and GC-MS suggested the presence of carotenoid-like compounds, with squalene identified as a major metabolite. The pigment extract exhibited antibacterial activity, with lower MIC and MBC values against Staphylococcus aureus compared with Pseudomonas aeruginosa, indicating greater susceptibility of Gram-positive bacteria under the tested conditions. Antioxidant analysis using the DPPH assay demonstrated dose-dependent radical-scavenging activity. Overall, the study suggests that P. maritimus KA01 is a promising source of carotenoid-containing pigments with antimicrobial and antioxidant properties. Further studies involving purification, toxicity assessment, and large-scale production are required to establish potential applications.