Streptomycetes are known as producers of bioactive substances, particularly antibiotics. Streptomyces netropsis IMV Ac-5025 simultaneously produces different classes of antibiotics, including polyene compounds, phytohormones, and sterols, but the metabolic pathways involved in their biosynthesis are largely understudied. The aim of this work was to explore the biosynthesis of polyene antibiotics, sterols, and phytohormones when the producer is cultivated in a nutrient medium supplemented with exogenous β-sitosterol. Gas chromatography and high-performance liquid chromatography were applied to analyze the spectrum of bioactive compounds. The obtained results demonstrated not only an increase in the accumulation of biomass but also polyene antibiotics, intracellular sterols, auxins, and cytokinins, when cultivating S. netropsis IMV Ac-5025 in a liquid medium with the addition of β-sitosterol. The amount of biomass raised 1.5–2-fold, whilst the sum of polyene antibiotics increased 4.5-fold, sterols’ sum (ergosterol, cholesterol, stigmasterol, β-sitosterol, and 24-epibrassinolide) by 2.9-fold, auxins’ sum (indole-3-acetic acid, indole-3-acetic acid hydrazide, indole-3-carbinol, indole-3-butyric acid, indole-3-carboxaldehyde, and indole-3-carboxylic acid) by 6-fold, and cytokinins’ sum (zeatin, isopentyladenine, zeatin riboside, and isopentenyladenosine) by 11-fold. Thus, we put forward the hypothesis that β-sitosterol plays a regulatory role in the network of biosynthetic reactions of S. netropsis IMV Ac-5025.

Introduction: Streptomyces species are renowned for producing bioactive natural products, particularly those that induce plant resistance against pathogens and nematodes. This study aimed to investigate the ability of metabolic bioproducts from Streptomyces netropsis IMV Ac-5025, Streptomyces violaceus IMV Ac-5027, and Streptomyces avermitilis IMV Ac-5015 to affect RNAi-mediated resistance in tomato plants against the root-knot nematode. Methods: Spectrodensitometric Thin-Layer Chromatography (TLC), High-Performance Liquid Chromatography (HPLC), and Gas Chromatography (GC) were used to identify natural products of streptomycetes. The resistance of tomato plants to Meloidogyne incognita was evaluated through artificial nematode inoculation coupled with phenological viability assessment. The extent of si/miRNA-driven gene silencing was determined via dot blot hybridization and inhibition of protein synthesis in a wheat germ cell-free translation system. Results: Soil-derived Streptomyces strains were shown to produce diverse bioactive compounds, including antibiotics, lipids, phytohormones, and sterols, and novel bioproducts were developed based on their secondary metabolites (Phytovit, Violar, Averkom, and Averkom nova). Incorporation of these bioproducts into the nutrient medium significantly improved shoot regeneration rates in isolated plant explants. Dot blot hybridization and translational inhibition assays in a wheat germ cell-free system confirmed their phytoprotective effect via the RNA interference mechanism. In vitro cultivation of tomato plants supplemented with biotreatment resulted in a marked enhancement of resistance to M. incognita . Discussion: The secondary metabolic complexes produced by Streptomyces strains promote plant growth and development while enhancing immunity and supporting the efficient operation of signaling networks involved in cellular responses to nematodes. Their activity is mediated through elicitor signals that trigger the de novo synthesis of plant si/miRNAs, which confer protection against M. incognita . These findings highlight the potential of these metabolites to advance eco-friendly strategies for controlling root-knot nematodes and to develop resistant plant lines. Conclusion: Soil-streptomycete metabolites could be utilized in RNA interference to enhance tomato resistance to root-knot nematodes via de novo synthesis of protective small interfering and microRNAs, supporting agrobiological applications.

Background. Breast cancer remains the leading cause of cancer mortality in women due to the resistance to chemotherapy and severe side effects of doxorubicin (Doxo). One of the approaches to overcome this problem is to search for phytocompounds that can enhance the efficacy of chemotherapy and prevent the development of side effects. Objective. This work aimed to investigate in vitro whether the polyphenol curcumin (Cur) from turmeric (Curcuma longa) in combination with the commercial drug Doxo-HCl can enhance the cytotoxic effect of Doxo on breast cancer cell lines MDA-MB-231 and MCF-7 and to exhibit chemoprotective activity against normal HEK-293 cells. Methods. Cell viability was assessed with MTT assay, apoptosis induction by flow cytometry with Annexin V–eGFP and PI, reactive oxygen species (ROS) generation by the DCFH-DA probe. The combination index (CI) calculation method and CompuSyn, Biosoft software were used to determine the synergism or antagonism of the components. Results. The study revealed dose-dependent cytotoxicity, increased ROS formation, and increased morphological aberrations in cells when using the combination of Cur with Doxo-HCl compared to Doxo-HCl. Cur acted as a chemosensitizer, which synergistically enhanced the antitumor activity of Doxo-HCl while simultaneously reducing its cytotoxic effects in normal cells by reducing ROS production. Conclusions. The use of Cur in combination with Doxo-HCl will likely reduce the effective therapeutic dose of Doxo and increase the effectiveness of breast cancer chemotherapy. Keywords: apoptosis, breast cancer cell lines, cell viability, chemosensitizer, combination index, combined treatment, curcumin, doxorubicin, oxidative stress

The actinomycete strain Amycolatopsis roodepoortensis Y13, isolated from war-impacted soil, was subjected to whole-genome sequencing, biosynthetic gene clusters for secondary metabolites together with resistance determinants for heavy metals were detected in the genome. The strain tolerated elevated concentrations of copper and zinc as well as increased salinity, displayed high sensitivity to aminoglycosides and vancomycin, and exhibited antagonistic activity against several phytopathogenic fungi, including Sclerotinia sclerotiorum, Bipolaris sorokiniana, Alternaria arborescens, Fusarium graminearum and Aspergillus niger. In a Triticum aestivum L. germination bioassay, strain Y13 significantly (p<0.001) stimulated root and stem growth, increasing primary root length by 18.0 % and stem length by 27.4 %. These findings indicate that A. roodepoortensis Y13 combines multi-stress resistance with antimicrobial and phytostimulatory potential. Keywords: Amycolatopsis roodepoortensis; whole-genome sequencing; heavy metal resistance; antagonistic activity; phytostimulation.

Fifty streptomycete isolates were recovered from war-impacted soils, of which nine of the most antagonistically active strains were selected for further study based on dual-culture screening against fungi and bacteria. Strains Y15, SK4, SK14 and SK16 displayed the strongest and broadest inhibitory activity, with Y15 producing the largest inhibition zones overall, notably against Bipolaris sorokiniana (27.9 ± 0.2 mm) and Xanthomonas campestris (15.8 ± 0.5 mm). Whole-genome sequencing and orthoANI analysis identified Streptomyces sp. SK4 as S. lidicus (100% identity), while Y15, SK16 and SK14 showed at most 88–92 % identity to their closest relatives. Genome mining with antiSMASH revealed a conserved biosynthetic core shared by Y15 and SK4 alongside seven strain-specific biosynthetic gene clusters in each, and LC-HRMS profiling confirmed production of reedsmycin F and youssoufene A1 by Y15 and streptolydigin by SK4. These findings highlight war-impacted soils as a valuable, underexplored source of biotechnologically promising streptomycetes. Keywords: Streptomyces; war-impacted soil; whole-genome sequencing; biosynthetic gene clusters; antagonistic activity, antibiotics.