Search Results (460)

Glyphosate [N-(phosphonomethyl)glycine] is the most widely used herbicide worldwide, and its environmental persistence has prompted increasing interest in microbial processes that may contribute to its dissipation. This study evaluated a collection of 15 soil-derived actinobacterial strains for plant growth-promoting traits, extracellular enzymatic activities, glyphosate tolerance, and glyphosate removal under nutrient-sufficient and phosphate-starved conditions. Herbicide tolerance evaluated on agar plates was widespread across the collection, with all strains sustaining growth at 10 and 50 g L⁻¹ of glyphosate. Under nutrient-sufficient conditions glyphosate removal remained limited, with maximum values of 16.15 ± 2.08% (Streptomyces sp. Con7.16) and 15.34 ± 2.89% (Streptomyces sp. Z38). In contrast, prior phosphate starvation markedly enhanced removal efficiency, reaching 42.21 ± 3.59% in Streptomyces sp. Z38 and 39.46 ± 1.94% in Streptomyces sp. Con7.16. Transmission electron microscopy coupled with X-ray microanalysis in the selected Streptomyces sp. Z38 revealed starvation-associated depletion of intracellular polyphosphate granules, followed by partial replenishment when glyphosate was supplied as the sole phosphorus source, consistent with indirect evidence of glyphosate-derived phosphorus acquisition. Genome mining of Streptomyces sp. Z38 identified candidate genes potentially consistent with a non-canonical, C-P lyase-independent phosphonate utilization route; however, these assignments are based exclusively on bioinformatic evidence and require experimental validation. Collectively, these findings indicate that phosphate limitation enhances glyphosate removal in the selected actinobacteria, and the physiological and genomic data are consistent with a starvation-triggered shift toward alternative phosphorus scavenging strategies. Because this strain is intended for future phytoremediation applications in glyphosate-contaminated agricultural soils, elucidating the underlying phosphorus dynamics is essential for anticipating its functional behavior and environmental relevance. Full article

Postharvest rot caused by Neopestalotiopsis rosae severely threatens strawberry production globally. Here, a novel species of Streptomyces was isolated and identified through polyphasic taxonomy, for which we propose the name Streptomyces hanimojiang sp. nov. AMJ-169. Its volatile organic compounds (VOCs) inhibited N. rosae hyphal growth by 70 ± 3.81%, with (1S)-(-)-α-pinene identified as the key antifungal component (EC₅₀ = 0.018 mL·L⁻¹). Fumigation with 6× EC₅₀ α-pinene reduced fruit rot by 97.52% in a concentration-dependent manner. SEM observations showed that α-pinene caused severe hyphal damage and suppressed pathogen colonization on fruit surfaces. Transcriptomic analysis further indicated that α-pinene treatment was associated with redox regulation, glutathione metabolism, phenylpropanoid metabolism, and carbon-metabolism-related responses in strawberry fruit. These findings suggest that α-pinene controls postharvest anthracnose through direct antifungal activity on fungal hyphae together with host-associated physiological regulation, highlighting its potential as a sustainable postharvest biocontrol candidate. Full article

Cannabinoids are high-value bioactive compounds whose sustainable production remains challenging, prompting interest in biocatalytic and microbial platforms as alternatives to plant extraction. In this study, we investigated the heterologous expression and functionality of two key cannabinoid-related enzymes in the photosynthetic microalga Chlamydomonas reinhardtii: the aromatic prenyltransferase, NphB_G286S/Y288A from Streptomyces sp., and the plant-derived cannabidiolic acid synthase (CBDAS) from Cannabis sativa. Codon-optimized genes were introduced into the nuclear genome of C. reinhardtii using several construct configurations and promoters, and stable transformants were generated and characterized for genomic integration, transcript accumulation, protein production, enzymatic activity, and cannabinoid-related metabolite formation. While NphB protein accumulation was achieved under the PSAD promoter control, CBDAS was not detected at the protein level under any condition tested. In vitro enzymatic assays using soluble algal protein extracts from NphB-expressing lines confirmed catalytic activity, yielding cannabigerolic acid (CBGA), reaching up to 633 ± 58 µg L⁻¹. However, no CBGA production was detected in vivo, despite substrate supplementation. These results indicate that, although bacterial prenyltransferase can be functionally expressed in C. reinhardtii, efficient metabolic conversion in vivo is limited by cellular and biochemical constraints, including substrate availability, intracellular compartmentalization, and potential competition with endogenous pathways. In contrast, the absence of detectable CBDAS highlights the challenges associated with expressing complex plant oxidocyclases in this photosynthetic host. Overall, this work provides mechanistic insights into enzyme compatibility and metabolic bottlenecks in microalgal systems and outlines key considerations for the future development of photosynthetic platforms for cannabinoid biocatalysis. Full article

Actinomycetes are among the richest sources of bioactive secondary metabolites in biotechnology, owing to their remarkable metabolic diversity. Although the genus Streptomyces has been extensively explored and has yielded many clinically important antibiotics, rare actinomycetes remain comparatively underinvestigated. In this study, Kitasatospora sp. SeTe27, isolated from uncontaminated soil in Sicily (Italy), was investigated for its antibacterial activity and fermentation-driven enhancement of secondary metabolite production. The strain inhibited Staphylococcus aureus ATCC 25923, prompting physiological and genomic analyses. Spore conditioning was evaluated in four media (R5A, GYM, TSB, and YEME) to enhance antibiotic production. Conditioned cultures exhibited markedly increased antibacterial activity in TSB and YEME, moderate production in R5A, and no detectable activity in GYM. Whole-genome sequencing revealed an 8.5 Mb genome (73.5% GC) containing 48 biosynthetic gene clusters (BGCs), including NRPS, PKS, terpene, and hybrid pathways. Several clusters showed high similarity to known antibiotic-associated BGCs, such as clifednamide- and phenazine-related pathways, while numerous orphan clusters indicated significant unexplored biosynthetic potential. These findings identify Kitasatospora sp. SeTe27 as a promising antimicrobial producer and demonstrate that spore conditioning in complex media is an effective strategy to enhance antibiotic production in rare actinomycetes. Full article

Maize (Zea mays L.) cultivation is severely affected by Fusarium verticillioides, a highly adaptable systemic pathogen that causes serious yield losses, reduces grain quality, and produces toxic fumonisin, posing significant health risks to humans and livestock. A biological control approach to combating it was investigated. Streptomyces sp. BPTC-684 showed strong inhibitory activity (53.11%) against F. verticillioides BNGO-16, isolated from a diseased tissue sample. Based on physiological and biochemical characteristics, 16S rRNA gene sequencing, average nucleotide identity, and digital DNA–DNA hybridization, strain BPTC-684 is considered a candidate new species belonging to the genus Streptomyces. In silico analysis of Streptomyces sp. BPTC-684 showed that it expresses diverse biosynthetic gene clusters encoding potential bioactive compounds, notably antibiotics (kinamycin, antimycin, fuelimycins A-C, hangtaimycin, and deoxyhangtaimycin) and siderophores (desferrioxamines B and E). In addition, plant growth-promoting behaviors, such as indole-3-acetic acid production; phosphate solubilization; and the production of extracellular lytic enzymes that degrade cellulose, chitin, proteins, amylose, and xylan, were also discovered in Streptomyces sp. BPTC-684. The pot experiments demonstrated that plant height, fresh weight, and dry root weight were increased in strain BPTC-684 by 37.88%, 132.50%, and 223.81%, respectively, compared to F. verticillioides BNGO-16 on the 15th day of infection. These findings suggest that Streptomyces sp. BPTC-684 is a promising biological control agent for inhibiting fungal diseases and promoting maize growth. Full article

Polyethylene terephthalate (PET) is a synthetic polymer that is widely used in the production of textiles, packaging materials, and beverage bottles. However, its high durability and resistance to abiotic degradation result in serious environmental and health problems. PETase is an enzyme that can depolymerize PET into value-added products, thereby providing an environmentally friendly strategy for PET recycling. PETaseSM14 from a marine sponge, Streptomyces sp. SM14, has a high salt tolerance and thermal stability, thus suggesting its potential for PET degradation applications. However, the substrate recognition mechanism of PETase remains unclear because the catalytic residue is buried within residues that form the substrate-binding cleft. To elucidate the molecular mechanism of PETaseSM14, all-atom molecular dynamics simulations were performed at 300, 320, and 340 K. The results revealed that the overall α/β fold remained stable at all temperatures, whereas temperature-dependent local fluctuations and conformational changes were observed in the substrate-binding cleft and N-terminal region. At 300 and 320 K, positional shifts and conformational changes in Tyr88 exposed the catalytic Ser156 to the solvent, thereby forming a potential substrate-binding cleft. In contrast, at 340 K, which is higher than the melting temperature of PETaseSM14, disruption of the charge-relay system of the catalytic triad occurs through conformational changes in His234. Substantial temperature-dependent conformational and positional changes in the N-terminal region of PETaseSM14 were observed at 320 and 340 K. These results provide mechanistic insight into the temperature-dependent active-site rearrangements and offer rational engineering strategies to enhance the efficiency of PETase for PET biodegradation. Full article

Background/Objectives/Methods: A bioassay-informed investigation of the Australian pasture soil-derived Streptomyces sp. S4S-00193A39 yielded the anthelmintic principals as three new spiroketal polyketide alkaloids, goondoxazoles A–C (1–3), with structures assigned by detailed spectroscopic analysis. Results: A structure–activity relationship based on the ability to inhibit the motility of Dirofilaria immitis microfilariae (mf) revealed a positive correlation for the benzoxazole moiety present in 2 and 3 (EC₅₀ 55–85 nM) versus the ring-opened aminobenzoic acid moiety evident in 1 (EC₅₀ 1.38 µM). This hypothesis was strengthened by extension of the SAR assessment to the known benzoxazole natural products A-33583 (12), UK-1 (13) and nataxazole (14), and the new analogue 5-hydroxynataxazole (15), which were isolated in our lab from three additional Australian pasture soil-derived Streptomyces spp. Of note, while the benzoxazole methyl esters 13–15 exhibited approximately 9- to 65-fold lower potency against D. immitis mf compared with 2 and 3, the carboxylic acid substituted benzoxazole 12 displayed comparable activity (EC₅₀ 72 nM) against D. immitis mf, and >5-fold improved potency against D. immitis L4 larvae (EC₅₀ 0.43 µM). Conclusions: These observations reveal the promising anthelmintic potential (against D. immitis) for the new structurally complex and chiral goondoxazoles (e.g., 2 and 3), and demonstrate that this effect can be replicated, even improved, by simpler, achiral benzoxazole microbial natural products (e.g., 12). Full article

Members of the genus Streptomyces are prominent inhabitants of the plant rhizosphere and endosphere and are increasingly recognized for their roles in plant growth promotion and disease suppression. In this study, we isolated genetically distinct Streptomyces from the tomato (Solanum lycopersicum L.) rhizosphere, designated as TOM isolates, and assembled them into a defined 12-member TOM consortium. Application of the TOM consortium significantly promoted root and shoot growth in tomato. RNA-seq analysis revealed coordinated local and systemic transcriptional responses characterized by a predominance of down-regulated genes in both roots and leaves. In roots, differential gene expression reflected selective attenuation of defense- and cell wall-related processes, alongside increased expression of genes associated with phytoalexin biosynthesis, phosphate starvation responses, and hormonal regulation. In leaves, transcriptional reprogramming was dominated by reduced stress-related responses together with activation of metabolic and growth-associated functions. The TOM consortium also reduced disease severity caused by Fusarium oxysporum f. sp. radicis-lycopersici by approximately 60% compared to infected controls. To further characterize functional traits of individual consortium members, isolates were evaluated in vitro for antifungal activity and five strains displaying inhibition were selected for hybrid whole-genome sequencing. Genome analyses revealed diverse taxonomic affiliations and a rich repertoire of biosynthetic gene clusters, including clusters associated with known antimicrobial metabolites as well as numerous low-similarity clusters indicative of substantial unexplored biosynthetic potential. Collectively, this study provides new insights into plant interactions with beneficial Streptomyces, while revealing molecular signatures involved in Streptomyces-mediated plant growth promotion and pathogen suppression. Full article

Agriculture is an essential activity in Mexico, representing the main source of income of numerous families. Crops are negatively affected by many diseases, particularly caused by phytopathogenic fungi, whose control by biological agents emerges as an advantageous alternative. The aim of the present study was to evaluate the antagonistic activity of microorganisms isolated from Larrea tridentata L. (Sessé & Moc. Ex DC.) Coville leaves, stems, roots, and rhizospheric soil against Fusarium spp. and other phytopathogen fungi. We identified 54 microorganisms: 30 bacteria species and 24 actinobacteriota. Initial dual-confrontation experiments with phytopathogenic fungi determined the bacillus and actinobacteriota inhibited growth from 57 to 100% and 42 to 83%, respectively. Based on our initial results, selected isolates were confronted with Rhizoctonia sp. and two Fusarium spp. isolates (orchid and garlic isolates). All microorganisms inhibited Rhizoctonia, but only 13 bacillary bacteria and eight actinobacteriota isolates inhibited Fusarium and were selected for the third confrontation, in which firmicutes –Bacilli:Bacilliales- and actinobacteriota isolates inhibited Fusarium spp. growth from 55 to 92% and 14 to 74%, respectively. In addition, supernatant fluids from six selected actinobacteriota were evaluated, and the results determined that the strains OP-AGsD3, OP-AGsM4R7, and OP-AGsM1R5 possessed the highest antagonist activity against all Fusarium spp. isolates. Molecular identification analysis indicated that actinobacteriota belonged to the Streptomyces genus. Our results revealed the potential of native Streptomyces spp. from L. tridentata rhizosphere soil as biocontrol agents against phytopathogenic Fusarium spp. Full article

Triple-negative breast cancer (TNBC) is a highly aggressive subtype with limited targeted therapies, underscoring an urgent need for novel agents. The soil-derived Streptomyces sp. CB00271, isolated from a biodiversity hotspot, was investigated for its bioactive metabolites. Bioassay-guided isolation led to the identification of actinolactomycin (1), alongside daidzein (2) and genistein (3). Remarkably, actinolactomycin (1) exhibited potent cytotoxicity against TNBC models, with IC₅₀ values of 0.72 ± 0.12 μM (MDA-MB-231) and 0.15 ± 0.02 μM (4T1), demonstrating approximately 9-fold and 31-fold greater potency than cisplatin, respectively, and suggesting action through targeted pathway inhibition. This study constitutes the first report to systematically highlight the exceptional anti-TNBC potential of this rare natural product, establishing it as a promising lead compound against this challenging subtype. Furthermore, Streptomyces sp. CB00271 is identified as a valuable and scarce microbial resource for actinolactomycin, providing a new avenue to address its supply limitation and facilitate future development. Full article

Background: The SARS-CoV-2 3CLpro is essential for viral replication and an attractive target for antiviral intervention. While most strategies target the catalytic site, recent studies suggest that the dimerization interface and cryptic allosteric pockets offer alternative mechanisms for inhibition. Objective: This study investigated lipid metabolites from the marine sediment-derived Streptomyces sp. DSD454^T as potential multi-site 3CLpro inhibitors. Methods: Metabolites were extracted from cultured biomass and characterized using LCMS-QTOF, MS/MS (LCMS-TQ), and ¹H NMR, with identities confirmed against authentic standards. 3CLpro inhibition was assessed using a FRET-based assay, and ligand–protein interactions were evaluated through molecular docking and MM/GBSA calculations. Lipid content and comparative lipidomic signatures were examined across bioactive Streptomyces strains through LCMS-TQ and BODIPY^TM 493/503 staining. Results: Palmitoleic and linoleic acids were identified as major constituents and inhibited SARS-CoV-2 3CLpro with IC₅₀ values of 1.59 µg/mL (6.25 µM) and 5.29 µg/mL (18.88 µM). Molecular docking predicted that both fatty acids bind not only to the catalytic site but also to the dimerization interface and cryptic allosteric pocket. Additional lipids, including 9-heptadecenoic acid, linolenic acid, 9-HODE, and monoacylglycerols such as aggrecerides A–C and glyceryl-based lipids, showed similarly favorable multi-site binding profiles. Streptomyces sp. DSD454^T also exhibited substantial lipid accumulation (~63% of crude extract). Across bioactive Streptomyces strains, a conserved lipid signature correlated strongly with 3CLpro inhibition. Conclusions: This study highlights the potential of microbial lipids as promising scaffolds for developing catalytic and allosteric SARS-CoV-2 3CLpro inhibitors and underscore marine Streptomyces as a valuable source of structurally simple yet mechanistically versatile antiviral metabolites. Full article

Soil salinity is a major abiotic stress that limits agricultural productivity worldwide. The aim of this study was to evaluate whether biogenic silver nanoparticles (AgNPs) can mitigate salt stress in maize while preserving soil biological health under realistic soil conditions. Biogenic AgNPs were synthesized using biomolecules from the actinobacterium Streptomyces sp. Z38 and characterized, confirming spherical morphology, colloidal stability, and surface functionalization. Maize plants grown under greenhouse conditions were treated with biogenic or chemically synthesized AgNPs, and plant performance, oxidative stress responses, and soil biological properties were evaluated. Under saline conditions (6 mS cm⁻¹), biogenic AgNPs markedly improved plant growth, almost fully restoring leaf dry weight (165.08 ± 23.68 mg) to values comparable with non-saline controls (171.81 ± 15.00 mg), while chemical AgNPs induced only partial recovery. Biogenic AgNPs also enhanced antioxidant defenses, increasing catalase activity by ~15% above non-saline levels and reducing lipid peroxidation from 232.34 ± 31.74 to 102.63 ± 5.75 Eq. MDA g⁻¹. In parallel, chlorophyll a content increased by ~29% relative to non-saline plants, indicating improved photosynthetic performance. Transmission electron microscopy of leaves confirmed AgNPs internalization, with nanoparticles primarily sequestered in vacuoles. Analyses of experimental soils showed that biogenic AgNPs enhanced microbial enzymatic activity and respiration, while chemical AgNPs had inhibitory effects. Ecotoxicological assays further indicated low soil toxicity following biogenic AgNPs plant treatment, as reflected by high lettuce germination rates. Overall, these findings highlight the potential of biogenic AgNPs obtained from actinobacteria as sustainable nanobiotechnological tools to mitigate salt stress in crops while improving soil health. Future field-scale studies will be required to validate their agronomic applicability. Full article

Background: Staurosporine is a potent broad-spectrum alkaloid antibiotic originally isolated from Streptomyces sp. It is renowned for its strong inhibitory activity against protein kinases by competitively binding to their ATP-binding sites. Therefore, staurosporine and its derivatives have been extensively investigated for their potential as anticancer agents. However, a major challenge in its utilization is the low production yield in wild-type strains. To overcome this limitation, this study aimed to enhance staurosporine yield in marine-derived staurosporine-producing strain OUCMDZ-3118. Methods: The fermentation conditions were tested by single-factor experiment, Plackett–Burman experiment, steepest ascent path and Box–Benhnken response surface method. Subsequently, the ultraviolet mutagenesis was employed to generate high-yielding mutant strain. Results: The optimal culture conditions were 50 g/L rice, 50 g/L soybean powder, 3 g/L NaCl, 10 g/L L-tryptophan, inoculum concentration of 3% (v/v) in 150 mL of medium within a 500 mL flask, and fermentation time of 10 days. Following UV mutagenesis, the mutant strain produced a final staurosporine titer of 496 mg/L, an approximately 9.5-fold higher titer than that of the wild-type strain. In a 30-day solid-state fermentation under the conditions of 40 g rice, 40 g soybean powder, moistened with 80 mL water containing NaCl (3 g/L) and L-tryptophan (10 g/L), a yield of 578 mg per 80 g of substrate was also achieved. A consistent yield of 7.22 g/kg was achieved across approximately 1000 replicate fermentations under identical conditions, demonstrating the robustness of the process. Conclusions: This study yielded a stable, high-yielding strain for staurosporine production, paving the way for the development of staurosporine-based antitumor drugs and their derivatives. Full article

Obtaining enzymes through bioconversion depends on a complex relationship between the microorganisms and the biomass used. Here, we evaluate xylanase production by diverse actinobacterial species, cultivated using xylan as the sole carbon source and complex media containing sorghum as the substrate. Fifty-three actinobacteria were tested for xylanase production in a solid medium. Seventeen strains produced xylanase and were tested for their ability to produce xylanase, total cellulases (filter paper activity, FPase), and endoglycanase in submerged culture using a defined liquid medium. The best xylanase-producing species was Streptomyces capoamus, yielding 24 IU·mL⁻¹. For FPase, Streptomyces sp. showed the highest yield (1.12 IU·mL⁻¹); for endoglycanase, the best producer was Streptomyces ossamyceticus (0.99 IU·mL⁻¹). When sweet sorghum was used alone, S. curacoi, S. ossamyceticus, and S. capoamus showed xylanase activities of 4.5 IU·mL⁻¹, 4.4 IU·mL⁻¹, and 0.8 IU·mL⁻¹, respectively. However, FPase activity was not detected under the assay conditions. The results showed that there is an intraspecific difference in xylanase, endoglucanase, and FPase production by actinobacteria, with the species S. curacoi, S. ossamyceticus, and S. capoamus able to use sorghum as a carbon source, demonstrating biotechnological potential. Full article

Three new pyrrole alkaloids, streptopyrroles D–F (1–3), along with four known analogs (4–7) were isolated from Sea Anemone-Associated Streptomyces sp. S1502 via an OSMAC (One Strain Many Compounds)-based strategy. Their structures were elucidated through comprehensive spectroscopic analyses, including HRESIMS and 1D/2D NMR experiments (COSY, HSQC, and HMBC), and further confirmed by X-ray crystallography. Biological evaluation identified streptopyrrole (4) as an anti-MRSA (methicillin-resistant Staphylococcus aureus) agent, while 4 and 6 displayed broad-spectrum cytotoxicity and good selectivity against a panel of human cancer cell lines. Notably, 4 and 6 showed particularly potent activity against the lung cancer cell lines H1299, SW1573, and A549, with IC₅₀ values ranging from 5.43 to 16.24 μM. Further mechanistic investigation revealed that both compounds suppress the proliferation of lung cancer cells by inducing cell cycle arrest at the G₀/G₁ phase and impair metastatic potential by inhibiting migration and invasion. These findings not only expand the structural diversity of marine-derived pyrrole alkaloids but also reveal the anticancer mechanisms of 4 and 6, highlighting their promise as active candidates for further antitumor drug development, particularly in lung cancer. Full article