Search Results (691)

Phosphate tailings (PTs) are typical industrial byproducts that can rapidly neutralize soil acidity. However, their acid-neutralizing efficacy, long-term application optimization mechanisms, and high-yield regulation pathways for crops remain unclear. This study conducted a corn-potato crop rotation field trial on acidic soils, investigating the effect of different PT application rates (T: CK, 0 t·ha⁻¹; PTs-1, 6 t·ha⁻¹; PTs-2, 9 t·ha⁻¹; PTs-3, 15 t·ha⁻¹) in a multiple cropping system (C: late autumn potatoes (LAP)-early spring potatoes (ESP)-summer maize (SM)). The results showed that two consecutive applications of 9 t·ha⁻¹ of PTs produced optimal results, increasing the LAP yield by 12.82% and the soil quality by 76.51%, while improving the ESP soil quality by 46.21%. The higher yield was mainly attributed to a significant increase in the soil pH (0.72–1.58 units) and enhanced chemical and biological properties (higher exchangeable calcium (ExCa), exchangeable magnesium (ExMg), the total exchangeable salt base ion (TEB), and catalase (CAT) and urease (UE) content and lower soil exchangeable acidity (EA), exchangeable hydrogen ion (ExH), and exchangeable aluminum (ExAl) levels). Notably, a synchronized increase in the total phosphorus (TP) and total potassium (TK) during LAP cultivation, combined with simultaneous growth of TP, available nitrogen (AN), and available phosphorus (AP) during ESP cultivation, and a significant increase in TP and AP during SM cultivation, effectively promoted crop yield. Furthermore, continuous PT application significantly enriched phosphorus (P)-soluble functional bacteria, such as Actinomycetes and Chloroflexota, and enhanced the stability of bacterial-fungal cross-boundary networks. In summary, optimal acidity levels and favorable soil texture improved soil quality, consequently increasing corn and potato yields. This study reveals for the first time that PTs can substantially increase crop production via a synergistic mechanism involving acid-base balance, structural improvement, and microbial activation. Not only does this provide a novel strategy for rapidly improving acidic soils, but it also establishes a solid theoretical and technical foundation for utilizing PT resources. Full article

Tea plantations are one of the most intensive land-use systems in subtropical China, but the long-term effects on soil microbial functioning remain insufficiently understood. This study combined extracellular enzyme activity, ecoenzymatic stoichiometry, and partial least squares path modeling (PLS-PM) to assess the impacts of forest-to-tea conversion and plantation age on microbial nutrient acquisition and metabolic limitations. The results showed that tea plantations had significantly higher activities of carbon (C)-, nitrogen (N)-, and phosphorus (P)-acquiring hydrolases compared to adjacent pine forests, and oxidase activity increased significantly with plantation age, reaching a fivefold higher level in the oldest plantation. Soil acidification, decreased soil organic carbon, and shifts in microbial composition (decline in bacteria and actinomycetes, increase in fungi) were the main drivers of these changes. The study indicates that tea planting intensifies microbial limitations on carbon and phosphorus and shifts microbial metabolism toward oxidative pathways, which may destabilize soil carbon pools and reduce long-term fertility. These findings highlight the importance of balanced nutrient management in tea plantation practices. However, the study is limited by the short duration of field sampling. Future research should focus on long-term monitoring to better understand the sustained impacts of tea cultivation on soil microbial functions and explore the role of different management practices in mitigating these effects. Full article

Tetracenomycins are anticancer polyketides that arrest cancer cell proliferation via binding to the large mammalian ribosomal subunit near the polypeptide exit channel. The tetracenomycins are natural products that many members of the actinomycete family produce. The first goal of this study was to improve the biosynthesis of tetracenomycin analogs via metabolic engineering. The second goal was to probe more deeply into the antiproliferative activity of tetracenomycin aglycones. The tetracenomycins were assessed via several assays, including cell viability assays, clonogenic assays, and flow cytometry apoptosis assays. The data suggest that tetracenomycins C and X inhibit cell proliferation and arrest cell growth, supporting their cytostatic action mechanism. In addition, tetracenomycins C and X induced degeneration of 3D spheroid cultures and exhibited concentration-dependent inhibition of cell survival and colony formation in clonogenic assays. This work demonstrates that tetracenomycins act mainly as cytostatic rather than apoptotic agents. Full article

Actinomycetes, especially Streptomyces, are prolific producers of bioactive metabolites, including pigments with potential applications in foods, textiles, cosmetics, and pharmaceuticals. Motivated by increasing concerns about the safety and environmental impact of synthetic pigments, this study aimed to optimize the production of an extracellular pigment-rich fraction from Streptomyces parvulus and to evaluate its bioactivities relevant for cosmeceuticals. A Plackett–Burman design was used to identify key variables influencing metabolite production, followed by optimization with a Box–Behnken design. The pigment-rich fraction was obtained after extraction with ethyl acetate from lyophilized supernatants and chemically characterized by IR and LC–MS. Biological assays were conducted to assess anti-tyrosinase, immunomodulatory, and antimicrobial activities. Temperature, incubation time, and agitation speed were identified as the most significant factors, with optimal conditions of 30 °C, 50 rpm, and 7 days yielding a pigment concentration of 465.3 μg/mL. LC–MS analysis revealed three 1,4-naphthoquinone-containing compounds, annotated as juglomycin Z (1), WS-5995B (2), and naphthopyranomycin (3), as the main constituents. The pigment-rich fraction showed modest anti-tyrosinase activity (10.9% at 300 μg/mL), immunomodulatory effects (TNF-α inhibition up to 36.9% and IL-10 stimulation up to 38.4% in macrophages), and antimicrobial activity against Staphylococcus epidermidis (15.8 mm inhibition halo, 91% growth reduction). The optimized fermentation model enhances pigment yield while reducing resource consumption, and the pigment-rich fraction exhibits multifunctional bioactivities, underscoring its potential as a natural cosmeceutical ingredient. Full article

Actinomycetes are a representative group of bacteria that inhabit soil; in particular, Streptomyces coelicolor M511 produces actinorhodin and undecylprodiginine. Among them, undecylprodiginine has antibiotic and immunosuppression activity and is a secondary metabolite with high potential applications in biotechnological and pharmaceutical fields. High temperature stress (37 °C) reduced the biosynthesis of undecylprodiginine and induced specific branched chain alkylprodiginine derivatives, compared with the optimal growth temperature (30 °C). Also, the stress stimulated the synthesis of straight-chain FA for enhancing membrane rigidity. The inhibition of undecylprodiginine biosynthesis under high temperature stress seems to be induced by the heat sensitivity of the RedP enzyme, and this inhibition is compensated by FAS FabH. Since FabH, a homologue of RedP, has a broader substrate specificity, it leads to the production of methylundecylprodiginine and methyldodecylprodiginine. The external addition of isoleucine (as well as that of leucine and valine to a far lesser extent) enhances the synthesis of these derivatives since isoleucine catabolism generates precursors used for the biosynthesis of these compounds. These findings reveal temperature-dependent changes in precursor utilization and prodiginine diversity, providing insights into metabolic plasticity and strategies establishing a foundation for secondary metabolite derivatives engineering strategies through precursor supplementation or temperature regulation. Full article

The microbiota associated with Vanilla planifolia grown in three production systems in Puebla, México, was evaluated: shade cloth, cocuite, and acahual. Rhizosphere and soil samples were analyzed, from which bacteria, fungi, yeasts, and actinomycetes were isolated. The bacterial and actinomycete isolates were characterized morphologically and biochemically, and their potential as growth promoters was evaluated. Morphological and microscopic characteristics identified the fungi. In parallel, agronomic variables were measured in five plants per system, and the data were analyzed using ANOVA and Tukey’s test (p ≤ 0.05). The results showed that the shade cloth favored a greater number of internodes, total leaves, and biomass, although with a higher incidence of diseased leaves. The cocuite presented intermediate values, while the acahual had lower leaf density but fewer leaf health problems. Microbial composition varied across systems, with potentially beneficial bacteria and actinomycetes, as well as both beneficial and pathogenic fungi, being prominent. These findings demonstrate the influence of the management system on the microbiota and health of V. planifolia, providing a basis for more sustainable production strategies for vanilla cultivation in Mexico. Full article

The marine invertebrate-associated microbiome has garnered significant interest in recent years due to its wealth of novel genes that can be explored for biomining. By combining genomics with untargeted data-dependent mass spectrometry (MS) and molecular networking, we characterized the secreted metabolome of Streptomyces sp. In a previous study, we isolated and characterized a strain of Streptomyces, designated as strain 34, from the nudibranch Chromodoris quadricolor, collected by SCUBA diving in the Red Sea near El Tor in the Gulf of Suez, Egypt. In the present study, the Streptomyces isolate was identified as Streptomyces tunisiensis GCF 039538125 1 (p-value: 0). Genomic and metabolomic analysis reveal 36 predicted biosynthetic gene clusters. A total of 569 metabolites were detected in the culture, with 86 of these being identified based on standards and public spectral libraries. Moreover, a single lassopeptide synthesis gene cluster was found in both the genome and the metabolic extract, along with various sets of siderophores identified in the metabolic extract. Since the metabolic processes of marine invertebrate microbiomes are poorly understood, our findings are a significant addition to the research on metabolism in host microbiomes. Full article

Marine actinomycetes constitute a vigorous source of bioactive compounds with potential anti-tumor activity. This study investigates the antitumor activity and classification of actinomycetes isolated from 32 marine soil samples collected across four seasons from Tyr City Beach, Lebanon. A total of 80 morphologically diverse isolates were recovered and characterized, with dominant genera including Streptomyces, Kocuria, and Micrococcus. Among these, three promising strains—Kocuria rosea, Micrococcus luteus, and Streptomyces longisporoflavus—were selected for further analysis. Crude extracts were tested against human colorectal adenocarcinoma (Caco-2) and human hepatocellular carcinoma (HepG-2) cancer cell lines using MTT and Western blot assays. At the highest concentration (8 µg/µL), the extracts reduced cell viability to 24–37% in Caco-2 and 12–25% in HepG-2. The IC₅₀ values ranged from 1.72 to 3.53 µg/µL, depending on the extract and cell line. Western blot analysis showed dose-dependent increases in the Bax/Bcl-2 ratio, with fold changes reaching 4.35 (Kocuria), 11.39 (Micrococcus), and 14.25 (Streptomyces) in HepG-2 cells. The p53 protein expression also increased significantly, with fold changes up to 7.79 in Caco-2 and 3.0 in HepG-2 cells. These results indicate that marine actinomycetes from the Lebanese coastline hold strong potential as a source of antitumor agents targeting apoptosis pathways. Full article

Keratinous wastes, generated from various industries such as poultry processing, slaughterhouses, and salons, accumulate in the environment due to their slow degradation caused by high disulfide cysteine bonds. Traditional methods of managing these wastes, including incineration, composting, open-air burning, and landfilling, have several disadvantages, such as environmental pollution, release of toxic compounds, and breeding of pathogenic and multidrug-resistant microorganisms. Microbial keratinases, produced by bacteria, fungi, and actinomycetes, offer an eco-friendly alternative for valorizing keratinous waste into valuable peptides and amino acids. The biodegradation of keratinous biomass involves four sequential steps: adhesion, colonization, production of keratinolytic enzymes, and breakdown of the keratin substrate. Optimization of culture conditions, such as pH, temperature, substrate concentration, and metal ions, can enhance keratinase production for industrial applications. Keratinases have multifaceted applications in various sectors, including cosmetics, organic fertilizers, leather treatment, animal feed, detergents, and pharmaceuticals. This review highlights the need to explore keratinolytic strains further and improve keratinase yields to develop sustainable solutions for keratinous waste management and generate value-added products, promoting a circular economy. The techno-economic considerations and current limitations in industrial-scale keratinase production are also discussed, emphasizing the importance of future research in this field. Full article

This study aimed to develop a sustainable bioinput using Streptomyces sp. BEI-18A cultivated in an alternative culture medium (ACM) formulated with winery spent yeast and composting leachate. Actinomycetes were initially isolated from grape waste composting piles and screened for agricultural potential in vitro. Streptomyces sp. BEI-18A was selected for further bioinput development based on its high siderophore production. The ACM formulation was optimized in three steps: (I) determining the optimal concentration of winery spent yeast through mixture design; (II) assessing the effect of composting leachate addition on microbial growth; and (III) establishing the final composition of ACM components. The optimized ACM consisted of 3 g/L spent yeast, 2 g/L sucrose, 1 g/L soybean extract, and 10% (v/v) composting leachate. Cultivation of Streptomyces sp. BEI-18A in this medium resulted in a bioinput containing 7.80 × 10⁷ CFU/mL. Its agricultural potential was validated in pot experiments with wheat and soybean, where application of the bioinput promoted significant improvements in early plant growth, enhancing several phytometric parameters. The results highlight the feasibility of valorizing agro-industrial residues as low-cost substrates for microbial bioinput production. This approach represents a promising strategy to foster sustainability in agriculture while reducing environmental impacts. Full article

We identified Streptomyces globisporus bja209 through a targeted screen of actinomycetes from natural habitats using an E. coli JW5503 ΔtolC DualRep2(c) reporter strain. This strain produced antibacterial compounds whose action depended on the growth medium. HPLC-MS and genomic analysis revealed two metabolites: albomycin δ2 (a translation inhibitor) and desferrioxamine E. The latter induced the SOS response. Desferrioxamine E exhibited a narrow spectrum of antagonistic activity against carbapenem-resistant A. baumannii and C. michiganensis, and its production was critically regulated by iron concentration. Notably, the structurally similar desferrioxamine B was inactive. Contrary to previous reports, pangenome analysis of published GenBank genomes revealed that albomycin BGC is restricted to specific S. globisporus strains and not present in other Streptomycetes phylogenetic clades. The C-1027 BGC was found in a large linear plasmid (165.5 kb) of the S. globisporus bja209 strain and also found exclusively on linear plasmids in some of the published S. globisporus genomes. Full article

In view of the increasing environmental pollution caused by bisphenol A (BPA), understanding its impact on the microbiological properties of soil, which play a key role in maintaining soil fertility and consequently ecosystem stability, is particularly important. Therefore, the aim of this study was to assess the sensitivity of the soil microbiome to this xenobiotic and to evaluate the potential of organic materials such as starch (St), grass compost (Co), and fermented bark (B) to restore the balance of soil cultivated with Zea mays. The negative effects of BPA on the abundance, diversity, and structure of bacterial and fungal communities in soil contaminated with 500 and 1000 mg kg⁻¹ d.m. of soil were confirmed. Changes in the phospholipid profile, including phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylglycerol (PG), and ergosterol (E), were also assessed. BPA applied at 1000 mg kg⁻¹ d.m. of soil inhibited the proliferation of organotrophic bacteria and actinomycetes, while stimulating fungal growth. This xenobiotic’s impact is also reflected by a decrease in PC and PG levels in soil under BPA pressure. Through amplification of the V3-V4 16S rRNA region (for bacteria) and the ITS1 region (for fungi), the dominant bacterial phylum Proteobacteria was identified, with genera including Cellulosimicrobium, Caulobacter, Rhodanobacter, Sphingomonas, Mucilaginibacter, and Pseudomonas. Among fungi, Ascomycota dominated, primarily represented by the genus Penicillium. Of all the organic materials tested for mitigating BPA’s negative effects, grass compost was identified as the most promising, not only restoring soil homeostasis but also enhancing the growth and development of Zea mays cultivated in BPA-contaminated soil. Full article

Antimicrobial resistance represents a critical global health challenge, intensifying the urgency of discovering novel antibiotics. Actinomycetota species, the most prolific source of clinical antibiotics, remain underexplored in unique ecosystems. In this study, we isolated 340 Actinomycetota strains from soils of the Brazilian semiarid Caatinga biome. Screening revealed that 122 isolates (35.9%) exhibited antimicrobial activity against clinically relevant pathogens (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans). Notably, 19 isolates showed activity against Mycobacterium tuberculosis H37Ra. MALDI-TOF MS analysis successfully provided genus-level identification for a subset of isolates, with approximately 32% assigned to the Streptomyces genus. However, the limited resolution of the database for the majority of the strains indicates high phylogenetic diversity and suggests the presence of potentially novel species. Metabolomic profiling via LC-MS/MS and GNPS molecular networking suggested the production of known antibiotics such as actinomycins, cyclomarins and anthracyclines and unveiled distinct molecular families putatively assigned to undescribed metabolites. Our work establishes the Caatinga biome as a valuable reservoir of bioactive Actinomycetota, encoding both known and potentially novel antimicrobial compounds. These results underscore the potential of underexplored and extreme environments in the quest to overcome antibiotic resistance. Full article

Marine-derived Actinomycetota have emerged as promising sources of bioactive natural products, particularly filamentous actinomycetes (e.g., Streptomyces). However, members from non-filamentous genera have showed potential biotechnological importance. In this study, we performed a comprehensive genomic characterization of two bioactive Brevibacterium strains, Brevibacterium luteolum (B. luteolum) 26C and Brevibacterium casei (B. casei) 13A, isolated from two Red Sea sponges. Whole-genome sequencing and taxonomic analysis confirmed species-level identification, marking the first documented report of these species within the Red Sea ecosystem. The two strains displayed antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans. Additionally, functional annotation revealed multiple genomic islands (GIs) enriched with genes conferring heavy metal resistance, DNA repair enzymes, nutrient acquisition, and mobile genetic elements, highlighting potential evolutionary adaptations to the harsh physicochemical conditions of the Red Sea. Genome mining identified biosynthetic gene clusters, including those encoding ε-poly-L-lysine, tropodithietic acid, ectoine, and carotenoids. The comparative analysis of orthologous gene clusters from both strains and their counterparts from terrestrial ecosystems highlighted potential marine adaptive genetic mechanisms. This study highlights the biosynthetic potential of B. luteolum 26C and B. casei 13A and their ecological role as active competitors and potential defensive associates within the sponge microbiome. Full article

Humic substances and beneficial microorganisms are key biostimulants for sustainable agriculture and global food security in the face of climate change. Marine bacteria are emerging as a promising source of plant-beneficial microbes, tapping into a microbial diversity as immense as the oceans themselves. However, their potential, limitations, and mechanisms of action––especially in combination with other biostimulants––remain largely unexplored. In this study, we isolated the Streptomyces sp. LAP3 strain from the giant limpet Scutellastra mexicana. We evaluated the efficacy of the marine bacterium, applied alone or in combination with the humic product Leonardite hydrolate (L), in enhancing tomato performance under field conditions. Treatments included: (1) marine Streptomyces (MS), (2) Leonardite hydrolate (L), (3) both biostimulants (MS + L), and (4) a control (CTRL). We assessed growth, photosynthetic performance, antioxidant responses, and fruit yield and quality. Both biostimulants individually improved plant performance, but their combination had a significant synergistic effect, markedly boosting tomato productivity, thermotolerance, and resilience during a heatwave. Enhanced photosynthetic efficiency and antioxidant enzyme activity were associated with improved agronomic traits. These results highlight the potential of combining Streptomyces sp. LAP3 and Leonardite hydrolate as an eco-friendly strategy to increase crop productivity, strengthen stress resilience, promote sustainable agriculture, and reduce reliance on agrochemicals. Full article