Search Results (401)

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 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

Mining novel Streptomyces species from extreme environments provides a valuable strategy for the discovery of new antibiotics. Here, we report a strain of Streptomyces sp. HMX87^T, which exhibits antimicrobial activity and was isolated from desert soil collected in the Tuha Basin, China. Molecular taxonomic analysis revealed that the 16S rRNA gene sequence of strain HMX87^T shares the highest similarity with those of Streptomyces bellus CGMCC 4.1376^T (98.5%) and Streptomyces coerulescens DSM 40146^T (98.43%). In phylogenetic trees, it formed a distinct branch. The average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values between strain HMX87^T and the above two type strains were below the thresholds of 95% and 70%, respectively, confirming that strain HMX87^T represents a novel species within the genus Streptomyces, for which the name Streptomyces hamibioticus sp. nov. is proposed. Physiologically, the strain HMX87^T grew at temperatures ranging from 25 to 37 °C, tolerated pH values from 5 to 12, and survived in NaCl concentrations of 0% to 8% (w/v). Chemotaxonomic characterization indicated the presence of LL-diaminopimelic acid (LL-DAP) in the cell wall, ribose and galactose as whole-cell hydrolysate sugars, MK-9(H8) (66.3%) as the predominant menaquinone, and iso-C_16:0 (25.94%) and anteiso-C_15:0 (16.98%) as the major fatty acids characteristics that clearly distinguish it from its closest relatives. Whole-genome sequencing of strain HMX87^T revealed an abundance of genes associated with high-temperature tolerance, salt-alkali resistance, and antimicrobial activity. The genomic features and secondary metabolic potential reflect its adaptation to extreme environmental conditions, including high temperature, salinity, alkalinity, strong ultraviolet radiation, and oligotrophic nutrients. The strain HMX87^T has been deposited in the Czech Collection of Microorganisms (CCM 9454^T) and the Guangdong Microbial Culture Collection Center (GDMCC 4.391^T). The 16S rRNA gene and whole-genome sequences have been submitted to GenBank under accession numbers PQ182592 and PRJNA1206124, respectively. 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

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

Using the one-strain-many-compounds (OSMAC) culturing approach, metabolomic studies, and bioassay-guided purification, we have isolated and characterised three new chlorinated natural products, agelolines B-D (1–3), together with two known compounds, ageloline A (4) and gausemycin A (5), which have been identified by high-resolution mass spectrometry and 1D and 2D NMR analyses. The preliminary evaluation of three small-scale extracts (M400, R358 and SGG) against the fish pathogen, Aeromonas salmonicida subsp. achromogenes KELDUR265-87, showed that the R358 extract displayed significant activity. Furthermore, the natural products (1–5) were evaluated against the fish pathogen Aeromonas salmonicida and human pathogens (Stenotrophomonas maltophilia L2125, Staphylococcus aureus ATCC6538P, and S. pneumoniae L44) using a serial dilution assay. Compound 3 displayed activity against Staphylococcus aureus ATCC6538P, S. maltophilia L2125, and S. pneumoniae L44 with MIC values of 6, 32, and 64 µg/mL, respectively. Interestingly, only gausemycin A (5) exhibited considerable inhibition against A. salmonicida with an MIC value of 32 µg/mL, and the activity increased by two-fold when supplemented with 0.45 mM calcium salt, while 2 and 4 showed moderate inhibition against S. maltophilia L2125. The biosynthetic pathways of compounds 1–4 were proposed. This is the first report of specific inhibition of A. salmonicida by 5. Full article

True morels (Morchella spp., Morchellaceae, Ascomycota) are a rare and highly valuable edible fungus. As the morel cultivation scale has expanded, obstacles to continuous cropping have come to the fore. This study investigates the specific biological mechanisms that may hinder the continuous cropping of Morchella by means of microbiome and metabolome analysis of the soil. Using amplicon sequencing-based microbiome analysis, 5288 bacterial operational taxonomic units (OTUs) and 1847 fungal OTUs were identified. Bacterial genera such as Arthrobacter, Tychonema, Rhodanobacter, Luteimonas, and Streptomyces, along with pathogenic fungi, likely play specific roles in hindering continuous cropping of Morchella. Metabolomic analysis revealed 368 metabolites, including lipids and lipid-like molecules, organic acids and derivatives, benzene-containing compounds, and heterocyclic compounds. Eighteen metabolites showed significant differences between Morchella continuous cropping and control soil, including toxic compounds such as 2,4,5-Trichloro-6-Hydroxybenzene-1,3-Dicarbonitrile, 2,4-Dichloro-6-nitrophenol, and Aflatoxin B2. These results indicate that alterations in soil microbial structure and toxic metabolites secreted by Morchella collectively contribute to the hindrance of continuous cropping. Full article

Arid and semi-arid regions show distinctive bacterial groups important for the sustainability of ecosystems and soil health. This study aims to investigate how environmental factors across five Qatari soils influence the taxonomic composition of bacterial communities and their predicted functional roles using 16S rRNA amplicon sequencing and soil chemical analysis. Soil samples from five different locations in Qatar (three coastal and two inland) identified 26 bacterial phyla, which were dominated by Actinomycetota (35–43%), Pseudomonadota (12–16%), and Acidobacteriota (4–13%). Species-level analysis discovered taxa such as Rubrobacter tropicus, Longimicrobium terrae, Gaiella occulta, Kallotenue papyrolyticum, and Sphingomonas jaspsi, suggesting the presence of possible novel microbial families. The functional predictions showed development in pathways related to amino acid metabolism, carbohydrate metabolism, and stress tolerance. In addition, heavy-metal-related taxa, which are known to harbor genes for metal resistance mechanisms including efflux pumps, metal chelation, and oxidative stress tolerance. The presence of Streptomyces, Pseudomonas, and Bacillus highlights their roles in stress tolerance, biodegradation, and metabolite production. These findings improve the understanding of microbial roles in dry soils, especially in nutrient cycling and ecosystem resilience. They highlight the importance of local bacteria for sustaining desert soil functions. Further research is needed to validate these relationships, using metabolomic approaches while monitoring microbial-community-changing aspects under fluctuating environmental conditions. Full article

The most common reason for a decrease in the quantity and quality of produced crops is microbial diseases. The aims of this study were to evaluate the antagonistic activity of Streptomyces sp. CACIS-1.16CA against plant pathogenic fungi and to assess its bioactive metabolites to inhibit fungal conidial germination. Antagonistic evaluations of fungal phytopathogens were performed using dual and multiple confrontation assays. Additionally, the inhibitory effect of the bioactive extract (BE) containing secondary metabolites produced by the CACIS-1.16CA strain on the germination of conidia from some fungi was tested. The results indicate that Streptomyces sp. CACIS-16CA inhibited the growth of all tested pathogens (16 strains) with percentages of inhibition (PIs) ranging from 43.3% to 72%, while S. lydicus inhibited 13 of the 16 fungi, with PI values from 35.6% to 68.5%. Moreover, CACIS-1.16CA exerted superior PI values (significant differences at p < 0.05) than S. lydicus against the damping-off fungi consortia with Phytophthora capsici, Fusarium oxysporum, and Rhizoctonia solani. Otherwise, an inhibitory effect was observed on the germination of conidial cells due to the interaction with the BE in Alternaria sp., Botrytis cinerea, and Colletotrichum spp. In conclusion, Streptomyces sp. CACIS-1.16CA may serve as an effective and natural alternative for managing several fungal plant diseases. Full article

Background/Objectives: Resistance of pathogenic microorganisms to antibiotics poses a serious threat to public health and often leads to devastating consequences. In this context, one of the pressing challenges in pharmacochemistry is the search for new, effective antibiotics to combat severe human diseases. Cyclic lipopeptides have emerged as some of the most promising candidates and have been widely studied. These compounds are a class of microbial secondary metabolites produced by various microorganisms, and they possess significant medical and biotechnological importance. The defining structural feature of these compounds is the presence of both a hydrophobic fragment, primarily a hydrocarbon tail of varying length, and a hydrophilic cyclic peptide moiety. This hydrocarbon tail confers amphiphilic properties to the lipopeptides, which are essential for their broad spectrum of biological activities. Their mechanism of action involves disruption of the cell membrane, and in many cases, the formation of ion-permeable defects has also been shown. Results: This review summarizes the data on cyclic lipopeptides produced by Pseudomonas spp., Streptomyces spp., and Bacillus spp. that modify membrane permeability through the formation of ion channels. The main emphasis is on understanding how the structure of the CLP can be related to the probability and mode of pore formation. Conclusions: The findings can contribute to expanding the arsenal of effective antimicrobial agents with a mechanism of action that reduces the risk of developing resistance. Full article

Background: Streptomyces bacteria are prolific producers of secondary metabolites (SMs), including many antibiotics. However, most biosynthetic gene clusters (BGCs) remain silent under laboratory conditions. Global transcriptional regulators, such as AdpA, can activate these BGCs, but their roles in secondary metabolism are not fully understood. This study investigates the regulatory function of AdpA in Streptomyces venezuelae (AdpA_Sv), a fast-growing model species and natural chloramphenicol producer that encodes over 30 BGCs. Methods: We applied RNA-seq and ChIP-seq at 12 and 20 h—corresponding to vegetative and aerial hyphae stages—to profile the AdpA_Sv regulatory network. Results: AdpA_Sv influenced the expression of approximately 3000 genes, including those involved in primary metabolism, quorum sensing, sulfur metabolism, ABC transporters, and all annotated BGCs, and it bound to around 200 genomic sites. Integration of RNA-seq and ChIP-seq data identified a core regulon of 49–91 directly regulated genes, with additional effects likely mediated indirectly via other transcription factors or non-canonical binding sites. Motif analysis confirmed similarity to the canonical Streptomyces griseus AdpA-binding sequence, with a novel 5-bp 3′ extension. AdpA_Sv directly regulated several SM pathways, including chloramphenicol biosynthesis, potentially alleviating Lsr2-mediated repression. Conclusions: This study defines, for the first time, the direct AdpA regulon in S. venezuelae and establishes AdpA_Sv as a central regulator of secondary metabolism. Our findings highlight S. venezuelae as a promising chassis strain for heterologous expression and suggest strategies for activating silent BGCs in other Streptomyces species. Full article

Cyclic lipopeptides (CLPs) are secondary metabolites produced by plant-beneficial bacteria, including Bacillus, Pseudomonas, Paenibacillus, Burkholderia, Serratia, and Streptomyces species. Of these bacterial sources, CLPs from Bacillus and Pseudomonas have been studied most extensively for their role in plant immunity, particularly in mediating induced systemic resistance. With this review, we provide a unique and comprehensive survey of CLPs from plant-beneficial bacteria described for this function. We consolidate existing knowledge on their role in triggering induced systemic resistance across various plant–pathogen systems and elucidate the underlying mechanisms of symptom suppression. We also discuss the need for further mechanistic studies, but also for implementing each step of the process, leading to marketable CLP-based products used as alternatives to chemicals in sustainable agriculture. Full article

The increase in antibiotic-resistant pathogens has prompted the search for alternative therapies. One such alternative is the use of probiotic microorganisms. However, growing interest is now turning toward postbiotics—non-viable microbial cells and/or their components or metabolites—that can confer health benefits without the risks associated with administering live microbes. Marine ecosystems, characterized by extreme and diverse environmental conditions, are a promising yet underexplored source of microorganisms capable of producing unique postbiotic compounds. These include bioactive peptides, polysaccharides, lipoteichoic acids, and short-chain fatty acids produced by marine bacteria. Such compounds often exhibit enhanced stability and potent biological activity, offering therapeutic potential across a wide range of applications. This review explores the current knowledge on postbiotics of marine origin, highlighting their antimicrobial, anti-inflammatory, immunomodulatory, and anticancer properties. We also examine recent in vitro and in vivo studies that demonstrate their efficacy in human and animal health. Some marine bacteria that have been studied for use as postbiotics belong to the genera Bacillus, Halobacillus, Halomonas, Mameliella, Shewanella, Streptomyces, Pseudoalteromonas, Ruegeria, Vibrio, and Weissella. In conclusion, although the use of the marine environment as a source of postbiotics is currently limited compared to other environments, studies conducted to date demonstrate its potential. Full article

Streptomycetes are vital microbial resources used in agriculture and biotechnology and are diverse secondary metabolites. The Streptomyces olivoreticuli YNK-FS0020 strain was isolated from the rhizosphere soil in Yunnan’s Wuliangshan Forest; its functions were explored via a series of experiments and genomic analysis. Indoor assays showed that this strain inhibits seven plant pathogens (including Fusarium oxysporum f. sp. cubense Tropical Race 4) and exhibits phosphorus solubilization, siderophore production, and plant-growth promotion. Genomic analysis revealed 47 secondary metabolite biosynthetic gene clusters: 12 shared over 60% similarity with known clusters (4 exhibited 100% similarity, involving antimycin and ectoine), while 19 showed low similarity or unknown functions, indicating the strain’s potential in the development of novel compounds. Genes related to tryptophan-IAA synthesis, phosphate metabolism, and siderophore systems were annotated, while metabolomics detected indole-3-acetic acid and kitasamycin, revealing mechanisms like hormonal regulation and antimicrobial secretion. In summary, YNK-FS0020 has potential for use in plant-growth promotion and disease control, aiding agricultural microbial resource utilization. Full article