Explore the vast range of titles available.

In this study, metabolites involved in the free-biomass filtrates for three endophytic actinomycetes of Streptomyces capillispiralis Ca-1, Streptomyces zaomyceticus Oc-5, and Streptomyces pseudogriseolus Acv-11 were used as biocatalysts for green synthesis of silver nanoparticles (Ag-NPs). Characterization of biosynthesized Ag-NPs was accomplished using UV-Vis spectroscopy, X-ray diffraction patterns (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM-EDX), transmission electron microscopy (TEM), and particle size analyzer. The biosynthesized Ag-NPs showed maximum surface plasmon resonance (SPR) at 440 for strain Ca-1 and 450 for both strains of OC-5 and Acv-11. Nanoparticle spherical shape was recorded with size ranging from 23.77 to 63.14 nm, 11.32 to 36.72 nm, and 11.70 to 44.73 nm for Ca-1, Oc-5, and Acv-11, respectively. SEM-EDX analysis exhibited the weight percentages of 17.3, 22.3, and 48.7% for Ag-NPs synthesized by strains Ca-1, Oc-5 and Acv-11, respectively. The activities of biosynthesized Ag-NPs were concentration dependent and the obtained results confirmed the efficacy of Ag-NPs as antimicrobial agents against Gram-positive and Gram-negative bacteria as well unicellular and multicellular fungi. The MIC for Gram-positive bacteria, Gram-negative bacteria (E. coli), and eukaryotic microorganisms was 0.25 mM with clear zone ranging from 10.3 to 14.6 mm, while MIC for Pseudomonas aeruginosa was 1.0 mM for Ag-NPs synthesized by strain Ca-1 and 0.25 mM for those synthesized by strains Oc-5 and Acv-11. Moreover, Ag-NPs exhibited antimicrobial activity against four plant pathogenic fungi represented by Alternaria alternata, Fusarium oxysporum, Pythium ultimum, and Aspergillus niger at 2.0, 1.5, 1.0, and 0.5 mM of Ag-NPs with different degree. In vitro assessment of the antioxidant efficacy of biosynthesized Ag-NPs was achieved by scavenging assay of H2O2, reducing power of Fe3+, or total antioxidant assay. The results showed that antioxidant activities of Ag-NPs were concentration dependent with the highest activity at Ag-NP concentration of 2.0 mM. Furthermore, the biosynthesized NPs have prospective bioinsecticidal activity against Culex pipiens and Musca domestica. Green synthesis of NPs could be quite potential for the development of new bioactive compounds used in different biomedical applications.

Type I polyketide synthases (T1PKSs) are one of the most extensively studied PKSs, which can act either iteratively or via an assembly-line mechanism. Domains in the T1PKSs can readily be predicted by computational tools based on their highly conserved sequences. However, to distinguish between iterative and noniterative at the module level remains an overwhelming challenge, which may account for the seemingly biased distribution of T1PKSs in fungi and bacteria: small iterative monomodular T1PKSs that are responsible for the enormously diverse fungal natural products exist almost exclusively in fungi. Here we report the discovery of iterative T1PKSs that are unexpectedly both abundant and widespread in Streptomyces. Seven of 11 systematically selected T1PKS monomodules from monomodular T1PKS biosynthetic gene clusters (BGCs)were experimentally confirmed to be iteratively acting, synthesizing diverse branched/nonbranched linear intermediates, and two of them produced bioactive allenic polyketides and citreodiols as end products, respectively. This study indicates the huge potential of iterative T1PKS BGCs from streptomycetes in the discovery of novel polyketides.

Worldwide cancer incidence and mortality have always been a concern to the community. The cancer mortality rate has generally declined over the years; however, there is still an increased mortality rate in poorer countries that receives considerable attention from healthcare professionals. This suggested the importance of the prompt detection, effective treatment, and prevention strategies. The genus Streptomyces has been documented as a prolific producer of biologically active secondary metabolites. Streptomycetes from mangrove environments attract researchers’ attention due to their ability to synthesize diverse, interesting bioactive metabolites. The present review highlights research on mangrove-derived streptomycetes and the production of anticancer-related compounds from these microorganisms. Research studies conducted between 2008 and 2019, specifically mentioning the isolation of streptomycetes from mangrove areas and described the successful purification of compound(s) or generation of crude extracts with cytotoxic activity against human cancer cell lines, were compiled in this review. It is anticipated that there will be an increase in prospects for mangrove-derived streptomycetes as one of the natural resources for the isolation of chemotherapeutic agents.

The genus Streptomyces has been recently proven to be a valuable and rich source of producing several bioactive compounds with substantial biological activity and applications in many fields such as medicine, environmental science, food industries, and agronomy. This study highlights the importance of Streptomyces as an antimicrobial, antibiofilm, and anticancer. Out of the 75 actinobacteria isolated from both marine and soil habitats, one isolate, HG2, was selected based on its potent antimicrobial activity. The isolate has been identified morphologically by studying colony and spore chain morphology using TEM and genetically by sequencing their 16 sr RNA gene as Streptomyces sp. 22SH with Accession number OK326829.1. Bioassay-guided fractionation of the Streptomyces sp. 22SH crude extract led to the isolation and purification of Cis-9-Octadecenoic. Biological evaluation including antimicrobial and antibiofilm activity of the crude and purified compound was performed on four clinical microbes (S. aureus ATCC6538-P, B. subtilis ATCC6633, and P. aeruginosa ATCC27853). The compound showed the ability to eradicate the biofilm formation by the tested pathogens. Additionally, the antitumor activity was assessed, and the compound showed a cytotoxic effect against liver carcinoma and breast cancer cells, with IC50 values of 17.48 ± 0.94 and 88.73 ± 4.78 µg/ml, respectively. While it displayed anti-topoisomerase activity with an IC 50 of 0.65 ± 0.023 µg/ml. Furthermore, the compound’s ADME-related physicochemical features and docking analysis were investigated.

The escalating challenge of antibiotic resistance in aquaculture critically threatens global fish health and food security, underscoring an urgent need for novel antimicrobial strategies. This study explored the bioactive potential of metabolites from the marine actinomycete Streptomyces zaomyceticus , isolated from a deep-sea sediment sample off Sharm El-Sheikh, Egypt. Bioactivity-guided fractionation led to the isolation and structural elucidation of SPIROST-8-EN-11-ONE, 3-HYDROXY- (SEOH), identified as a novel spirostenoid. SEOH exhibited significant broad-spectrum in vitro growth inhibition against a diverse panel of aquaculture-relevant pathogens, including Gram-positive and Gram-negative bacteria, and opportunistic fungi. It demonstrated potent minimum inhibitory concentrations (MICs) ranging from 0.25 to 1.0 µg/mL, notably effective against multidrug-resistant (MDR) Klebsiella pneumoniae (0.25 µg/mL) and Enterococcus faecalis (0.5 µg/mL). Scanning electron microscopy (SEM) revealed that SEOH treatment (2× MIC) induced significant morphological alterations, including visible cell surface modifications and reduced cell numbers, in both bacterial ( E. faecalis , K. pneumoniae , P. aeruginosa ) and fungal ( C. albicans ) pathogens. Preliminary cytotoxicity assessment using the MTT assay on HepG2 cells yielded a promising IC₅₀ value of 71.76 ± 0.62 µg/ml, indicating a favorable in vitro safety profile. The novel structure of SEOH coupled with its potent, broad-spectrum in vitro antimicrobial activity against crucial aquaculture pathogens positions it as a highly promising candidate. These compelling in vitro findings strongly warrant comprehensive in vivo efficacy and safety studies to fully establish SEOH’s potential as a novel therapeutic agent or feed additive for advancing aquaculture sustainability and animal health. Key points • Novel Spirostenoid Discovery: SEOH, a new spirostenoid from Streptomyces zaomyceticus, was identified • Potent Broad-Spectrum Activity: It shows strong inhibition against MDR aquaculture pathogens (MICs = 1.0 µg/mL) • Warrants Further Study: Its promising safety profile and potency merit in vivo testing for aquaculture use

A polyphasic study was undertaken to establish the taxonomic status of Streptomyces strains isolated from hyper-arid Atacama Desert soils. Analysis of the 16S rRNA gene sequences of the isolates showed that they formed a well-defined lineage that was loosely associated with the type strains of several Streptomyces species. Multi-locus sequence analysis based on five housekeeping gene alleles showed that the strains form a homogeneous taxon that is closely related to the type strains of Streptomyces ghanaensis and Streptomyces viridosporus . Representative isolates were shown to have chemotaxonomic and morphological properties consistent with their classification in the genus Streptomyces. The isolates have many phenotypic features in common, some of which distinguish them from S. ghanaensis NRRL B-12104 T , their near phylogenetic neighbour. On the basis of these genotypic and phenotypic data it is proposed that the isolates be recognised as a new species within the genus Streptomyces , named Streptomyces asenjonii sp. nov. The type strain of the species is KNN35.1b T (NCIMB 15082 T  = NRRL B-65050 T ). Some of the isolates, including the type strain, showed antibacterial activity in standard plug assays. In addition, MLSA, average nucleotide identity and phenotypic data show that the type strains of S. ghanaensis and S. viridosporus belong to the same species. Consequently, it is proposed that the former be recognised as a heterotypic synonym of the latter and an emended description is given for S. viridosporus .

Resorting to a One Strain Many Compounds (OSMAC) approach, the marine Streptomyces sp. BRB081 strain was grown in six different media settings over 1, 2, 3 or 7 days. Extractions of mycelium and broth were conducted separately for each media and cultivation period by sonication using methanol/acetone 1:1 and agitation with ethyl acetate, respectively. All methanol/acetone and ethyl acetate crude extracts were analysed by HPLC-MS/MS and data treatment was performed through GNPS platform using MZmine 2 software. In parallel, the genome was sequenced, assembled and mined to search for biosynthetic gene clusters (BGC) of secondary metabolites using the AntiSMASH 5.0 software. Spectral library search tool allowed the annotation of desferrioxamines, fatty acid amides, diketopiperazines, xanthurenic acid and, remarkably, the cyclic octapeptides surugamides. Molecular network analysis allowed the observation of the surugamides cluster, where surugamide A and the protonated molecule corresponding to the B-E isomers, as well as two potentially new analogues, were detected. Data treatment through MZmine 2 software allowed to distinguish that the largest amount of surugamides was obtained by cultivating BRB081 in SCB medium during 7 days and extraction of culture broth. Using the same data treatment, a chemical barcode was created for easy visualization and comparison of the metabolites produced overtime in all media. By genome mining of BRB081 four regions of biosynthetic gene clusters of secondary metabolites were detected supporting the metabolic data. Cytotoxic evaluation of all crude extracts using MTT assay revealed the highest bioactivity was also observed for extracts obtained in the optimal conditions as those for surugamides production, suggesting these to be the main active compounds herein. This method allowed the identification of compounds in the crude extracts and guided the selection of best conditions for production of bioactive compounds.

To meet the increasing demands of drug discovery and biosynthetic studies, we established a precise quantitative method based on flow cytometry at single-cell (protoplast) resolution in Streptomyces for the identification of regulatory elements. A series of native or synthetic promoters and ribosomal binding sites has been characterized. Moreover, an insulator was demonstrated to eliminate element–element interference. As a proof of concept, a native silent gene cluster was activated by the synthetic modular regulatory elements in a predictable manner. The universality of these elements is of high value to the synthetic biology of Streptomyces . There is a great demand for precisely quantitating the expression of genes of interest in synthetic and systems biotechnology as new and fascinating insights into the genetics of streptomycetes have come to light. Here, we developed, for the first time to our knowledge, a quantitative method based on flow cytometry and a superfolder green fluorescent protein (sfGFP) at single-cell resolution in Streptomyces . Single cells of filamentous bacteria were obtained by releasing the protoplasts from the mycelium, and the dead cells could be distinguished from the viable ones by propidium iodide (PI) staining. With this sophisticated quantitative method, some 200 native or synthetic promoters and 200 ribosomal binding sites (RBSs) were characterized in a high-throughput format. Furthermore, an insulator (RiboJ) was recruited to eliminate the interference between promoters and RBSs and improve the modularity of regulatory elements. Seven synthetic promoters with gradient strength were successfully applied in a proof-of-principle approach to activate and overproduce the cryptic lycopene in a predictable manner in Streptomyces avermitilis . Our work therefore presents a quantitative strategy and universal synthetic modular regulatory elements, which will facilitate the functional optimization of gene clusters and the drug discovery process in Streptomyces .

Actinobacteria from the unique intertidal ecosystem of the mangroves are known to produce novel, bioactive secondary metabolites. A novel strain known as MUSC 136 T (=DSM 100712 T  = MCCC 1K01246 T ) which was isolated from Malaysian mangrove forest soil has proven to be no exception. Assessed by a polyphasic approach, its taxonomy showed a range of phylogenetic and chemotaxonomic properties consistent with the genus of Streptomyces . Phylogenetically, highest similarity was to Streptomyces misionensis NBRC 13063 T (99.6%) along with two other strains (>98.9% sequence similarities). The DNA–DNA relatedness between MUSC 136 T and these type strains ranged from 22.7 ± 0.5% to 46.5 ± 0.2%. Overall, polyphasic approach studies indicated this strain represents a novel species, for which the name Streptomyces malaysiense sp. nov. is proposed. The potential bioactivities of this strain were explored by means of antioxidant and cytotoxic assays. Intriguingly, MUSC 136 T exhibited strong antioxidative activities as evaluated by a panel of antioxidant assays. It was also found to possess high cytotoxic effect against HCT-116 cells, which probably mediated through altering p53 protein and intracellular glutathione levels. Chemical analysis of the extract using GC-MS further affirms that the strain produces chemopreventive related metabolites.

The structure of lincomycin A consists of the unusual eight-carbon thiosugar core methyllincosamide (MTL) decorated with a pendent N-methylprolinyl moiety. Previous studies on MTL biosynthesis have suggested GDP-D-erythro-α-D-gluco-octose and GDP-D-α-D-lincosamide as key intermediates in the pathway. However, the enzyme-catalyzed reactions resulting in the conversion of GDP-D-erythro-α-D-gluco-octose to GDP-D-α-D-lincosamide have not yet been elucidated. Herein, a biosynthetic subpathway involving the activities of four enzymes—LmbM, LmbL, CcbZ, and CcbS (the LmbZ and LmbS equivalents in the closely related celesticetin pathway)—is reported. These enzymes catalyze the previously unknown biosynthetic steps including 6-epimerization, 6,8-dehydration, 4-epimerization, and 6-transamination that convert GDP-D-erythro-α-D-gluco-octose to GDP-D-α-D-lincosamide. Identification of these reactions completes the description of the entire lincomycin biosynthetic pathway. This work is significant since it not only resolves the missing link in octose core assembly of a thiosugar-containing natural product but also showcases the sophistication in catalytic logic of enzymes involved in carbohydrate transformations.