Streptomyces Research Articles

Novel Rapid In Vitro Method for Screening of Potato Genotypes Against Streptomyces sp.

Novel Rapid In Vitro Method for Screening of Potato Genotypes Against Streptomyces sp.

Nonenzymatic Sequestering of Formaldehyde into the Antibiotic Methylene-Bridged Dimer Phaeochromycin F by Streptomyces sp. OUCMDZ-4982 as a Possible Multipronged Chemical Defense Mechanism.

Metabolites with high chemical reactivity serve important roles in chemical defenses of organisms. Formaldehyde, as a simple and highly reactive small molecule, can be produced by microorganisms, plants, and animals. Its toxicity is well known, but information about its other biological functions remains scarce. Here, we report that the natural product SEK34b produced by Streptomyces species can react nonenzymatically with formaldehyde in water to yield the methylene-bridged dimer phaeochromycin F. This process can eliminate the toxic substance formaldehyde produced by Staphylococcus aureus. Furthermore, there is a substantial inhibitory impact of phaeochromycin F on S. aureus. We hypothesize that these constitute an integrated system of defense and attack of Streptomyces species against competitors. Our study indicates that formaldehyde can react with vancomycin and tigecycline under mild conditions to generate the derivatives bearing an imidazolidin-4-one moiety, thereby reducing the antibacterial activity of these antibiotics. These data provide a possible chemical interaction mechanism of bacteria involving the nonenzymatic reactions of formaldehyde with highly reactive natural products.

Ignored microbial-induced taste and odor in drinking water reservoirs: Novel insight into actinobacterial community structure, assembly, and odor-producing potential

The presence of actinobacteria in reservoirs can lead to taste and odor issues, posing potential risks to the safety of drinking water supply. However, the response of actinobacterial communities to environmental factors in drinking water reservoirs remains largely unexplored. To address this gap, this study investigated the community structure and metabolic characteristics of odor-producing actinobacteria in water reservoirs across northern and southern China. The findings revealed differences in the actinobacterial composition across the reservoirs, with Mycobacterium sp. and Candidatus Nanopelagicus being the most prevalent genera. Notably, water temperature, nutrient levels, and metal concentrations were associated with differences in actinobacterial communities, with stochastic processes playing a major role in shaping the community assembly. In addition, three strains of odor-producing actinobacteria were cultured in raw reservoir water, namely Streptomyces antibioticus LJH21, Streptomyces sp. ZEU13, and Streptomyces sp. PQK19, with peak ATP concentrations of 51 nmol/L, 66 nmol/L, and 70 nmol/L, respectively, indicating that odor-producing actinobacteria could remain metabolically active under poor nutrient pressure. Additionally, Streptomyces antibioticus LJH21 produced the highest concentration of geosmin at 24.4 ng/L. These findings enhance our understanding of regional variances and reproductive metabolic mechanisms of actinobacteria in drinking water reservoirs, providing a solid foundation for improving drinking water quality control, especially for taste and odor.

Apoptosis-inducing Metabolite from Marine Mangrove Actinobacteria VITGAP173.

Marine actinobacteria have proven to be a remarkable source of bioactive metabolites. The present study focused on the isolation of anticancer metabolites from marine actinobacteria. Streptomyces sp. VITGAP173 was found to have promising anticancer activity against breast cancer cell lines (MCF-7). Bioassay-guided fractionation was followed to identify the bioactive metabolites from crude ethyl acetate extract of VITGAP173, which yielded four fractions. Fraction B exhibited the highest cytotoxic activity against MCF-7 cell lines among the four fractions. Further structural characterization of the fraction was done by FTIR and NMR spectroscopy. The fraction-2 induced cytotoxicity against MCF-7 cell lines and the half maximal inhibition (IC50) value was calculated as 4.7 μg/ml. To elucidate the possible mechanism of cell death, MCF-7 cells were treated with fraction-2 for 24 hours and the morphological changes were examined using acridine orange - ethidium bromide (AO/EB) staining. The fraction also increased the reactive oxygen species (ROS) generation (Flow cytometry, DCFHDA). The molecular mechanism of fraction-induced cell death was analysed by real-time PCR, which revealed that the fraction promotes apoptosis through the CHOP-ATF-4 pathway involved in ER stress signalling. The present findings suggested the apoptosis-inducing potential of fraction-2 in breast cancer therapy.

Quinomycins with an unusual N-methyl-3-methylsulfinyl-alanine residue from a Streptomyces sp.

Four new echinomycin congeners, quinomycins M-P (1-4) were isolated from the cultures of the soil-derived Streptomyces sp. CPCC205575. The planar structures were determined by comprehensive analyses of NMR and HRESIMS/MS data. The absolute configurations were elucidated by the advanced Marfey's method combined with biosynthetic gene analysis. Compounds 1-4 represent the first examples of quinomycin-type natural products with the sulfur atom at the N,S-dimethylcysteine residue oxidized as a sulfoxide group forming the unusual N-methyl-3-methylsulfinyl-alanine residue. Bioassay results revealed that the oxidation of the sulfur atom at the Cys or Cys' residues led to dramatic decrease of cytotoxicity and antimicrobial activity.

Antibiofilm Efficacy and Mechanism of the Marine Chlorinated Indole Sesquiterpene Against Methicillin-Resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) can easily form biofilms on food surfaces, thus leading to cross-contamination, which is difficult to remove. Therefore, there is an urgent need to find alternatives with good antibacterial and antibiofilm effects. In this study, two indole sesquiterpene compounds, xiamycin (1) and chlorinated metabolite chloroxiamycin (2), were isolated from the fermentation liquid of marine Streptomyces sp. NBU3429 for the first time. The chemical structures of the two compounds were characterized by spectroscopic data interpretation, including 1D NMR and HRESIMS analysis. Antimicrobial test showed that chloroxiamycin (2) (minimum inhibitory concentration, MIC = 16 μg/mL) exhibited superior antibacterial activity than xiamycin (1) (MIC = 32 μg/mL) against MRSA ATCC43300. Moreover, compound (2) decreased the biofilm formation rate of MRSA ATCC43300 by 12.7%-84.6% in the concentration range of 32-512 μg/mL, which is relatively stronger than xiamycin (1) (4.1%-49.9%) as well. Antibacterial/antibiofilm mechanism investigation indicated that chloroxiamycin (2) could disrupt the cell wall and membrane of MRSA, inhibiting the production of biofilm extracellular polysaccharides. All these results illustrated that chloroxiamycin (2) is an effective antibacterial/antibiofilm agent, which makes it an attractive candidate for food preservatives.

Role of Carbon, Nitrogen, Phosphate and Sulfur Metabolism in Secondary Metabolism Precursor Supply in Streptomyces spp.

The natural soil environment of Streptomyces is characterized by variations in the availability of nitrogen, carbon, phosphate and sulfur, leading to complex primary and secondary metabolisms. Their remarkable ability to adapt to fluctuating nutrient conditions is possible through the utilization of a large amount of substrates by diverse intracellular and extracellular enzymes. Thus, Streptomyces fulfill an important ecological role in soil environments, metabolizing the remains of other organisms. In order to survive under changing conditions in their natural habitats, they have the possibility to fall back on specialized enzymes to utilize diverse nutrients and supply compounds from primary metabolism as precursors for secondary metabolite production. We aimed to summarize the knowledge on the C-, N-, P- and S-metabolisms in the genus Streptomyces as a source of building blocks for the production of antibiotics and other relevant compounds.

New secondary metabolites produced by an engineered strain Streptomyces sp. XZQH13OEΔastC

Two previously undescribed alkaloids (1–2), five known alkaloids (3–7) and five cyclodipeptides (8–12) were obtained from an ansatrienin-producing mutant strain Streptomyces sp. XZQH13OEΔ astC. Their structures were elucidated by analysis of the 1D, 2D NMR and ESI HRMS data and by comparison with the reported data. The antibacterial activities of compounds 1–12 were evaluated.

In Silico Analysis and Biochemical Characterization of Streptomyces PET Hydrolase with Bis(2-Hydroxyethyl) Terephthalate Biodegradation Activity.

Polyethylene terephthalate (PET), one of the most widely used plastics in the world, causes serious environmental problems. Recently, scientists have been focused on the enzymatic degradation of PET, an environmentally friendly method that offers an attractive approach to the degradation and recycling of PET. In this work, PET hydrolase from Streptomyces sp. W2061 was biochemically characterized, and the biodegradation of PET was performed using the PET model substrate bis (2- hydroxyethyl terephthalate) (BHET). PET hydrolase has an isoelectric point of 5.84, and a molecular mass of about 50.31 kDa. The optimum pH and temperature were 7.0 and 40°C, respectively. LC-MS analysis of the enzymatic products showed that the PET hydrolase successfully degraded a single ester bond of BHET, leading to the formation of MHET. Furthermore, in silico characterization of the PET hydrolase protein sequence and its predicted three-dimensional structure was designed and compared with the well-characterized IsPETase from Ideonella sakaiensis. The structural analysis showed that the (Gly-x1-Ser-x2-Gly) serine hydrolase motif and the catalytic triad (Ser, Asp, and His) were conserved in all sequences. In addition, we integrated molecular dynamics (MD) simulations to analyze the variation in the structural stability of the PET hydrolase in the absence and presence of BHET. These simulations showed the formation of a stable complex between the PET hydrolase and BHET. To the best of our knowledge, this is the first study on Streptomyces sp. W2061 to investigate the BHET degradation activity of PET hydrolase, which has potential application in the biodegradation of plastics in the environment.

Two‐Step Biocatalytic Synthesis of (1S)‐Nor(pseudo)ephedrine Catalyzed by Immobilized Enzymes

AbstractNor(pseudo)ephedrines [N(P)Es] are naturally occurring compounds showing sympathomimetic activity that have many applications especially in the chemical industry and in the pharmaceutical field. Recently a two‐step biocatalytic cascade for the preparation of (1S)‐N(P)E was designed, consisting of a benzoin‐type condensation catalyzed by the (S)‐selective acetoin:dichlorophenolindophenol oxidoreductase (Ao : DCPIP OR) followed by a transamination mediated by either a (S)‐ or (R)‐selective amine transaminase (ATA). In this study, we successfully immobilized both Ao : DCPIP OR and two ATAs of opposite enantioselectivity and used them in the biosynthetic cascade to N(P)Es. Immobilization yield, activity recovery, and stability of the immobilized enzymes, both after use (enzyme recycling) and storage (shelf‐life), were assessed. Ao : DCPIP OR immobilized on glyoxyl‐agarose exhibited remarkable stability under storage conditions throughout the 30‐days monitoring period. Moreover, it was successfully reused in the synthesis of (S)‐phenylacetylcarbinol [(S)‐PAC] yielding high conversion (>94 %) and enantiomeric excess (>99 %). The (R)‐selective At‐ATA from Aspergillus terreus, immobilized on Eupergit® C, demonstrated a slightly higher storage stability when compared to the (S)‐selective Sbv333‐ATA from Streptomyces sp. Bv333 immobilized on the same carrier. Remarkably, both enzymes were effectively reused for ten reaction cycles in the synthesis of N(P)Es, starting from the enzymatically synthesized (S)‐PAC, achieving complete conversions and excellent diastereoselectivity (>99 %).

Bioactive Naphthoquinone and Phenazine Analogs from the Endophytic Streptomyces sp. PH9030 as α-Glucosidase Inhibitors.

A talented endophytic Streptomyces sp. PH9030 is derived from the medicinal plant Kadsura coccinea (Lem.) A.C. Smith. The undescribed naphthoquinone naphthgeranine G (5) and seven previously identified compounds, 6-12, were obtained from Streptomyces sp. PH9030. The structure of 5 was identified by comprehensive examination of its HRESIMS, 1D NMR, 2D NMR and ECD data. The inhibitory activities of all the compounds toward α-glucosidase and their antibacterial properties were investigated. The α-glucosidase inhibitory activities of 5, 6, 7 and 9 were reported for the first time, with IC50 values ranging from 66.4 ± 6.7 to 185.9 ± 0.2 μM, as compared with acarbose (IC50 = 671.5 ± 0.2 μM). The molecular docking and molecular dynamics analysis of 5 with α-glucosidase further indicated that it may have a good binding ability with α-glucosidase. Both 9 and 12 exhibited moderate antibacterial activity against methicillin-resistant Staphylococcus aureus, with minimum inhibitory concentration (MIC) values of 16 μg/mL. These results indicate that 5, together with the naphthoquinone scaffold, has the potential to be further developed as a possible inhibitor of α-glucosidase.

Enhanced inhibitory efficiency against toxic bloom forming Raphidiopsis raciborskii by Streptomyces sp. HY through triple algicidal modes: Direct and indirect attacks combined with bioflocculation

Raphidiopsis raciborskii (R. raciborskii) forms harmful cyanobacterial blooms globally, and poses a great threat to the safety of drinking water and public health. There is a great need to develop eco-friendly biological alternative measures to mitigate mass blooms of R. raciborskii. However, previous rare studies on algicidal microorganisms against R. raciborskii restricted this aim. Recently, an algicidal bacterium Streptomyces sp. HY (designated HY) was identified with flavones producing ability, and could remove up to 98.73 % of R. raciborskii biomass within 48 h by directly attacking the cyanobacterium and release of algicidal substances (i.e., flavonoids) with a inoculum ratio of 5 %. Algicidal rate of HY was enhanced by 88.05 %, 89.33 % under dark and light, and full-light conditions respectively, when compared with the dark condition. Its algicidal substances were stable in a broad range of temperature (−80–55 °C) and pH (3−11) conditions, and all treated groups exhibited ≈ 100 % algicidal rate at day 3. HY treatment disrupted the photosynthesis system and triggered serious oxidative stress resulting in severe morphological injury. Thereby, HY treatment significantly affected expression levels of several essential genes (i.e., psbA, psaB, rbcL, ftsZ, recA, grpE), and simultaneously inhibited the biosynthesis and release of cylindrospermopsin. Yet, HY treatment didn’t show any toxicity to zebrafish test embryos. Such results indicate that HY is a promising algicidal candidate strain to control global R. raciborskii blooms, and holds great promises for an effective biological measure to sustain water safety.

Whole-genome sequence of Streptomyces sp. F41, a potent insecticidal Streptomyces isolated from soil in Sichuan, China.

Streptomyces sp. F41 is a potent insecticidal metabolite producing actinomycetes isolated from the topsoil, and the complete genome sequence was determined. The genome consists of 8,343,496 bp, with 7,221 genes and a GC content of 71.84%.

Atroposelective Synthesis of Axial Biaryls by Dynamic Kinetic Resolution Using Engineered Imine Reductases.

Axially chiral biaryl compounds are ubiquitous scaffolds in natural products, bioactive molecules, chiral ligands and catalysts, but biocatalytic methods for their asymmetric synthesis are limited. Herein, we report a highly efficient biocatalytic route for the atroposelective synthesis of biaryls by dynamic kinetic resolution (DKR). This DKR approach features a transient six-membered aza-acetal-bridge-promoted racemization followed by an imine reductase (IRED)-catalyzed stereoselective reduction to construct the axial chirality under ambient conditions. Directed evolution of an IRED from Streptomyces sp. GF3546 provided a variant (S-IRED-Ss-M11) capable of catalyzing the DKR process to access a variety of biaryl aminoalcohols in high yields and excellent enantioselectivities (up to 98 % yield and >99 : 1 enantiomeric ratio). Molecular dynamics simulation studies on the S-IRED-Ss-M11 variant revealed the origin of its improved activity and atroposelectivity. By exploiting the substrate promiscuity of IREDs and the power of directed evolution, our work further extends the biocatalysts' toolbox to construct challenging axially chiral molecules.

Indolizidines from Actinomycetes: An Overview of Producers, Biosynthesis and Bioactivities.

Indolizidines have long been recognized for their valuable bioactivities, their common feature being a bicyclic structure connected via a nitrogen atom. Traditionally, plants have been identified as the primary producers. However, recent discoveries have revealed that certain bacterial strains belonging to the genus of actinomycetes also possess the ability to synthesize various indolizidine-based compounds. Among these strains, Streptomyces sp. HNA39, Saccharopolyspora sp. RL78, and Streptomyces NCIB 11649 have been identified as producers of cyclizidines, characterized by their distinctive cyclopropyl moiety. Additionally, Streptomyces griseus OS-3601 synthesizes a unique class of indolizidine derivatives known as iminimycins, distinguished by their rare imine-cation structure. Protoplast fusion of a Streptomyces griseus strain with Streptomyces tenjimariensis resulted in a new indolizidine named indolizomycin. This review aims to provide an overview of known bacterial indolizidine producers, summarize current knowledge regarding the biosynthesis of cyclizidines and iminimycins, and assess their respective bioactivities.

Antibiofilm Metabolites from Marine-Derived Streptomyces sp. ZS-A31.

A novel compound streptothiomycin F (1), and a new natural product, N-(5-nitropentyl)acetamide (2), were discovered alongside ten previously identified compounds (3-12) through solid fermentation of marine-derived Streptomyces sp. ZS-A31 based on rice. The chemical structures of compounds 1-2 were elucidated using 1D and 2D NMR, as well as HRESIMS data analysis. Evaluation of all isolated compounds for their antibiofilm and antibacterial activities against P. aeruginosa was carried out using microdilution and crystal violet staining methods. Results highlighted the weak potency of the known compounds lumichrome (3) and vanillic acid (7) in inhibiting biofilm formation.

Antibacterial activity and biosynthetic potential of Streptomyces sp. PBR19, isolated from forest rhizosphere soil of Assam.

An Actinomycetia isolate, designated as PBR19, was derived from the rhizosphere soil of Pobitora Wildlife Sanctuary (PWS), Assam, India. The isolate, identified as Streptomyces sp., shares a sequence similarity of 93.96% with its nearest type strain, Streptomyces atrovirens. This finding indicates the potential classification of PBR19 as a new taxon within the Actinomycetota phylum. PBR19 displayed notable antibacterial action against some ESKAPE pathogens. The ethyl acetate extract of PBR19 (EtAc-PBR19) showed the lowest minimum inhibitory concentration (MIC) of ≥ 0.195µg/mL against Acinetobacter baumannii ATCC BAA-1705. A lower MIC indicates higher potency against the tested pathogen. Scanning electron microscope (SEM) findings revealed significant changes in the cytoplasmic membrane structure of the pathogen. This suggests that the antibacterial activity may be linked to the disruption of the microbial membrane. The predominant chemical compound detected in the EtAc-PBR19 was identified as phenol, 3,5-bis(1,1-dimethylethyl), comprising 48.59% of the area percentage. Additionally, PBR19 was found to contain the type II polyketide synthases (PKS type II) gene associated with antibiotic synthesis. The predicted gene product of PKSII was identified as the macrolide antibiotic Megalomicin A. The taxonomic distinctiveness, potent antibacterial effects, and the presence of a gene associated with antibiotic synthesis suggest that PBR19 could be a valuable candidate for further exploration in drug development and synthetic biology. The study contributes to the broader understanding of microbial diversity and the potential for discovering bioactive compounds in less-explored environments.

Australian Marine and Terrestrial Streptomyces-Derived Surugamides, and Synthetic Analogs, and Their Ability to Inhibit Dirofilaria immitis (Heartworm) Motility.

A bioassay-guided chemical investigation of a bacterium, Streptomyces sp. CMB-MRB032, isolated from sheep feces collected near Bathurst, Victoria, Australia, yielded the known polyketide antimycins A4a (1) and A2a (2) as potent inhibitors of Dirofilaria immitis (heartworm) microfilaria (mf) motility (EC50 0.0013-0.0021 µg/mL), along with the octapeptide surugamide A (3) and the new N-methylated analog surugamide K (4). With biological data suggesting surugamides may also exhibit activity against D. immitis, a GNPS molecular network analysis of a library of microbes sourced from geographically diverse Australian ecosystems identified a further five taxonomically and chemically distinct surugamide producers. Scaled-up cultivation of one such producer, Streptomyces sp. CMB-M0112 isolated from a marine sediment collected at Shorncliff, Qld, Australia, yielded 3 along with the new acyl-surugamides A1-A4 (5-8). Solid-phase peptide synthesis provided additional synthetic analogs, surugamides S1-S3 (9-11), while derivatization of 3 returned the semi-synthetic surugamide S4 (12) and acyl-surugamides AS1-AS3 (13-15). The natural acyl-surugamide A3 (7) and semi-synthetic acyl-surugamide AS3 (15) were shown to selectively inhibit D. immitis mf motility (EC50 3.3-3.4 µg/mL), however, unlike antimycins 1 and 2, were inactive against the gastrointestinal nematode Haemonchus contortus L1-L3 larvae (EC50 > 25 µg/mL) and were not cytotoxic to mammalian cells (human colorectal carcinoma SW620, IC50 > 30 µg/mL). A structure-activity relationship (SAR) study on the surugamides 3-15 revealed that selective acylation of the Lys3-ε-NH2 correlates with anthelmintic activity.

Study on the biocontrol effect of Streptomyces sp. NEAU-KT41 and its cell-free culture filtrate against wheat root rot

Wheat root rot, caused by Bipolaris sorokiniana, is a significant and extensive soilborne disease. Streptomyces sp. NEAU-KT41 was isolated from healthy wheat root soil and possessed strong antifungal activity against B. sorokiniana. Findings from the pot test indicated that strain NEAU-KT41 (108 CFU/mL) and its 10 % cell-free culture filtrate had significant biocontrol efficiency against wheat root rot, with 66.67 % and 64.4 %, respectively, resulting in significant increases in biomass and chlorophyll content. For 108 CFU/mL spore suspension, the plant height increased by 167.52 %; root length by 141.64 %, fresh weight by 65 %, chlorophyll a by 13.43 %, and chlorophyll b by 51.02 % under disease stress. For the 10 % cell-free culture filtrate, the plant height increased by 21.93 %, root length by 17.92 %, dry weight by 29.35 %, chlorophyll a by 17.92 %, and chlorophyll b by 82.15 % under disease stress. Moreover, strain NEAU-KT41 could produce proteases, amylases, lipases, and ACC deaminase, and had the ability to decompose organic phosphorus and fix nitrogen. The cell-free culture filtrate affected B. sorokiniana in several manners, including increasing the cell membrane permeability, diminishing the soluble protein content in the mycelia, impeding conidia germination and germ tube extension, and affecting B. sorokiniana invasion of plants. Briefly, Streptomyces sp. NEAU-KT41 is a prospective biocontrol agent that can be used to manage root rot in wheat and has potential applications.

Chromomycins from soil-derived Streptomyces sp. inhibit the growth of human non-small cell lung cancer cells by targeting c-FLIP

Three chromomycin derivatives, chromomycins A3 (1, CA3), A5 (2, CA5), and monodeacetylchromomycin A3 (3, MDA-CA3), were identified from the soil-derived Streptomyces sp. CGMCC 26516. A reinvestigation of the structure of CA5 is reported, of which the absolute configuration was unambiguously determined for the first time to be identical with that of CA3 based on nuclear magnetic resonance (NMR) data analysis as well as NMR and electronic circular dichroism calculations. Compounds 1–3 showed potent cytotoxicity against the non-small-cell lung cancer (NSCLC) cells (A549, H460, H157-c-FLIP, and H157-LacZ) and down-regulated the protein expression of c-FLIP in A549 cells. The IC50 values of chromomycins in H157-c-FLIP were higher than that in H157-LacZ. Furthermore, si-c-FLIP promoted anti-proliferation effect of chromomycins in NSCLC cells. In nude mice xenograft model, 1 and 2 both showed more potent inhibition on the growth of H157-lacZ xenografts than that of H157-c-FLIP xenografts. These results verify that c-FLIP mediates the anticancer effects of chromomycins in NSCLC.