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Streptomyces are a genus of ubiquitous soil bacteria from which the majority of clinically utilized antibiotics derive 1 . The production of these antibacterial molecules reflects the relentless competition Streptomyces engage in with other bacteria, including other Streptomyces species 1 , 2 . Here we show that in addition to small-molecule antibiotics, Streptomyces produce and secrete antibacterial protein complexes that feature a large, degenerate repeat-containing polymorphic toxin protein. A cryo-electron microscopy structure of these particles reveals an extended stalk topped by a ringed crown comprising the toxin repeats scaffolding five lectin-tipped spokes, which led us to name them umbrella particles. Streptomyces coelicolor encodes three umbrella particles with distinct toxin and lectin composition. Notably, supernatant containing these toxins specifically and potently inhibits the growth of select Streptomyces species from among a diverse collection of bacteria screened. For one target, Streptomyces griseus , inhibition relies on a single toxin and that intoxication manifests as rapid cessation of vegetative hyphal growth. Our data show that Streptomyces umbrella particles mediate competition among vegetative mycelia of related species, a function distinct from small-molecule antibiotics, which are produced at the onset of reproductive growth and act broadly 3 , 4 . Sequence analyses suggest that this role of umbrella particles extends beyond Streptomyces , as we identified umbrella loci in nearly 1,000 species across Actinobacteria. Streptomyces are discovered to produce antibacterial protein complexes that selectively inhibit the hyphal growth of related species, a function distinct from that of the small-molecule antibiotics they are known for.

Some of the most metabolically diverse species of bacteria (e.g., Actinobacteria) have higher GC content in their DNA, differ substantially in codon usage, and have distinct protein folding environments compared to tractable expression hosts like Escherichia coli . Consequentially, expressing biosynthetic gene clusters (BGCs) from these bacteria in E. coli often results in a myriad of unpredictable issues with regard to protein expression and folding, delaying the biochemical characterization of new natural products. Current strategies to achieve soluble, active expression of these enzymes in tractable hosts can be a lengthy trial-and-error process. Cell-free expression (CFE) has emerged as a valuable expression platform as a testbed for rapid prototyping expression parameters. Here, we use a type III polyketide synthase from Streptomyces griseus , RppA, which catalyzes the formation of the red pigment flaviolin, as a reporter to investigate BGC refactoring techniques. We applied a library of constructs with different combinations of promoters and rppA coding sequences to investigate the synergies between promoter and codon usage. Subsequently, we assess the utility of cell-free systems for prototyping these refactoring tactics prior to their implementation in cells. Overall, codon harmonization improves natural product synthesis more than traditional codon optimization across cell-free and cellular environments. More importantly, the choice of coding sequences and promoters impact protein expression synergistically, which should be considered for future efforts to use CFE for high-yield protein expression. The promoter strategy when applied to RppA was not completely correlated with that observed with GFP, indicating that different promoter strategies should be applied for different proteins. In vivo experiments suggest that there is correlation, but not complete alignment between expressing in cell free and in vivo. Refactoring promoters and/or coding sequences via CFE can be a valuable strategy to rapidly screen for catalytically functional production of enzymes from BCGs, which advances CFE as a tool for natural product research.

The LitR/CarH family comprises adenosyl B 12 -based photosensory transcriptional regulators that control light-inducible carotenoid production in nonphototrophic bacteria. In this study, we established a blue–green light-inducible hyperexpression system using LitR and its partner ECF-type sigma factor LitS in streptomycin-producing Streptomyces griseus NBRC 13350. The constructed multiple-copy number plasmid, pLit19, carried five genetic elements: pIJ101 rep , the thiostrepton resistance gene, litR , litS , and σ LitS -recognized light-inducible crtE promoter. Streptomyces griseus transformants harboring pLit19 exhibited a light-dependent hyper-production of intracellular reporter enzymes including catechol-2,3-dioxygenase and β-glucuronidase, extracellular secreted enzymes including laccase and transglutaminase, and secondary metabolites including melanin, flaviolin, and indigoidine. Cephamycin-producing Streptomyces sp. NBRC 13304, carrying an entire actinorhodin gene cluster, exhibited light-dependent actinorhodin production after the introduction of the pLit19 shuttle-type plasmid with the pathway-specific activator actII-ORF4 . Insertion of sti fragment derived from Streptomyces phaeochromogenes pJV1 plasmid into pLit19 increased its light sensitivity, allowing gene expression under weak light irradiation. The two constructed Escherichia coli–Streptomyces shuttle-type pLit19 plasmids were found to have abilities similar to those of pLit19. We successfully established an optogenetically controlled hyperproduction system for S. griseus NBRC 13350 and Streptomyces sp. NBRC 13304.

Polycyclic tetramate macrolactams (PTMs) are a widely distributed class of natural products with important biological activities. However, many of these PTMs have not been characterized. Here we apply a plug-and-play synthetic biology strategy to activate a cryptic PTM biosynthetic gene cluster SGR810-815 from Streptomyces griseus and discover three new PTMs. This gene cluster is highly conserved in phylogenetically diverse bacterial strains and contains an unusual hybrid polyketide synthase-nonribosomal peptide synthetase, which resembles iterative polyketide synthases known in fungi. To further characterize this gene cluster, we use the same synthetic biology approach to create a series of gene deletion constructs and elucidate the biosynthetic steps for the formation of the polycyclic system. The strategy we employ bypasses the traditional laborious processes to elicit gene cluster expression and should be generally applicable to many other silent or cryptic gene clusters for discovery and characterization of new natural products. Polycyclic tetramate macrolactams (PTMs) are natural products with important antifungal, antibiotic and antioxidant properties. Here, the authors apply a synthetic biology strategy to activate a cryptic PTM biosynthetic gene cluster from Streptomyces griseus and identify three putative PTMs.

Background Trypsin has many applications in food and pharmaceutical manufacturing. Although commercial trypsin is usually extracted from porcine pancreas, this source carries the risks of infectivity and immunogenicity. Microbial Streptomyces griseus trypsin (SGT) is a prime alternative because it possesses efficient hydrolysis activity without such risks. However, the remarkable hydrolysis efficiency of SGT causes autolysis, and five autolysis sites, R21, R32, K122, R153, and R201, were identified from its autolysate. Results The tbcf (K101A, R201V) mutant was screened by a directed selection approach for improved activity in flask culture (60.85 ± 3.42 U mL −1 , increased 1.5-fold). From the molecular dynamics simulation, in the K101A/R201V mutant the distance between the catalytical residues D102 and H57 was shortened to 6.5 Å vs 7.0 Å in the wild type, which afforded the improved specific activity of 1527.96 ± 62.81 U mg −1 . Furthermore, the production of trypsin was increased by 302.8% (689.47 ± 6.78 U mL −1 ) in a 3-L bioreactor, with co-overexpression of chaperones SSO2 and UBC1 in Pichia pastoris . Conclusions SGT protein could be a good source of trypsin for insulin production. As a result of the hydrolysates analysis and direct selection, the activity of the tbcf (K101A, R201V) mutant increased 1.5-fold. Furthermore, the production of trypsin was improved threefold by overexpressing chaperone protein in Pichia pastoris . Future studies should investigate the application of SGT to insulin and pharmaceutical manufacturing.

The present study aims to obtain manganese ferrite nanoparticles functionalized with chitosan (C-MNP) or ethylenediamine (E-MNP) by coprecipitation and polyol one-step methods, characterize their interaction with S. griseus demonstrating cell immobilization, and evaluate the antimicrobial activity of the free cell extracts obtained from immobilized S. griseus fermentation in the presence of different concentrations of MNP. The adsorption isotherms were analyzed mathematically using Langmuir and Freundlich models. The highest coefficient of determination (R 2 ) for the S. griseus cell adsorption isotherm with C-MNP was observed with a linear function of the Langmuir model. The adsorption isotherm of S. griseus cells with E-MNP was better fitted to the Freundlich model. Cell immobilization by adsorption on magnetic nanoparticles was demonstrated in both cases. Different concentrations of C-MNP and E-MNP were used in fermentations to prepare cell-free extracts with antifungal activity. The best results were obtained with E-MNP, with a 91.5% inhibition of radial fungal growth. Magnetic nanoparticles offer potential applications in different fields and easy biomass separation.

Abstract Despite their importance in the chemical industry, the significance of rare earths in biology has been largely overlooked. Here, it is reported that the rare earth, scandium (Sc), causes antibiotic overproduction by 2–25-fold when added at a low concentration (10–100 µM) to cultures of Streptomyces coelicolor A3(2) (actinorhodin producer), Streptomyces antibioticus (actinomycin producer), and Streptomyces griseus (streptomycin producer). Not just for enhancement of antibiotic production, scandium was also effective in activating the dormant ability to produce actinorhodin in Streptomyces lividans. The effects of scandium were exerted at the level of transcription of pathway-specific positive regulatory genes, as demonstrated by marked up-regulation of actII-ORF4 in S. coelicolor cells exposed to this element. The bacterial alarmone, guanosine 5′-diphosphate 3′-diphosphate, was essential for actinorhodin overproduction provoked by scandium.

Conventional refolding methods are associated with low yields due to misfolding and high aggregation rates or very dilute proteins. In this study, we describe the optimization of the conventional methods of reverse dilution and affinity chromatography for obtaining high yields of a cysteine rich recombinant glycoside hydrolase family 19 chitinase from Streptomyces griseus HUT6037 (SgChiC). SgChiC is a potential biocontrol agent and a reference enzyme in the study and development of chitinases for various applications. The overexpression of SgChiC was previously achieved by periplasmic localization from where it was extracted by osmotic shock and then purified by hydroxyapatite column chromatography. In the present study, the successful refolding and recovery of recombinant SgChiC (r-SgChiC) from inclusion bodies (IB) by reverse dilution and column chromatography methods is respectively described. Approximately 8 mg of r-SgChiC was obtained from each method with specific activities of 28 and 52 U/mg respectively. These yields are comparable to that obtained from a 1 L culture volume of the same protein isolated from the periplasmic space of E. coli BL21 (DE3) as described in previous studies. The higher yields obtained are attributed to the successful suppression of aggregation by a stepwise reduction of denaturant from high, to intermediate, and finally to low concentrations. These methods are straight forward, requiring the use of fewer refolding agents compared with previously described refolding methods. They can be applied to the refolding of other cysteine rich proteins expressed as inclusion bodies to obtain high yields of actively folded proteins. This is the first report on the recovery of actively folded SgChiC from inclusion bodies.

The name phenoxazinone synthase (PHS, 2-aminophenol:oxygen oxidoreductase, EC 1.10.3.4) is used for the enzyme catalysing the oxidative coupling of substituted o-aminophenols to produce phenoxazinones. This review reveals that the traditional classification of PHS conflicts with recent sequence-based information that shows its relationship with two distinct copper protein groups. Different PHS roles, namely spore pigmentation in Streptomyces antibioticus (phsA) and biosynthesis of the antibiotic grixazone in Streptomyces griseus subsp. griseus (GriF), indicate an example of convergent evolution. Here, we review the classification, distribution and roles of PHSs, comparing them with copper oxidases at genetic and structural levels and exploring their potential application in the production of new antibiotics.

Amino acid‐based surfactants are valuable compounds for cosmetic formulations. The chemical synthesis of acyl amino acids is conventionally performed by the Schotten–Baumann reaction using fatty acyl chlorides, but aminoacylases have also been investigated for use in biocatalytic synthesis with free fatty acids. Aminoacylases and their properties are diverse; they belong to different peptidase families and show differences in substrate specificity and biocatalytic potential. Bacterial aminoacylases capable of synthesis have been isolated from Burkholderia, Mycolicibacterium, and Streptomyces. Although several proteases and peptidases from S. griseus have been described, no aminoacylases from this species have been identified yet. In this study, we investigated two novel enzymes produced by S. griseus DSM 40236T. We identified and cloned the respective genes and recombinantly expressed an α‐aminoacylase (EC3.5.1.14), designated SgAA, and an ε‐lysine acylase (EC3.5.1.17), designated SgELA, in S. lividans TK23. The purified aminoacylase SgAA was biochemically characterized, focusing on its hydrolytic activity to determine temperature‐ and pH optima and stabilities. The aminoacylase could hydrolyze various acetyl amino acids at the Nα‐position with a broad specificity regarding the sidechain. Substrates with longer acyl chains, like lauroyl amino acids, were hydrolyzed to a lesser extent. Purified aminoacylase SgELA specific for the hydrolysis of Nε‐acetyl‐l‐lysine was unstable and lost its enzymatic activity upon storage for a longer period but could initially be characterized. The pH optimum of SgELA was pH 8.0. While synthesis of acyl amino acids was not observed with SgELA, SgAA catalyzed the synthesis of lauroyl‐methionine. Two novel aminoacylases were identified in Streptomyces griseus DSM 40236T. The genes for the putative aminoacylases, designated SgAA and SgELA, have been cloned for expression in Streptomyces lividans TK23. The resulting strains have been cultivated in bioreactors for recombinant expression, and the two aminoacylases have been purified and biochemically characterized. With SgAA, synthesis of lauroyl‐methionine was achieved.