Biosynthesis of the nucleoside antibiotic angustmycins: identification and characterization of the biosynthetic gene cluster reveal unprecedented dehydratase required for exo-glycal formation.

The nucleoside antibiotic angustmycin, produced by some Streptomyces strains, is composed of adenine and C6 sugar and shows antibiotic and antitumor activities. In this study, we propose a biosynthetic pathway for angustmycin using a heterologous expression experiment coupled with in silico analysis of the angustmycin biosynthetic gene (agm) cluster. The biochemical characterization of Agm6 demonstrated its role in angustmycin biosynthesis as an unprecedented dehydratase.

Androgen receptor antagonists produced by Streptomyces overcome resistance to enzalutamide.

Prostate cancer (PC) is a leading cause of cancer-related death in men in Western countries. Androgen receptor (AR) signaling is a major driver of PC; therefore, androgen deprivation by medical and surgical castration is the standard treatment for patients with PC. However, over time, most patients will progress to metastatic castration-resistant PC. Enzalutamide is the only AR antagonist approved by the Food and Drug Administration for the treatment of metastatic castration-resistant PC. However, resistance to enzalutamide also develops in most patients with castration-resistant PC. Thus, there is an urgent need to develop new AR antagonists with new structures. For this purpose, we conducted both in silico and natural product screenings. From the in silico screening, we obtained T5853872 and more potent compound, STK765173. From the natural product screening, the novel compound arabilin was isolated from Streptomyces sp. MK756-CF1. Unlike STK765173, arabilin could overcome resistance to enzalutamide. Furthermore, we also extracted a novel compound, antarlide A, and its geometric isomers from Streptomyces sp. BB47. Antarlides A-F have novel 22-membered-ring macrocyclic structures, while antarlides G and H have 20-membered-ring structures. Both antarlides B and G showed potent AR antagonist activity in prostate cancer cells and could overcome resistance to enzalutamide.

Genetic analysis of Streptomyces albus J1074 mia mutants suggests complex relationships between post-transcriptional tRNAXXA modifications and physiological traits.

Proteins MiaA and MiaB catalyze sequential isopentenylation and methylthiolation, respectively, of adenosine residue in 37th position of tRNAXXA. The mia mutations were recently shown by us to affect secondary metabolism and morphology of Streptomyces. However, it remained unknown as to whether both or one of the aforementioned modifications is critical for colony development and antibiotic production. Here, we addressed this issue through analysis of Streptomyces albus J1074 strains carrying double miaAmiaB knockout or extra copy of miaB gene. The double mutant differed from wild-type and miaA-minus strains in severity of morphological defects, growth dynamics, and secondary metabolism. Introduction of extra copy of miaB gene into miaA mutant restored aerial mycelium formation to the latter on certain solid media. Hence, miaB gene might be involved in tRNA thiomethylation in the absence of miaA; either MiaA- or MiaB-mediated modification appears to be enough to support normal metabolic and morphological processes in Streptomyces.

Actividad antimicrobiana de Streptomyces sp. 6E3 aislado de concentrado de mineral* / Streptomyces sp. 6E3 antimicrobial activity isolated from mineral concentrate

RESUMEN El objetivo de este estudio fue determinar la actividad antimicrobiana de un cultivo de Streptomyces sp. 6E3 aislado de minerales frente a diferentes cepas patógenas, producir un extracto y estimar la concen tración mínima inhibitoria (CMI) de las fracciones contra Staphylococcus aureus resistente a meticilina (SARM). La cepa Streptomyces sp. 6E3 mostró actividad antimicrobiana principalmente contra Staphy lococcus aureus (S. aureus). Cinco de las seis fracciones presentaron actividad antimicrobiana y la más efectiva dio una CMI de 0,88 ug/mL frente a S. aureus ATCC 33862, 0,44 ug/mL frente a S. aureus ATCC 43300 y 1,76 ug/mL frente a S. aureus cepa SARM. Streptomyces sp. 6E3 tiene un potencial antimicrobiano frente a cepas de S. aureus resistentes a meticilina y no resistentes, siendo de interés la realización de más estudios sobre sus metabolitos activos.

ABSTRACT The objectives of this study were to determine the antimicrobial activity of a culture of Streptomyces sp. 6E3 isolated from minerals against different pathogenic strains, to produce an extract and to estimate the minimum inhibitory concentration (MIC) of the fractions against methicillin-resistant Staphylococ cus aureus (MRSA). Streptomyces sp. 6E3 showed antimicrobial activity primarily against Staphylococcus aureus (S. aureus). Five of the six fractions presented antimicrobial activity and the most effective gave a MIC of 0.88 ug / mL against S. aureus ATCC 33862, 0.44 ug / mL against S. aureus ATCC 43300 and 1.76 ug / mL vs. a S. aureus MRSA strain. Streptomyces sp. 6E3 has an antimicrobial potential against S. aureus strains resistant to methicillin and non-resistant, being of interest carrying out of more studies on its active metabolites.

Development and Evaluation of Antimicrobial and Modulatory Activity of Inclusion Complex of Euterpe oleracea Mart Oil and ß-Cyclodextrin or HP-ß-Cyclodextrin.

The development of inclusion complexes is used to encapsulate nonpolar compounds and improve their physicochemical characteristics. This study aims to develop complexes made up of Euterpe oleracea Mart oil (EOO) and ß-cyclodextrin (ß-CD) or hydroxypropyl-ß-cyclodextrin (HP-ß-CD) by either kneading (KND) or slurry (SL). Complexes were analyzed by molecular modeling, Fourier-transform infrared spectroscopy, scanning electron microscopy, powder X-ray diffraction, thermogravimetry analysis and differential scanning calorimetry. The antibacterial activity was expressed as Minimum Inhibitory Concentration (MIC), and the antibiotic resistance modulatory activity as subinhibitory concentration (MIC/8) against Escherichia coli, Streptomyces aureus, Pseudomonas aeruginosa and Enterococcus faecalis. Inclusion complexes with ß-CD and HP-ß-CD were confirmed, and efficiency was proven by an interaction energy between oleic acid and ß-CD of -41.28 ± 0.57 kJ/mol. MIC values revealed higher antibacterial activity of complexes compared to the isolated oil. The modulatory response of EOO and EOO-ß-CD prepared by KND as well as of EOO-ß-CD and EOO-HP-ß-CD prepared by SL showed a synergistic effect with ampicillin against E. coli, whereas it was not significant with the other drugs tested, maintaining the biological response of antibiotics. The antimicrobial response exhibited by the complexes is of great significance because it subsidizes studies for the development of new pharmaceutical forms.

Three putative DNA replication/repair elements encoding genes confer self-resistance to distamycin in Streptomyces netropsis.

Distamycin (DST) is a well-characterized DNA minor groove binder with antivirus activity and antitumor potency. Two separate gene clusters (a 28-kb cluster and a 7-kb cluster) have recently been identified to coordinately encode the biosynthetic machinery of DST in Streptomyces netropsis. Here we report a gene cassette, which is linked to the aforementioned smaller dst gene cluster and plays an important role in the self-resistance to DST in S. netropsis. This cassette consists of three uncharacterized genes that might be implicated in DNA replication/repair. Knockout of the cassette led to the decrease in the production of DST, while heterologous expression of part of the cassette in S. lividans made it become resistant to both DST and mitomycin C, another DNA-binding agent. More interestingly, homologs of these three genes were found in genomes of other actinomyces that produce DNA-binding antibiotics, suggesting that a novel common mechanism in addition to pumping may enable these strains to resist the cytotoxic metabolites they produced.

Synthesis, antimicrobial and antiproliferative properties of epi-oligomycin A, the (33S)-diastereomer of oligomycin A.

We describe the synthesis of epi-oligomycin A, a (33S)-diastereomer of the antibiotic oligomycin A. The structure of (33S)-oligomycin A was determined by elemental analysis, spectroscopic studies, including 1D and 2D NMR spectroscopy, and mass spectrometry. Isomerization of C33 hydroxyl group led to minor changes in the potency against Aspergillus niger, Candida spp., and filamentous fungi whereas the activity against Streptomyces fradiae decreased by approximately 20-fold compared to oligomycin A. We observed that 33-epi-oligomycin A had the same activity on the human leukemia cell line K562 as oligomycin A but was more potent for the multidrug resistant subline K562/4. Non-malignant cells were less sensitive to both oligomycin isomers. Finally, our results pointed at the dependence of the cytotoxicity of oligomycins on oxygen supply.

Antioxidative, protein kinase inhibition and antibacterial potential of seven mango varieties cultivated in Pakistan.

Peel, pulp and kernel extracts of seven mango fruit (varieties) were analyzedsubjected for antibacterial and antioxidative potential. Langra peel showed good activity against B. subtilis, S. aureus and E. aerogenes. Good zone of inhibition by chaunsa kernel (28mm) and pulp (22mm) against Streptomyces stipulate its potential as anticarcinogencancerous. Dosehri and almashil pulp and sindhri peel asserted free radical scavenger (upto 79%) determined through DPPH assay. The peel and kernel of almashil contained maximum (total) flavonoids contents (58 & 43µgQE/100mg, respectively) while; total phenolics were higher in kernel of sindhri, chaunsa, langra and hujra and almashil pulp. Reducing power potential demonstrated variation from 300 to 554µgAAE/100mg. Total antioxidant potential was maximum in hujra pulp (512µg AAE/100mg). Concluded This study concludes that mango has vast beneficial potential for prone to human health and may also be used for isolation of antioxidative and antimicrobial as well as a protein kinase inhibition agent.

Identification of BMI1 promoter inhibitors from Streptomyces sp. IFM-11958.

B-cell-specific Moloney murine leukemia virus region 1 (BMI1) is a central component of polycomb repressive complex 1 (PRC1), which maintains epigenetic repression of genes expression via chromatin condensation. BMI1 overexpression downregulates the expression of tumor suppressor genes, such as p16Ink4a and PTEN. BMI1 expression is upregulated in cancer stem cells (CSCs). Therefore, inhibitors of BMI1 expression have potential as therapeutic agents for cancer. This study aimed to identify BMI1 promoter inhibitors from actinomycetes. Using a recently constructed BMI1 promoter assay, we isolated three known compounds, elaiophylin (1), 2-methylelaiophylin (2), and nocardamin (3), from Streptomyces sp. IFM-11958 that inhibited BMI1 promoter activity with IC50 values of 30 nM, 447 nM, 22 µM, respectively. Elaiophylin (1) was the most potent. Western blot and PCR analyses revealed that elaiophylin (1) inhibited BMI1 expression at the mRNA level in human prostate cancer cells (DU145). Elaiophylin (1) also inhibited the sphere-forming activity of human hepatocellular carcinoma cells (Huh7), indicating that elaiophylin (1) suppresses the self-renewal capacity of CSCs. Elaiophylin (1) is the first BMI1 promoter inhibitor isolated from actinomycete metabolites.

Streptomycin-induced ribosome engineering complemented with fermentation optimization for enhanced production of 10-membered enediynes tiancimycin-A and tiancimycin-D.

Tiancimycins (TNMs) are a group of 10-membered anthraquinone-fused enediynes, newly discovered from Streptomyces sp. CB03234. Among them, TNM-A and TNM-D have exhibited excellent antitumor performances and could be exploited as very promising warheads for the development of anticancer antibody-drug conjugates (ADCs). However, their low titers, especially TNM-D, have severely limited following progress. Therefore, the streptomycin-induced ribosome engineering was adopted in this work for strain improvement of CB03234, and a TNMs high producer S. sp. CB03234-S with the K43N mutation at 30S ribosomal protein S12 was successfully screened out. Subsequent media optimization revealed the essential effects of iodide and copper ion on the production of TNMs, while the substitution of nitrogen source could evidently promote the accumulation of TNM-D, and the ratio of produced TNM-A and TNM-D was responsive to the change of carbon and nitrogen ratio in the medium. Further amelioration of the pH control in scaled up 25 L fermentation increased the average titers of TNM-A and TNM-D up to 13.7 ± 0.3 and 19.2 ± 0.4 mg/L, respectively. The achieved over 45-fold titer improvement of TNM-A, and 109-fold total titer improvement of TNM-A and TNM-D enabled the efficient purification of over 200 mg of each target molecule from 25 L fermentation. Our efforts have demonstrated a practical strategy for titer improvement of anthraquinone-fused enediynes and set up a solid base for the pilot scale production and preclinical studies of TNMs to expedite the future development of anticancer ADC drugs.

Antiproliferative, antioxidant and binding mechanism analysis of prodigiosin from newly isolated radio-resistant Streptomyces sp. strain WMA-LM31.

Streptomyces genus are filamentous Gram positive bacteria, of great intrest, producing biologically active compounds. Recent market and consumer curiosity in natural products have forced scientist and industry for the development of new products with therapeutic potential. This study focuses on evaluation of antioxidant and anticancerous properties of prodigiosin from radio-resistant Streptomyces sp. strain WMA-LM31. A molecular docking approach was adopted to understand theoretical binding mechanism and affinity for anticancer targets. A radio-resistant bacterium, labelled as strain WMA-LM31, was isolated from desert soil and screened for its radio-resistant potential and prodigiosin production. 16S rRNA gene sequencing showed that the bacterium clusters to genus Streptomyces and found resistant to ultraviolet radiation (dosage of 2 × 103 J/m2). Strain WMA-LM31 produced a red color pigment in tryptone glucose yeast (TGY) medium.The LC-MS analysis of the purified compound showed a molar mass of 324 [m/z]+ matched the chemical formula C20H25N3O, identified as prodigiosin. The compound showed strong antioxidant (62.51%) activities along with significant inhibitory action against oxidative damages to bovine serum albumin (BSA) and mice liver lipids in comparison to standard ascorbic acid. IC50 values of HepG2 and HeLa cell lines was found at 12.66 and 14.83 µg/mL of prodigiosin concentration, respectively. Furthermore, molecular docking was performed with two different cancers macromolecular targets: [2O2F (Bcl-2) and 1DI8 (CDK-2)], and BSA (PDB id: 3V03). The results indicated that the binding affinity of prodigiosin to its target molecules is due to the presence of terminal pyrrole rings. It is concluded from the results that prodigiosin from Streptomyces sp. strain WMA-LM31 has strong antioxidant, anticancer and apoptotic properties. The knowledge of binding mechanisms and interactions of prodigiosin could provide future directions in designing potent target specifc drugs.

Synthesis and preclinical evaluation of bactericidal agent isolated from soil bacterium (Streptomyces): a novel diagnostic technique to enhance anticancer efficacy through radiosynthesis.

OBJECTIVES: Dactinomycin is a well-known antitumor-antibiotic drug isolated from soil bacterium Streptomyces, which exhibits broad-spectrum pharmacological and biochemical effects. In this study, dactinomycin was successfully labeled with technetium-99m for early diagnosis of bacterial infection and to discriminate it from acute inflammation. MATERIALS AND METHODS: Various labeling parameters such as pH, ligand concentration, reducing agent, and stabilizing agent were investigated. Radio-TLC technique was used to calculate percent radiochemical purity of radiopharmaceutical. Characterization studies were carried out using electrophoresis and radio-high-performance liquid chromatography techniques. Furthermore, saline and serum stability studies were performed to investigate biocompatibility. Biodistribution and scintigraphy studies were performed in infected and inflamed animal models to discriminate between bacterial infections (Escherichia coli and Staphylococcus aureus) and acute inflammations (heat-killed S. aureus). RESULTS: The results demonstrated that the highest radiochemical purity of at least 95% was achieved using 100-500 µg ligand and 3-8 µg SnCl2·2H2O as reducing agent at 4-9 pH. Technetium-99m-dactinomycin (Tc-DTN) was observed clearly bounded to the infection site having target/nontarget ratio 2.96±0.64 at 30 min after administration, which increased to 5.21±1.03 at 4 h after administration. Further accumulation was seen in heart, lungs, liver, stomach, kidneys, spleen, and intestine. An in-vitro cell-binding study was also performed, which showed high binding affinity of Tc-DTN with S. aureus-induced infectious lesions. CONCLUSION: Tc-DTN can easily be synthesized using standardized optimization conditions. The radiopharmaceutical has the highest accumulation potential at targeted site induced by S. aureus without any prominent in-vivo cytotoxicity. Tc-DTN may be used as a potential diagnostic agent to locate S. aureus-induced infection lesions at an early stage. Tc-DTN can successfully discriminate between infection and inflammatory models which cannot be achieved from other radiopharmaceuticals developed in the past few decades.

Antimicrobial and structural insights of a new snakin-like peptide isolated from Peltophorum dubium (Fabaceae).

Snakins are antimicrobial peptides (AMPs) found, so far, exclusively in plants, and known to be important in the defense against a wide range of pathogens. Like other plant AMPs, they contain several positively charged amino acids, and an even number of cysteine residues forming disulfide bridges which are considered important for their usual function. Despite its importance, studies on snakin tertiary structure and mode of action are still scarce. In this study, a new snakin-like gene was isolated from the native plant Peltophorum dubium, and its expression was verified in seedlings and adult leaves. The deduced peptide (PdSN1) shows 84% sequence identity with potato snakin-1 mature peptide, with the 12 cysteines characteristic from this peptide family at the GASA domain. The mature PdSN1 coding sequence was successfully expressed in Escherichia coli. The purified recombinant peptide inhibits the growth of important plant and human pathogens, like the economically relevant potato pathogen Streptomyces scabies and the opportunistic fungi Candida albicans and Aspergillus niger. Finally, homology and ab initio modeling techniques coupled to extensive molecular dynamics simulations were used to gain insight on the 3D structure of PdSN1, which exhibited a helix-turn-helix motif conserved in both native and recombinant peptides. We found this motif to be strongly coded in the sequence of PdSN1, as it is stable under different patterns of disulfide bonds connectivity, and even when the 12 cysteines are considered in their reduced form, explaining the previous experimental evidences.

Resistance to Enediyne Antitumor Antibiotics by Sequestration.

The enediynes, microbial natural products with extraordinary cytotoxicities, have been translated into clinical drugs. Two self-resistance mechanisms are known in the enediyne producers-apoproteins for the nine-membered enediynes and self-sacrifice proteins for the ten-membered enediyne calicheamicin. Here we show that: (1) tnmS1, tnmS2, and tnmS3 encode tiancimycin (TNM) resistance in its producer Streptomyces sp. CB03234, (2) tnmS1, tnmS2, and tnmS3 homologs are found in all anthraquinone-fused enediyne producers, (3) TnmS1, TnmS2, and TnmS3 share a similar ß barrel-like structure, bind TNMs with nanomolar KD values, and confer resistance by sequestration, and (4) TnmS1, TnmS2, and TnmS3 homologs are widespread in nature, including in the human microbiome. These findings unveil an unprecedented resistance mechanism for the enediynes. Mechanisms of self-resistance in producers serve as models to predict and combat future drug resistance in clinical settings. Enediyne-based chemotherapies should now consider the fact that the human microbiome harbors genes encoding enediyne resistance.

Development of an efficient conjugal DNA transfer system between Escherichia coli and a non-sporulating Streptomyces strain.

Bacterial conjugation is a powerful tool used for DNA transfer from Escherichia coli into various bacteria including streptomycetes. In this methodology, spores are usually employed as recipient cells of the genetic information. However, some industrially important Streptomyces do not produce spores making difficult their genetic manipulation. In these strains, the use of mechanically fragmented mycelia allows DNA transfer with low efficiency. Streptomyces peucetius var. caesius is a non-sporulating bacteria which produces the antitumor compound doxorubicin. The use of aerial mycelia of this microorganism, failed to get intergeneric conjugation with E. coli. In the present work, by using young aerial mycelia of this microorganism and an excess of E. coli cells (~7×108cellsmL-1) in soybean-mannitol medium (MS) supplemented with 20mMMgCl2 resulted in a high number of exconjugant colonies (5×10-4) when compared to other reports from this genus (1.1×10-5 to 2.5×10-8). The effectiveness of these conditions was confirmed by isolating null mutants of two different glucokinases from S. peucetius var. caesius. The novelty in using young aerial mycelia as receptor cells, allowed an efficient conjugative process and opened the way for genetic manipulation of additional non-spore forming actinobacteria exhibiting natural resistance to be genetically manipulated.

Polarity directed optimization of phytochemical and in vitro biological potential of an indigenous folklore: Quercus dilatata Lindl. ex Royle.

BACKGROUND: Plants have served either as a natural templates for the development of new chemicals or a phytomedicine since antiquity. Therefore, the present study was aimed to appraise the polarity directed antioxidant, cytotoxic, protein kinase inhibitory, antileishmanial and glucose modulatory attributes of a Himalayan medicinal plant- Quercus dilatata. METHODS: Total phenolic and flavonoid contents were determined colorimetrically and various polyphenols were identified by RP-HPLC analysis. Brine shrimp lethality, SRB and MTT assays were employed to test cytotoxicity against Artemia salina and human cancer cell lines respectively. Antileishmanial activity was determined using standard MTT protocol. Glucose modulation was assessed by α-amylase inhibition assay while disc diffusion assay was used to establish protein kinase inhibitory and antifungal spectrum. RESULTS: Among 14 extracts of aerial parts, distilled water-acetone extract demonstrated maximum extract recovery (10.52% w/w), phenolic content (21.37 ± 0.21 µg GAE/mg dry weight (DW)), total antioxidant capacity (4.81 ± 0.98 µg AAE/mg DW) and reducing power potential (20.03 ± 2.4 µg/mg DW). On the other hand, Distilled water extract proficiently extracted flavonoid content (4.78 ± 0.51 µg QE/mg DW). RP-HPLC analysis revealed the presence of significant amounts of phenolic metabolites (0.049 to 15.336 µg/mg extract) including, pyrocatechol, gallic acid, catechin, chlorogenic acid, p-coumaric acid, ferulic acid and quercetin. Highest free radical scavenging capacity was found in Methanol-Ethyl acetate extract (IC50 8.1 ± 0.5 µg/ml). In the brine shrimp toxicity assay, most of the tested extracts (57%) showed high cytotoxicity. Among these, Chloroform-Methanol extract had highest cytotoxicity against THP-1 cell line (IC50 3.88 ± 0.53 µg/ml). About 50% of the extracts were found to be moderately antiproliferative against Hep G2 cell line. Methanol extract exhibited considerable protein kinase inhibitory activity against Streptomyces 85E strain (28 ± 0.35 mm bald phenotype at 100 µg/disc; MIC = 12.5 µg/ disc) while, Chloroform extract displayed maximum antidiabetic activity (α-amylase inhibition of 21.61 ± 1.53% at 200 µg/ml concentration). The highest antileishmanial potential was found in Ethyl acetate-Acetone extract (12.91 ± 0.02% at 100 µg/ml concentration), while, Q. dilatata extracts also showed a moderate antifungal activity. CONCLUSION: This study proposes that multiple-solvent system is a crucial variable to elucidate pharmacological potential of Q. dilatata and the results of the present findings prospects its potential as a resource for the discovery of novel anticancer, antidiabetic, antileishmanial and antioxidant agents.

DrrC protein of Streptomyces peucetius removes daunorubicin from intercalated dnrI promoter.

DrrC is a DNA-binding protein of Streptomyces peucetius that provides self-resistance against daunorubicin, the antibiotic produced by the organism. DrrC was expressed in E.coli and purified by using N-terminal MBP-tag which retained DNA-binding property in spite of the tag. Mobility shift assay confirmed the interaction of 313bp DNA that has the dnrI promoter, daunorubicin and MBP-DrrC in the presence of ATP. Biotinylated and immobilized 313bp DNA was intercalated with daunorubicin to observe the release of the drug when MBP-DrrC is allowed to act on the DNA. The release of daunorubicin was recorded by absorption and fluorescence spectroscopy. The experiments proved that daunorubicin was released from DNA in the presence of MBP-DrrC. Fluorescence emission of daunorubicin had a maximum peak at 591nm. However, emission spectrum of released daunorubicin showed hypochromism with a maximum peak at 584nm that is possibly because it is in complex with MBP-DrrC. We propose that DrrC naturally binds at intercalated sites to eject daunorubicin; in the process both drug and protein are dislodged from DNA. Like UvrA, DrrC possibly scans the DNA for intercalated daunorubicin. When it encounters daunorubicin, DrrC dislodges it, thereby allowing DNA replication and transcription to go on unhindered. Thus a novel self resistance mechanism by DNA repair is mediated by DrrC.

Streptomyces asenjonii sp. nov., isolated from hyper-arid Atacama Desert soils and emended description of Streptomyces viridosporus Pridham et al. 1958.

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-12104T, 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 KNN35.1bT (NCIMB 15082T = NRRL B-65050T). 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.

Ohmyungsamycins promote antimicrobial responses through autophagy activation via AMP-activated protein kinase pathway.

The induction of host cell autophagy by various autophagy inducers contributes to the antimicrobial host defense against Mycobacterium tuberculosis (Mtb), a major pathogenic strain that causes human tuberculosis. In this study, we present a role for the newly identified cyclic peptides ohmyungsamycins (OMS) A and B in the antimicrobial responses against Mtb infections by activating autophagy in murine bone marrow-derived macrophages (BMDMs). OMS robustly activated autophagy, which was essentially required for the colocalization of LC3 autophagosomes with bacterial phagosomes and antimicrobial responses against Mtb in BMDMs. Using a Drosophila melanogaster-Mycobacterium marinum infection model, we showed that OMS-A-induced autophagy contributed to the increased survival of infected flies and the limitation of bacterial load. We further showed that OMS triggered AMP-activated protein kinase (AMPK) activation, which was required for OMS-mediated phagosome maturation and antimicrobial responses against Mtb. Moreover, treating BMDMs with OMS led to dose-dependent inhibition of macrophage inflammatory responses, which was also dependent on AMPK activation. Collectively, these data show that OMS is a promising candidate for new anti-mycobacterial therapeutics by activating antibacterial autophagy via AMPK-dependent signaling and suppressing excessive inflammation during Mtb infections.

Revelation and cloning of valinomycin synthetase genes in Streptomyces lavendulae ACR-DA1 and their expression analysis under different fermentation and elicitation conditions.

Streptomyces species are amongst the most exploited microorganisms due to their ability to produce a plethora of secondary metabolites with bioactive potential, including several well known drugs. They are endowed with immense unexplored potential and substantial efforts are required for their isolation as well as characterization for their bioactive potential. Unexplored niches and extreme environments are host to diverse microbial species. In this study, we report Streptomyces lavendulae ACR-DA1, isolated from extreme cold deserts of the North Western Himalayas, which produces a macrolactone antibiotic, valinomycin. Valinomycin is a K+ ionophoric non-ribosomal cyclodepsipeptide with a broad range of bioactivities including antibacterial, antifungal, antiviral and cytotoxic/anticancer activities. Production of valinomycin by the strain S. lavendulae ACR-DA1 was studied under different fermentation conditions like fermentation medium, temperature and addition of biosynthetic precursors. Synthetic medium at 10°C in the presence of precursors i.e. valine and pyruvate showed enhanced valinomycin production. In order to assess the impact of various elicitors, expression of the two genes viz. vlm1 and vlm2 that encode components of heterodimeric valinomycin synthetase, was analyzed using RT-PCR and correlated with quantity of valinomycin using LC-MS/MS. Annelid, bacterial and yeast elicitors increased valinomycin production whereas addition of fungal and plant elicitors down regulated the biosynthetic genes and reduced valinomycin production. This study is also the first report of valinomycin biosynthesis by Streptomyces lavendulae.