Streptomyces Somaliensis Research Articles

First report on mycetoma in Turkana County-North-western Kenya.

Mycetoma is one of the six Neglected Tropical Diseases that are prevalent in Turkana County (northwest Kenya). The aim of the study was to estimate the prevalence of mycetoma in the county, as well as to describe the main causative agents involved in the disease using methods affordable locally. Based on the data collected by the team of cooperative medicine Cirugia en Turkana (Surgery in Turkana), a specific study for mycetoma was started during the 16th humanitarian medicine campaign in February 2019. Patients with suspected mycetoma were studied at the Lodwar County Referral Hospital (LCRH). After informing the patient and getting their consent, the lesions were examined and sampled (mainly by biopsy) and clinical data were recorded. Samples were washed in sterile saline solution and cut in fragments. Some of these were inoculated on Sabouraud Dextrose Agar, Malt Extract Agar, and diluted Nutrient Agar plates. One fragment of each sample was used for DNA extraction. The DNA and the rest of the fragments of samples were kept at -20°C. All cultures were incubated at room temperature at the LCRH laboratory. The DNA obtained from clinical samples was submitted to PCR amplification of the ITS-5.8S and the V4-V5 16S rRNA gene region, for the detection and identification of fungi and bacteria respectively. From February 2019 till February 2022, 60 patients were studied. Most of them were men (43, 74,1%) between 13 and 78 y.o. (mean age 37). Half of the patients were herdsmen but, among women 40% (6) were housewives and 26.7% (4) charcoal burners. Lesions were mainly located at the feet (87.9%) and most of the patients (54; 93.1%) reported discharge of grains in the exudate, being 27 (46.6%) yellow or pale colored and 19 (32.8%) of them dark grains. Culture of clinical samples yielded 35 fungal and bacterial putative causative agents. Culture and molecular methods allowed the identification of a total of 21 causative agents of mycetoma (39.6% of cases studied). Most of them (17) corresponded to fungi causing eumycetoma (80.9%) being the most prevalent the genus Madurella (7; 41.2%), with two species involved (M. mycetomatis and M. fahalii), followed by Aspergillus (2; 11.8%). Other minority genera detected were Cladosporium, Fusarium, Acremonium, Penicillium, and Trichophyton (5.9% each of them). Actinobacteria were detected in 19.1% of samples, but only Streptomyces somaliensis was identified as a known agent of mycetoma, the rest being actinobacteria not previously described as causative agents of the disease, such as Cellulosimicrobium cellulans detected in two of the patients. Although Kenya is geographically located in the mycetoma belt, to our knowledge this is the first report on mycetoma in this country from 1973, and the first one for Turkana County.

Genetic and Physiological Diversity of Marine Actinobacteria from the Okha Coast, Gujarat, India

Saline and alkaline habitats of the Okha coastline, Gujarat, India, were explored for the diversity of actinobacteria. Based on the phenotypic and genotypic heterogeneity, nine haloalkaliphilic actinobacterial strains were characterized and identified. The PCR amplification of 16S rDNA using universal and genus-specific primers corroborated the trends that emerged through cultural and physiological characterization. Streptomyces was the most abundant genus amplified with the Streptomyces-specific primers (StreptB/E, StreptB/F), whereas other actinobacterial strains were amplified by the universal primers U1 and U2. Further molecular diversity was investigated by the gradient PCR-DGGE as a fingerprinting tool that generated group-specific DGGE patterns. Based on the nucleotide homology and phylogenetic analysis, strains OK-1 and OK-2 were identified as Streptomyces somaliensis. At the same time, OK-3 and OK-7 were detected as Streptomyces sp., while OK-5, OK-6, OK-8, OK-9, and OK-10 belonged to Nocardiopsis alba. Further, the cluster analysis using the UPGMA method generated 3 clusters based on biochemical characterization, sugar utilization, and enzyme production. The dendrogram based on the DGGE band pattern created with Jaccard-distance revealed two major clades with 33.33% similarity. Further, the study of alpha diversity calculation using phenotypic characteristics discloses highly diverse sugar utilization abilities. Moreover, a stress value of 0.1236 was obtained based on the NMDS analysis of the plots using Bary-Curties dissimilarity. Overall, the distinct phenotypic, metabolic, and molecular profiling illustrated the diversity among marine actinobacteria.

Somalactams A-D: Anti-inflammatory Macrolide Lactams with Unique Ring Systems from an Arctic Actinomycete Strain.

Four new PKS-NRPS-derived macrolide lactams with three unique ring fusion types were discovered from the Arctic sponge associated actinomycete Streptomyces somaliensis 1107 using a genome mining strategy. Their structures were elucidated by a combination of MS, NMR spectroscopic analysis, and single-crystal X-ray diffraction. Biosynthetically, a novel gene cluster sml consisting of three polyketide synthases and one hybrid polyketide synthase-nonribosomal peptide synthetase together with cytochrome P450s and flavin-containing monooxygenases and oxidoreductases was demonstrated to assemble the unique skeleton. Pharmacological studies revealed that compound 1 displayed a potent anti-inflammatory effect without cytotoxicity. It inhibited IL-6 and TNF-α release in the serum of LPS-stimulated RAW264.7 macrophage cells with IC50 values of 5.76 and 0.18 μM, respectively, and modulated the MAPK pathway. Moreover, compound 1 alleviated LPS-induced systemic inflammation in our transgenic fluorescent zebrafish model.

Somalactams A–D: Anti‐inflammatory Macrolide Lactams with Unique Ring Systems from an Arctic Actinomycete Strain

AbstractFour new PKS‐NRPS‐derived macrolide lactams with three unique ring fusion types were discovered from the Arctic sponge associated actinomycete Streptomyces somaliensis 1107 using a genome mining strategy. Their structures were elucidated by a combination of MS, NMR spectroscopic analysis, and single‐crystal X‐ray diffraction. Biosynthetically, a novel gene cluster sml consisting of three polyketide synthases and one hybrid polyketide synthase‐nonribosomal peptide synthetase together with cytochrome P450s and flavin‐containing monooxygenases and oxidoreductases was demonstrated to assemble the unique skeleton. Pharmacological studies revealed that compound 1 displayed a potent anti‐inflammatory effect without cytotoxicity. It inhibited IL‐6 and TNF‐α release in the serum of LPS‐stimulated RAW264.7 macrophage cells with IC50 values of 5.76 and 0.18 μM, respectively, and modulated the MAPK pathway. Moreover, compound 1 alleviated LPS‐induced systemic inflammation in our transgenic fluorescent zebrafish model.

Head and neck mycetoma: Clinical findings, investigations, and predictors for recurrence of the disease in Sudan: A retrospective study.

IntroductionMycetoma is a unique neglected tropical disease which is found endemic in areas known as the “mycetoma belt”. Head and neck mycetoma is a rarity and it has many devastating impacts on patients and communities. In this study, we assessed clinical findings, investigations, and predictors for recurrence of head and neck mycetoma in Sudan.MethodologyA retrospective study was conducted at Mycetoma Research Center in Khartoum between January 1999 and December 2020 for all patients with head and neck mycetoma. Data were analyzed using R software version 4.0.2.ResultsWe included 107 patients with head and neck mycetoma. 65.4% were young adult males from mycetoma endemic areas in Sudan, and most of them were students (33.6%). Most of patients (64.4%) had actinomycetoma. Before presenting with head and neck mycetoma, majority (75.7%) had a long duration with mycetoma, and 30.8% had a history of trauma. The commonest invaded site was the parietal region (30.8%). The lesion started gradually in most of the patients (96.3%). 53.3% of the patients had large size lesions with no sweating, regional lymph nodes involvement, or distal vein involvement. CT scan was the most accurate diagnostic tool while 8.4% of patients were diagnosed by clinical examinations only. Laboratory investigations confirmed that 24/45 (44.4%) of actinomycetoma was caused by Streptomyces somaliensis while 13/28 (46.4%) of eumycetoma was caused by Madurella mycetomatis. All patients with recurrence of head and neck mycetoma underwent surgical excision of the lesion (n = 41/41 {100%}, p < 0.001).ConclusionIn head and neck mycetoma, the most common type was actinomycetes in Sudan. Majority had a long course of mycetoma and the commonest causative organism was Streptomyces somaliensis. The treatment outcome was poor and characterized by a low cure rate.

Systematic whole-genome sequencing reveals an unexpected diversity among actinomycetoma pathogens and provides insights into their antibacterial susceptibilities.

Mycetoma is a neglected tropical chronic granulomatous inflammatory disease of the skin and subcutaneous tissues. More than 70 species with a broad taxonomic diversity have been implicated as agents of mycetoma. Understanding the full range of causative organisms and their antibiotic sensitivity profiles are essential for the appropriate treatment of infections. The present study focuses on the analysis of full genome sequences and antibiotic inhibitory concentration profiles of actinomycetoma strains from patients seen at the Mycetoma Research Centre in Sudan with a view to developing rapid diagnostic tests. Seventeen pathogenic isolates obtained by surgical biopsies were sequenced using MinION and Illumina methods, and their antibiotic inhibitory concentration profiles determined. The results highlight an unexpected diversity of actinomycetoma causing pathogens, including three Streptomyces isolates assigned to species not previously associated with human actinomycetoma and one new Streptomyces species. Thus, current approaches for clinical and histopathological classification of mycetoma may need to be updated. The standard treatment for actinomycetoma is a combination of sulfamethoxazole/trimethoprim and amoxicillin/clavulanic acid. Most tested isolates had a high IC (inhibitory concentration) to sulfamethoxazole/trimethoprim or to amoxicillin alone. However, the addition of the β-lactamase inhibitor clavulanic acid to amoxicillin increased susceptibility, particularly for Streptomyces somaliensis and Streptomyces sudanensis. Actinomadura madurae isolates appear to have a particularly high IC under laboratory conditions, suggesting that alternative agents, such as amikacin, could be considered for more effective treatment. The results obtained will inform future diagnostic methods for the identification of actinomycetoma and treatment.

Mycetoma in north-western Yemen: Clinico-epidemiological and histopathological study.

Background Mycetoma is widespread in Yemen; however, there are only a few documented reports on the entity from this geographical area. Methods A prospective study of 184 cases of mycetoma (male 145 and female 39) from different regions of north-western Yemen was conducted between July 2000 and May 2014. Clinical profile was recorded in a standardized protocol. The diagnosis was based on clinical features, X-ray studies, examination of grains, and histopathology. Results Eumycetoma was diagnosed in 129, caused by Madurella mycetomatis in 124, Leptosphaeria senegalensis in one and pale grain fungus in four, whereas actinomycetoma occurred in 55, caused by Streptomyces somaliensis in 29, Actinomadura madurai in nine, Actinomadura pelletieri in one, and Nocardia in sixteen. Eumycetoma cases were treated with prolonged course of antifungal drugs, mostly ketoconazole, with itraconazole being used in four patients, along with excision or debulking. Results were better when antifungal drugs were given two to three months before surgery and in those who received itraconazole. Actinomycetoma cases were initially treated with co-trimoxazole monotherapy; later streptomycin was added in 30 cases. Six patients who did not show adequate improvement and two others from the start were treated with modified Welsh regimen and with good results. Limitations Identification of different causative agents was done by histopathology and could not be reconfirmed by culture. Conclusion Mycetoma is widespread in north-western Yemen with a higher incidence of eumycetoma and a majority of the cases were caused by Madurella mycetomatis. Modified Welsh regimen in actinomycetoma and itraconazole with excision in eumycetoma showed the best results.

Targeted isolation of new polycyclic tetramate macrolactams from the deepsea-derived Streptomyces somaliensis SCSIO ZH66.

With a combined strategy of bioinformatics analysis, gene manipulation coupled with variation of growth conditions, the targeted activation of polycyclic tetramate macrolactams (PTMs) in the deepsea-derived Streptomyces somaliensis SCSIO ZH66 was conducted, which afforded a new (1) PTM, named somamycin A, along with three enol-type tetramic acid tautomers (2-4, somamycins B-D) of 10-epi-hydroxymaltophilin, 10-epi-maltophilin and 10-epi-HSAF, respectively. The structures of compounds 1-4 were elucidated by extensive spectroscopic analyses together with ECD calculations. Compound 1 exhibited notable growth inhibition against plant pathogenic fungi Fusariumoxysporum MHKW and Alternariabrassicae BCHB with the MIC values of 1.6 and 3.1μg/mL, respectively, which were more potent than those of the positive control nystatin; and compounds 3 and 4 displayed moderate antifungal activities. Moreover, compounds 1-4 exhibited moderate cytotoxicity against the human cancer cell lines of HCT116 and K562.

The Accuracy of Histopathological and Cytopathological Techniques in the Identification of the Mycetoma Causative Agents

Mycetoma is a devastating neglected tropical disease, caused by various fungal and bacterial pathogens. Correct diagnosis to the species level is mandatory for proper treatment. In endemic areas, various diagnostic tests and techniques are in use to achieve that, and that includes grain culture, surgical biopsy histopathological examination, fine needle aspiration cytological (FNAC) examination and in certain centres molecular diagnosis such as PCR. In this retrospective study, the sensitivity, specificity and diagnostic accuracy of grain culture, surgical biopsy histopathological examination and FNAC to identify the mycetoma causative organisms were determined. The histopathological examination appeared to have better sensitivity and specificity. The histological examination results were correct in 714 (97.5%) out of 750 patients infected with Madurella mycetomatis, in 133 (93.6%) out of 142 patients infected with Streptomyces somaliensis, in 53 (74.6%) out of 71 patients infected with Actinomadura madurae and in 12 (75%) out of 16 patients infected with Actinomadura pelletierii. FNAC results were correct in 604 (80.5%) out of 750 patients with Madurella mycetomatis eumycetoma, in 50 (37.5%) out of 133 Streptomyces somaliensis patients, 43 (60.5%) out of 71 Actinomadura madurae patients and 11 (68.7%) out of 16 Actinomadura pelletierii. The mean time required to obtain the FNAC result was one day, and for the histopathological examinations results it was 3.5 days, and for grain it was a mean of 16 days. In conclusion, histopathological examination and FNAC are more practical techniques for rapid species identification than grain culture in many endemic regions.

Mycetoma: reviewing a neglected disease.

Mycetoma caused by either filamentous fungi (eumycotic) or bacteria (actinomycotic) has recently been recognized by the World Health Organization as a neglected tropical disease. Although mycetoma is preventable and treatable, especially in the early stages, it carries high morbidity and a huge socioeconomic burden. Skin and subcutaneous tissue is affected, with a classic presentation of hard woody swellings, discharging sinuses and presence of grains (containing the causative organism). Variants with swelling without sinuses have also been described. Left untreated it may involve underlying bone and muscle, leading to permanent disability. Common actinomycotic species include Streptomyces somaliensis, Actinomadura madurae, Actinomadura pelletieri, Nocardia brasiliensis and Nocardia asteroides, while Madurella mycetomatis, Madurella grisea, Pseudoallescheria boydii and Leptosphaeria senegalensis are common eumycotic agents. Men are more commonly affected than women, and the leg is the most frequently affected site. Diagnosis in suspected lesions is made with the help of grain examination, microscopy, imaging (radiography, ultrasonography, magnetic resonance imaging) and culture, and more recently by molecular methods such as PCR and molecular sequencing. Molecular sequencing for both fungi and bacteria is important for rapid and correct diagnosis, especially in culture-negative cases. Treatment is long, more successful in actinomycetoma than eumycetoma, and may require a holistic approach comprising antimicrobials, surgery and rehabilitation. Mycetoma can be prevented by simple measures such as wearing protective garments and shoes, especially in rural areas and during outdoor activities.

Overexpression of a type III PKS gene affording novel violapyrones with enhanced anti-influenza A virus activity

BackgroundType III polyketide synthases (PKSs) are simple homodimer ketosynthases that distribute across plants, fungi, and bacteria, catalyzing formation of pyrone- and resorcinol-types aromatic polyketides with various bioactivities. The broad substrate promiscuity displayed by type III PKSs makes them wonderful candidates for expanding chemical diversity of polyketides.ResultsViolapyrone B (VLP B, 10), an α-pyrone compound produced by deepsea-derived Streptomyces somaliensis SCSIO ZH66, is encoded by a type III PKS VioA. We overexpressed VioA in three different hosts, including Streptomyces coelicolor M1146, Streptomyces sanyensis FMA as well as the native producer S. somaliensis SCSIO ZH66, leading to accumulation of different violapyrone compounds. Among them, S. coelicolor M1146 served as the host producing the most abundant violapyrones, from which five new (2–4, 7 and 12) and nine known (1, 5, 6, 8–11, 13 and 14) compounds were identified. Anti-influenza A (H1N1) virus activity of these compounds was then evaluated using ribavirin as a positive control (IC50 = 112.9 μM), revealing that compounds 11–14 showed considerable activity with IC50 values of 112.7, 26.9, 106.7 and 28.8 μM, respectively, which are significantly improved as compared to that of VLP B (10) (IC50 > 200 μM). The productions of 10 and 13 were increased by adding P450 inhibitor metyrapone. In addition, site-directed mutagenesis experiment led to demonstration of the residue S242 to be essential for the activity of VioA.ConclusionsBiological background of the expression hosts is an important factor impacting on the encoding products of type III PKSs. By using S. coelicolor M1146 as cell factory, we were able to generate fourteen VLPs compounds. Anti-H1N1 activity assay suggested that the lipophilic nature of the alkyl chains of VLPs plays an important role for the activity, providing valuable guidance for further structural optimization of VLPs.

Epitope-Based Peptide Vaccine Against Fructose-Bisphosphate Aldolase of Madurella mycetomatis Using Immunoinformatics Approaches

Background:Mycetoma is a distinct body tissue destructive and neglected tropical disease. It is endemic in many tropical and subtropical countries. Mycetoma is caused by bacterial infections (actinomycetoma) such as Streptomyces somaliensis and Nocardiae or true fungi (eumycetoma) such as Madurella mycetomatis. To date, treatments fail to cure the infection and the available marketed drugs are expensive and toxic upon prolonged usage. Moreover, no vaccine was prepared yet against mycetoma.Aim:The aim of this study is to predict effective epitope-based vaccine against fructose-bisphosphate aldolase enzymes of M. mycetomatis using immunoinformatics approaches.Methods and materials:Fructose-bisphosphate aldolase of M. mycetomatis sequence was retrieved from NCBI. Different prediction tools were used to analyze the nominee’s epitopes in Immune Epitope Database for B-cell, T-cell MHC class II and class I. Then the proposed peptides were docked using Autodock 4.0 software program.Results and conclusions:The proposed and promising peptides KYLQ show a potent binding affinity to B-cell, FEYARKHAF with a very strong binding affinity to MHC I alleles and FFKEHGVPL that shows a very strong binding affinity to MHC II and MHC I alleles. This indicates a strong potential to formulate a new vaccine, especially with the peptide FFKEHGVPL which is likely to be the first proposed epitope-based vaccine against fructose-bisphosphate aldolase of M. mycetomatis. This study recommends an in vivo assessment for the most promising peptides especially FFKEHGVPL.

Discovery of Antimycin-Type Depsipeptides from a wbl Gene Mutant Strain of Deepsea-Derived Streptomyces somaliensis SCSIO ZH66 and Their Effects on Pro-inflammatory Cytokine Production.

Deepsea microbes are a rich source of novel bioactive compounds, which have developed unique genetic systems as well as biosynthetic pathways compared with those of terrestrial microbes in order to survive in extreme living environment. However, a large variety of deepsea-microbial secondary metabolic pathways remain “cryptic” under the normal laboratory conditions. Manipulation of global regulators is one of the effective approaches for triggering the production of cryptic secondary metabolites. In this study, by combination of various chromatographic purification process, we obtained somalimycin (1), a new antimycin-type depsipeptide, with an unusual substitution of 3-aminosalicylate instead of conserved 3-formamidosalicylate moiety, along with two known (2 and 3) analogs from the ΔwblAso mutant strain of deepsea-derived Streptomyces somaliensis SCSIO ZH66. The structures of 1–3 were elucidated on the basis of extensive spectroscopic analyses including LC-MS and NMR. In the evaluation of potent anti-inflammatory activity, compound 2 exhibited strong inhibitory activity on the IL-5 production in ovalbumin-stimulated splenocytes with IC50 value of 0.57 μM, while 1 and 3 displayed mild effect (>10 μM), which might be attributed to their different side-chain substitutions. Moreover, compounds 1–3 showed very weak cytotoxicity against human umbilical vein endothelial cells with LD50 values of 62.6, 34.6, and 192.9 μM, respectively, which were far over their IL-5 inhibitory activity. These results indicated that these compounds have good potential for further use in anti-inflammatory drug development.

A New Dioic Acid from a wbl Gene Mutant of Deepsea-Derived Streptomyces somaliensis SCSIO ZH66.

The wblAso gene functions as a global regulatory gene in a negative manner in deepsea-derived Streptomyces somaliensis SCSIO ZH66. A new dioic acid (1) as well as two known butenolides (2 and 3) were isolated from the ΔwblAso mutant strain of S. somaliensis SCSIO ZH66. The structure of 1 was elucidated by a combination of spectroscopic analyses, including MS and NMR techniques. In the cell growth inhibitory evaluation, compound 3 exhibited moderate activity against the human hepatic carcinoma cell line (Huh7.5) with an IC50 value of 19.4 μg/mL, while compounds 1 and 2 showed null activity up to 100 μg/mL.

Streptomyces atlanticus sp. nov., a novel actinomycete isolated from marine sponge Aplysina fulva (Pallas, 1766).

The taxonomic position of a novel marine actinomycete isolated from a marine sponge, Aplysina fulva, which had been collected in the Archipelago of Saint Peter and Saint Paul (Equatorial Atlantic Ocean), was determined by using a polyphasic approach. The organism showed a combination of morphological and chemotaxonomic characteristics consistent with its classification in the genus Streptomyces and forms a distinct branch within the Streptomyces somaliensis 16S rRNA gene tree subclade. It is closely related to Streptomyces violascens ISP 5183T (97.27% 16S rRNA gene sequence similarity) and Streptomyces hydrogenans NBRC 13475T (97.15% 16S rRNA gene sequence similarity). The 16S rRNA gene similarities between the isolate and the remaining members of the subclade are lower than 96.77%. The organism can be distinguished readily from other members of the S. violacens subclade using a combination of phenotypic properties. On the basis of these results, it is proposed that isolate 103T (=NRRL B-65309T=CMAA 1378T) merits recognition as the type strain of a new Streptomyces species, namely Streptomyces atlanticus sp. nov.

Activation of a plasmid-situated type III PKS gene cluster by deletion of a wbl gene in deepsea-derived Streptomyces somaliensis SCSIO ZH66.

BackgroundActinomycete genome sequencing has disclosed a large number of cryptic secondary metabolite biosynthetic gene clusters. However, their unavailable or limited expression severely hampered the discovery of bioactive compounds. The whiB-like (wbl) regulatory genes play important roles in morphological differentiation as well as secondary metabolism; and hence the wblAso gene was probed and set as the target to activate cryptic gene clusters in deepsea-derived Streptomyces somaliensis SCSIO ZH66.ResultswblAso from deepsea-derived S. somaliensis SCSIO ZH66 was inactivated, leading to significant changes of secondary metabolites production in the ΔwblAso mutant, from which α-pyrone compound violapyrone B (VLP B) was isolated. Subsequently, the VLP biosynthetic gene cluster was identified and characterized, which consists of a type III polyketide synthase (PKS) gene vioA and a regulatory gene vioB; delightedly, inactivation of vioB led to isolation of another four VLPs analogues, among which one was new and two exhibited improved anti-MRSA (methicillin-resistant Staphylococcus aureus, MRSA) activity than VLP B. Moreover, transcriptional analysis revealed that the expression levels of whi genes (whiD, whiG, whiH and whiI) and wbl genes (wblC, wblE, wblH, wblI and wblK) were repressed by different degrees, suggesting an intertwined regulation mechanism of wblAso in morphological differentiation and secondary metabolism of S. somaliensis SCSIO ZH66.ConclusionswblA orthologues would be effective targets for activation of cryptic gene clusters in marine-derived Streptomyces strains, notwithstanding the regulation mechanisms might be varied in different strains. Moreover, the availability of the vio gene cluster has enriched the diversity of type III PKSs, providing new opportunities to expand the chemical space of polyketides through biosynthetic engineering.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-016-0515-6) contains supplementary material, which is available to authorized users.

CHARACTERISTIC OF SELECTED SOIL STREPTOMYCETES WITH ANTIMICROBIAL POTENTIAL AGAINST PHYTOPATHOGENIC MICROORGANISMS

The main objective of the present study was isolation and identification of soil streptomycetes, having antibacterial and antifungal activity against 8 selected phytopathogenic microorganisms, which attack crops in Slovakia. Out of 27 morphologically different streptomycete isolates, 14 of them demonstrated antimicrobial activity against at least two tested microorganisms in primary screening. Ethylacetate extract used for secondary screening showed different inhibitory pattern in comparison with primary screening. The tested isolates were mostly active against Gram-positive bacterium Clavibacter michiganensis subps. sepedonicus, the causal agent of bacterial canker of tomaten and against fungus Fusarium poae, pathogen of cereals, which can also infest stored grains. Only three isolates, namely VY59, VY87 and VY47 showed broad spectrum of inhibition activity and therefore were used for further identification. On the basis of various morphological (color of aerial and substrate mycelium, growth, production of pigments and melanin on ISP media), physiological (optimal pH, temperature, NaCl tolerance and C-utilization) and biochemical (ApiZym and ApiCoryne stripes) methods these strains belonged to the genus Streptomyces. In addition to the antimicrobial profile, the strains differed in API ZYM test results, which imply that the selected strains might produce different antimicrobial substances. Throught the comparative analysis of 16S rRNA gene, the most active isolates contained different nucleotide sequences for the 16S rRNA gene. Sequence similarity search by BLAST program revealed that they show sequence similarities to Streptomyces somaliensis (VY59), Streptomyces sp. (VY87) and Streptomyces albidoflavus (VY47). These three isolates with broader spectrum of antimicrobial activity can be used in the development of substances for agriculture purposes.

Giant cervico-facial mycetoma caused by Streptomyces somaliensis in a 14-year-old girl

Giant cervico-facial mycetoma caused by Streptomyces somaliensis in a 14-year-old girl

WITHDRAWN: Identification of an antimycin gene cluster and characterization of the tryptophan 2,3-dioxygenase from the deep sea-derived Streptomyces somaliensis HND1201

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Streptomyces somaliensis mediated green synthesis of silver nanoparticles

Objective(s): The development of reliable and ecofriendly process for the synthesis of nano-metals is an important aspect in the field of nanotechnology. Nano-metals are a special group of materials with broad area of applications. Materials and Methods: In this study, extracellular synthesis of silver nanoparticles (SNPs) performed by use of the gram positive soil Streptomycetes. Streptomycetes isolated from rice fields of Guilan Province, Iran (5 isolates). Initial characterization of SNPs was performed by visual change color. To determine the bacterium taxonomical identity, its colonies characterized morphologically by use of scanning electron microscope. The PCR molecular analysis of active isolate represented its identity partially. In this regard, 16S rDNA of isolate G was amplified using universal bacterial primers FD1 and RP2. The PCR products were purified and sequenced. Sequence analysis of 16S rDNA was then conducted using NCBI GenBank database using BLAST. Also SNPs were characterized by, transmission electron microscopy (TEM) and X-ray diffraction spectroscopy (XRD). Results: From all 5 collected Streptomyces somaliensis isolates, isolate G showed highest extracellular synthesis of SNPs via in vitro. SNPs were formed immediately by the addition of (AgNO3) solution (1 mM). UV-visible spectrophotometry for measuring surface plasmon resonance showed a single absorption peak at 450 nm, which confirmed the presence of SNPs. TEM revealed the extracellular formation of spherical silver nanoparticles in the size range of 5-35 nm. Conclusions: The biological approach for the synthesis of metal nanoparticles offers an environmentally benign alternative to the traditional chemical and physical synthesis methods. So, a simple, environmentally friendly and cost-effective method has been developed to synthesize AgNPs using Streptomycetes.