Discovery and biosynthetic assessment of 'Streptomyces ortus' sp. nov. isolated from a deep-sea sponge.

The deep sea is known to host novel bacteria with the potential to produce a diverse array of undiscovered natural products. Thus, understanding these bacteria is of broad interest in ecology and could also underpin applied drug discovery, specifically in the area of antimicrobials. Here, we isolate a new strain of Streptomyces from the tissue of the deep-sea sponge Polymastia corticata collected at a depth of 1869 m from the Gramberg Seamount in the Atlantic Ocean. This strain, which was given the initial designation A15ISP2-DRY2T, has a genome size of 9.29 Mb with a G+C content of 70.83 mol%. Phylogenomics determined that A15ISP2-DRY2T represents a novel species within the genus Streptomyces as part of the Streptomyces aurantiacus clade. The biosynthetic potential of A15ISP2-DRY2T was assessed relative to other members of the S. aurantiacus clade via comparative gene cluster family (GCF) analysis. This revealed a clear congruent relationship between phylogeny and GCF content. A15ISP2-DRY2T contains six unique GCFs absent elsewhere in the clade. Culture-based assays were used to demonstrate the antibacterial activity of A15ISP2-DRY2T against two drug-resistant human pathogens. Thus, we determine A15ISP2-DRY2T to be a novel bacterial species with considerable biosynthetic potential and propose the systematic name 'Streptomyces ortus' sp. nov.

Streptomyces corallincola and Kineosporia corallincola sp. nov., two new coral-derived marine actinobacteria.

Two new marine actinobacteria, designated as J2-1T and J2-2T, were isolated from a coral, Favites pentagona, collected from Rayong Province, Thailand. The taxonomic positions of the two strains were identified based on polyphasic taxonomy. Based on morphological characteristics and chemotaxonomy, strains J2-1T and J2-2T were identified as members of the genus Streptomyces and Kineosporia, respectively. Strains J2-1T and J2-2T showed the highest 16S rRNA gene sequence similarity to Streptomyces broussonetiae T44T (98.62 %) and Kineosporia babensis VN05A0415T (98.08 %), respectively. Strain J2-1T had chemotaxonomic properties resembling members of the genus Streptomyces. ll-Diaminopimelic acid, glucose and ribose were detected in the whole-cell hydrolysate. Diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositolmannoside, unidentified aminolipid and five unidentified phospholipids were detected as the polar lipids. The major cellular fatty acids were C16 : 0 iso, C15 : 0 anteiso, C15 : 0 iso, C16 : 0, C17 : 0 anteiso, C14 : 0 iso and C17 : 0 iso. Strain J2-2T a showed similar cell composition to members of the genus Kineosporia. Both isomers of ll- and meso-diaminopimelic acid were detected in the peptidoglycan. Arabinose, galactose, madurose and xylose were observed in the whole-cell hydrolysate. The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside, phosphatidylcholine, an unidentified phospholipid and an unidentified glycolipid. The major cellular fatty acids were C16 : 0, C18 : 1 ω9c, C18 : 0 10-methyl, tuberculostearic acid, C18 : 0 and C17 : 0. Both strains could be distinguished from their closely related type strains according to their phenotypic characteristics. Comparative genome analysis indicated the delineation of two novel species based on digital DNA-DNA hybridization and average nucleotide identity values, which were below 70 and 95 %, respectively. The names proposed are Streptomyces corallincola sp. nov. (J2-1T=TBRC 13503T=NBRC 115066T) and Kineosporia corallincola sp. nov. (J2-2T=TBRC 13504T=NBRC 114885T).

Antifungal potential of Streptomyces rameus GgS 48 against mungbean root rot [Rhizoctonia bataticola (Taub.) Butler].

Mungbean root rot caused by Rhizoctonia bataticola (Taub.) Butler is the most devastating disease inflicting yield loss up to 60%. The use of beneficial antagonist, viz., Streptomyces with diverse antifungal activity and prolific secondary metabolites production, is the ecofriendly and environmentally acceptable alternative to the existing chemical control methods. In this investigation we have identified the promising isolate of Streptomyces sp. which potentially reduced the mungbean root rot. A total of nine mungbean rhizospheric actinobacterial isolates were evaluated for their antagonistic potential against root rot pathogen and growth promoting trait of mungbean. The actinobacterial isolate GgS 48 was shown to be effective in reducing the mycelial growth of R. bataticola by 65.3% in dual culture technique and enhancing the growth of mugbean under in vitro condition. Morphological, biochemical and molecular characterization confirmed the isolate GgS 48 as Streptomyces rameus. The actinobacteria S. rameus GgS 48 exerted antifungal action against R. bataticola by hyphal coiling, which was confirmed under scanning electron microscopy (SEM), and promoted the growth through the production of IAA. It showed positive for the production of siderophore and hydrolytic enzymes, viz., chitinase and protease. The chitinase produced by the GgS 48 was purified and its molecular weight was determined as 40 kDa and it had great potential in reducing the mycelial growth of R. bataticola. The talc-based formulation of S. rameus GgS 48 was found to be promising in suppressing the root rot severity and enhancing the growth and yield attributes of mungbean both under glass house and field conditions.

Antiviral Properties of Streptomyces tuirus DBZ39 Mediated Gold Nanoparticles Against Bluetongue virus.

<b>Background and Objective:</b> The proposed study involves the approach from the point of anti-viral activity of gold nanoparticles against the <i>Bluetongue virus</i>. Among viral diseases, Bluetongue is regarded as an economically scouring disease. Neither a vaccine nor an antiviral drug is available for the prevention or treatment of this disease. The antiviral activity of gold nanoparticles synthesized by a novel isolate of <i>Streptomyces tuirus</i> DBZ39 is the breakthrough of the study. <i>Streptomyces tuirus </i>DBZ39, a novel isolate obtained from alkaline soil was proved to be efficient actinomycetes, for the extracellular synthesis of gold nanoparticles. <b>Materials and Methods:</b> An upstream bioprocess was optimized and developed for the synthesis of controlled size gold nanoparticles with solitary mono dispersal pattern in aurum chloride solution. The characterization and confirmation of gold nanoparticles were illustrated by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Analysis (EDAX) and Fourier Transmission Infrared Radiation Analysis (FTIR). <b>Results:</b> Biomass size of 3 g, substrate concentration of 1 mM, pH of 8.5 and temperature of 45°C were observed as optimum conditions for the synthesis of 15-24 nm size gold nanoparticles. The <i>Bluetongue virus</i> (BTV) which belongs to the genus Orbivirus in the family Reoviridae with 26 serotypes is an etiological agent of infectious and non-contagious Bluetongue disease of main sheep and several other domestic animals. <b>Conclusion:</b> Gold nanoparticles for the 1st time, at a higher concentration of 1:64 dilutions revealed a very promising and novel antiviral property against the <i>Bluetongue virus</i>.

Streptomyces caniscabiei sp. nov., which causes potato common scab and is distributed across the world.

Fourteen strains of Streptomyces isolated from scab lesions on potato are described as members of a novel species based on genetic distance, morphological observation and biochemical analyses. Morphological and biochemical characteristics of these strains are distinct from other described phytopathogenic species. Strain NE06-02DT has white aerial mycelium and grey, cylindrical, smooth spores on rectus-flexibilis spore chains. Members of this species group can utilize most of the International Streptomyces Project sugars, utilize melibiose and trehalose, produce melanin, grow on 6-7 % NaCl and pH 5-5.5 media, and are susceptible to oleandomycin (100 µg ml-1), streptomycin (20 µg ml-1) and penicillin G (30 µg ml-1). Though the 16S rRNA gene sequences from several members of this novel species are identical to the Streptomyces bottropensis 16S rRNA gene sequence, whole-genome average nucleotide identity and multi-locus sequence analysis confirm that the strains are members of a novel species. Strains belonging to this novel species have been isolated from the United States, Egypt and China with the earliest known members being isolated in 1961 from common scab lesions of potato in both California, USA, and Maine, USA. The name Streptomyces caniscabiei sp. nov. is proposed for strain NE06-02DT (=DSM111602T=ATCC TSD-236T) and the other members of this novel species group.

Streptomyces apricus sp. nov., isolated from soil.

A novel Streptomyces strain, SUN51T, was isolated from soils sampled in Wisconsin, USA, as part of a Streptomyces biogeography survey. Genome sequencing revealed that this strain had less than 90 % average nucleotide identity (ANI) to type species of Streptomyces: SUN51T was most closely related to Streptomyces dioscori A217T (99.5 % 16S rRNA gene identity, 89.4 % ANI). Genome size was estimated at 8.81 Mb, and the genome DNA G+C content was 72 mol%. The strain possessed the cellular fatty acids anteiso-C15 : 0, iso-C16 : 0, 16 : 1 ω7c, anteiso-C17 : 0, iso-C14 : 0 and C16 : 0. The predominant menaquinones were MK-9 H4, MK-9 H6 and MK-9 H8. Strain SUN51T contained the polar lipids phosphatidic acid, phosphatidyl ethanolamine, phosphatidyl glycerol and diphosphatidyl glycerol. The cell wall contained ll-diaminopimelic acid. The strain could grow on a broad range of carbon sources and tolerate temperatures of up to 40 °C. The results of the polyphasic study confirmed that this isolate represents a novel species of the genus Streptomyces, for which the name Streptomyces apricus sp. nov. is proposed. The type strain of this species is SUN51T (=NRRL B-65543T=JCM 33736T).

Streptomyces epipremni sp. nov., an endophytic actinomycete isolated from the root of Epipremnum aureum.

An endophytic Streptomyces-like micro-organism, designated strain PRB2-1T was isolated from root tissue of Epipremnum aureum (Linden and André) G.S. Bunting. The typical morphological and chemotaxonomic characteristics, i.e. the ability to produce straight spore chains directly on aerial mycelium and the presence of ll-diaminopimelic acid in cell-wall peptidoglycan, were consistent with its assignment to the genus Streptomyces. 16S rRNA gene analysis showed that strain PRB2-1T is a member of the genus Streptomyces with the highest similarity to Streptomyces bryophytorum DSM 42183T (98.4 %). Moreover, the draft genome sequence of strain PRB2-1T exhibited low average nucleotide identity by blast (79.9-83.8 %) and digital DNA-DNA hybridization (24.9-28.3 %) values to the reference strains, which were well below the species circumscription threshold. The DNA G+C content of genomic DNA was 73.6 mol%. Comparison of phenotypic characteristics and whole-genome sequence between strain PRB2-1T and its close relatives indicated that strain PRB2-1T could be classified as a novel species of the genus Streptomyces. Thus the name, Streptomyces epipremni sp. nov. is proposed for the strain. The type strain is PRB2-1T (=TBRC 7642T=NBRC 113169T).

Streptomyces silvae sp. nov., isolated from forest soil.

A bacterial strain, named For3T, was isolated from forest soil sampled in Champenoux, France. Based on its 16S rRNA gene sequence, the strain was affiliated to the family Streptomycetaceae and, more specifically, to the genus Streptomyces. The strain had 99.93% 16S rRNA gene sequence similarity to its closest relative strains Streptomyces pratensis ATCC 33331T, Streptomyces anulatus ATCC 27416T, Streptomyces setonii NRRL ISP-5322T and Kitasatospora papulosa NRRL B-16504T. The phylogenomic tree using the genome blast distance phylogeny method showed that the closest relative strain was Streptomyces atroolivaceus NRRL ISP-5137T and that For3T represents a new branch among the Streptomyces. Genome relatedness indexes revealed that the average nucleotide identity and digital DNA-DNA hybridization values between For3T and its closest phylogenomic relative (S. atroolivaceus NRRL ISP-5137T) were 88.39 and 39.2 %, respectively. The G+C content of the genome was 71.4 mol% and its size was 7.96 Mb with 7492 protein-coding genes. Strain For3T harboured complete metabolic pathways absent in the closest relative strains such as cellulose biosynthesis, glycogen degradation I, glucosylglycerate biosynthesis I. Anteiso-C15:0, iso-C15:0, anteiso-C17:0 and MK-9(H4)/MK-9(H6) were the predominant cellular fatty acids and respiratory quinones, respectively. Phenotypic and genomic data supported the assignment of strain For3T to a novel species Streptomyces silvae sp. nov., within the genus Streptomyces, for which the type strain is For3T (=CIP 111908T=LMG 32186T).

Antagonistic activity of endophytic actinobacteria from native potatoes (Solanum tuberosum subsp. tuberosum L.) against Pectobacterium carotovorum subsp. carotovorum and Pectobacterium atrosepticum.

BACKGROUND: The native potatoes (Solanum tuberosum subsp. tuberosum L.) grown in Chile (Chiloé) represent a new, unexplored source of endophytes to find potential biological control agents for the prevention of bacterial diseases, like blackleg and soft rot, in potato crops. RESULT: The objective of this study was the selection of endophytic actinobacteria from native potatoes for antagonistic activity against Pectobacterium carotovorum subsp. carotovorum and Pectobacterium atrosepticum, and their potential to suppress tissue maceration symptoms in potato tubers. This potential was determined through the quorum quenching activity using a Chromobacterium violaceaum ATCC 12472 Wild type (WT) bioassay and its colonization behavior of the potato plant root system (S. tuberosum) by means of the Double labeling of oligonucleotide probes for fluorescence in situ hybridization (DOPE-FISH) targeting technique. The results showed that although Streptomyces sp. TP199 and Streptomyces sp. A2R31 were able to inhibit the growth of the pathogens, only the Streptomyces sp. TP199 isolate inhibited Pectobacterium sp. growth and diminished tissue maceration in tubers (p ≤ 0.05). Streptomyces sp. TP199 had metal-dependent acyl homoserine lactones (AHL) quorum quenching activity in vitro and was able to colonize the root endosphere 10 days after inoculation. CONCLUSIONS: We concluded that native potatoes from southern Chile possess endophyte actinobacteria that are potential agents for the disease management of soft rot and blackleg.

Secondary Metabolites with Cytotoxic Activities from Streptomyces sp. BM-8 Isolated from the Feces of Equusquagga.

A new aliphatic acid, compound 1, together with six known metabolites, including nonactic acid (2), homononactic acid (3), ethyl homononactate (4), homononactylhomononactate (5), valinomycin (6), and cyclo-(Pro-Leu) (7), was isolated from the culture broth of Streptomyces sp. BM-8, an actinobacterial strain isolated from the feces of Equus quagga. The structures of these compounds were established by analyses of spectroscopic data, including 1D and 2D nuclear magnetic resonance spectra (NMR), as well as by HR-ESI-MS spectrometry and chemical derivative analyses. Additionally, a serial analogue of nonactic acid and homononacticacid (8-21) was synthesized. The cytotoxicity of 1-21 wastested against a panel of cancer cell lines, such as HT-29, MCF-7, A375 and K562, with MTT assay. In addition, the cytotoxicity tests revealed that 1 was less cytotoxic toward a panel of cancerous cells, as compared with valinomycin (6).

Streptomyces spirodelae sp. nov., isolated from duckweed.

A novel actinobacterium, designated strain DW4-2T, was isolated from duckweed (Spirodela sp.) collected from an agricultural pond in Kasetsart University, Bangkok, Thailand. The morphological, chemotaxonomic and phylogenetic characteristics were consistent with its classification in the genus Streptomyces. Strain DW4-2T showed the highest 16S rRNA gene sequence similarity values to Streptomyces qinglanensis DSM 42035T (98.5 %), Streptomyces smyrnaeus DSM 42105T (98.4 %) and Streptomyces oryzae S16-07T (98.4 %). Digital DNA-DNA hydridization and average nucleotide identity values between the genome sequences of strain DW4-2T with S. qinglanensis DSM 42035T (29.8 and 87.8 %), S. smyrnaeus DSM 42105T (33.1 and 89.0 %) and S. oryzae S16-07T (33.0 and 88.9 %) were below the thresholds of 70 and 95-96 % for prokaryotic conspecific assignation. Chemotaxonomic data revealed that strain DW4-2T possessed MK-9(H6) and MK-9(H8) as the predominant menaquinones. It contained ll -diaminopimelic acid as the diagnostic diamino acid and glucose, ribose and trace amount of madurose in whole-cell sugars. The polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside, an unidentified aminolipid, an unidentified lipid and an unidentified phospholipid. The predominant cellular fatty acids were anteiso-C17 : 0, anteiso-C15 : 0 and iso-C16 : 0. The genomic DNA size of the strain DW4-2T was 7 310 765 bp with DNA G+C content 71.0 mol%. Genomic analysis of the genome indicated that the strain DW4-2T had the potential to produce bioactive compounds. On the basis of these genotypic and phenotypic data, it is supported that strain DW4-2T represents a novel species of the genus Streptomyces, for which the name Streptomyces spirodelae sp. nov. is proposed. The type strain is strain DW4-2T (=TBRC 13095T=NBRC 114803T).

The microbiome of a shell mound: ancient anthropogenic waste as a source of Streptomyces degrading recalcitrant polysaccharides.

Metagenome amplicon DNA sequencing and traditional cell culture techniques are helping to uncover the diversity and the biotechnological potential of prokaryotes in different habitats around the world. It has also had a profound impact on microbial taxonomy in the last decades. Here we used metagenome 16S rDNA amplicon sequencing to reveal the microbiome composition of different layers of an anthropogenic soil collected at a shell mound Sambaqui archeological site. The Samabaqui soil microbiome is mainly composed by phyla Acidobacteria, Rokubacteria, Proteobacteria and Thaumarchaeota. Using culture-dependent analysis we obtained few Streptomyces isolates from the Sambaqui soil. One of the isolates, named Streptomyces sp. S3, was able to grow in minimal medium containing recalcitrant polysaccharides including chitin, xylan, carboxymethylcellulose or microcrystalline cellulose as sole carbon sources. The activities of enzymes degrading these compounds were confirmed in cell free supernatants. The genome sequence revealed not only an arsenal of genes related to polysaccharides degradation but also biosynthetic gene clusters which may be involved in the production of biotechnologically interesting secondary metabolites.

Bhimamycin J, a Rare Benzo[f]isoindole-dione Alkaloid from the Marine-Derived Actinomycete Streptomyces sp. MS180069.

Chemical investigation on a Streptomyces sp. strain MS180069 isolated from a sediment sample collected from the South China Sea, yielded the new benzo[f]isoindole-dione alkaloid, bhimamycin J (1). The structure was determined by extensive spectroscopic analysis, including HRMS, 1D, 2D NMR, and X-ray diffraction techniques. A molecular docking study revealed 1 as a new molecular motif that binds with human angiotensin converting enzyme2 (ACE2), recently described as the cell surface receptor responsible for uptake of 2019-CoV-2. Using enzyme assays we confirm that 1 inhibits human ACE2 79.7 % at 25 µg/mL.

Streptomyces botrytidirepellens sp. nov., a novel actinomycete with antifungal activity against Botrytis cinerea.

The fungal pathogen Botrytis cinerea is the causal agent of devastating gray mold diseases in many economically important fruits, vegetables, and flowers, leading to serious economic losses worldwide. In this study, a novel actinomycete NEAU-LD23T exhibiting antifungal activity against B. cinerea was isolated, and its taxonomic position was evaluated using a polyphasic approach. Based on the genotypic, phenotypic and chemotaxonomic data, it is concluded that the strain represents a novel species within the genus Streptomyces, for which the name Streptomyces botrytidirepellens sp. nov. is proposed. The type strain is NEAU-LD23T (=CCTCC AA 2019029T=DSM 109824T). In addition, strain NEAU-LD23T showed a strong antagonistic effect against B. cinerea (82.6±2.5%) and varying degrees of inhibition on nine other phytopathogenic fungi. Both cell-free filtrate and methanol extract of mycelia of strain NEAU-LD23T significantly inhibited mycelial growth of B. cinerea. To preliminarily explore the antifungal mechanisms, the genome of strain NEAU-LD23T was sequenced and analyzed. AntiSMASH analysis led to the identification of several gene clusters responsible for the biosynthesis of bioactive secondary metabolites with antifungal activity, including 9-methylstreptimidone, echosides, anisomycin, coelichelin and desferrioxamine B. Overall, this research provided us an excellent strain with considerable potential to use for biological control of tomato gray mold.

Isolation and Characterization of Antagonistic Activity of Some Streptomycetes and their Specific Actinophages from Soil.

<b>Background and Objective:</b> Phages specific to actinomycetes are common, active in the soil and gladly detected. Soil streptomycetes are having antibiosis activities against numerous bacteria, fungi and plant viruses. Thus, this study was designed to isolate, purify and characterize some streptomycetes active against some microorganisms from soil followed by isolation of their specific phages. <b>Materials and Methods:</b> Antagonistic activities of these streptomycetes isolates were tested against <i>Bacillus subtilis</i>,<i> Pseudomonas</i> sp., <i>Serratia</i> sp. and <i>Aspergillus niger</i>. To confirm their biological characterization of the streptomycetes isolates under investigation, the 16SrRNA gene was also used. The presence of specific lysate actinophages in the soil samples were tested by spot test technique and then propagated and purified for further characterization. The morphology of the purified actinophages was determined by electron microscopy. <b>Results:</b> The five selected <i>Streptomyces</i> isolates having effective antagonistic activity were biologically and molecularly identified as <i>Streptomyces sclerogranulatus </i>(QQ06), <i>Streptomyces mutabilis </i>(QQ07), <i>Streptomyces heilongjiangensis </i>(QQ08), <i>Streptomyces sparsus </i>(QQ09) and <i>Streptomyces purpurascens </i>(QQ10) strains. Electron micrographs showed the presence of filamentous virus-like particles with lengths of 21.4×928.57, 25×750, 21.4×857.14, 21.4×885.7 and 21.4×857.14 nm specific to <i>Streptomyces</i> strains QQ06, QQ07, QQ08, QQ09 and QQ10, respectively and belong to the family Inoviridae. <b>Conclusion:</b> Phage of Inoviridae was considered as the first time against streptomycetes isolates, therefore, additional and advanced studies should be carried out at the level of molecular characterization.

Differences in the skin microbial community between patients with active and stable vitiligo based on 16S rRNA gene sequencing.

BACKGROUND/OBJECTIVE: Recent studies have described an association between altered skin microbial community and epidemiology of skin diseases, such as vitiligo, atopic dermatitis and psoriasis. In this study, we conducted microbiological analysis on patients at different stages of vitiligo to determine whether the dysbiosis is associated with disease progression. METHODS: To characterise the skin microbes in vitiligo patients, we profiled samples collected from 40 patients with active and stable vitiligo using the Novaseq sequencer. Alpha diversity was used to measure richness and uniformity, while Beta diversity (Non-Metric Multi-Dimensional Scaling) analysis was used to show the differences. Moreover, the species differences were evaluated by LEfSe analysis and the flora gene function was predicted using Statistical Analysis of Metagenomic Profiles (STAMP). RESULTS: The alpha diversity results showed no significant differences between active vitiligo and stable vitiligo, while beta diversity and LEfSe analysis results showed the differences in community composition. Streptomyces and Streptococcus were enriched in active vitiligo compared to stable vitiligo. In addition, the flora gene function of mixed acid fermentation was more pronounced in active vitiligo, while the function of lipid IVA biosynthesis was more significant in stable vitiligo. CONCLUSION: This study has shown the differences in epidermal microbes between active vitiligo and stable vitiligo. Our results suggest that maintaining the flora balance might be a potential therapeutic target for vitiligo.

Streptomyces sp.-A Treasure Trove of Weapons to Combat Methicillin-Resistant Staphylococcus aureus Biofilm Associated with Biomedical Devices.

Biofilms formed by methicillin-resistant S. aureus (MRSA) are among the most frequent causes of biomedical device-related infection, which are difficult to treat and are often persistent and recurrent. Thus, new and effective antibiofilm agents are urgently needed. In this article, we review the most relevant literature of the recent years reporting on promising anti-MRSA biofilm agents derived from the genus Streptomyces bacteria, and discuss the potential contribution of these newly reported antibiofilm compounds to the current strategies in preventing biofilm formation and eradicating pre-existing biofilms of the clinically important pathogen MRSA. Many efforts are evidenced to address biofilm-related infections, and some novel strategies have been developed and demonstrated encouraging results in preclinical studies. Nevertheless, more in vivo studies with appropriate biofilm models and well-designed multicenter clinical trials are needed to assess the prospects of these strategies.

Streptomyces poriferorum sp. nov., a novel marine sponge-derived Actinobacteria species expressing anti-MRSA activity.

Marine sponges represent a rich source of uncharacterized microbial diversity, and many are host to microorganisms that produce biologically active specialized metabolites. Here, a polyphasic approach was used to characterize two Actinobacteria strains, P01-B04T and P01-F02, that were isolated from the marine sponges Geodia barretti (Bowerbank, 1858) and Antho dichotoma (Esper, 1794), respectively. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strains P01-B04T and P01-F02 are closely related to Streptomyces beijiangensis DSM 41794T, Streptomyces laculatispora NRRL B-24909T, and Streptomyces brevispora NRRL B-24910T. The two strains showed nearly identical 16S rRNA gene sequences (99.93%), and the average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) relatedness values were 99.96% and 99.6%, respectively, suggesting that these strains are affiliated with the same species. Chemotaxonomic and culture characteristics of both strains were also consistent with the genus Streptomyces, while phenotypic properties, genome-based comparisons, and phylogenomic analyses distinguished strains P01-B04T and P01-F02 from their closest phylogenetic relatives. In silico analysis predicted that the 8.9 Mb genome of P01-B04T contains at least 41 biosynthetic gene clusters (BGCs) encoding secondary metabolites, indicating that this strain could express diverse bioactive metabolites; in support of this prediction, this strain expressed antibacterial activity against Gram-positive bacteria including a clinical isolate of methicillin-resistant Staphylococcus aureus (MRSA) EAMC30. Based on these results, the marine sponge-associated isolates represent a novel species of the genus Streptomyces, for which the name Streptomyces poriferorum sp. nov. is proposed, with P01-B04T (=DSM 111306T = CCM 9048T) as the type strain.

Streptomyces genisteinicus sp. nov., a novel genistein-producing actinomycete isolated from a Chinese medicinal plant and proposal of Streptomyces michiganensis Corbaz et al. 1957 as a later heterotypic synonym of Streptomyces xanthochromogenes Arishima et al. 1956.

A novel genistein-producing actinobacterial strain, designated strain CRPJ-33T, was isolated from the healthy leaves of a medicinal plant Xanthium sibiricum collected from Hunan Province, PR China. 16S rRNA gene sequence analysis indicated strain CRPJ-33T belonged to the genus Streptomyces and had 99.7, 99.0, 98.9, 98.9, 98.8 and 98.7% sequence similarities to Streptomyces zhihengii YIM T102T, Streptomyces eurocidicus NRRL B-1676T, Streptomyces xanthochromogenes NRRL B-5410T, Streptomyces michiganensis NBRC 12797T, Streptomyces mauvecolor LMG 20100T and Streptomyces lavendofoliae NBRC 12882T, respectively. Phylogenetic analysis of 16S rRNA gene sequences showed that strain CRPJ-33T was most closely related to S. zhihengii YIM T102T. However, digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values between them were much less than the recommended threshold values. Furthermore, differential comparisons of the phenotypic characteristics were enough to distinguish strain CRPJ-33T from S. zhihengii YIM T102T. Meanwhile, the ANI and dDDH values or MLSA distances between strain CRPJ-33T and other type strains, which exhibited ≥98.7 % 16S rRNA gene sequence similarities to strain CRPJ-33T, were far away from the recommended threshold values. Based on these results, it is thought that strain CRPJ-33T should represent a novel species of the genus Streptomyces, for which the name Streptomyces genisteinicus sp. nov. is proposed. The type strain is CRPJ-33T (=MCCC 1K04965T=JCM 34526T). In addition, the phenotypic, chemotaxonomic and genotypic characteristics, as well as phylogenetic information revealed that the type strains of S. xanthochromogenes and S. michiganensis should belong to same genomic species. Consequently, it is proposed that S. michiganensis is a heterotypic synonym of S. xanthochromogenes for which an emended description is given.

Isolation, Identification, Biocontrol Activity, and Plant Growth Promoting Capability of a Superior Streptomyces tricolor Strain HM10.

Streptomyces is a genus with known biocontrol activity, producing a broad range of biologically active substances. Our goal was to isolate local Streptomyces species, evaluate their capacity to biocontrol the selected phytopathogens, and promote the plant growth via siderophore and indole acetic acid (IAA) production and phosphate solubilization. Eleven isolates were obtained from local soil samples in Saudi Arabia via the standard serial dilution method and identified morphologically by scanning electron microscope (SEM) and 16S rRNA amplicon sequencing. The biocontrol of phytopathogens was screened against known soil-borne fungi and bacteria. Plant growth promotion capacity was evaluated based on siderophore and IAA production and phosphate solubilization capacity. From eleven isolates obtained, one showed 99.77% homology with the type strain Streptomyces tricolor AS 4.1867, and was designated S. tricolor strain HM10. It showed aerial hyphae in SEM, growth inhibition of ten known phytopathogens in in vitro experiments, and the production of plant growth promoting compounds such as siderophores, IAA, and phosphate solubilization capacity. S. tricolor strain HM10 exhibited high antagonism against the fungi tested (i.e., Colletotrichum gloeosporides with an inhibition zone exceeding 18 mm), whereas the lowest antagonistic effect was against Alternaria solani (an inhibition zone equal to 8 mm). Furthermore, the most efficient siderophore production was recorded to strain HM8, followed by strain HM10 with 64 and 22.56 h/c (halo zone area/colony area), respectively. Concerning IAA production, Streptomyces strain HM10 was the most effective producer with a value of 273.02 µg/ml. An autochthonous strain S. tricolor HM10 should be an important biological agent to control phytopathogens and promote plant growth.