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Streptomyces is a diverse genus, well known for producing a wide array of metabolites that have significant industrial utilization. The present study investigates the genetic and functional diversity of Streptomyces spp. isolated from the Pachmarhi Biosphere Reserve (PBR), India, an unexplored site. The 16S rRNA gene sequencing and analysis revealed 96 isolates belonging to 40 different species indicating a substantial phylogenetic diversity. The strains were clustered into two groups: a major cluster with 94 strains and a small cluster with two strains. BOX- PCR analyses revealed an incredible genetic diversity existing among the strains of Streptomyces spp. in PBR. The analyses revealed the intra-species diversity and inter-species closeness within the genus Streptomyces in the study area. Qualitative screening for enzyme production has shown that 53, 42, 41, 11, and 54 strains tested positive for CMCase, xylanase, amylase, pectinase, and β-glucosidase, respectively. Additionally, 54 strains tested positive for PHB production. The strains were assayed quantitatively for the production of CMCase, xylanase, amylase, and pectinase. Streptomyces sp. MP9-2, Streptomyces sp. MP10-11, Streptomyces sp. MP10-18, and Streptomyces sp. MP10-6 recorded maximum CMCase (0.604 U/mL), xylanase (0.553 U/mL), amylase (1.714 U/mL), and pectinase (13.15 U/mL) activities, respectively. Furthermore, several strains demonstrated plant growth-promoting traits, viz. zinc and phosphate solubilization and production of ammonia, HCN (hydrogen cyanide), and IAA (Indole acetic acid), and nitrogen fixation. Fifty strains showed antifungal activity against Fusarium oxysporum f. sp. lycopersici with inhibitions ranging from 7.5 to 47.5%. Current findings underscore the ecological and biotechnological significance of Streptomyces spp. in the unexplored habitat of PBR., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Marine invertebrates represent an underexplored reservoir for actinobacteria, which are known to synthesize novel bioactive compounds. This study isolated 37 actinobacterial strains from five distinct marine invertebrate hosts, namely Chondrilla australiensis, Palythoa sp., Favia sp., Porites lutea, and Acropora cervicornis, while no strains were obtained from Lissoclinum sp. and Lithophyllon sp. These isolates were taxonomically classified into six genera: Gordonia, Microbacterium, Micromonospora, Nocardia, Rhodococcus, and Streptomyces, with Streptomyces and Micromonospora being notably predominant. Comparative genomic analysis facilitated the identification of two novel species: Micromonospora palythoicola sp. nov. (strain S2-005 T  = TBRC 18343 T and NBRC 116545 T ) and Streptomyces poriticola sp. nov. (strain C6-003 T , =TBRC 17807 T and NBRC 116425 T ). Both species exhibited substantial genetic differences from their nearest known species as demonstrated by digital DNA-DNA hybridization and average nucleotide identity scores, which fell below the thresholds of 70% and 95%, respectively. Streptomyces poriticola C6-003 T displayed significant antimicrobial activity and selective cytotoxicity against human breast cancer MCF-7 cells, with reduced toxicity towards human dermal papilla cells. Micromonospora palythoicola S2-005 T manifested antimicrobial properties against Streptococcus mutans and Kocuria rhizophila. These findings highlight the considerable diversity of actinobacteria within marine invertebrates and underscore their potential as a source of new species with promising biological properties for therapeutic applications., (© 2024. The Author(s).)

In the present study, using genome mining, Streptomyces sp. JL1001, which possesses a leinamycin-type gene cluster, was identified from 14 strains of Streptomyces originating from the rhizosphere soil of Polygonatum cyrtonema Hua. The complete genome of Streptomyces sp. JL1001 was sequenced and analyzed. The genome of Streptomyces sp. JL1001 consists of a 7,943,495 bp chromosome with a 71.71% G+C content and 7315 protein-coding genes. We also identified 36 biosynthetic gene clusters (BGCs) for secondary metabolites in Streptomyces sp. JL1001. Twenty-seven BGCs had low (< 50%) or moderate (50-80%) similarity to other known secondary metabolite BGCs. In addition, a comparative analysis was conducted between the leinamycin-type gene cluster in Streptomyces sp. JL1001 and the biosynthetic gene clusters of leinamycin and largimycin. This study aims to provide a comprehensive analysis of the genomic features of rhizosphere Streptomyces sp. JL1001. It establishes the foundation for further investigation into experimental trials involving novel bioactive metabolites such as AT-less type I polyketides that have important potential applications in medicine and agriculture., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

This study reports the isolation and characterization of a Streptomyces sp. from soil, capable of producing bioactive secondary metabolites active against a variety of bacterial human pathogens. We targeted the antimicrobial activity against Escherichia coli ATCC-BAA 2469, a clinically relevant strain of bacteria harbouring resistance genes for carbapenems, extended spectrum beta-lactams, tetracyclines, fluoroquinones, etc. Preliminary screening using the spot inoculation technique identified Streptomyces sp. NP73 as the potent strain among the 74 isolated Actinomycetia strain. 16S rRNA gene and whole genome sequencing (WGS) confirmed its taxonomical identity and helped in the construction of the phylogenetic tree. WGS revealed the predicted pathways and biosynthetic gene clusters responsible for producing various types of antibiotics including the isolated compound. Bioactivity guided fractionation and chemical characterization of the active fraction, carried out using liquid chromatography, gas chromatography-mass spectrometry, infra-red spectroscopy, and nuclear magnetic resonance spectroscopy, led to the tentative identification of the active compound as Pyrrolo[1,2-a] pyrazine-1,4-dione, hexahydro-, a diketopiperazine molecule. This compound exhibited excellent antimicrobial and anti-biofilm properties against E. coli ATCC-BAA 2469 with an MIC value of 15.64 µg ml-1, and the low cytotoxicity of the compound identified in this study provides hope for future drug development., (© The Author(s) 2024. Published by Oxford University Press on behalf of Applied Microbiology International.)

Six bacterial strains, Mut1 T , Mut2, Alt1, Alt2, Alt3 T , and Alt4, were isolated from soil samples collected in parks in Gothenburg, Sweden, based on their ability to utilize the insoluble polysaccharides α-1,3-glucan (mutan; Mut strains) or the mixed-linkage α-1,3/α-1,6-glucan (alternan; Alt strains). Analysis of 16S rRNA gene sequences identified all strains as members of the genus Streptomyces . The genomes of the strains were sequenced and subsequent phylogenetic analyses identified Mut2 as a strain of Streptomyces laculatispora and Alt1, Alt2 and Alt4 as strains of Streptomyces poriferorum, while Mut1 T and Alt3 T were most closely related to the type strains Streptomyces drozdowiczii NBRC 101007 T and Streptomyces atroolivaceus NRRL ISP-5137 T , respectively. Comprehensive genomic and biochemical characterizations were conducted, highlighting typical features of Streptomyces , such as large genomes (8.0-9.6 Mb) with high G+C content (70.5-72.0%). All six strains also encode a wide repertoire of putative carbohydrate-active enzymes, indicating a capability to utilize various complex polysaccharides as carbon sources such as starch, mutan, and cellulose, which was confirmed experimentally. Based on phylogenetic and phenotypic characterization, our study suggests that strains Mut1 T and Alt3 T represent novel species in the genus Streptomyces for which the names Streptomyces castrisilvae sp. nov. and Streptomyces glycanivorans sp. nov. are proposed, with strains Mut1 T (=DSM 117248 T =CCUG 77596 T ) and Alt3 T (=DSM 117252 T =CCUG 77600 T ) representing the respective type strains.

Streptomyces is among the most extensively studied genera of bacteria but its complex taxonomy remains contested and is suspected to contain significant species-level misclassification. Resolving the classification of Streptomyces would benefit many areas of applied microbiology that rely on an accurate ground truth for grouping of related organisms, including comparative genomics-based searches for novel antimicrobials. We survey taxonomic conflicts between 16S rRNA and whole genome-based Streptomyces classifications using 2276 publicly available Streptomyces genome assemblies and 48 981 publicly available full-length 16S rRNA Streptomyces sequences from silva, Greengenes, Ribosomal Database Project (RDP), and NCBI (National Centre for Biotechnology Information) databases. We construct a full-length 16S gene tree for 14 239 distinct Streptomyces sequences that resolves three major lineages of Streptomyces , but whose topology is not consistent with existing taxonomic assignments. We use these sequence data to delineate 16S and whole genome landscapes for Streptomyces , demonstrating that 16S and whole-genome classifications are frequently in disagreement, and that 16S zero-radius Operational Taxonomic Units (zOTUs) are often inconsistent with Average Nucleotide Identity (ANI)-based taxonomy. Our results strongly imply that 16S rRNA sequence data does not map to taxonomy sufficiently well to delineate Streptomyces species routinely. We propose that alternative marker sequences should be adopted by the community for classification and metabarcoding. Insofar as Streptomyces taxonomy has been determined or supported by 16S sequence data and may in parts be in error, we also propose that reclassification of the genus by alternative approaches may benefit the Streptomyces community.

Strain HUAS CB01 T was a novel actinobacterium which was isolated from the rhizosphere soil of Cathaya argyrophylla, Chengbu Miao Autonomous County of Hunan Province, China. The strain formed well-growing substrate mycelium, diffusible pigments, and aerial mycelium, and differentiated into spiral-type spore chains composed of smooth-surface rod-shaped spores. Phylogenetic analysis on account of 16 S rRNA gene sequence demonstrated the strain HUAS CB01 T was a member of the genus Streptomyces and had a close relationship with Streptomyces wuyuanensis CGMCC 4.7042  T (100%) and Streptomyces marianii ICN19 T (99.86%). Genome-based comparisons indicated that strain HUAS CB01 T could be distinctly different from its closest species, Streptomyces wuyuanensis CGMCC 4.7042  T , Streptomyces marianii ICN19 T , with ANIm and dDDH results of 92.78% and 45.90%, 92.22% and 43.30%, respectively, far less than 96.7 and 70% cut-off points recommended for delineating species. The main cellular fatty acids concluded anteiso-C 15:0 , iso-C 14:0 , iso-C 16:0 , C 16:0 and C 16:1 2OH. The menaquinones were MK-9(H 4 ), MK-9(H 6 ) and MK-9(H 8 ) and the whole-cell sugars consisted of ribose and mannose. The polar lipids included phosphatidyl ethanolamine, diphosphatidylglycerol, phosphatidylglycerol, mannosides and unidentified phospholipids. According to these genotypic and phenotypic characteristics, strain HUAS CB01 T can be distinguished and representative to be a novel species of the genus Streptomyces, for which the name Streptomyces chengbuensis is proposed. The type strain is HUAS CB01 T ( = MCCC 1K08666 T  = JCM 36277  T )., (© 2024. The Author(s), under exclusive licence to the Japan Antibiotics Research Association.)

An actinobacteria strain was isolated from an olive waste mill and tested for protease production on skimmed milk media. The strain identification was achieved through both 16 S rDNA sequencing and phenotypic characterization. The enzyme was purified using the ammonium sulfate/t-butanol three-phase partitioning (TPP) method, followed by characterization to investigate the effect of pH, temperature, and various chemical agents. Subsequently, the enzyme was assessed for its milk coagulation activity. The strain belonging to the Streptomyces genera, exhibits significant phylogenetic and phenotypic differences from the aligned species, suggesting its novelty as a new strain. The enzyme was best separated in the TPP aqueous phase with a 5.35 fold and 56.25% yield. Optimal activity was observed at pH 9.0 and 60 °C, with more than half of the activity retained within the pH range of 7-10 over one hour. The protease demonstrated complete stability between 30 and 60 °C. While metallic ions enhanced enzyme activity, EDTA acted as an inhibitor. The enzyme displayed resistance to H 2 O 2, SDS, Tween 80, and Triton X-100. Notably, it was activated in organic solvents (ethyl acetate, petroleum ether, and xylene), maintaining > 75% of its original activity in butanol, ethanol, and methanol. Additionally, the enzyme yielded high milk coagulant activity of 11,478 SU/mL. The new Streptomyces sp. protease revealed high activity and stability under a wide range of biochemical conditions. Its use in the dairy industry appears particularly promising. Further industrial process investigations will be valuable in determining potential uses for this enzyme., (© 2024. The Author(s) under exclusive licence to Sociedade Brasileira de Microbiologia.)

Streptomyces species are experts in the production of bioactive secondary metabolites; however, their taxonomy has fallen victim of the tremendous interest shown by the scientific community, evident in the discovery of numerous synonymous in public repositories. Based on genomic data from NCBI Datasets and nomenclature from the LPSN database, we compiled a dataset of 600 Streptomyces species along with their annotations and metadata. To pinpoint the most suitable taxonomic classification method, we conducted a comprehensive assessment comparing multiple methodologies, including analysis of 16S rRNA, individual housekeeping genes, multilocus sequence analysis (MLSA), and Fast Average Nucleotide Identity (FastANI) on a subset of 409 species with complete data. Due to insufficient resolution of 16S rRNA and inconsistency observed in individual housekeeping genes, we performed a more in-depth analysis, comparing only FastANI and MLSA, which expanded our dataset to include 502 species. With FastANI validated as the preferred method, we conducted pairwise analysis on the entire dataset identifying 59 non-unique species among the 600, and subsequently refined the dataset to 541 unique species. Additionally, we collected data on 724 uncharacterized Streptomyces strains to investigate the uniqueness potential of the unannotated fraction of the Streptomyces genus. Utilizing FastANI, 289 strains could be successfully classified into one of the 541 Streptomyces species. KEY POINTS: • Evaluation of taxonomic classification methods for Streptomyces species. • Whole genome analysis, specifically FastANI, has been chosen as preferred method. • Various reclassifications are proposed within the Streptomyces genus., (© 2024. The Author(s).)

Application of actinobacteria has grown exponentially in recent years in sustainable agricultural. Most actinobacterial inoculants are tailored to function as either biocontrol agents or biofertilizers. Hence, there is the need to obtain and include multifunctional actinobacterial strains in inocula formulations. In this research, 90 actinobacterial isolates were isolated from rhizospheric and non-rhizospheric soils of Algerian Saharan arid regions and were screened for their activity against the phytopathogenic fungi Alternaria alternata, Aspergillus flavus, Botrytis cinerea, Fusarium oxysporum, and Fusarium solani. Five isolates that inhibited at least three of these fungi were characterized according to morphological, environmental and biochemical parameters, and were preliminarily identified as Streptomyces enissocaesilis A1, Streptomyces olivoverticillatus A5, Streptomyces erumpens A6, Streptomyces cavourensis A8, and Streptomyces microflavus A20. These strains were then screened for plant growth promoting activities. All strains produced siderophores, hydrocyanic acid, ammonia and the auxin indole-3-acetic acid (IAA) and were capable of solubilizing phosphate. The highest producer of siderophores (69.19 percent siderophore units), ammonia (70.56 μg mL -1 ) and IAA (148.76 μg mL -1 ) was strain A8, A20, and A5, respectively. These findings showed that the five actinobacteria are multipurpose strains with simultaneous antifungal and plant growth promoting activities and have the potential to be used for sustainable agricultural practices, particularly in arid regions., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is the first-line method for the rapid identification of most cultured microorganisms. As for Streptomyces strains, MALDI-TOF MS identification is complicated by the characteristic incrustation of colonies in agar and the strong cell wall of Actinomycetes cells requiring the use of alternative protein extraction protocols. In this study, we developed a specific protocol to overcome these difficulties for the MALDI-TOF MS identification of Actinomycetes made on solid medium. This protocol includes incubation of colony removed from agar plate with the beta-agarase enzyme, followed by a mechanical lysis and two washes by phosphate buffer and ethanol. Twenty-four Streptomyces and two Lentzea strains isolated from Algerian desertic soils were first identified by 16S rRNA sequencing as gold standard method, rpoB gene was used as a secondary gene target when 16S rRNA did not allow species identification. In parallel the isolates were identified by using the MALDI-TOF MS protocol as reported. After the expansion of the database with the inclusion of this MSP S , the strains were analyzed again in MALDI Biotyper, and all were identified. This work demonstrates that the rapid identification of Actinomycetes can be obtained without protein extraction step frequently used in MALDI-TOF mass spectrometry with this type of microorganisms., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The taxonomic relationship between Streptomyces violarus and Streptomyces violaceus was reevaluated using a polyphasic taxonomic approach in this work. Phylogenetic analysis based on 16S rRNA gene sequences indicated that Streptomyces violarus JCM 4534  T was closely related to Streptomyces arenae ISP 5293  T . However, phylogenetic analysis based on five house-keeping gene (atpD, gyrB, recA, rpoB and trpB) showed that the evolutionary neighbor of Streptomyces violarus JCM 4534  T was Streptomyces violaceus CGMCC 4.1456  T , suggesting that there was a close genetic relationship between these two strains. The average nucleotide identity and digital DNA-DNA hybridization values between them were 97.0 and 72.9%, respectively, greater than the 96.7 and 70% cut-off points recommended for delineating a Streptomyces species. This result indicated that they belonged to the same genomic species which was also verified by a comprehensive comparison of phenotypic and chemotaxonomic characteristics between Streptomyces violarus JCM 4534  T and Streptomyces violaceus CGMCC 4.1456  T . According to all these data and the rule of priority in nomenclature, it is proposed the Streptomyces violarus (Artamonova and Krassilnikov 1960) Pridham 1970 is a later heterotypic synonym of Streptomyces violaceus (Rossi Doria 1891) Waksman 1953. In addition, based on dDDH, Streptomyces violaceus and Streptomyces violarus are simultaneously designated as two different subspecies, i.e., Streptomyces violaceus subsp. violaceus and Streptomyces violaceus subsp. violarus., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Botrytis cinerea is a necrotrophic phytopathogen able to attack more than 200 different plant species causing strong yield losses worldwide. Many synthetic fungicides have been developed to control this disease, resulting in the rise of fungicide-resistance B. cinerea strains. The aim of this study was to identify Streptomyces strains showing antagonistic activity against B. cinerea to contribute to plant protection in an environmentally friendly way. We isolated 15 Actinomycete strains from 9 different Swiss soils. The culture filtrates of three isolates showing antifungal activity inhibited spore germination and delayed mycelial growth of B. cinerea . Infection experiments showed that Arabidopsis thaliana plants were more resistant to this pathogen after leaf treatment with the Streptomyces filtrates. Bioassay-guided isolation of the active compounds revealed the presence of germicidins A and B as well as of oligomycins A, B, and E. While germicidins were mostly inactive, oligomycin B reduced the mycelial growth of B. cinerea significantly. Moreover, all three oligomycins inhibited this fungus' spore germination, suggesting that these molecules might contribute to the Streptomyces 's ability to protect plants against infection by the broad host-pathogen Botrytis cinerea ., Importance: This study reports the isolation of new Streptomyces strains with strong plant-protective potential mediated by their production of specialized metabolites. Using the broad host range pathogenic fungus Botrytis cinerea , we demonstrate that the cell-free filtrate of selected Streptomyces isolates efficiently inhibits different developmental stages of the fungus, including mycelial growth and the epidemiologically relevant spore germination. Beyond in vitro experiments, the strains and their metabolites also efficiently protected plants against the disease caused by this pathogen. This work further identifies oligomycins as active compounds involved in the observed antifungal activity of the strains. This work shows that we can harness the natural ability of soil-borne microbes and of their metabolites to efficiently fight other microbes responsible for significant crop losses. This opens the way to the development of environmentally friendly health protection measures for crops of agronomical relevance, based on these newly isolated strains or their metabolic extracts containing oligomycins., Competing Interests: The authors declare no conflict of interest.

Filamentous Actinobacteria, recently renamed Actinomycetia, are the most prolific source of microbial bioactive natural products. Studies on biosynthetic gene clusters benefit from or require chromosome-level assemblies. Here, we provide DNA sequences from >1000 isolates: 881 complete genomes and 153 near-complete genomes, representing 28 genera and 389 species, including 244 likely novel species. All genomes are from filamentous isolates of the class Actinomycetia from the NBC culture collection. The largest genus is Streptomyces with 886 genomes including 742 complete assemblies. We use this data to show that analysis of complete genomes can bring biological understanding not previously derived from more fragmented sequences or less systematic datasets. We document the central and structured location of core genes and distal location of specialized metabolite biosynthetic gene clusters and duplicate core genes on the linear Streptomyces chromosome, and analyze the content and length of the terminal inverted repeats which are characteristic for Streptomyces. We then analyze the diversity of trans-AT polyketide synthase biosynthetic gene clusters, which encodes the machinery of a biotechnologically highly interesting compound class. These insights have both ecological and biotechnological implications in understanding the importance of high quality genomic resources and the complex role synteny plays in Actinomycetia biology., (© The Author(s) 2024. Published by Oxford University Press on behalf of Nucleic Acids Research.)

Polycyclic tetramate macrolactams (PTMs) are bioactive natural products commonly associated with certain actinobacterial and proteobacterial lineages. These molecules have been the subject of numerous structure-activity investigations since the 1970s. New members continue to be pursued in wild and engineered bacterial strains, and advances in PTM biosynthesis suggest their outwardly simplistic biosynthetic gene clusters (BGCs) belie unexpected product complexity. To address the origins of this complexity and understand its influence on PTM discovery, we engaged in a combination of bioinformatics to systematically classify PTM BGCs and PTM-targeted metabolomics to compare the products of select BGC types. By comparing groups of producers and BGC mutants, we exposed knowledge gaps that complicate bioinformatics-driven product predictions. In sum, we provide new insights into the evolution of PTM BGCs while systematically accounting for the PTMs discovered thus far. The combined computational and metabologenomic findings presented here should prove useful for guiding future discovery. IMPORTANCE Polycyclic tetramate macrolactam (PTM) pathways are frequently found within the genomes of biotechnologically important bacteria, including Streptomyces and Lysobacter spp . Their molecular products are typically bioactive, having substantial agricultural and therapeutic interest. Leveraging bacterial genomics for the discovery of new related molecules is thus desirable, but drawing accurate structural predictions from bioinformatics alone remains challenging. This difficulty stems from a combination of previously underappreciated biosynthetic complexity and remaining knowledge gaps, compounded by a stream of yet-uncharacterized PTM biosynthetic loci gleaned from recently sequenced bacterial genomes. We engaged in the following study to create a useful framework for cataloging historic PTM clusters, identifying new cluster variations, and tracing evolutionary paths for these molecules. Our data suggest new PTM chemistry remains discoverable in nature. However, our metabolomic and mutational analyses emphasize the practical limitations of genomics-based discovery by exposing hidden complexity., Competing Interests: The authors declare no conflict of interest.

Two endophytic actinobacteria, strains MK5 T and MK7, were isolated from the surface-sterilized root of Jasmine rice (Oryza sativa KDML 105). These strains were aerobic actinobacteria with a well-developed substrate and aerial mycelia that formed spiral spore chains. The type strains that shared the high 16S rRNA gene sequence similarity with both strains were Streptomyces naganishii NBRC 12892 T (99.4%), "Streptomyces griseicoloratus" TRM S81-3 T (99.2%), and Streptomyces spiralis NBRC 14215 T (98.9%). Strains MK5 T and MK7 are the same species sharing a digital DNA-DNA hybridization (dDDH) value of 95.3% and a 16S rRNA gene sequence similarity of 100%. Chemotaxonomic data confirmed the affiliation of strains MK5 T and MK7 to the genus Streptomyces. Strains MK5 T and MK7 contained MK-9(H 4 ) as a major menaquinone; the whole-cell sugar of both strains was galactose and glucose. The strain MK5 T shared 93.4% average nucleotide identity (ANI)-Blast, 95.5% ANI-MUMmer, 93% average amino acid identity, and 61.3% dDDH with S. spiralis NBRC 14215 T . The polyphasic approach confirmed that strain MK5 T represents a novel species, and the name Streptomyces mahasarakhamensis sp. nov. is proposed. The type strain is MK5 T (= TBRC 17754 = NRRL B-65683). Genome mining, using an in silico approach and searching biosynthesis gene clusters of strains MK5 T and MK7, revealed that the genomes contained genes encoding proteins relating to plant growth promotion, bioactive compounds, and beneficial enzymes. Strains MK5 T and MK7 could produce indole acetic acid and solubilize phosphate in vitro., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Background: Antimicrobial resistance (AMR) is a serious worldwide public health concern that needs immediate action. Probiotics could be a promising alternative for fighting antibiotic resistance, displaying beneficial effects to the host by combating diseases, improving growth, and stimulating the host immune responses against infection. This study was conducted to evaluate the probiotic, antibacterial, and antibiofilm potential of Streptomyces levis strain HFM-2 isolated from the healthy human gut., Results: In vitro antibacterial activity in the cell-free supernatant of S. levis strain HFM-2 was evaluated against different pathogens viz. K. pneumoniae sub sp. pneumoniae, S. aureus, B. subtilis, VRE, S. typhi, S. epidermidis, MRSA, V. cholerae, M. smegmatis, E. coli, P. aeruginosa and E. aerogenes. Further, the ethyl acetate extract from S. levis strain HFM-2 showed strong biofilm inhibition against S. typhi, K. pneumoniae sub sp. pneumoniae, P. aeruginosa and E. coli. Fluorescence microscopy was used to detect biofilm inhibition properties. MIC and MBC values of EtOAc extract were determined at 500 and 1000 µg/mL, respectively. Further, strain HFM-2 showed high tolerance in gastric juice, pancreatin, bile, and at low pH. It exhibited efficient adhesion properties, displaying auto-aggregation (97.0%), hydrophobicity (95.71%, 88.96%, and 81.15% for ethyl acetate, chloroform and xylene, respectively), and showed 89.75%, 86.53%, 83.06% and 76.13% co-aggregation with S. typhi, MRSA, S. pyogenes and E. coli, respectively after 60 min of incubation. The S. levis strain HFM-2 was susceptible to different antibiotics such as tetracycline, streptomycin, kanamycin, ciprofloxacin, erythromycin, linezolid, meropenem, amikacin, gentamycin, clindamycin, moxifloxacin and vancomycin, but resistant to ampicillin and penicillin G., Conclusion: The study shows that S. levis strain HFM-2 has significant probiotic properties such as good viability in bile, gastric juice, pancreatin environment, and at low pH; proficient adhesion properties, and antibiotic susceptibility. Further, the EtOAc extract of Streptomyces levis strain HFM-2 has a potent antibiofilm and antibacterial activity against antibacterial-resistant clinical pathogens., (© 2024. The Author(s).)

Streptomyces sp. SN-593, a reveromycin producer, was previously thought to belong to the genus Streptomyces based on its morphological and chemotaxonomic characteristics. In this paper, we re-considered its taxonomic position according to the current criteria. Phylogenetic analysis using 16S rRNA gene sequences showed that the strain belongs to the genus Actinacidiphila. In multilocus sequence and phylogenomic analyses, the strain SN-593 represented a distinct evolutionary lineage within this genus, and its closest neighbor was A. yanglinensis. Digital DNA-DNA hybridization indicated that the strain shares less than 32% DNA-DNA relatedness with the type strains of closely related species, confirming this strain is a novel genomospecies. According to its phenotypic distinctiveness from the closest neighbor, we propose Actinacidiphila reveromycinica sp. nov. for the strain SN-593T. Additionally, as Streptomyces acidipaludis belonged to the genus Actinacidiphila in these analyses, it should be transferred to the genus, for which Actinacidiphila acidipaludis comb. nov. is proposed., (© The Author(s) 2024. Published by Oxford University Press on behalf of Japan Society for Bioscience, Biotechnology, and Agrochemistry.)

A novel actinobacterium strain, designated HUAS 2-6  T , was isolated from the rhizosphere soil of Camellia oleifera Abel collected from Taoyuan County, Northwestern Hunan Province, South China. This strain was subjected to a polyphasic taxonomic study. Strain HUAS 2-6  T is characterized by morphology typical of members of the genus Streptomyces, with deep purplish vinaceous aerial mycelia and deep dull lavender substrate mycelia. Strain HUAS 2-6  T , based on the full-length 16S rRNA gene sequence analysis, exhibited the highest similarities to S. puniciscabiei S77 T (99.31%), S. filipinensis NBRC 12860  T (99.10%), S. yaanensis CGMCC 4.7035  T (99.09%), S. fodineus TW1S1 T (99.08%), S. broussonetiae CICC 24819  T (98.76%), S. achromogenes JCM 4121  T (98.69%), S. barringtoniae JA03 T (98.69%), and less than 98.70% with other validly species. In phylogenomic tree, strain HUAS 2-6  T was clustered together with S. broussonetiae CICC 24819  T , suggesting that they were closely related to each other. However, average nucleotide identity (ANI) and digital DNA-DNA hybridisation (dDDH) between them were much less than the species cutoff values (ANI 96.7% and dDDH 70%). Moreover, in phenotypic and chemotaxonomic characteristics, strain HUAS 2-6  T is distinct from S. broussonetiae CICC 24819  T . On the basis of the polyphasic data, strain HUAS 2-6  T is proposed to represent a novel species, Streptomyces camelliae sp. nov. (= MCCC 1K04729 T  = JCM 35918  T )., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Fungi and bacteria coexist in a wide variety of environments, and their interactions are now recognized as the norm in most agroecosystems. These microbial communities harbor keystone taxa, which facilitate connectivity between fungal and bacterial communities, influencing their composition and functions. The roots of most plants are associated with arbuscular mycorrhizal (AM) fungi, which develop dense networks of hyphae in the soil. The surface of these hyphae (called the hyphosphere) is the region where multiple interactions with microbial communities can occur, e.g., exchanging or responding to each other's metabolites. However, the presence and importance of keystone taxa in the AM fungal hyphosphere remain largely unknown., Results: Here, we used in vitro and pot cultivation systems of AM fungi to investigate whether certain keystone bacteria were able to shape the microbial communities growing in the hyphosphere and potentially improved the fitness of the AM fungal host. Based on various AM fungi, soil leachates, and synthetic microbial communities, we found that under organic phosphorus (P) conditions, AM fungi could selectively recruit bacteria that enhanced their P nutrition and competed with less P-mobilizing bacteria. Specifically, we observed a privileged interaction between the isolate Streptomyces sp. D1 and AM fungi of the genus Rhizophagus, where (1) the carbon compounds exuded by the fungus were acquired by the bacterium which could mineralize organic P and (2) the in vitro culturable bacterial community residing on the surface of hyphae was in part regulated by Streptomyces sp. D1, primarily by inhibiting the bacteria with weak P-mineralizing ability, thereby enhancing AM fungi to acquire P., Conclusions: This work highlights the multi-functionality of the keystone bacteria Streptomyces sp. D1 in fungal-bacteria and bacterial-bacterial interactions at the hyphal surface of AM fungi. Video Abstract., (© 2024. The Author(s).)

Two novel actinobacteria, designated as LP05-1 T and LP11 T , were isolated from the lichen Pyxine cocoes (Sw.) Nyl. collected in Bangkok, Thailand. Genotypic and phenotypic analyses revealed that both strains represented members of the genus Streptomyces . The 16S rRNA gene of LP05-1 T showed the highest similarity to the genome of Streptomyces gelaticus (98.41 %), while the 16S rRNA gene of LP11 T was most similar to that of Streptomyces cinerochromogenes (98.93 %). The major menaquinones in LP05-1 T were MK-9(H 8 ), MK-9(H 6 ), MK-9(H 4 ) and MK-9(H 2 ), and in LP11 T , they were MK-9(H 8 ) and MK-9(H 6 ). Both strains exhibited the major fatty acids iso-C 15 : 0 , anteiso-C 15 : 0 , iso-C 16 : 0 and anteiso-C 17 : 0 , with LP05-1 T also possessing iso-C 17 : 0 . The polar lipids of LP05-1 T included phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside and an unidentified lipid, while those of LP11 T consisted of phosphatidylethanolamine, lyso -phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside, an unidentified aminolipid and an unidentified glycolipid. The digital DNA-DNA hybridisation (dDDH) and average nucleotide identity (ANI) values indicated that both strains are distinct from each other with values below 70 and 95 %, respectively. dDDH, ANI by blast (ANIb) and ANI by MUMmer (ANIm) values between LP05-1 T and its closely related type strains were 26.07-26.80 %, 81.24-82.01 % and 86.82-86.96 %, respectively, while those for LP11 T and its closely related type strains were 30.70-31.70 %, 84.09-85.31 % and 88.02-88.39 %, respectively. The results of the taxonomic investigation, including dDDH and ANI values, indicate that LP05-1 T and LP11 T are novel type strains of two novel species within the genus Streptomyces . The names proposed are Streptomyces pyxinae sp. nov. for strain LP05-1 T (=TBRC 15494 T , =NBRC 115434 T ) and Streptomyces pyxinicus sp. nov. for strain LP11 T (=TBRC 15493 T , =NBRC 115421 T ).

A Gram-stain-positive actinomycete, designated REN17 T , was isolated from fermented grains of Baijiu collected from Sichuan, PR China. It exhibited branched substrate mycelia and a sparse aerial mycelium. The optimal growth conditions for REN17 T were determined to be 28 °C and pH 7, with a NaCl concentration of 0 % (w/v). ll-Diaminopimelic acid was the diagnostic amino acid of the cell-wall peptidoglycan and the polar lipids were composed of phosphatidylethanolamine, phosphatidylinositol, an unidentified phospholipid, two unidentified lipids and four unidentified glycolipids. The predominant menaquinone was MK-9 (H 2 ), MK-9 (H 4 ), MK-9 (H 6 ) and MK-9 (H 8 ). The major fatty acids were iso-C 16 : 0 . The 16S rRNA sequence of REN17 T was most closely related to those of Streptomyces apricus SUN 51 T (99.8 %), Streptomyces liliiviolaceus BH-SS-21 T (99.6 %) and Streptomyces umbirnus JCM 4521 T (98.9 %). The digital DNA-DNA hybridization, average nucleotide identity and average amino acid identify values between REN17 T and its closest replated strain, of S. apricus SUN 51 T , were 35.9, 88.9 and 87.3 %, respectively. Therefore, REN17 T represents a novel species within the genus Streptomyces , for which the name Streptomyces beigongshangae sp. nov. is proposed. The type strain is REN17 T (=GDMCC 4.193 T =JCM 34712 T ). While exploring the function of the strain, REN17 T was found to possess the ability to transform major ginsenosides of Panax notoginseng (Burk.) F.H. Chen (Araliaceae) into minor ginsenoside through HPLC separation, which was due to the presence of β-glucosidase. The recombinant β-glucosidase was constructed and purified, which could produce minor ginsenosides of Rg3 and C-K. Finally, the enzymatic properties were characterized.

A novel actinobacterium, designated strain CWNU-1 T , was isolated from the rhizospheric soil of Fritillaria cirrhosa D. Don and examined using a polyphasic taxonomic approach. The organism developed pale blue aerial mycelia that was simply branched and terminated in open or closed coils of three or more volutions on International Streptomyces Project 3 agar. Spores were ellipsoidal to cylindrical with wrinkled surfaces. The strain showed high 16S rRNA gene sequence similarity to Streptomyces kurssanovii NBRC 13192 T (98.8 %), Streptomyces xantholiticus NBRC 13354 T (98.7 %) and Streptomyces peucetius JCM 9920 T (98.6 %). The phylogenetic result based on 16S rRNA gene and genome sequences clearly demonstrated that strain CWNU-1 T formed an independent phylogenetic lineage. On the basis of orthologous average nucleotide identity, CWNU-1 T was most closely related to Streptomyces inusitatus NBRC 13601 T with 79.3 % identity. The results of the digital DNA-DNA hybridization analysis also indicated low levels of relatedness with other species, as the highest value was observed with S. inusitatus NBRC 13601 T (25.3 %). With reference to phenotypic characteristics, phylogenetic data, orthologous average nucleotide identity and digital DNA-DNA hybridization results, strain CWNU-1 T was readily distinguished from its most closely related strains and classified as representing a novel species, for which the name Streptomyces albipurpureus sp. nov. is proposed. The type strain is CWNU-1 T (=CGMCC 4.7758 T =MCCC 1K07402 T =JCM 35391 T ).

The Gram-positive bacteria Streptomyces davaonensis and Streptomyces cinnabarinus have been the only organisms known to produce roseoflavin, a riboflavin (vitamin B 2 ) derived red antibiotic. Using a selective growth medium and a phenotypic screening, we were able to isolate a novel roseoflavin producer from a German soil sample. The isolation procedure was repeated twice, that is, the same strain could be isolated from the same location in Berlin 6 months and 12 months after its first isolation. Whole genome sequencing of the novel roseoflavin producer revealed an unusual chromosomal arrangement and the deposited genome sequence of the new isolate (G + C content of 71.47%) contains 897 genes per inverted terminal repeat, 6190 genes in the core and 107 genes located on an illegitimate terminal end. We identified the roseoflavin biosynthetic genes rosA, rosB and rosC and an unusually high number of riboflavin biosynthetic genes. Overexpression of rosA, rosB and rosC in Escherichia coli and enzyme assays confirmed their predicted functions in roseoflavin biosynthesis. A full taxonomic analysis revealed that the isolate represents a previously unknown Streptomyces species and we propose the name Streptomyces berlinensis sp. nov. for this roseoflavin producer., (© 2024 The Authors. Environmental Microbiology Reports published by John Wiley & Sons Ltd.)

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-DRY2 T , has a genome size of 9.29 Mb with a G+C content of 70.83 mol%. Phylogenomics determined that A15ISP2-DRY2 T represents a novel species within the genus Streptomyces as part of the Streptomyces aurantiacus clade. The biosynthetic potential of A15ISP2-DRY2 T 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-DRY2 T contains six unique GCFs absent elsewhere in the clade. Culture-based assays were used to demonstrate the antibacterial activity of A15ISP2-DRY2 T against two drug-resistant human pathogens. Thus, we determine A15ISP2-DRY2 T to be a novel bacterial species with considerable biosynthetic potential and propose the systematic name ' Streptomyces ortus' sp. nov.

Although 16S rRNA gene sequences are conventionally analysed in bacterial systematics, their resolution is not sufficient for species identification. Multilocus sequence analysis (MLSA) is a powerful method for species identification as well as the elucidation of phylogenetic relationships in the genus Streptomyces . Gene sequences of atpD, gyrB, recA, rpoB and trpB are generally used in MLSA for Streptomyces species. This study aims to evaluate the sequence analysis of one gene instead of all five genes to be employed for species identification. The resolution of atpD gene sequences was not necessarily able to distinguish closely related species. In contrast, trpB gene sequence similarities correlated to the MLSA-based evolutionary distances, especially among closely related strains. A pairwise similarity of 97.9 % in trpB gene sequences was proposed as the threshold for species delineation based on the feasibility examined using strain pairs that shared >99.93 % pairwise 16S rRNA gene sequence similarities. Resequencing the five housekeeping genes followed by MLSA suggested that Streptomyces anthocyanicus and Streptomyces tricolor are synonyms of Streptomyces violaceoruber .

Two new marine actinobacteria, designated as J2-1 T and J2-2 T , 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 J2-1 T and J2-2 T were identified as members of the genus Streptomyces and Kineosporia , respectively. Strains J2-1 T and J2-2 T showed the highest 16S rRNA gene sequence similarity to Streptomyces broussonetiae T44 T (98.62 %) and Kineosporia babensis VN05A0415 T (98.08 %), respectively. Strain J2-1 T 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 C 16 : 0 iso, C 15 : 0 anteiso, C 15 : 0 iso, C 16 : 0 , C 17 : 0 anteiso, C 14 : 0 iso and C 17 : 0 iso. Strain J2-2 T 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 C 16 : 0 , C 18 : 1  ω9 c , C 18 : 0 10-methyl, tuberculostearic acid, C 18 : 0 and C 17 : 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. (J2-1 T =TBRC 13503 T =NBRC 115066 T ) and Kineosporia corallincola sp. nov. (J2-2 T =TBRC 13504 T =NBRC 114885 T ).

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 NE06-02D T 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 NE06-02D T (=DSM111602 T =ATCC TSD-236 T ) and the other members of this novel species group.

Strains DS1-2 T and AZ1-7, which were isolated from roots of plants, were taxonomically characterized based on polyphasic taxonomic and taxogenomic approaches. Both strains were Gram-stain-positive and filamentous bacteria which contained LL-diaminopimelic acid in cell-wall peptidoglycan and glucose and ribose in whole-cell hydrolysates. MK-9(H 6 ), MK-10(H 6 ), MK-9(H 8 ), MK-10(H 8 ) and MK-10(H 4 ) were major menaquinones; iso-C 16:0 and iso-C 16:1 G were predominant cellular fatty acids; diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylinositol mannoside presented as major phospholipids; and the DNA G+C contents of 73.2 mol%. Strains DS1-2 T and AZ1-7 showed 97.6-98.0 % 16S rRNA gene sequence similarity, 81.0-82.0 % ANIb, 84.8-85.3 % ANIm and 22.0-23.1 % digital DDH to their related type strains: S. specialis GW41-1564 T and S. hoynatensis S1412 T . Comparative genomics results of these strains and their related type strains also revealed the differences and distributions of key genes associated with stress responses, environmental variables, plant interactions and bioactive metabolites. Based on the phenotypic, chemotaxonomic and genomic data, strains DS1-2 T and AZ1-7 could be assigned to the novel species within the genus Streptomyces for which the name Streptomyces radicis sp. nov. is proposed. The type strain is DS1-2 T (=JCM 32152 T =KCTC 39738 T =TISTR 2403 T )., (Copyright © 2021 Elsevier GmbH. All rights reserved.)

An endophytic Streptomyces -like micro-organism, designated strain PRB2-1 T 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 PRB2-1 T is a member of the genus Streptomyces with the highest similarity to Streptomyces bryophytorum DSM 42183 T (98.4 %). Moreover, the draft genome sequence of strain PRB2-1 T 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 PRB2-1 T and its close relatives indicated that strain PRB2-1 T 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 PRB2-1 T (=TBRC 7642 T =NBRC 113169 T ).

A novel Streptomyces strain, SUN51 T , 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 : SUN51 T was most closely related to Streptomyces dioscori A217 T (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-C 15 : 0 , iso-C 16 : 0 , 16 : 1 ω7c, anteiso-C 17 : 0 , iso-C 14 : 0 and C 16 : 0 . The predominant menaquinones were MK-9 H4, MK-9 H6 and MK-9 H8. Strain SUN51 T 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 SUN51 T (=NRRL B-65543 T =JCM 33736 T ).

A biologically active microbial strain, designated as "LS462," was isolated from a soil sample collected from Yaoli Virgin Forest of Jiangxi Province, China. The strain was able to produce a high yield of echinomycin (172 mg/l) even under nonoptimized culture conditions and is proposed to serve as a promising source of echinomycin. In this study, echinomycin exhibited strong anti-Mycobacterium tuberculosis H37Rv activity and synergistic antifungal effect with a greatly reduced dosage of posaconazole on Candida albicans SC5314. The strain belongs to the genus Streptomyces according to its morphological and 16S rDNA phylogenetic analysis. The 16S rDNA was found to have the highest sequence identity with Streptomyces fuscichromogenes (99.37% similarity). Extensive nuclear magnetic resonance and mass spectroscopic data were used to determine the structure of echinomycin. The strain S. fuscichromogenes has not been previously reported to produce echinomycin. Strain LS462 may be exploited as a new potential source for the commercial production of echinomycin. Also, this work is the first to report the new synergistic antifungal activity of echinomycin and further study of the synergistic mechanism will be helpful to guide the development of antifungal agents., (© The Author(s) 2021. Published by Oxford University Press on behalf of Society of Industrial Microbiology and Biotechnology.)

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., (© 2021. The Author(s).)

Genome homology and the presence of a putative biosynthetic gene cluster identified Streptomyces aureorectus DSM 41692 and Streptomyces virens DSM 41465 as candidate producers of the antibiotic nucleocidin 1. Indeed when these bacterial strains were cultured in a medium supplemented with fluoride (4 mM) they each produced nucleocidin 1 and the previously identified 4'-fluoro-3'- O -β-glucosylated adenosine 2 and its sulfamylated derivative 3. In both of these cases 4'-fluoroadenosine 9 is also identified as a natural product although it has never been observed during fermentations of Streptomyces calvus , the original source of nucleocidin 1. The identity of 4'-fluoroadenosine 9 was confirmed by a total synthesis as well as by its in vitro enzymatic conversion to metabolite 2 using the glucosyl transferase enzyme, NucGT.

A bacterial strain, named For3 T , 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 33331 T , Streptomyces anulatus ATCC 27416 T , Streptomyces setonii NRRL ISP-5322 T and Kitasatospora papulosa NRRL B-16504 T . The phylogenomic tree using the genome blast distance phylogeny method showed that the closest relative strain was Streptomyces atroolivaceus NRRL ISP-5137 T and that For3 T represents a new branch among the Streptomyces . Genome relatedness indexes revealed that the average nucleotide identity and digital DNA-DNA hybridization values between For3 T and its closest phylogenomic relative ( S. atroolivaceus NRRL ISP-5137 T ) 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 For3 T harboured complete metabolic pathways absent in the closest relative strains such as cellulose biosynthesis, glycogen degradation I, glucosylglycerate biosynthesis I. Anteiso-C 15:0 , iso-C 15:0 , anteiso-C 17:0 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 For3 T to a novel species Streptomyces silvae sp. nov., within the genus Streptomyces , for which the type strain is For3 T (=CIP 111908 T =LMG 32186 T ).

The genus Streptomyces includes, at the time of writing, eight subspecies with validly published names. Streptomyces thermoviolaceus subsp. apingens NBRC 15459 T and Streptomyces lavendulae subsp. grasserius NBRC 13045 T show 16S rRNA gene sequence similarities of >99.7% to their parent species Streptomyces thermoviolaceus subsp. thermoviolaceus NBRC 13905 T and Streptomyces lavendulae subsp. lavendulae NRRL B-2774 T , respectively. In contrast, the type strains of the remaining six subspecies, Streptomyces achromogenes subsp. rubradiris , Streptomyces albosporeus subsp. labilomyceticus , Streptomyces cacaoi subsp. asoensis , Streptomyces chrysomallus subsp. fumigatus , Streptomyces cinereoruber subsp. fructofermentans and Streptomyces hygroscopicus subsp. ossamyceticus , do not show >99.0% 16S rRNA gene sequence similarity to that of each parent species. Although S. chrysomallus subsp. fumigatus and S. hygroscopicus subsp. ossamyceticus were respectively reclassified to ' Kitasatospora fumigata ' and ' Streptomyces ossamyceticus ', these names have not been validly published yet. In this study, we investigated the taxonomic positions of S. achromogenes subsp. rubradiris , S. cacaoi subsp. asoensis , S. cinereoruber subsp. fructofermentans , S. hygroscopicus subsp. ossamyceticus and S. thermoviolaceus subsp. apingens given that their whole genome sequences are available. Except for S. thermoviolaceus subsp. apingens , these subspecies were discriminated from the parent and closely related species based on phylogenetic, genomic and phenotypic differences. Thus, we reclassify S. achromogenes subsp. rubradiris , S. cacaoi subsp. asoensis , S. cinereoruber subsp. fructofermentans and S. hygroscopicus subsp. ossamyceticus as Streptomyces rubradiris sp. nov., Streptomyces asoensis sp. nov., Streptomyces fructofermentans sp. nov. and Streptomyces ossamyceticus sp. nov., respectively. Multilocus sequence and 16S rRNA gene sequence analyses suggested that S. albosporeus subsp. labilomyceticus and S. lavendulae subsp. grasserius may also be reclassified as independent species.

A novel actinobacterium, designated strain DW4-2 T , 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 DW4-2 T showed the highest 16S rRNA gene sequence similarity values to Streptomyces qinglanensis DSM 42035 T (98.5 %), S treptomyces smyrnaeus DSM 42105 T (98.4 %) and Streptomyces oryzae S16-07 T (98.4 %). Digital DNA-DNA hydridization and average nucleotide identity values between the genome sequences of strain DW4-2 T with S. qinglanensis DSM 42035 T (29.8 and 87.8 %), S. smyrnaeus DSM 42105 T (33.1 and 89.0 %) and S. oryzae S16-07 T (33.0 and 88.9 %) were below the thresholds of 70 and 95-96 % for prokaryotic conspecific assignation. Chemotaxonomic data revealed that strain DW4-2 T possessed MK-9(H 6 ) and MK-9(H 8 ) 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 -C 17 : 0 , anteiso -C 15 : 0 and iso -C 16 : 0 . The genomic DNA size of the strain DW4-2 T was 7 310 765 bp with DNA G+C content 71.0 mol%. Genomic analysis of the genome indicated that the strain DW4-2 T had the potential to produce bioactive compounds. On the basis of these genotypic and phenotypic data, it is supported that strain DW4-2 T represents a novel species of the genus Streptomyces , for which the name Streptomyces spirodelae sp. nov. is proposed. The type strain is strain DW4-2 T (=TBRC 13095 T =NBRC 114803 T ).

The marine ecosystem has become the hotspot for finding antibiotic-producing actinomycetes across the globe. Although marine-derived actinomycetes display strain-level genomic and chemodiversity, it is unclear whether functional traits, i.e., antibiotic activity, vary in near-identical Streptomyces species. Here, we report culture-dependent isolation, antibiotic activity, phylogeny, biodiversity, abundance, and distribution of Streptomyces isolated from marine sediments across the west-central Philippines. Out of 2212 marine sediment-derived actinomycete strains isolated from 11 geographical sites, 92 strains exhibited antibacterial activities against multidrug-resistant Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. The 16S rRNA and rpoB gene sequence analyses confirmed that antibiotic-producing strains belong to the genus Streptomyces, highlighting Streptomyces parvulus as the most dominant species and three possible new species. Antibiotic-producing Streptomyces strains were highly diverse in Southern Antique, and species diversity increase with marine sediment depth. Multiple strains with near-identical 16S rRNA and rpoB gene sequences displayed varying strength of antibiotic activities. The genotyping of PKS and NRPS genes revealed that closely related antibiotic-producing strains have similar BGC domains supported by their close phylogenetic proximity. These findings collectively suggest Streptomyces' intraspecies adaptive characteristics in distinct ecological niches that resulted in outcompeting other bacteria through differential antibiotic production., (© 2021. The Author(s).)

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-LD23 T 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-LD23 T (=CCTCC AA 2019029 T =DSM 109824 T ). In addition, strain NEAU-LD23 T 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-LD23 T significantly inhibited mycelial growth of B. cinerea . To preliminarily explore the antifungal mechanisms, the genome of strain NEAU-LD23 T 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.

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-B04 T 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-B04 T and P01-F02 are closely related to Streptomyces beijiangensis DSM 41794 T , Streptomyces laculatispora NRRL B-24909 T , and Streptomyces brevispora NRRL B-24910 T . 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-B04 T and P01-F02 from their closest phylogenetic relatives. In silico analysis predicted that the 8.9 Mb genome of P01-B04 T 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-B04 T (=DSM 111306 T  = CCM 9048 T ) as the type strain., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier GmbH. All rights reserved.)

An endophytic actinobacterium, strain CAP261 T was isolated from the surface sterilized root of Callitris preissii (Australian native pine tree). As a result of a polyphasic taxonomy study, this strain was identified as a member of the genus Streptomyces. This strain was an aerobic actinobacterium with well-developed substrate mycelia with loop spore chains and the spore surfaces are verrucose. The closest phylogenetic members which shared the highest 16S rRNA gene sequences similarity was Streptomyces bottropensis ATCC 25435  T at 98.1%. Chemotaxonomic data including cell wall components, major menaquinones, and major fatty acids confirmed the affiliation of strain CAP261 T to the genus Streptomyces. The results of the phylogenetic analysis, including physiological and biochemical studies in combination with genome comparison study, allowed the genotypic and phenotypic differentiation of strain CAP261 T and the closest species with validly published names. ANIb, ANIm and dDDH values of strain CAP261 T and S. bottropensis ATCC 25435  T were 86.7%, 89.2% and 33.9%, respectively. The name proposed for the new species is Streptomyces adelaidensis sp. nov. The type strain is CAP261 T (= DSM 42026  T  = NRRL B-24814  T )., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

As two separate genomic species, Streptomyces calvus and Streptomyces aureorectus were approved in 1980 and 1986, respectively. However, recently, it has been found that the average nucleotide identity and digital DNA-DNA hybridization values between S. calvus JCM 4326 T and S. aureorectus DSM 41692 T were 99.19 and 92.70 %, respectively, much higher than 95-96 and 70  % cut-off points proposed and the generally accepted species boundaries. These data indicated that they should be classified as the same genomic species. Furthermore, this result was also supported by a comprehensive comparison of phenotypic, chemotaxonomic and physio-biochemical characteristics between the two type strains. All these data indicated that S. calvus and S. aureorectus had the same taxonomic position. In accordance with the principle of priority, it is proposed that S. aureorectus is a later heterotypic synonyms of S. calvus .

A novel genistein-producing actinobacterial strain, designated strain CRPJ-33 T , 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-33 T 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 T102 T , Streptomyces eurocidicus NRRL B-1676 T , Streptomyces xanthochromogenes NRRL B-5410 T , Streptomyces michiganensis NBRC 12797 T , Streptomyces mauvecolor LMG 20100 T and Streptomyces lavendofoliae NBRC 12882 T , respectively. Phylogenetic analysis of 16S rRNA gene sequences showed that strain CRPJ-33 T was most closely related to S. zhihengii YIM T102 T . 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-33 T from S. zhihengii YIM T102 T . Meanwhile, the ANI and dDDH values or MLSA distances between strain CRPJ-33 T and other type strains, which exhibited ≥98.7 % 16S rRNA gene sequence similarities to strain CRPJ-33 T , were far away from the recommended threshold values. Based on these results, it is thought that strain CRPJ-33 T should represent a novel species of the genus Streptomyces , for which the name Streptomyces genisteinicus sp. nov. is proposed. The type strain is CRPJ-33 T (=MCCC 1K04965 T =JCM 34526 T ). 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.

A novel actinomycete strain, designated strain QMT-12 T , was isolated from the rhizospheric soils of Fagopyrum tataricum and characterized using a polyphasic approach. Strain QMT-12 T was found to have morphological features typical of the genus Streptomyces. The predominant fatty acids included C 18:1 cis9 (35.9%), Summed feature 6 (C 18:2 cis9, 12/C 18:0 a or C 18:0 anteiso/C 18:2 c) (30.6%) and C 16:0 (16.3%). The whole-cell sugars were arabinose and glucose. The whole-cell-wall amino acids included alanine, aspartate, glutamic acid, glycine and LL-diaminopimelic acid. The menaquinones were MK-9, MK-9(H 2 ), MK-9(H 4 ), MK-9(H 6 ) and MK-9(H 8 ). The diagnostic phospholipids consisted of diphosphatidyl glycerol, phosphatidylethanolamine, phosphatidyl methyl ethanolamine, phospholipids, phosphotidyl inositol, phosphotidylinositol mannosides, and phospholipids of unknown structure containing glucosamine. The full-length 16S rRNA gene sequence analysis showed that strain QMT-12 T belonged to the genus Streptomyces and had 98.2, 98.1, 98.1 and ≤ 98.0% similarities to Streptomyces camponoticapitis 2H-TWYE14 T , Streptomyces scopuliridis NRRL B-24574 T , Streptomyces inhibens NEAU-D10 T and other Streptomyces species with validly published and correct names, respectively. Phylogenetic analysis indicated that strain QMT-12 T was closely related to Streptomyces inhibens NEAU-D10 T . However, the average nucleotide identity value and the digital DNA-DNA hybridization value between strain QMT-12 T and S. inhibens NEAU-D10 T were 85.0 and 22.3%, respectively, well below 95-96% and 70% cut-off point recommended for delineating species. Based on its phenotypic and genotypic characteristics, strain QMT-12 T (= CICC 11056 T  = JCM 33963 T ) represents the type strain of a novel species, for which the name Streptomyces liangshanensis sp. nov. is proposed., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Two strains of Actinobacteria, designated CRXT-Y-14 T and CRXT-G-22 T , were isolated from the healthy leaves and seeds, respectively, of a medicinal plant Xanthium sibiricum . Their taxonomic positions were determined using a polyphasic approach. Strain CRXT-Y-14 T produced flexuous chains of smooth-surfaced spores. Strain CRXT-G-22 T produced straight chains of smooth-surfaced spores. Their morphological features were consistent with the diagnostic characteristics of members of the genus Streptomyces . The results of 16S rRNA gene sequence analyses indicated two strains represented members of the genus Streptomyces . CRXT-Y-14 T shared 99.3, 98.9, 98.8 % sequence similarities to Streptomyces atriruber NRRL B-24165 T , Streptomyces avermitilis MA-4680 T and Streptomyces davaonensis JCM 4913 T , respectively. Whilst CRXT-G-22 T exhibited highest similarity to Streptomyces acidiscabies ATCC 49003 T (98.9 %). The results of phylogenetic analyses based on 16S rRNA gene sequences indicated that the closest phylogenetic neighbours of strains CRXT-Y-14 T and CRXT-G-22 T were S. atriruber NRRL B-24165 T and S. acidiscabies ATCC 49003 T , respectively. The phylogenomic analyses further confirmed the relative relationship between strain CRXT-G-22 T and S. acidiscabies ATCC 49003 T , but indicated that CRXT-Y-14 T could represent a novel species of the genus Streptomyce . However, the average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between CRXT-Y-14 T and strain CRXT-G-22 T , between CRXT-Y-14 T and S. atriruber NRRL B-24165 T , and between CRXT-G-22 T and S. acidiscabies ATCC 49003 T were 85.4 and 23.2 %, 85.8 and 23.9 % and 89.1 and 34.1 %, respectively, far below the 95~96 and 70 % cut-off points recommended for delineating species. Furthermore, these two novel isolates were distinctly differentiated from their relatives in the genus Streptomyces with respect to phenotypic and chemotaxonomic characteristics. On the basis of these data, CRXT-Y-14 T and CRXT-G-22 T clearly represent two novel species within the genus Streptomyces , for which the names Streptomyces xanthii sp. nov. (type strain CRXT-Y-14 T = MCCC 1K04966 T = JCM 34527 T ) and Streptomyces roseirectus sp. nov. (type CRXT-G-22 T = MCCC 1K04979 T = JCM 34565 T ) are proposed.

Three compounds were isolated from marine-derived Streptomyces sp. CNQ-031, and their inhibitory activities against monoamine oxidases (MAOs), acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and β-secretase (BACE-1) were evaluated. Compound 1 (5,7-dihydroxy-2-isopropyl-4H-chromen-4-one) was a potent and selective inhibitor of MAO-A, with a 50% inhibitory concentration (IC 50 ) of 2.70 μM and a selectivity index (SI) of 10.0 versus MAO-B. Compound 2 [5,7-dihydroxy-2-(1-methylpropyl)-4H-chromen-4-one] was a potent and low-selective inhibitor of MAO-B, with an IC 50 of 3.42 μM and an SI value of 2.02 versus MAO-A. Compound 3 (1-methoxyphenazine) did not inhibit MAO-A or MAO-B. All three compounds showed little inhibitory activity against AChE, BChE, and BACE-1. The K i value of compound 1 for MAO-A was 0.94 ± 0.28 μM, and the K i values of compound 2 for MAO-A and MAO-B were 3.57 ± 0.60 and 1.89 ± 0.014 μM, respectively, with competitive inhibition. The 1-methylpropyl group in compound 2 increased the MAO-B inhibitory activity compared with the isopropyl group in compound 1. Inhibition of MAO-A and MAO-B by compounds 1 and 2 was recovered by dialysis experiments. These results suggest that compounds 1 and 2 are reversible, competitive inhibitors of MAOs and can be considered potential therapies for neurological disorders such as depression and Alzheimer's disease.

Streptomyces thermoautotrophicus UBT1 T has been suggested to merit generic status due to its phylogenetic placement and distinctive phenotypes among Actinomycetia. To evaluate whether 'S. thermoautotrophicus' represents a higher taxonomic rank, 'S. thermoautotrophicus' strains UBT1 T and H1 were compared to Actinomycetia using 16S rRNA gene sequences and comparative genome analyses. The UBT1 T and H1 genomes each contain at least two different 16S rRNA sequences, which are closely related to those of Acidothermus cellulolyticus (order Acidothermales). In multigene-based phylogenomic trees, UBT1 T and H1 typically formed a sister group to the Streptosporangiales-Acidothermales clade. The Average Amino Acid Identity, Percentage of Conserved Proteins, and whole-genome Average Nucleotide Identity (Alignment Fraction) values were ≤58.5%, ≤48%, ≤75.5% (0.3) between 'S. thermoautotrophicus' and Streptosporangiales members, all below the respective thresholds for delineating genera. The values for genomics comparisons between strains UBT1 T and H1 with Acidothermales, as well as members of the genus Streptomyces, were even lower. A review of the 'S. thermoautotrophicus' proteomic profiles and KEGG orthology demonstrated that UBT1 T and H1 present pronounced differences, both tested and predicted, in phenotypic and chemotaxonomic characteristics compared to its sister clades and Streptomyces. The distinct phylogenetic position and the combination of genotypic and phenotypic characteristics justify the proposal of Carbonactinospora gen. nov., with the type species Carbonactinospora thermoautotrophica comb. nov. (type strain UBT1 T , = DSM 100163 T  = KCTC 49540 T ) belonging to Carbonactinosporaceae fam. nov. within Actinomycetia., (Copyright © 2021 The Author(s). Published by Elsevier GmbH.. All rights reserved.)

Two novel actinobacteria, strain PSKA28 T and PSKA54 T were isolated from soil sample of Kashmir-Himalaya, India (latitude 34°-01' N; longitude 74°-47' E; altitude 5328 ft). Polyphasic-taxonomic analysis revealed that these strains belong to the genus Streptomyces. The 16S rRNA gene-sequence similarity of these strain were highest (98.6%) with that of the Streptomyces torulosus NRRLB-3889 T . They showed 92.1% gyrB gene-sequence similarity but 92.9 and 94.6% rpoB gene-sequence similarity, respectively, with Streptomyces torulosus NRRLB-3889 T . The sequence similarities were significantly lower than the recommended threshold value for novel taxonomic position and the 16S rRNA sequence-based phylogenetic analysis indicated that these two isolates are in distinct clade. Phylogenomic analysis with their genome sequences, conferred by Type Strain Genome Server separated them from rest of the Streptomyces type strains. The cell wall contained LL-diaminopimelic acid and the whole-cell hydrolysate contained glucose and ribose. Major fatty acid methyl esters were 15:0 anteiso, 16:0 iso and 17:0 anteiso. Average nucleotide identity, average amino acid identity and digital DNA-DNA hybridization (dDDH) values as well as evolutionary distance based on multilocus sequence analysis, between closely related type strains and either of the strain PSKA28 T or PSKA54 T , were considerably lower than the recommended threshold value (< 70% dDDH or < 95-96% ANI/AAI or > 0.007 MLSA distance). Therefore, these isolates represent a novel Streptomyces species, for which we proposed the name Streptomyces himalayensis sp. nov. Genotypic and phenotypic analyses clearly split these strains into two closely related sub-clusters. Based on this, two novel subspecies Streptomyces himalayensis subsp. himalayensis subsp. nov. and Streptomyces himalayensis subsp. aureolus subsp. nov. are proposed, with type strains JCM33755 T (= MTCC12933 T , MCC4145 T ) and JCM33759 T (= MTCC12938, MCC4180), respectively.

An actinobacterium, strain CH5-8 T , which formed spiral chains of spore arising from the aerial mycelium, was isolated from rhizosphere soil of Musa spp . The organism exhibited vivid greenish yellow substrate mycelium and easily produced the medium grey aerial spore mass on ISP2 medium. The typical chemotaxonomic properties of members of the genus Streptomyces were observed for strain CH5-8 T , e.g. ll-diaminopimelic acid in cell peptidoglycan, MK-9(H 8 ), MK-9(H 6 ), and MK-9(H 4 ) as major menaquinones and anteiso-C 15 : 0 , iso-C 16 : 0 , and anteiso-C 17 : 0 as major fatty acids. Diphosphatidylglycerol, phosphatidylethanolamine, hydroxyphosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositol mannoside were detected in the cells. A combination of morphological and chemotaxonomic data supported the assignment to the genus Streptomyces . The analysis result obtained for the 16S rRNA gene sequence confirmed the taxonomic affiliation at the genus level of this strain. The novel strain CH5-8 T showed the highest 16S rRNA gene sequence values to Streptomyces echinatus NBRC 12763 T (98.9 %), followed by Streptomyces actinomycinicus RCU-197 T (98.9 %). The average nucleotide identity by blast (ANIb) and digital DNA-DNA hybridization values between CH5-8 T and its closest relatives, S. echinatus CECT 3313 T and S. actinomycinicus RCU-197 T , were ≤91.6 % and ≤47.4 %, respectively. The digital DNA G+C content of genomic DNA was 72.1 mol%. On the basis of these phenotypic and genotypic data, strain CH5-8 T represents a novel species, for which the name Streptomyces musisoli sp. nov. is proposed. The type strain is CH5-8 T (=TBRC 9950 T =NBRC 113997 T ).

Terrestrial actinomycetes are the important sources of secondary metabolites that serve as a major source of drugs. Recent advances in genome mining have revealed that Streptomyces genomes have a wide range of undiscovered secondary metabolite biosynthetic gene clusters. In the present study, genome mining was employed to discover biosynthetic potential of plant-associated strain Streptomyces BA2. Based on 16S rRNA gene sequencing, this strain was found to be closely related to Streptomyces durmitorensis, Streptomyces alboniger, and Streptomyces kanamyceticus with similarity of 99.71%, 99.64%, and 99.56%, respectively. The genome of BA2 contained 10.043.478 base pairs with G + C content of 69.92%. The annotation results revealed the presence of 9.056 protein coding genes, 88 tRNA and 18 rRNA genes. The dDDH and ANI values of genome sequences between strain BA2 and closely related type strains were considerably lower than the recommended threshold values. A total of 33 secondary metabolite biosynthetic gene clusters responsible for the biosynthesis of known and/or novel secondary metabolites, including non-ribosomal peptides, polyketides, terpenes, siderophores, bacteriocins, ectoines, and lassopeptides were identified. Metabolic profiling of Streptomyces sp. BA2 grown in three different culture media was determined by a non-targeted LC-MS/MS approach coupled with spectral networking. Significant bioactive natural products such as actinomycin D, desferrioxamine E, malyngamide K, and bouillonamide B were detected. Malyngamide K and bouillonamide B, known as marine cyanobacterial-derived compounds, were first reported from a Streptomyces strain in this study. Our study demonstrated the potentially novel strain Streptomyces sp. BA2 as a valuable source of new bioactive secondary metabolites.