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Actinomycetes are a prolific source of bioactive natural compounds many of which are used as antibiotics or other drugs. In this study we investigated the genomic and biochemical diversity of 32 actinobacterial strains that had been deposited at the DSMZ-German Collection of Microorganisms and Cell Cultures decades ago. Genome-based phylogeny and in silico DNA-DNA hybridization supported the assignment of these strains to 26 novel species and two novel subspecies and a reclassification of a Streptomyces species. These results were consistent with the biochemical, enzymatic, and chemotaxonomic features of the strains. Most of the strains showed antimicrobial activities against a range of Gram-positive and Gram-negative bacteria, and against yeast. Genomic analysis revealed the presence of numerous unique biosynthetic gene clusters (BGCs) encoding for potential novel antibiotic and anti-cancer compounds. Strains DSM 41636 T and DSM 61640 T produced the antibiotic compounds A33853 and SF2768, respectively. Overall, this reflects the significant pharmaceutical and biotechnological potential of the proposed novel type strains and underlines the role of prokaryotic systematics for drug discovery. In order to compensate for the gender gap in naming prokaryotic species, we propose the eponyms for all newly described species to honour female scientists., Competing Interests: 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., (© 2024 The Authors.)

Strain collections are a treasure chest of numerous valuable and taxonomically validated bioresources. The Leibniz Institute DSMZ is one of the largest and most diverse microbial strain collections worldwide, with a long tradition of actinomycetes research. Actinomycetes, especially the genus Streptomyces , are renowned as prolific producers of antibiotics and many other bioactive natural products. In light of this, five Streptomyces strains, DSM 40971 T , DSM 40484 T , DSM 40713 T , DSM 40976 T , and DSM 40907 T , which had been deposited a long time ago without comprehensive characterization, were the subject of polyphasic taxonomic studies and genome mining for natural compounds based on in vitro and in silico analyses. Phenotypic, genetic, and phylogenomic studies distinguished the strains from their closely related neighbors. The digital DNA-DNA hybridization and average nucleotide identity values between the five strains and their close, validly named species were below the threshold of 70% and 95%-96%, respectively, determined for prokaryotic species demarcation. Therefore, the five strains merit being considered as novel Streptomyces species, for which the names Streptomyces kutzneri sp. nov., Streptomyces stackebrandtii sp. nov. , Streptomyces zähneri sp. nov. , Streptomyces winkii sp. nov., and Streptomyces kroppenstedtii sp. nov. are proposed. Bioinformatics analysis of the genome sequences of the five strains revealed their genetic potential for the production of secondary metabolites, which helped identify the natural compounds cinerubin B from strain DSM 40484 T and the phosphonate antibiotic phosphonoalamide from strain DSM 40907 T and highlighted strain DSM 40976 T as a candidate for regulator-guided gene cluster activation due to the abundance of numerous " Streptomyces antibiotic regulatory protein" (SARP) genes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Nouioui, Zimmermann, Hennrich, Xia, Rössler, Makitrynskyy, Pablo Gomez-Escribano, Pötter, Jando, Döppner, Wolf, Neumann-Schaal, Hughes and Mast.)