Polyphasic taxonomic description of Streptomyces tritrimontium sp. nov., actinomycetes isolated from moonmilk in Szczelina Chochołowska cave of Tatra Mountains in Poland and emended descriptions of Streptomyces manipurensis Nimaichand et al. 2021 and Streptomyces nojiriensis Ishida et al. 1967.

In the present study the taxonomic position of two streptomycete strains, isolated from moonmilk in Szczelina Chochołowska cave located in Tatra Mountains in Poland, was established using a polyphasic taxonomic approach. Strains 2.9 and 4.24 have morphological characteristics and chemotaxonomic properties consistent with their classification in the genus Streptomyces. They are Gram-stain-positive filamentous bacteria which formed an extensively branched substrate mycelium and straight long chains of smooth surfaced spores. They contain LL-diaminopimelic acid, glucose and ribose in whole-organism hydrolysates, produce major proportions of straight, iso- and anteiso- fatty acids, hexa- and octa‑hydrogenated menaquinones with nine isoprene units and have a polar lipid pattern with phosphatidylethanolamine (diagnostic lipid). Strains 2.9 and 4.24 formed a distinct clade within the Streptomyces 16S rRNA gene tree sharing 100 % sequence similarity with Streptomyces stoeckheimensis DSM 116496ᵀ. Average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values calculated from the whole genome sequences of strains 2.9 and 4.24 and their closely related phylogenomic neighbour were found to be 90.4 and 36.3 %, respectively, indicating that they belong to different genomic species. Consequently, based on the genomic, phylogenetic and associated phenotypic data it is proposed that strains 2.9 and 4.24 be assigned to the genus Streptomyces as Streptomyces tritrimontium sp. nov. with strain 2.9 (DSM 119353 = PCM 3548) as the type strain. The genomes of strains 2.9 and 4.24 contain relatively high number of biosynthetic gene clusters (28 and 27, respectively), some of which were discontinuously distributed, indicating ones predicted to express for novel specialized metabolites. Data acquired in the present study have also been used to emend the descriptions of Streptomyces manipurensis and Streptomyces nojiriensis.