Two Saccharopolyspora isolates from archaeological excavation sites: polyphasic taxonomy, biosynthetic potential, bioactivity profiling and description of Saccharopolyspora antiqui sp. nov.
Archaeological excavation sites represent underexplored microbial habitats with the potential to recover taxonomically and biotechnologically valuable actinomycetes. In this study, two Saccharopolyspora strains, 5N708T and 5N102, were isolated from soil samples collected from the Gaziantep-Doliche-Dülük and Bitlis-Ahlat-Selçuklu Cemetery archaeological excavation sites in Türkiye. A polyphasic taxonomic approach, including 16S rRNA gene sequencing, phylogenetic and phylogenomic analyses, average nucleotide identity, digital DNA-DNA hybridization, phenotypic characterization, and chemotaxonomic analyses, showed that strain 5N708T represents a novel species of the genus Saccharopolyspora, for which the name Saccharopolyspora antiqui sp. nov. is proposed, whereas strain 5N102 was assigned to Saccharopolyspora elongata. Both isolates were further evaluated for their antimicrobial, antioxidant, and cytotoxic activities, and their biosynthetic potential was investigated by genome mining. Both strains showed activity against Staphylococcus aureus, with strain 5N708T producing the larger inhibition zone. Strain 5N102 exhibited markedly stronger antioxidant activity than strain 5N708T in radical scavenging, ferric reducing antioxidant power, and reducing power assays. In contrast, strain 5N708T showed more promising cytotoxic activity, with relative selectivity toward MIA PaCa-2 pancreatic cancer cells compared with HEK293 cells after prolonged incubation. Genome mining revealed multiple biosynthetic gene clusters in both isolates, supporting their capacity to produce secondary metabolites. These findings indicate that archaeological soils are promising reservoirs of taxonomically novel and biologically active Saccharopolyspora strains.