Blastococcus carthaginiensis sp. nov., isolated from a monument sampled in Carthage, Tunisia

A comprehensive polyphasic investigation was conducted to elucidate the taxonomic position of an actinobacterium, designated BMG 814^T, which was isolated from the historic ruins of Carthage city in Tunisia. It grew as pink-orange pigmented colonies and displayed versatile growth capabilities, thriving within a temperature range of 20-40 °C, across a pH spectrum ranging from pH 5.5 to 10 and in the presence of up to 4 % NaCl. Chemotaxonomic investigations unveiled specific cell components, including diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, glycophosphatidylinositol, an unidentified aminoglycophospholipid, six unidentified aminolipids, two unidentified phospholipids and one unidentified lipid in its polar lipid profile. Furthermore, galactose, glucose and ribose were identified as the primary cell-wall sugars. Major menaquinones identified were MK-9(H₄), MK-9(H₂) and MK-9, while major fatty acids comprised iso-C_15 : 0, iso-C_16 : 0, C_17 : 1  ω8c and C_18 : 1  ω9c. Through phylogenetic analysis based on the 16S rRNA gene sequence, the strain was positioned within the genus Blastococcus, with Blastococcus capsiensis BMG 804^T showing the closest relationship (99.1 %). In light of this, draft genomes for both strains, BMG 814^T and BMG 804^T, were sequenced in this study, and comparative analysis revealed that strain BMG 814^T exhibited digital DNA-DNA hybridization and average nucleotide identity values below the recommended thresholds for demarcating new species with all available genomes of type strains of validly names species. Based on the polyphasic taxonomy assessment, strain BMG 814^T (=DSM 46848^T=CECT 8878^T) was proposed as the type strain of a novel species named Blastococcus carthaginiensis sp. nov.