Blastococcus brunescens sp. nov., a member of the Geodermatophilaceae isolated from sandstone collected from the Sahara Desert in Tunisia.

The taxonomic position of strain BMG 8361T , isolated from sandstone collected in the Sahara Desert of Southern Tunisia, was refined through a polyphasic taxonomic investigation. Colonies of BMG 8361T were pale-orange coloured, irregular with a dry surface and produced a diffusible pink or brown pigment depending on media. The Gram-positive cells were catalase-positive and oxidase-negative. The strain exhibited growth at 10-40 °C and pH values ranging from 5.5 to 9.0, with optima at 28-35 °C and pH 6.5-8.0. Additionally, BMG 8361T demonstrated the ability to grow in the presence of up to 1 % NaCl (w/v) concentration. The peptidoglycan of the cell wall contained meso -diaminopimelic acid, glucose, galactose, xylose, ribose, and rhamnose. The predominant menaquinones consisted of MK-9(H4 ) and MK-9. The main polar lipids were phosphatidylcholine, phosphatidylinositol, glycophosphatidylinositol, diphosphatidylglycerol, phosphatidylethanolamine, and two unidentified lipids. Major cellular fatty acids were iso-C16 : 0 , iso-C16 : 1  h, and C17 : 1  ω 8 c . Phylogenetic analyses based on both the 16S rRNA gene and whole-genome sequences assigned strain BMG 8361T within the genus Blastococcus . The highest pairwise sequence similarity observed in the 16S rRNA gene was 99.5 % with Blastococcus haudaquaticus AT 7-14T . However, when considering digital DNA-DNA hybridization and average nucleotide identity, the highest values, 48.4 and 86.58 %, respectively, were obtained with Blastococcus colisei BMG 822T . These values significantly undershoot the recommended thresholds for establishing new species, corroborating the robust support for the distinctive taxonomic status of strain BMG 8361T within the genus Blastococcus . In conjunction with the phenotyping results, this compelling evidence leads to the proposal of a novel species we named Blastococcus brunescens sp. nov. with BMG 8361T (=DSM 46845T =CECT 8880T ) as the type strain.