Saccharothrix isguenensis sp. nov., an actinobacterium isolated from desert soil.

A novel actinobacterial strain, designated MB27T, was isolated from a Saharan soil sample collected in Mzab region (Ghardaïa province, South Algeria). Strain MB27T was characterized following a polyphasic taxonomic approach. This strain produced a branched and fragmented substrate mycelium, which was found to have a yellowish orange colour. A white scanty aerial mycelium was produced on most media tested. Chemotaxonomic and phylogenetic studies clearly demonstrated that strain MB27T belongs to the family Pseudonocardiaceae and is closely related to the genus Saccharothrix. Cell-wall hydrolysates contained meso-diaminopimelic acid but not glycine, and whole-cell hydrolysates contained galactose, glucose, ribose and small amounts of mannose and rhamnose. The detected phospholipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannosides. Mycolic acids were not detected while the predominant fatty acid was iso-branched hexadecanoate (iso-C16 : 0). The major menaquinone was MK-9(H4). Results of 16S rRNA gene sequence comparisons revealed that strain MB27T shairs the highest degree of similarity with Saccharothrix ecbatanensis DSM 45486T (99.8%), Saccharothrix hoggarensis DSM 45457T (99.3 %), Saccharothrix longispora DSM 43749T (98.6 %) and Saccharothrix yanglingensis DSM 45665T (98.6 %). However, it exhibited only 11-42 % DNA-DNA relatedness to the neighbouring Saccharothrixspecies. On the basis of phenotypic characteristics, 16S rRNA gene sequence comparisons and DNA-DNA hybridization, strain MB27T is shown to represent a novel species of the genus Saccharothrix, for which the name Saccharothrix isguenensis sp. nov. (type strain MB27T=DSM 46885T=CECT 9045T) is proposed.