Geodermatophilus siccatus sp. nov., isolated from arid sand of the Saharan desert in Chad

Abstract

A novel Gram-positive, aerobic, actinobacterial strain, CF6/1(T), was isolated in 2007 during environmental screening of arid desert soil in the Sahara near to Ourba, Chad. The isolate was found to grow best in a temperature range of 20-37 °C and at pH 6.0-8.5 and showed no NaCl tolerance, forming black-coloured and nearly circular colonies on GYM agar. Chemotaxonomic and molecular characteristics determined for the isolate match those previously described for members of the genus Geodermatophilus. The DNA G + C content of the novel strain was determined to be 74.9 mol %. The peptidoglycan was found to contain meso-diaminopimelic acid as the diagnostic diamino acid. The main phospholipids were determined to be phosphatidylethanolamine, phosphatidylinositol, phosphatidylcholine, diphosphatidylglycerol and traces of phosphatidylglycerol; MK-9(H(4)) was identified as the dominant menaquinone and galactose as the diagnostic sugar. The major cellular fatty acids were found to be the branched-chain saturated acids iso-C(16:0) and iso-C(15:0), as well as C(17:1ω8c). The 16S rRNA gene sequence shows 97.5-97.9 % sequence identity with the four validly named or at least effectively published members of the genus: Geodermatophilus obscurus (97.5 %), Geodermatophilus arenarius (97.7 %), Geodermatophilus ruber (97.9 %) and Geodermatophilus nigrescens (97.9 %). Based on the results from this polyphasic taxonomic analysis and DNA-DNA hybridizations with all type strains of the genus, we propose that strain CF6/1(T) represents a novel species, Geodermatophilus siccatus, with the type strain CF6/1(T) = DSM 45419(T) = CCUG 62765(T) = MTCC 11414(T).