The taxonomic position of a novel aerobic, Gram-positive actinobacteria, designated strain RB5^T, was determined using a polyphasic approach. The strain, isolated from the gut of the fungus-farming termite Macrotermes natalensis, showed morphological, physiological and chemotaxonomic properties typical of the genus Streptomyces. Based on 16S rRNA gene sequence analysis, the closest phylogenetic neighbour of RB5^T was Streptomyces polyrhachis DSM 42102^T (98.87%). DNA–DNA hybridization experiments between strain RB5^T and S. polyrhachis DSM 42102^T resulted in a value of 27.4% (26.8%). The cell wall of strain RB5^T contained ll-diaminopimelic acid as the diagnostic amino acid. Mycolic acids and diagnostic sugars in whole-cell hydrolysates were not detected. The strain produced the following major phospholipids: diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol-mannoside and phosphatidylserine. The menaquinone profile showed hexa-and octahydrogenated menaquinones containing nine isoprene units [MK-9(H₆ ) and MK-9(H₈ )]. The strain exhibited a fatty acid profile containing the following major fatty acids: 12-methyltridecanoic acid (iso-C_14:0 ) 12-methyltetradecanoic acid (anteiso-C_15:0 ), 13-methyltetradecanoic acid (iso-C_15:0 ) and 14-methylpentadecanoic acid (iso-C_16:0 ). Here, we propose a novel species of the genus Streptomyces – Streptomyces smaragdinus with the type strain RB5^T (=VKM Ac-2839^T=NRRL B65539^T).