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).