Nocardia macrotermitis sp. nov. and Nocardia aurantia sp. nov., isolated from the gut of the fungus-growing termite Macrotermes natalensis

Abstract

The taxonomic positions of two novel aerobic, Gram-stain-positive Actinobacteria, designated RB20 T and RB56 T , were determined using a polyphasic approach. Both were isolated from the fungus-farming termite Macrotermes natalensis . Results of 16S rRNA gene sequence analysis revealed that both strains are members of the genus Nocardia with the closest phylogenetic neighbours Nocardia miyunensis JCM12860 T (98.9 %) and Nocardia nova DSM44481 T (98.5 %) for RB20 T and Nocardia takedensis DSM 44801 T (98.3 %), Nocardia pseudobrasiliensis DSM 44290 T (98.3 %) and Nocardia rayongensis JCM 19832 T (98.2 %) for RB56 T . Digital DNA–DNA hybridization (DDH) between RB20 T and N. miyunensis JCM12860 T and N. nova DSM 44481 T resulted in similarity values of 33.9 and 22.0 %, respectively. DDH between RB56 T and N. takedensis DSM44801 T and N. pseudobrasiliensis DSM44290 T showed similarity values of 20.7 and 22.3 %, respectively. In addition, wet-lab DDH between RB56 T and N. rayongensis JCM19832 T resulted in 10.2 % (14.5 %) similarity. Both strains showed morphological and chemotaxonomic features typical for the genus Nocardia , such as the presence of meso -diaminopimelic acid (A 2 pm) within the cell wall, arabinose and galactose as major sugar components within whole cell-wall hydrolysates, the presence of mycolic acids and major phospholipids (diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol), and the predominant menaquinone MK-8 (H 4 , ω-cyclo). The main fatty acids for both strains were hexadecanoic acid (C 16 : 0 ), 10-methyloctadecanoic acid (10-methyl C 18 : 0 ) and cis -9-octadecenoic acid (C 18 : 1 ω9 c ). We propose two novel species within the genus Nocardia : Nocardia macrotermitis sp. nov. with the type strain RB20 T (=VKM Ac-2841 T =NRRL B65541 T ) and Nocardia aurantia sp. nov. with the type strain RB56 T (=VKM Ac-2842 T =NRRL B65542 T ).