In the course of screening novel secondary metabolites, an acidophilic actinomycete strain, designated Aac-30(T), was isolated from forest soil and subjected to a polyphasic taxonomic characterization study. It grew well on media in which the pH ranged from 4 to 6, but not on medium with pH adjusted to 7. It possessed ll-diaminopimelic acid and glycine in the cell-wall peptidoglycan, MK-9(H6) and MK-9(H8) as major isoprenoid quinones, iso-C(16 : 0) and anteiso-C(17 : 0) as major cellular fatty acids, and phosphatidylglycerol and phosphatidylinositol as polar lipids. The G+C content of the genomic DNA was 69.1 mol%. Phylogenetic analyses based on 16S rRNA gene sequences showed that the organism belonged to the family Catenulisporaceae and consistently formed a monophyletic cluster with members of the genus Catenulispora. Physiological, biochemical and chemotaxonomic data revealed that this novel organism could be readily differentiated from recognized members of the genus Catenulispora and that it merits separate species status. Based on the phenotypic and genetic evidence presented, strain Aac-30(T) is considered to represent a novel species of the genus Catenulispora, for which the name Catenulispora rubra sp. nov. is proposed. The type strain is Aac-30(T) (=NBRC 101179(T)=DSM 44948(T)).