A Gram-reaction-negative, yellow-pigmented strain, designated EX36(T), was characterized using a polyphasic approach comprising phylogenetic, morphological and genotypic analyses. The endophytic strain was isolated from Zn/Cd-accumulating Salix caprea in Arnoldstein, Austria. Analysis of the 16S rRNA gene demonstrated that the novel strain is most closely related to members of the genus Spirosoma (95% sequence similarity with Spirosoma linguale). The genomic DNA G+C content was 47.2 mol%. The predominant quinone was and the major cellular fatty acids were summed feature 3 (iso-C-15:0 2-OH and/or C-16:1 omega 7c), C-16:1 omega 5c, iso-C-17:0 3-OH and iso-C-15:0. On the basis of its phenotypic and genotypic properties, strain EX36(T) should be classified as a novel species of the genus Spirosoma, for which the name Spirosoma endophyticum sp. nov. is proposed. The type strain is EX36(T) (=DSM 26130(T)=LMG 27272(T)).