Two novel actinomycetes, designated strains NEAU-Jh1-3(T) and NEAU-Jh2-5(T), were isolated from muddy soil collected from a riverbank in Jiaohe, Jilin Province, north China. A polyphasic study was carried out to establish the taxonomic positions of these strains. The 16S rRNA gene sequence analysis showed that the two novel isolates exhibited 99.9 % 16S rRNA gene sequence similarity with each other and that they are closely related to Actinomadura viridis IFO 15238(T) (99.6, 99.6 %) and Actinomadura vinacea IFO 14688(T) (99.3, 99.3 %). Phylogenetic analysis based on the 16S rRNA gene sequences indicated that the two cultures clustered together and formed a cluster with A. viridis IFO 15238(T), A. vinacea IFO 14688(T) and Actinomadura rugatobispora IFO 14382(T). However, the DNA-DNA hybridization value between strains NEAU-Jh1-3(T) and NEAU-Jh2-5(T) was 63.6 %, and the values between the two strains and their close phylogenetic relatives were also below 70 %. With reference to phenotypic characteristics, phylogenetic data and DNA-DNA hybridization results, the two strains can be distinguished from each other and their close phylogenetic relatives. Thus, strains NEAU-Jh1-3(T) and NEAU-Jh2-5(T) represent two novel species of the genus Actinomadura, for which the names Actinomadura jiaoheensis sp. nov. and Actinomadura sporangiiformans sp. nov. are proposed. The type strains are NEAU-Jh1-3(T) (=CGMCC 4.7197(T) = JCM 30341(T)) and NEAU-Jh2-5(T) (=CGMCC 4.7211(T) = JCM 30342(T)), respectively.
Keywords: 16S rRNA gene; Actinomadura jiaoheensis sp. nov.; Actinomadura sporangiiformans sp. nov.; Polyphasic taxonomy.