Proposal of Sphaerimonospora cavernae gen. Nov., sp. nov. and transfer of Microbispora mesophila (Zhang et al., 1998) to Sphaerimonospora mesophila comb. nov. and microbispora thailandensis (Duangmal et al., 2012) to Sphaerimonospora thailandensis comb. nov

The actinomycete strain N74^T, isolated from cave soil, was studied using a polyphasic taxonomic approach. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain N74^T formed a stable, distinct lineage cluster together with Microbispora thailandensis NN276^T (99.3 % similarity) and Microbispora mesophila JCM 3151^T (97.5 %). Strain N74^T was observed to produce single spherical spores on aerial mycelium as reported for M. mesophila JCM 3151^T and M. thailandensis NN276^T but different from other known species of the genus Microbispora, which are characterized by pairs of spores on aerial hyphae. Multilocus sequence analyses based on concatenated partial gyrB, rpoB, atpD, recA and 16S rRNA gene sequences showed a clear distinction of strain N74^T, M. mesophila JCM 3151^T and M. thailandensis NN276^T from other members of the genus Microbispora, although the chemotaxonomic characteristics of strain N74^T were similar to the genus Microbispora; the cell wall contained meso-diaminopimelic acid and the whole-cell hydrolysate contained madurose as the diagnostic sugar. The major menaquinone was MK-9(H₄). The fatty acid profile contained iso-C₁₆:₀. On the basis of morphological, chemotaxonomic and phylogenetic evidence, strain N74^T is assigned to a novel species of a new genus, for which the name Sphaerimonospora cavernae gen. nov., sp. nov. is proposed. The type strain of Sphaerimonospora cavernae is N74^T (=BCC 77604^T=NBRC 111481^T). It is also proposed that M. mesophila and M. thailandensis be transferred to this genus as Sphaerimonospora mesophila comb. nov. (type strain JCM 3151^T=NBRC 14179^T=DSM 43048^T) and Sphaerimonospora thailandensis comb. nov. (type strain NN276^T=BCC 41490^T=NBRC 107569^T), respectively.