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 N74T, isolated from cave soil, was studied using a polyphasic taxonomic approach. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain N74T formed a stable, distinct lineage cluster together with Microbispora thailandensis NN276T (99.3% similarity) and Microbispora mesophila JCM 3151T (97.5%). Strain N74T was observed to produce single spherical spores on aerial mycelium as reported for M. mesophila JCM 3151T and M. thailandensis NN276T 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 N74T, M. mesophila JCM 3151T and M. thailandensis NN276T from other members of the genus Microbispora, although the chemotaxonomic characteristics of strain N74T 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 N74T 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 N74T (=BCC 77604T=NBRC 111481T). It is also proposed that M. mesophila and M. thailandensis be transferred to this genus as Sphaerimonospora mesophila comb. nov. (type strain JCM 3151T=NBRC 14179T=DSM 43048T) and Sphaerimonospora thailandensis comb. nov. (type strain NN276T=BCC 41490T=NBRC 107569T), respectively.