Taxonomic Positions and Secondary Metabolite-Biosynthetic Gene Clusters of Akazaoxime- and Levantilide-Producers

Micromonospora sp. AKA109 is a producer of akazaoxime and A-76356, whereas Micromonospora sp. AKA38 is that of levantilide C. We aimed to clarify their taxonomic positions and identify biosynthetic gene clusters (BGCs) of these compounds. In 16S rRNA gene and DNA gyrase subunit B gene (gyrB) sequence analyses, strains AKA109 and AKA38 were the most closely related to Micromonospora humidisoli MMS20-R2-29(T) and Micromonospora schwarzwaldensis HKI0641(T), respectively. Although Micromonospora sp. AKA109 was identified as M. humidisoli by the gyrB sequence similarity and DNA–DNA relatedness based on whole genome sequences, Micromonospora sp. AKA38 was classified to a new genomospecies. M. humidisoli AKA109 harbored six type-I polyketide synthase (PKS), one type-II PKS, one type-III PKS, three non-ribosomal peptide synthetase (NRPS) and three hybrid PKS/NRPS gene clusters, among which the BGC of akazaoxime and A-76356 was identified. These gene clusters are conserved in M. humidisoli MMS20-R2-29(T). Micromonospora sp. AKA38 harbored two type-I PKS, one of which was responsible for levantilide C, one type-II PKS, one type-III PKS, two NRPS and five hybrid PKS/NRPS gene clusters. We predicted products derived from these gene clusters through bioinformatic analyses. Consequently, these two strains are revealed to be promising sources for diverse non-ribosomal peptide and polyketide compounds.