Mongolia has an undisturbed ecosystem with rich biodiversity, but only a few research groups have focused attention on the region for its actinomycetes diversity and their antimicrobial activities.1, 2 The genus Actinoplanes is representative of rare actinomycetes and the reported source of more than 120 antibiotics.3 This study was designed to assess the individual abilities of taxonomically diverse Actinoplanes strains, isolated from Mongolian soil, to produce biologically active compounds. First, the antimicrobial activities of culture samples were examined, using a conventional assay that was facile and suitable for preliminary screening, to check the strains’ abilities to produce antibiotics. Discrimination of distinct strains and identification of the producers of already reported compounds, called dereplication, were the next important steps for efficient screening and further assessing the isolates. In contrast to culture-dependent methods, genetic analysis is not influenced by culture conditions, and thus can address genes unexpressed under normal laboratory culture conditions. As nonribosomal peptides and polyketides represent two of the major antibiotic classes prevalent in the genus Actinoplanes,4, 5, 6, 7 two biosynthetic gene types, nonribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) genes, were analyzed to evaluate the isolates’ potential for production of these types of compounds.8, 9, 10 In this study, the diversity of the NRPS and PKS genes in these isolates as well as their relationships in Actinoplanes taxonomy were investigated.

In July 2007, 39 soil samples were collected at three sampling sites in Tov, Uvs and Dornad Provinces, Mongolia, and actinomycetes were isolated from these samples. Genomic DNA was extracted using FastBreak Cell Lysis Reagent, SV Lysis Buffer and MagneSil RED (Promega Corp., Madison, WI, USA). Polymerase chain reaction (PCR) amplification of 16S rDNA was performed as described by Tamura et al.11 Purified PCR products were directly sequenced, using an ABI Prism BigDye Terminator Cycle Sequencing Kit and a 3730xl Genetic Analyzer (Applied Biosystems, CA, USA). For phylogenetic analysis, the 16S rDNA sequences were aligned with genus Actinoplanes reference sequences using the CLUSTAL_X software and a phylogenetic tree constructed using the neighbor-joining method.12

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