Actinopolymorpha singaporensis gen. nov., sp nov., a novel actinomycete from the tropical rainforest of Singapore

A novel actinomycete was isolated from soil in the tropical rainforest of S ingapore. The cells of this actinomycete are highly pleomorphic. In the ear ly stages of growth, most cells are of irregular squarish shape and varied sizes. Cells remain attached after cell division, often forming chains or a ggregates of a few cells. Cells at the end of a chain tend to elongate. Wit h prolonged cultivation, cells show different degrees of elongation and enl argement, producing branched hyphae of uneven thickness. At the periphery o f the colony, long hyphae form, which are divided into alternating segments of elongated cells and chains of squarish cells. This actinomycete is cons iderably salt-tolerant, able to grow in the presence of 15% NaCl. Chemotaxo nomically, it contains LL-diaminopimelic acid (DAP) in the cell wall, type PI phospholipids and MK-9(H-6) as the predominant menaquinone, 16S rDNA seq uence analysis assigned this actinomycete to the family Nocardioidaceae, bu t its 16S rDNA shared no more than 91.2% sequence similarity with other mem bers of the family. Based on phenotypic. chemotaxonomic and phylogenetic ev idence, it is proposed that this actinomycete be classified as a new specie s in a new genus, Actinopolymorpha singaporensis gen. nov., sp. nov.