Generic Diversity of Rare Actinomycetes from Thai Cave Soils and Their Possible Use as New Bioactive Compounds

Abstract

A total of 377 actinomycetes were isolated from eight soil samples collected from the Phatup Cave Forest Park and Phanangkhoi cave in northern Thailand. One hundred and sixty eight isolates (44.56%) were non-streptomycete based on their spore formations and isomeric forms of diaminopimelic acid. Among these, 50 isolates belong to the genus Micromonospora due to their characteristic single spore formation. Eleven randomly selected isolates of these rare actinomycetes were identified by using phenotypic data combined with 16S rDNA sequence-based phylogenetic analysis. Very rare genera such as Spirillospora, Catellatospora and Nonomuraea were also found. This is the first recorded isolation of Spirillospora and Nonomuraea from a cave soil. Phylogenetic analysis of 16S rRNA gene sequence data revealed that 5 of 11 randomly selected isolates might represent a new species. Two of them showed anti Gram-positive bacteria and anti-cancer activity. Caves are attractive places to look for new actinomycete species that might be a source of novel bioactive compounds.