An actinomycete, designated as CMU-PNK470, was isolated from the soil in Phanangkoi cave in northern Thailand and subjected to phenotypic and genotypic characterization. Morphological and chemical properties indicated that this isolate belonged to the genus Spirillospora. Phylogenetic analysis based on 16S rRNA gene sequencing confirmed its placement in the genus Spirillospora and it was most closely related to Spirillospora albida (98.86%). This is the first reported isolation of Spirillospora albida from a cave habitat. The crude extract of this strain showed antimicrobial activity against three Gram-positive bacteria, Bacillus cereus and Methicillin-resistant Staphylococcus aureus with a MIC value of 23.1 μg/ml and Paenibacillus larvae with a MIC value of 185 μg/ml. It also reduced the number of viable Human Small lung cancer cells (NCI-H187) to less than 50% at a concentration of 10.18 μg/ml.
To collect new kinds of microorganisms for screening of biologically active substances, we focused on spider materials (webs, cuticle, egg sac), previously uninvestigated sources of such organisms. Using a new method of pre-treatment with 70% ethanol, 1,159 strains of actinomycetes were isolated from 196 spider materials, based on their morphological features. Of these, 293 strains were identified as non-filamentous actinomycetes from their 16S rRNA gene sequences. More detailed examination indicated that 139 strains belonged to the suborders Micrococcineae, Frankineae and Propionibacterineae, and they included some novel strains of non-filamentous actinomycetes. Thus, spider materials provide a more useful source of non-filamentous actinomycetes than do soil samples.
Based on a Blast search of 16S rRNA sequences of Streptomyces from marine environments of Nagasaki, Japan, 64 isolates showed the highest similarity scores with NBRC strains. Only 5 out of these 64 strains showed exactly the same biological profiles as the approximately 900 strains preserved at NBRC strains, while the remaining isolates showed different biological profiles. This suggests that the genus Streptomyces has the ability to produce a wide variety of unknown bioactive metabolites.