Characterization of Streptomyces MITKK-103, a newly isolated actinomycin X2-producer

Appl Microbiol Biotechnol. 2006 Aug;72(1):145-154. doi: 10.1007/s00253-005-0240-2. Epub 2005 Dec 23.


A new actinomycete strain designated MITKK-103 was isolated from the soil of a flowerpot using a humic acid agar medium. The newly isolated strain was able to produce a large amount of actinomycin X2 even under nonoptimized growing conditions and serves as a promising source of this antibiotic. Actinomycin X2 has higher cytotoxicity toward cultured human leukemia (HL-60) cells than does actinomycin D, and it induces cell death via apoptosis. A nearly complete 16S ribosomal DNA (rDNA) sequence from the isolate was determined and found to have high identity (98.5-100%) with Streptomyces galbus, Streptomyces griseofuscus, and Streptomyces padanus, indicating that MITKK-103 belongs to the genus Streptomyces. The isolate clustered with species belonging to the S. padanus clade in a 16S-rDNA-based phylogenetic tree and showed 75% overall homology to S. padanus ATCC 25646 in DNA-DNA relatedness analysis. Although the growth of the isolate was somewhat different from the three species mentioned, the strain MITKK-103 most closely resembles S. padanus on the basis of the morphological and phenotypic characteristics, phylogenetic analysis, and genotypic data. As such, this is the first report of a strain of S. padanus capable of producing actinomycins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Typing Techniques
  • DNA, Bacterial / chemistry
  • DNA, Bacterial / genetics
  • DNA, Ribosomal / chemistry
  • DNA, Ribosomal / genetics
  • Dactinomycin / analogs & derivatives*
  • Dactinomycin / biosynthesis
  • Dactinomycin / toxicity
  • HL-60 Cells
  • Humans
  • Microscopy, Electron, Scanning
  • Molecular Sequence Data
  • Nucleic Acid Hybridization
  • Phylogeny
  • Pigments, Biological / biosynthesis
  • RNA, Ribosomal, 16S / genetics
  • Sequence Analysis, DNA
  • Sequence Homology, Nucleic Acid
  • Soil Microbiology*
  • Streptomyces / classification
  • Streptomyces / isolation & purification
  • Streptomyces / metabolism*
  • Streptomyces / ultrastructure


  • DNA, Bacterial
  • DNA, Ribosomal
  • Pigments, Biological
  • RNA, Ribosomal, 16S
  • Dactinomycin
  • actinomycin X

Associated data

  • GENBANK/AY941253