Identification of Genes Putatively Involved in the Biosynthesis of Antitubercular Peptide in Streptomyces ribosidificus NRRL B-11466

Aims: To determine the potential antitubercular activity of Streptomyces ribosidificus NRRL B-11466 both on genotypic and phenotypic levels.

Methodology: Standard methods and software programs were used for nucleotide/protein sequence analysis and phenotypic detection of antitubercular activity.

Results: Analysis of the submitted DNA segment (accession code = AJ744850) harbouring the ribostamycin biosynthetic gene cluster showed that the respective gene cluster was flanked in the upstream region by three open reading frames (ORFs), encoding putative type II thioesterase (SribL03.14c) and two nonribosomal peptide synthases (SribL03.14c and SribL03.14c). These ORFs were of high amino acid similarities (about 80%) to those located in the viomycin and related antibiotic biosynthetic gene clusters. A DNA segment harbouring three ORFs, putatively involved in capreomycidine biosynthesis was submitted into the GenBank database under the accession code HQ327309. Comparative analysis of the respective DNA segment with viomycin and related antibiotic biosynthetic gene clusters showed: firstly, location of the respective DNA segment in the neighbourhood and upstream to the ribostamycine biosynthetic gene cluster; secondly, conservation of six ORFs: SriC (putative L-arginine hydroxylase); SriD (putative L-capreomycidine synthase), SriE (putative permease) located on our submitted DNA fragment; and SribL03.14c, SribL03.15c, SribL03.16c located on the DNA fragment harboring ribostamycin biosynthetic gene cluster, among the tested biosynthetic gene clusters. Phenotypically, S. ribosodificus inhibited growth of Mycobacterium smegmatis ATCC 19420 and Mycobacterium phlei ATCC 11758.

Conclusion: Streptomyces ribosidificus NRRL B-11466 produces antimycobacterial agents and this was confirmed genotypically via detection of 6 ORFs with high amino acid similarities (about 80%) to those located in the viomycin and related antibiotic biosynthetic gene clusters as well as phenotypically by determining its inhibitory activity against Mycobacterium smegmatis ATCC 19420. This is the first report about identification of genes putatively involved capreomycidine biosynthesis in Streptomyces ribosidificus NRRL B-11466.