Phylogenetic Characterization of Culturable Antibiotic Producing Streptomyces from Rhizospheric Soils

Abstract

Streptomyces spp. were isolated from rhizospheric soils collected from Ngaka Modiri Molema District, North West Province, South Africa. Ten of these bacterial isolates were found to exhibit broad spectrum antimicrobial activity against test organisms with varying degree of activity. The cultural characteristics of the bacterial isolates were consistent with that of the members of the genus Streptomyces. Molecular identification of the potent bacterial isolates was carried out by amplifying the 16S rDNA gene; this gave the expected size of 1.5 kb and was sequenced. Further computational analysis including BLAST search and phylogenetic analysis were performed to correlate the bacterial isolates with other species of the genera in the database library. The computational analysis of the amplified 16S rDNA gene confirmed that the bacterial isolates are members of the genus Streptomyces with 89-100% sequence similarity. The phylogenetic analysis showed that the 10 bacterial isolates were divided into 3 major clusters with varying bootstrap values. The strain NWU195 formed a distinct phyletic line in the Streptomyces 16S rDNA gene tree suggesting a new strain. The 16S rDNA sequences of the bacterial isolates was submitted to the GenBank under the accession numbers JX284398-JX284407. The 16S rDNA gene sequence analysis is a significant tool for phylogenetic analysis of Streptomyces spp.