Evaluation of Antibiotic Biosynthetic Potential of Actinomycete Isolates to Produce Antimicrobial Agents

Aim: To assess the antibiotic biosynthetic potential of actinomycete isolates from rhizospheric soil samples collected from Ngaka Modiri Molema district in North West Province of South Africa.
Study Design: The analysis of biosynthetic gene clusters through PCR-based approach presents a useful foundation for the discovery of bioactive compounds.
Place and Duration of Study: Microbial Biotechnology Laboratory, Department of Biological Sciences, North-West University, Mafikeng Campus, South Africa, between June 2011 and November, 2013.
Methodology: Through PCR-based approach 341 actinomycete isolates were screened for thepolyketide synthases (PKS) and non-ribosomal peptide synthetases (NRPS) biosynthetic gene clusters. The amplification of the genes from some of the actinomycete isolates is an indication of their potential as antibiotic producers. Phylogenetic analysis using PKS-I, PKS-II and NRPS gene sequences were conducted.
Results: Sixteen isolates (4.69%) were identified as PKS-I gene positive strains, 15.25% for PKS-II and 13.48% for NRPS gene. Through the screening, it was found that Streptomyces have higher prevalence of PKS-I, PKS-II and NRPS genes compared to others genera. Phylogenetic analysis of the nucleotide sequences from the amplified biosynthetic genes confirmed that the isolates formed a close phylogenetic relationship with known antibiotic producers.
Conclusion: PCR-based approach using degenerative primers to screen for the presence of biosynthetic gene clusters responsible for the biosynthesis of bioactive secondary metabolites, is an effective approach for discovering diverse antibiotics from actinomycetes.