Novel classes of antibiotics are constantly required due to the expanding population of patients at risk and the growing prevalence of resistant pathogens in hospital- or community-acquired infections. Many options for drug discovery are still available to researchers. Recent estimates indicate that nearly 50% of the20,000 bioactive secondary metabolites described from 1900 onwards are produced by filamentous actinomycetes that originated in the soil. Among them, the easiest to isolate from soils are Streptomyces species as a rich source of novel bioactive.
A number of approaches have been developed to study molecular microbial diversity. These include DNA re association, DNA–DNA and mRNA:DNA hybridization, DNA cloning and sequencing, and other PCR-based methods such as denaturing gradient gel electrophoresis (DGGE), temperature gradient gel electrophoresis (TGGE), ribosomal intergenic spacer analysis (RISA) and automated ribosomal intergenic spacer analysis (ARISA).
Many techniques have been developed to assess microbial community diversity. In these methods, DNA is extracted from the environmental sample and purified. Target DNA (16S, 18S or ITS) is amplified using universal or specific primers and the resulting products are separated in different ways. Thus, novel elements have to be introduced to streptomycetes screening.