Towards the High-Throughput Discovery of Novel Antibiotics in Streptomyces

In the past several decades, microbial antibiotic resistance has emerged as a serious threat towards public health worldwide. Simultaneously, the rate of antibiotic discovery has slowed significantly. Therefore, in order to meet the challenge of antibiotic resistance, novel methods of antibiotic discovery are necessary. In the past, screening of microorganisms, especially bacteria in the genus Streptomyces, has proven to be a rich source of new antibiotics, while recent advances in the molecular biology of microbes have greatly facilitated the directed discovery of antibiotics not expressed under normal laboratory conditions. The aim of this project is, therefore, to utilize a combination of directed and “brute force” methods to maximize discovery of novel antimicrobial compounds. Our group has previously shown that the cAMP receptor protein (Crp) acts as a pleiotropic regulator affecting antibiotic production in Streptomyces coelicolor. Crp overexpressing mutants demonstrated increased production of the antibiotic actinorhodin. To this end, a Crp overexpression construct was conjugated into 60 wild Streptomyces isolates using high-throughput conjugation techniques. Of 43 strains where the construct was successfully introduced, five showed increased inhibitory activity against Escherichia coli. This increase in inhibitory activity was interpreted as either the overexpression of a previously known antibiotic or, more excitingly, the production of a hitherto undiscovered compound. These five strains will therefore be tested for inhibitory activity against more robust organisms such as Pseudomonas aeruginosa and Burkholderia cepacia in hopes of ultimately isolating a novel antibiotic with activity against these, and other, clinically relevant pathogens.