The Development of Protocols to Engineer and Screen Streptomyces in High Throughput to Test for the Activation of Cryptic Clusters by the Heterologous Expression of Pleiotropic Regulators

Abstract

<p>The Gram-positive, soil dwelling bacteria of the genus <em>Streptomyces</em> produce greater than 50% of the clinically relevant antibiotics in use today. Thanks to the falling price of DNA sequencing, <em>Streptomyces</em> genomes are revealing that they encode more secondary metabolites (potential antibiotics) than they produce under standard laboratory conditions. By heterologously overexpressing the known pleiotropic regulators of antibiotic expression from <em>Streptomyces coelicolor</em> in several other <em>Streptomyces</em> species it has been shown that the secondary metabolite profile of these species can be influenced. While present-day methods of introducing genes (conjugation) and screening for antibiotics work well on a small scale, the low throughput nature of these protocols stand as a barrier to testing this hypothesis on a larger scale. The focus of the research presented here was to develop high throughput (HTP) methods of engineering and screening <em>Streptomyces</em>. With these two technologies in place, an attempt was to made to introduce three plasmids (pSET152-<em>ermE*</em>p-null, pSET152-<em>ermE</em>*p-<em>atrA</em> and pSET152-<em>ermE</em>*p-<em>lsr2_NTD</em>) into 120 wild-isolate <em>Streptomyces</em> species from the Wright Actinomycete Collection. Exconjugants were successfully obtained for all three plasmids in 48 species of <em>Streptomyces</em> and were screened for increased antimicrobial activity using a HTP, <em>lux</em>-based bioassay. Numerous strains showed increased antimicrobial activity but WAC00206, WAC00230 and WAC00263 with pSET152-<em>ermE</em>*p-<em>lsr2_NTD</em>showed the most promising improvement in antimicrobial activity. These hits have been designated as high priority for future investigation. These results suggest that HTP conjugation and the <em>lux</em>-based bioassay are powerful methods for introducing plasmids into and screening engineered streptomycetes.</p>