Discovery of\nCryptic Natural Products Using High-Throughput\nElicitor Screening on Agar Media

It\nis now well-established that microbial genomes carry\nsparingly\nexpressed biosynthetic gene clusters (BGCs) that need to be induced\nin order to characterize their products. To do so, we herein subjected\ntwo well-known producers, <i>Burkholderia plantarii</i> and <i>Burkholderia gladioli</i>, to high-throughput elicitor screening\n(HiTES), an emerging approach for accessing the products of these\n“cryptic” BGCs. Both organisms have previously been\nexamined extensively in liquid cultures. We therefore applied HiTES\non agar and found several novel natural products that are only produced\nin this format and not in liquid cultures. Most notably we found two\nmetabolites, termed burkethyl A and B, that contain an unusual <i>m</i>-ethylbenzoyl group and for which we identified the cognate\nBGC using bioinformatic and genetic studies. Our results indicate\nthat agar-based HiTES is a promising approach for natural product\ndiscovery and are in line with the notion that even “drained”\nstrains remain sources of new metabolites as long as alternative approaches\nare employed.