Cryptic antibiotics and methods for detecting bioactive cryptic metabolites

Abstract

Bacteria harbor an immense reservoir of potentially new and therapeutic small molecules in the form of 'silent' biosynthetic gene clusters. These clusters can be identified bioinformatically but are at best sparingly expressed under normal laboratory growth conditions; their products are therefore not interrogated during bioactivity screening exercises. An estimated 80-90% of biosynthetic loci are silent, meaning that routine bioactivity screens miss the majority of microbial biosynthetic potential. Disclosed herein is a method that allows access to this vast hidden metabolome, thereby allowing researchers to screen the complete metabolomes of microorganisms in the search of new therapeutic leads. The disclosed approach, “Bioactivity-HiTES”, broadly activates the secondary metabolomes of bacteria and links the cryptic metabolites produced to a desired biological activity. Using the disclosed method, induction of cryptic antibiotics was detected in all four actinomycete bacterial strains that were tested as proof-of-concept. Follow-up in two cases demonstrated the production of two new antibiotics: In one case, the taylorflavins, pyrimidine antibiotics that harbor selective growth-inhibitory activity toward Gram-negative bacteria, were identified. For example, taylorflavin B shows potent minimal inhibitory concentration towardand, but not against a panel of Gram-positive bacteria. In the second case, the lanthipeptide cebulantin, which is specific toward Gram-negativepathogens, but does not affect the growth of Gram-positive bacteria tested, was identified. These compounds, taylorflavins and cebulantin, may serve as useful leads in the future. At the same time, Bioactivity-HiTES may be applied broadly to identify cryptic metabolites with the desired biological properties.