Expanding small molecule functional metagenomics through shuttle BAC expression i

Wu, Chengcang

Abstract

There is societal need for new therapeutic agents in our arsenal of defenses against bacterial and fungal pathogens, many of which are increasingly resistant to existing antibiotics. Filamentous fungi are considered promising resources for the development of novel bioactive compounds because of their great potential to produce various kinds of secondary metabolites (SM), however, antibiotic discovery and production in fungi lags far behind bacteria. This research proposal advances sciences of fungal functional genomics using shuttle cloning of large DNA containing the entire SM pathways and their regulatory elements in order to discover novel antibiotics and identify the best lead candidates for clinical development. Scientists at Lucigen Corporation and the University of Wisconsin at Madison will develop, utilize, and combine four aspects of novel technology innovation and genomic tools to enable therapeutic agent discovery in fungi. Specifically, the proposed research will identify antibiotic compounds using: i) large-insert unbiased Random Shear Shuttle BAC libraries, ii) at least 56 large secondary metabolic pathways (about 20~100 kb) in the completely sequenced genome of A. terreus, iii) the knowledge of global secondary metabolite cluster regulation in Aspergillus, iv) an engineered fungal host A. nidulans to provide a robust background in which to search for new metabolites. The primary objectives are to build two shuttle BAC libraries and identify BACs containing 56 SM pathways and their regulatory elements for proof-of-concept using the above technologies and to screen these BAC clones against bacterial and fungal tester strains to discover novel antibacterial and antifungal properties. Our long-term goals are to develop a high through-put small molecule discovery platform in fungi in order to discover novel natural products from at least 500 SM pathways from completely sequenced fungal genomes. Moreover, we will characterize identified antimicrobial agents to determine the best lead candidates for clinical development. Lead candidates will have novel chemical structures, high potency against bacterial and or fungal pathogens, and minimal toxicity for eukaryotic cells. Each of the different technologies necessary for the proposed research has been proven effective separately;therefore, the combination of these different techniques has a high probability of success and also represents a significant advancement for the science of antibiotic discovery. In addition, the libraries produced from this research are a valuable genomic resource that may be screened for other bioactive compounds (e.g., with anticancer or antiviral activities) in subsequent research. 1

Public Health Relevance

The need for new antimicrobial agents has reached an intensity not experienced since the commercialization of antibiotics in the 1940s, but many traditionally fruitful sources of chemistry have ceased to yield new compounds. The proposed research will develop, utilize, and combine four technology innovations and genomic tools to enable therapeutic agent discovery from fungi. An engineered fungal host, Aspergillus nidulans, will be used for harvesting and expressing fungal secondary metabolic pathways and their regulatory elements directly, without the need to cultivate and engineer the different fungi in a laboratory. This technology will allow access to a wide variety of novel small molecules produced by a great diversity of filamentous fungi, many of which are currently unknown to science. The ultimate goal of this work is to identify novel therapeutic compounds for use in treating bacterial and fungal diseases. 1