PROJECT SUMMARY With antibiotic resistance mechanisms spreading rapidly among disease-causing bacteria, our ability to treat common infections is becoming increasingly difficult. To combat resistance, we desperately need new antibiotic agents possessing novel modes of action. Natural products, also called secondary metabolites, are small molecules produced in nature. Secondary metabolites play pivotal roles in many cellular processes and represent some of the most important pharmaceutical agents in human health care. This especially holds true in the antibiotic arena as a majority of the clinically prescribed antibiotics are natural products or derivatives thereof and have been isolated primarily from soil-dwelling bacteria. In recognition that microorganisms have been the most prolific source of new antibiotics, this project turns back to Nature to exploit the completely unexplored hypersaline microbes in the Great Salt Lake as a resource for drug discovery. Our observations are that environmental pressures influence the structural diversity of compounds produced in Nature and microorganisms thriving in extreme environments often produce chemical agents not observed in their terrestrial counterparts. The Great Salt Lake, also recognized as “America's Dead Sea”, is an endorheic (fully isolated) hypersaline lake located near the University of Utah in Salt Lake City, Utah. While seawater has an average salinity of ~3.3%, the Great Salt Lake ranges between 8-28%. Our preliminary data demonstrate that the unexplored hypersaline microorganisms of the Great Salt Lake possess antimicrobial activity against Gram-negative and Gram-positive bacterial pathogens, produce metabolites containing molecular scaffolds never before observed, and their genomes contain unprecedented biosynthetic machinery. Thus, these microbes serve as an ideal resource for the discovery of new antimicrobial agents possessing novel modes of action. To access and develop these agents, we have developed an integrated project that will leverage the strengths of our collaborative team including expertise in natural products isolation and structural elucidation, microbial biochemistry, genome mining, bioinformatics and bioengineering of recombinant natural products. From this project, unique antibiotic agents can be discovered along with information defining their biosynthetic pathways, their molecular targets, and likely other mechanisms of drug resistance. To exploit this novel resource, our specific aims will focus on: 1) Creating a hypersaline microbial library from sediment collected from the Great Salt Lake and screening the isolates using innovative methods for antimicrobial activity; 2) Identifying and validating new antibiotic agents using chemical and molecular networks; and 3) Identifying the biosynthetic machinery and molecular targets of the newly discovery antibiotic agents using genomic and bioinformatic approaches.