Bacteria have developed resistance to all of the antibiotics currently in use. A major concern regarding the use of bacterial pathogens as biological weapons is the possibility that they have been engineered to be resistant to current chemotherapeutic agents. The goal of this project is to develop new classes of anti-infectives that are not susceptible to natural or engineered resistance mechanisms. The bacterial ribosome is a proven drug target. We have developed new genetic technology ('instant evolution') that allows high-throughput in vivo isolation and analysis of ribosomal RNA mutations that might lead to drug resistance. This information will be used to identify anti-infectives that recognize the wild-type and all viable mutants of the drug target. Instant evolution was initially developed using Escherichia coli, but was recently applied to the rRNA genes of several other major human pathogens including Yersinia species. The proposed multidisciplinary project brings four groups together with expertise microbial genetics, structural biology, in vitro selections, organic synthesis, drug screening, and combinatorial chemistry to create a unique collaborative team focused on the development of entirely new classes of antimicrobial therapeutics. Antimicrobials produced using this platform will provide new therapies for the treatment of infections caused by human pathogens that are resistant to current antibiotics. In addition, the new therapeutics will be less susceptible to de novo development of resistance because instant evolution allows all mutations of the target that might lead to resistance to be identified during the earliest stages of the drug discovery process. [unreadable] [unreadable]