RECOMBINANT MICROORGANISMS AS TOOLS FOR HIGH-THROUGHPUT SCREENING FORNONANTIBIOTIC COMPOUNDS

Microorganisms were among the first tools used for the discovery of bi ologically active compounds. Their utility reached a zenith during the era of antibiotic development in the 1950s and 1960s, then declined, Subsequently, a substantial role for microorganisms in the pharmaceuti cal industry developed with the realization that microbial fermentatio ns were intriguing sources of nonantibiotic natural products. From rec ombinant DNA technology emerged another important role for microorgani sms in pharmaceutical research: the expression of heterologous protein s for therapeutic products or for in vitro high throughput screens (HT Ss), Recent developments in cloning, genetics, and expression systems have opened up new applications for recombinant microorganisms in scre ening for nonantibiotic compounds in HTSs. These screens employ microo rganisms that depend upon the function of a heterologous protein for s urvival under defined nutritional conditions, Compounds that specifica lly target the heterologous protein can be identified by measuring via bility of the microorganism under different nutrient selection. Advant ages of this approach include a built-in selection for target selectiv ity, an easily measured end point that can be used for a multitude of different targets, and compatibility with automation required for HTSs . Mechanism-based HTSs using recombinant microorganisms can also addre ss drug targets that are not readily approachable in other HTS formats , including certain enzymes; ion channels and transporters; and protei n::protein, protein::DNA, and protein::RNA interactions.