Flow cytometric sorting of bacterial surface-displayed libraries

The protocols herein detail methods for isolating binding peptides from a combinatorial library displayed on the surface of bacterial cells. These methods are appropriate for a variety of display scaffolds and a large range of library sizes, up to approximately 5 x 10(9) or more. Instructions have been provided for isolating peptides that bind to both proteins and non-protein targets, such as whole cells or inorganic particles. Qualitative analysis by flow cytometry can be exploited for bacterial libraries to characterize a displayed peptide's binding properties with a target of interest, and sorting conditions can be tuned to maximize binding affinity.