Abstract: The present invention has identified the Caulobacter RsaFa and RsaFb proteins as the OMP components of the S-layer protein secretion machinery. The present invention has also identified that an enhanced production of a heterologous protein from Caulobacter can be achieved by increased production of RsaFa and/or RsaFb. Expression vectors, genetically engineered Caulobacter strains, as well as methods are provided that are useful for producing a heterologous protein in Caulobacter.

Abstract: Caulobacter optimized for use in expression of heterologous peptides as part of a hybrid Caulobacter S-layer protein are provided as well as methods for producing such Caulobacter. Caulobacter of this invention are deficient in a native Caulobacter protease that cleaves hybrid S-layer proteins. Also provided are Caulobacter libraries and methods for sorting such libraries using cell sorting technoloey such as FACS.