Abstract: The present invention is directed generally to compositions and methods for obtaining secretion of antibodies or antigen-binding antibody fragments from prokaryotes without the need for a signal peptide through making use of mutant host strains with altered secretory properties. In particular, the invention provides host cells and methods for obtaining secretion of antibodies or antigen-binding antibody fragments from bacteria without the need for a signal peptide and provides diverse libraries of antibody sequence resulting from such methods. The invention additionally provides diverse libraries.