Abstract: Novel vectors are provided for identifying secretory signal sequences from DNA fragments of unicellular microorganisms. The plasmids comprise a multiple cloning site with restriction sites in reading frame with a structural gene which permits rapid screening of the screted expression product. Optionally, the vectors may include a promoter region upstream from the multiple cloning site. The invention is exemplified with Bacillus. Specific secretory signal sequence have been isolated with those vectors, allowing for efficient secretion into the supernatant, and not just to the periplasmic space to provide proteins in economically high yields. Secretory sequences are provided superior to other previously known sequences.