An expression system based on the Staphylococcus aureus protein A gene (spa) was developed to allow the production and export of proteins in Lactobacillus. Plasmid shuttle vectors were constructed that carried the eZZ gene, a synthetic gene based on the Protein A gene (spa) but lacking the carboxy-terminal membrane-anchoring region. A gene fusion was created between the eZZ gene and the VD4 region of a chlamydial major outer-membrane protein gene. Expression studies demonstrated the recognition of the spa regulatory signals by several Lactobacillus, with the recombinant protein being expressed (from 0.1 mu g of EZZVD4 fusion protein per mi in L. plantarum up to 10 mu g of EZZ protein per mi in L. fermentum) and exported (levels up to 20% in L. fermentum) in several Lactobacillus strains.