Heterologous Protein Secretion in Lactobacilli with Modified pSIP Vectors

<div><p>We describe new variants of the modular pSIP-vectors for inducible gene expression and protein secretion in lactobacilli. The basic functionality of the pSIP system was tested in <i>Lactobacillus</i> strains representing 14 species using pSIP411, which harbors the broad-host-range <i>Lactococcus lactis</i> SH71_rep replicon and a β-glucuronidase encoding reporter gene. In 10 species, the inducible gene expression system was functional. Based on these results, three pSIP vectors with different signal peptides were modified by replacing their narrow-host-range <i>L. plantarum</i> 256_rep replicon with SH71_rep and transformed into strains of five different species of <i>Lactobacillus</i>. All recombinant strains secreted the target protein NucA, albeit with varying production levels and secretion efficiencies. The Lp_3050 derived signal peptide generally resulted in the highest levels of secreted NucA. These modified pSIP vectors are useful tools for engineering a wide variety of <i>Lactobacillus</i> species.</p>