Cloning, expression of proU of Lactobacillus plantarum ST-Ⅲ

Lactobacillus plantarum ST-Ⅲ, isolated from kimchi, could grow in 8% NaCl environment. The gene cluster proU, which located in the plasmid, involved in a transport system for glycine betaine.Through phylogenetic analysis, the similarity of the proU to the corresponding gene of the L. peutosus IG1 is 100%. proU had been speculated to relate to salt tolerance of L. plantarum ST- Ⅲ. The proU, and its three open reading frames proX, proW, and proV were cloned into pNZ8148, resulting in the construction of Lactococcus lactis expression systems.Introduction of expression vectors in osmotic sensitive strain Lactococcus lactis NZ9000 were achieved by electrotransformation.To determine the ability of salt tolerance, recombinant strains were cultured in CDM with 3%NaCl and 1mmol /L betaine.The results showed that, the gene proU, proX, proW, proV in recombinant strains were expressed, and the expression level were at least 106 times higher than control strain.The salt tolerance ability of recombinant strains were more exceed than control strain.The results proved that proU was directly related to salt tolerant ability of L.plantarum ST-Ⅲ.