Complete genome sequencing of Lactobacillus plantarum CAUH2 reveals a novel plasmid pCAUH203 associated with oxidative stress tolerance.

Lactobacillus plantarum is remarkably adaptable to diverse habitats and is widely used in food industry. In this study, the genome sequence of L. plantarum CAUH2 was analyzed and compared with other L. plantarum genome sequences. A comparison of the genome sequence of CAUH2 to L. plantarum ST-III reveals that the similarity of these two genomes reached up to 99% identity with 98% coverage, but the plasmid profiles of CAUH2 and ST-III are different. Notably, plasmid pCAUH203 in L. plantarum CAUH2 harbors seven genes involved in oxidative stress response, such as genes encoding thioredoxin-disulfide reductase, thioredoxin and DNA protection protein. Due to plasmid pCAUH203, the thioredoxin reductase activity of CAUH2 was 2.1-fold higher than that of ST-III. When exposed to 5 mM H2O2, this activity was further increased to 9.87 ± 1.60 mU per mg protein in CAUH2, which was 2.7-fold higher than that of ST-III, indicating that thioredoxin antioxidant system encoded by pCAUH203 might contribute to the H2O2 resistance. This hypothesis was further confirmed by survival assay under 10 mM H2O2 stress. The survival rate of CAUH2 was 12-fold higher than that of ST-III. Therefore, the complete genome sequencing of L. plantarum CAUH2 provides new insights into the molecular mechanism of its oxidative stress resistance.