Complete nucleotide sequence of plasmid pST-III from Lactobacillus plantarum ST-III

The complete nucleotide sequence of the 53,560-bp plasmid pST-III from Lactobacillus plantarum ST-III has been determined. The plasmid contains 42 predicted protein-coding sequences, and the functions of 34 coding sequences could be assigned. Homology analysis for the replication protein and the typical features of the origin of replication suggested that pST-III replicates via the theta-type mechanism. Among the predicted genes, we identified a kdp gene cluster (a high-affinity K+-transport system) for the first time in the Lactobacillus genus and a system for osmolyte transport. Analysis of the plasmid-encoded functions and the plasmid-cured experiment showed that the genes of pST-III could serve for the niche adaptations of L. plantarum ST-III and make significant contributions to its viability under hyperosmotic conditions. Furthermore, the relative copy number of pST-III was determined to be 6.79 ± 1.55 copies per cell.

► We sequence and characterize one of the largest plasmids of lactic acid bacteria.
► This is the first report of a Kdp system in the Lactobacillus genus.
► The plasmid contain some genes which are related with the hyperosmotic resistance.