Gene cluster for biosynthesis of thermophilin 1277--a lantibiotic produced by Streptococcus thermophilus SBT1277, and heterologous expression of TepI, a novel immunity peptide

Aims: To identify genes cluster for thermophilin 1277 produced by Streptococcus thermophilus SBT1277. Methods and Results: To identify genes for thermophilin 1277 production, the chromosomal DNA region surrounding the structural gene, tepA, was sequenced using a primer‐walking method. The thermophilin 1277 biosynthesis gene locus (tep) is a 9·9‐kb region, which consists of at least ten open reading frames (ORFs) in the following order: tepAMTFEGKRI and ORF4. Homology analysis showed high similarity to genes involved in bovicin HJ50 production by Streptococcus bovis HJ50. tepI encodes a novel, small, positively charged hydrophobic peptide of 52 amino acids, which contains a putative transmembrane segment. By heterologous expression in Lactococcus lactis ssp. cremoris MG1363, the TepI‐expressing strain exhibited at least 1·3 times higher resistance to thermophilin 1277. Conclusions: Thermophilin 1277 biosynthesis genes were encoded by a 9·9‐kbp region containing at least ten ORFs. TepI is a novel immunity peptide, which protected Strep. thermophilus SBT1277 against thermophilin 1277 in addition to TepFEG, a putative ABC transporter. Significance and Impact of the Study: This is the first report regarding a lantibiotic gene cluster produced by Strep. thermophilus strain.