Identification, characterization and purification of the lantibiotic staphylococcin T, a natural gallidermin variant

Staphylococcin T (StT), an antibacterial agent produced by a Staphylococcus cohnii T strain, was purified to homogeneity by ammonium sulphate precipit ation, gel filtration, cation exchange and fast performance liquid chromato graphy (FPLC). The final yield was about 20%, and over a 1000-fold increase in the specific activity was obtained. Mass determination (2166 Da), amino acid sequencing (Ile-Ala-Xaa-Lys-Phe-Leu-Xaa-Xaa-Pro-Gly-Xaa-Ala-Lys-block ) and DNA sequencing demonstrated that StT is identical to gallidermin, a l anthionine-containing antimicrobial peptide. StT has a broad spectrum of ba ctericidal activity against Gram-positive and some Gram-negative bacteria. StT appears to damage cell membrane, and as a result causes an efflux of io ns and an immediate block in macromolecular synthesis. Moreover, electron m icroscopic observations reveal morphological changes, with a loss of riboso mes and condensation of the nucleoid DNA. These changes are followed by a d issolution of the cell contents resulting in a bacterial ghost composed of seemingly intact cell walls with remnants of the cytoplasmic membrane and i nternal structure. Since StT exhibits antimicrobial activity especially aga inst the Staphylococcus species, this compound may be of use in the treatme nt of staphylococcal infections.