Preparation of lantibiotics.

Lantibiotics were purified and antimicrobial activity was tested as discussed in the supplemental material. Freeze-dried high-performance liquid chromatography (HPLC)-purified samples were reconstituted in 0.1% (vol/vol) TFA for antimicrobial assays and phosphate-buffered saline (PBS) (pH 7.4) for animal trials. Peptide concentrations were determined using the BCA protein assay according to the manufacturer's instructions. Lantibiotics were prepared to a final concentration of 50 μM in 0.1% (vol/vol) TFA for antimicrobial assays and 250 μM in PBS (pH 7.4) containing 2.5% (wt/vol) PVA for animal trials. The lantibiotic suspensions were stored at 4°C throughout each animal trial. In the case of AmyA, the α- and β-peptides were combined in a 1:1 molar ratio. The suspensions were freshly prepared before each trial.