Toxic lactonic lipopeptide from food poisoning isolates of Bacillus licheniformis

Toxins from three Bacillus licheniformis strains connected to a fatal food poisoning were isolated and their structures elucidated. Toxins were purifi ed from methanol extracts of the B. licheniformis biomass using boar sperm cells as the toxicity indicator. The HPLC purified toxins showed protonated masses m/z 1007, 1021 and 1035 in MALDI-TOF-MS. The toxins isolated from t he strains of different origins contained the same three components of whic h and each had a same amino-acid residues L-Gln, L-Leu, D-Leu, L-Val, L-Asp , D-Leu and L-Ile in that order. Toxins were identified as lichenysin A, a cyclic lactonic heptalipopeptide in which the main 3-hydroxy fatty acids ar e 13-15 carbons in length. We showed that the toxins from food and food poi soning isolates of B. licheniformis were identical to lichenysin A both in the structure and in the toxic symptoms induced to boar spermatozoa. Confoc al laser scanning microscopy showed that the acrosome and the plasma membra ne of boar spermatozoa were the targets of lichenysin A toxicity.