Elucidation of sevadicin, a novel non-ribosomal peptide secondary metabolite produced by the honey bee pathogenic bacterium P aenibacillus larvae.

American foulbrood ( AFB) caused by the bee pathogenic bacterium P aenibacillus larvae is the most devastating bacterial disease of honey bees worldwide. From AFB-dead larvae, pure cultures of P . larvae can normally be cultivated indicating that P . larvae is able to defend its niche against all other bacteria present. Recently, comparative genome analysis within the species P . larvae suggested the presence of gene clusters coding for multi-enzyme complexes, such as non-ribosomal peptide synthetases ( NRPSs). The products of these enzyme complexes are known to have a wide range of biological activities including antibacterial activities. We here present our results on antibacterial activity exhibited by vegetative P . larvae and the identification and analysis of a novel antibacterially active P . larvae tripeptide (called sevadicin; Sev) produced by a NRPS encoded by a gene cluster found in the genome of P . larvae. Identification of Sev was ultimately achieved by comparing the secretome of wild-type P . larvae with knockout mutants of P . larvae lacking production of Sev. Subsequent mass spectrometric studies, enantiomer analytics and chemical synthesis revealed the sequence and configuration of the tripeptide, D-Phe- D- ALa-Trp, which was shown to have antibacterial activity. The relevance of our findings is discussed in respect to host-pathogen interactions. [ABSTRACT FROM AUTHOR]