Characterization of Amylolysin, a Novel Lantibiotic from <i>Bacillus amyloliquefaciens</i> GA1

<div><p>Background</p><p>Lantibiotics are heat-stable peptides characterized by the presence of thioether amino acid lanthionine and methyllanthionine. They are capable to inhibit the growth of Gram-positive bacteria, including <i>Listeria monocytogenes, Staphylococcus aureus</i> or <i>Bacillus cereus</i>, the causative agents of food-borne diseases or nosocomial infections. Lantibiotic biosynthetic machinery is encoded by gene cluster composed by a structural gene that codes for a pre-lantibiotic peptide and other genes involved in pre-lantibiotic modifications, regulation, export and immunity.</p> <p>Methodology/Findings</p><p><i>Bacillus amyloliquefaciens</i> GA1 was found to produce an antimicrobial peptide, named amylolysin, active on an array of Gram-positive bacteria, including methicillin resistant <i>S. aureus</i>. Genome characterization led to the identification of a putative lantibiotic gene cluster that comprises a structural gene (<i>amlA</i>) and genes involved in modification (<i>amlM</i>), transport (<i>amlT</i>), regulation (<i>amlKR</i>) and immunity (<i>amlFE</i>). Disruption of <i>amlA</i> led to loss of biological activity, confirming thus that the identified gene cluster is related to amylolysin synthesis. MALDI-TOF and LC-MS analysis on purified amylolysin demonstrated that this latter corresponds to a novel lantibiotic not described to date. The ability of amylolysin to interact <i>in</i><i>vitro</i> with the lipid II, the carrier of peptidoglycan monomers across the cytoplasmic membrane and the presence of a unique modification gene suggest that the identified peptide belongs to the group B lantibiotic. Amylolysin immunity seems to be driven by only two AmlF and AmlE proteins, which is uncommon within the <i>Bacillus</i> genus.</p> <p>Conclusion/Significance</p><p>Apart from mersacidin produced by <i>Bacillus amyloliquefaciens</i> strains Y2 and HIL Y-85,544728, reports on the synthesis of type B-lantibiotic in this species are scarce. This study reports on a genetic and structural characterization of another representative of the type B lantibiotic in <i>B. amyloliquefaciens</i>. </p>