Isolation And Characterization Of Lantibiotic Elgicins Produced By Paenibacillus Elgii B69 And Analysis Of The Related Gene Cluster

Lantibiotics are unique class of peptide antibiotics containing unusual amino acids, such as lanthionine and P-methyllanthionine. Due to the various biological activities, stable structure, unusual binding site and low frequency of antibiotic resistance of lantibiotics, they are not only employed in the food preservation, but also have been proposed for treatment of infections with antibiotic resitance bacteria. Lantibiotics are ribosomally synthesized prepeptides that subsequently undergo posttranslational modification to became mature antibiotics. Therefore, many research works have been taken to identify novel lantibiotics and study on the meachnism for biosythesis of lantibiotics. Paenibacillus elgii B69, exhibiting a potential in biological control, was isolated from a soil sample. In this study, data mining for the silent gene clusters of B69 genome sequence resulted in the identification of a NRPS gene cluster, a PKS gene cluster, three hybrid PKS/NRPS gene clusters, and a novel lantibiotic-like gene cluster, i.e. elg gene cluster. In addition to this, we described the identification of four novel lantibiotics from the elg gene cluster.The elg gene cluster consisted of five ORFs (elgTl, elgC, elgT2, elgB, and elgA), in which elgA gene encodes the so-called prepeptide. elgB and elgC encode the enzymes responsible for modification in the posttranslational pathway. Moreover, the proteins ElgTl and ElgT2 are responsible for the transportation of elgicins. Screening of culture extracts for active substances with the predicted properties of the product from this gene cluster, led to the isolation of three novel peptides (elgicin A, elgicin B, and elgicin C). Further analysis of elgicin A revealed that this component contains two compounds, designated as elgicin AI and elgicin All, respectively. The molecular weights of these peptides were 4536,4593,4706, and 4820 Da, respectively. The molecular weight of elgicin All was 57 Da larger than that of elgicin AI; this difference corresponded to the molecular weight of a glycine residue. The molecular weight of elgicin B was 113 Da larger than that of AⅡ; this difference corresponded to the molecular mass of a leucine/isoleucine residue. The molecular mass of elgicin C was 114 Da larger than that of elgicin B; this difference was consistent with the molecular mass of an asparagine residue. The N-terminal sequence of elgicins was Leu-Gly-Asp-Tyr, corresponding to the partial sequence of the peptide ElgA encoded by elgA. The result of Edman degradation suggested that elgicin B is the product stem from ElgA. By combining the results of ESI-MS analyses of elgicin AⅠ, AⅡ, and C, thses peptides were originate from the same precursor, ElgA. To the best of our knowledge, reports regarding four novel lantibiotics stem from the same prepeptide have not yet been published. Therefor, the mechanism for the biosynthesis of elgicins should be studied deeply. Antimicrobial activity assay revealed that elgicins have broad inhibitory activities against several Gram-positive and Gram-negative bacteria.