Here we report on a novel thiazole/oxazole-modified microcin (TOMM) from Bacillus amyloliquefaciens FZB42, a Gram-positive soil bacterium. This organism is well known for stimulating plant growth and biosynthesizing complex small molecules that suppress the growth of bacterial and fungal plant pathogens. Like microcin B17 and streptolysin S, the TOMM from B. amyloliquefaciens FZB42 undergoes extensive posttranslational modification to become a bioactive natural product. Our data show that the modified peptide bears a molecular mass of 1,335 Da and displays antibacterial activity toward closely related Gram-positive bacteria. A cluster of 12 genes that covers ϳ10 kb is essential for the production, modification, export, and self-immunity of this natural product. We have named this compound plantazolicin (PZN), based on the association of several producing organisms with plants and the incorporation of azole heterocycles, which derive from Cys, Ser, and Thr residues of the precursor peptide.Bacillus amyloliquefaciens FZB42 is a Gram-positive, plant growth-promoting bacterium with an impressive capacity to produce secondary metabolites with antimicrobial activity (7). The nonribosomal syntheses of polyketides (bacillaene, difficidin, and macrolactin), lipopeptides (surfactin, fengycin, and bacillomycin D), and siderophores (bacillibactin and the product of the nrs cluster) are carried out by large gene clusters distributed over the entire genome of B. amyloliquefaciens FZB42. While these compounds are biosynthesized in a 4Ј-phosphopantetheine transferase (Sfp)-dependent fashion, the production of the antibacterial dipeptide bacilysin is independent of Sfp (8,9). In total, 8.5% of the entire genomic capacity of B. amyloliquefaciens FZB42 is devoted to the nonribosomal synthesis of secondary metabolites, exceeding that of the model Gram-positive bacterium Bacillus subtilis 168 by more than 2-fold (6). Prophage sequences that often harbor biosynthetic gene clusters of ribosomally synthesized peptides (microcins, lantibiotics/lantipeptides), which are common in B. subtilis strains, were not previously detected within the FZB42 genome. However, the presence of an antimicrobial compound(s) active against sigW mutant strain HB0042 of B. subtilis has been reported. SigW is an extracytoplasmic sigma factor that provides intrinsic resistance to antimicrobial compounds produced by other Bacilli (4).The driving force for the current report was the finding that FZB42 mutant RS6, which is deficient in the Sfp-dependent synthesis of lipopeptides and polyketides and in Sfp-independent bacilysin production (9), still produced an antibacterial substance active against Bacillus subtilis HB0042. This finding underscores the diversity of biosynthetic strategies employed by FZB42 and offers new possibilities for discovering novel natural products with biomedically relevant activities. Recent genomic analysis of FZB42 revealed a ribosomally encoded biosynthetic gene cluster that is conserved among many species across two domains of life ...

Lantibiotics are a large group of ribosomally synthesized peptides post-translationally modified to incorporate the amino acid lanthionine. They are classified, according to their biosynthetic pathway and bioactivity, into three major subtypes. Of Actinomycetes type III lantibiotics, only four peptides (SapB, SapT, LabA1, and LabA2) have been described and structurally characterized, although homologous gene clusters are abundant in other Actinomycetes. All these gene clusters share a similar architecture with a characteristic Ser/Ser/Cys motif in precursor peptides, which has previously been suggested to act as a precursor for lanthionine (SapB) and labionin (LabA2) rings. Mass spectrometry screening led to the discovery and characterization of three new representatives of type III lantibiotics: Avermipeptin (Avi), Erythreapeptin (Ery), and Griseopeptin (Gri) from Streptomyces avermitilis DSM 46492, Saccharopolyspora erythraea NRRL 2338, and Streptomyces griseus DSM 40236, respectively. Apart from the assignment of these peptides to their corresponding gene clusters, additional investigations on Avi, Ery and Gri peptides indicate stepwise leader processing by putative aminopeptidase-like protease(s), thus yielding mixtures of differently N-terminal-processed lantibiotic peptides. Similar peptide processing was observed for a heterologously expressed eryth biosynthetic gene cluster expressed in a Streptomyces host system. Remarkably, all isolates of the new type III lantibiotics contain both the amino acids lanthionine and labionin, thus implying dual-mode cyclase activity of the processing lyase-kinase-cyclase enzymes. These findings have implications for the structures and maturation of other type III lantibiotics from Actinomycetes.

Summary Mycotoxin‐producing Fusarium graminearum and related species cause Fusarium head blight on cultivated grasses, such as wheat and barley. However, these Fusarium species may have had a longer evolutionary history with North American grasses than with cultivated crops and may interact with the ancestral hosts in ways which are biochemically distinct.We assayed 25 species of asymptomatic native grasses for the presence of Fusarium species and confirmed infected grasses as hosts using re‐inoculation tests. We examined seed from native grasses for the presence of mycotoxin‐producing Fusarium species and evaluated the ability of these fungi to produce mycotoxins in both native grass and wheat hosts using biochemical analysis.Mycotoxin‐producing Fusarium species were shown to be prevalent in phylogenetically diverse native grasses, colonizing multiple tissue types, including seeds, leaves and inflorescence structures. Artificially inoculated grasses accumulated trichothecenes to a much lesser extent than wheat, and naturally infected grasses showed little to no accumulation.Native North American grasses are commonly inhabited by Fusarium species, but appear to accommodate these toxigenic fungi differently from cultivated crops. This finding highlights how host identity and evolutionary history may influence the outcome of plant–fungal interactions and may inform future efforts in crop improvement.

The structures of the ribosomally synthesized peptide antibiotics from Bacillus amyloliquefaciens FZB42, plantazolicin A and B, have been elucidated by high resolving ESI-MSMS, 2D (1)H-(13)C-correlated NMR spectroscopy as well as (1)H-(15)N-HMQC/(1)H-(15)N-HMBC NMR experiments. (15)N-labeling prior to the experiments facilitated the structure determination, unveiling a hitherto unusual number of thiazoles and oxazoles formed from a linear 14mer precursor peptide. This finding further extends the number of known secondary metabolites from B. amyloliquefaciens and represents a new type of secondary metabolites from the genus Bacillus.