The genetic basis for the biosynthesis of large polypeptide antibiotics such as nisin has not been explained so far. We show here that the structural gene epiA encoding the antibiotic epidermin from Staphylococcus epidermidis is located on a 54-kilobase plasmid and codes for a 52-amino-acid prepeptide, which is processed to the tetracyclic 21-peptide amide antibiotic. The mature sequence of epidermin corresponds to the C-terminal 22-peptide segment of pre-epidermin and contains the precursor amino acids Ser, Thr and Cys, from which the unusual amino-acid constituents are derived. The more lipophilic epidermin is cleaved at a hydrophilic turn between Arg-1 and Ile+1 from the N-terminal segment-30 to -1, which probably assumes a partially amphiphilic alpha-helix conformation. We propose that the N-terminus (-30 to -1) plays a cooperative role during modification reactions and prevents toxicity of the mature epidermin to the producing strain before the antibiotic is cleaved off and secreted.

The bafilomycins A1, A2, B1, B2, C1 and C2, a new type of macrolide antibiotics with a 16-membered lactone ring, were isolated from the fermentation broth of three Streptomyces griseus strains (TO 1922, TO 2437, TO 2599 by ethyl acetate extraction and column chromatography on silica gel. The bafilomycins exhibit activity against Gram-positive bacteria and fungi. Physico-chemical data, chemical structures and biological activities are reported.The strain, Streptomyces griseus sp. sulphurus (TO 1922) is a good example for the ability of microorganisms to produce various secondary metabolites, depending on the culture conditions. The recognition of these metabolites depends on the screening method used for their detection. Under certain culture conditions Streptomyces griseus produce mainly the iron-complex of tirandamycin B as biologically active compound1). A change in culture conditions leads to the production of the Mg-complex of tirandamycin A2) and the bafilomycins as biological active compounds and pyrrol-2-carbonic acid, detected in a chemical screening procedure. In this paper we describe the fermentation (strain TO 1922), isolation, purification, chemical structure and biological properties of the bafilomycins, a new class of 16-membered macrolides. Materials and Methods Bacterial StrainsThe standard strains for the activity spectrum of the bafilomycins were obtained from the stock culture collection in our laboratories or from ATCC. The antibiotic-producing microorganisms (TO 1922, TO 2437, TO 2599 were new soil isolates, classified according to HOTTER and BERGEY as Streptomyces griseus3,4).Fermentation Studies S. griseus was cultured for 96 hours at 27°C in a medium (100 ml in a 500-ml Erlenmeyer flask with one intrusion) consisting of 2 % meat meal, 2 % malt extract, 1 % CaCO3 (NL 111). The pH was adjusted to 7.2 before autoclaving. These cultures were used as inoculum for the 10-liter fermentor. Bafilomycins were produced in a 10-liter fermentor under the following culture conditions: 5 % inoculum was ' Part 223: KoNIG , W.; H. HAHN, B. FISCHER and H. ZAHNER: Identifizierung and Synthese von 2,5-Diamino-4-hydroxy-6-methylheptansaure, eines Abbauproduktes des Glutaminantagonisten aus Nannizzia gypsea. Liebigs Ann. Chem., in press.

A screening method was established to detect inhibitors of the biosynthetic pathways of aromatic amino acids and para-aminobenzoic acid, the precursor of folic acid, using an agar A successful search for novel antibacterial metabolites has to meet three criteria, first, a specific target which is essential for the metabolism of a bacterium and not yet provided with an known inhibitor. Second, a set of taxonomically characterized and dereplicated microorganisms as producers of secondary metabolites, and last but not least a lucky but experienced hand for strain isolation and cultivation. We have chosen the shikimate pathway as an essential target of bacterial metabolism, with special consideration of the biosynthesis of aromatic amino acids and para-aminobenzoic (pAba) acid derived from the keymetabolite chorismate. Only a few antimetabolites are known as inhibitors of aromatic amino acids, such as L-2,5-dihydrophenylalanine2), an antagonist of phenlyalanine, and glyphosate that inhibits 3-enolpyruvylshikimate-3-phosphate synthase3,4). To our knowledge, no natural product inhibitor of pAba biosynthesis has been described in the literature. This pathway, which is catalyzed by two enzymes, 4-amino-4-deoxychorismic acid (ADC) synthase and ADC lyase, seems to be of considerable interest for the development of novel antibiotics since it is directly linked to folic acid biosynthesis, which is established in plants, fungi, prokaryotes and parasites of the apicomplexa group (Plasmodium, Toxoplasma) but not in vertebrates.As suitable producers of bioactive metabolites we screened within the order Actinomycetales terrestrial and marine members of the families Streptomycetaceae and Micromonosporaceae and rare actinomycete genera. A total of 930 extracts derived from 201 actinomycetes were subjected to the screening. Among them, only AB-18-032, an extract from a marine isolate from a sediment collected from the Sea of Japan, was found to exhibit activity against

Plumbing the depths: Abyssomicin C (structure shown) from ocean floor sediment is a novel antibiotic that inhibits the biosynthesis steps between chorismate and p‐aminobenzoic acid. Its activity may be explained by the irreversible trapping of the targeted enzymes by a Michael addition. Blocking the biosynthesis of p‐aminobenzoic acid may be one approach to developing new antibiotics.

Gallidermin is a new member of the class of lanthionine-containing peptide antibiotics, which are summarized under the common name lantibiotics. The lantibiotic gallidermin is produced by Staphylococcus gallinarum (F16/P57) Tü3928, and it exhibits activities against the Propionibacteria, involved in acne disease. Gallidermin differs from the recently discovered tetracyclic 21-residue peptide antibiotic epidermin only in a Leu/Ile exchange in position 6. The isolation procedures for gallidermin included adsorption directly from the culture broth, ion-exchange chromatography of the amphiphilic and basic polypeptide followed by desalting, and final purification by reversed-phase HPLC. The structural elucidation of the polypeptide containing four thioether bridges involved mainly a combination of automated gas-phase sequencing, thermospray liquid chromatography/mass spectrometry and fast-atom-bombardment mass spectrometry.

Epidermin is a large peptide antibiotic, which is synthesized in the ribosome via a precursor protein, followed by enzymatic modifications. It was isolated from the culture filtrate of Staphylococcus epidermidis TU 3298 by adsorption on Amberlite XAD-8. The basic heneicosapeptide amide was chromatographed on Sephadex LH-20 and purified to homogeneity via multiplicative counter-current distributions in one acidic and one neutral system. Tryptic digestion gave the soluble N-terminal fragment epidermin-(I -13)-peptide (Pl) and the insoluble Cterminal fragment 2-oxobutyryl-epidermin-(l5 -21)-peptide amide (P2), each possessing two sulfide ring systems. The heterodetic rings consisted of meso-lanthionine and (2S,3S,6R)-3-methyllanthionine (Pl), meso-lanthionine and C-terminally the new amino acid S-(2-aminovinyl)-~-cysteine (P2). The complex sequence was elucidated via a combination of desulfurization with Raney nickel, enzymatic and acidolytic degradations, gas-phase sequencing, fast-atom bombardment and field-desorption mass spectrometry and NMR spectroscopy.

From cultures of Yersinia enterocolitica H1852, an iron‐complexing and iron‐transporting compound named yersiniabactin was isolated. The structure of the siderophore was determined by a variety of spectroscopic methods, including 2D NMR experiments on the metal‐free ligand as well as its gallium complex. The metal‐free ligand, derivatives, as well as iron and gallium complexes were examined by high‐resolution FAB‐MS, API‐MS, API‐MS/MS and GC‐MS. The novel siderophore contains a benzene and a thiazolidine ring, as well as two thiazoline rings (Figure 1). Its stereochemistry is noteworthy for the presence of five chiral centers, one of which is considerably epimerized. The compound forms stable complexes with trivalent cations such as ferric iron and gallium.

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