Discovery of the lomaiviticin biosynthetic gene cluster in .

The lomaiviticins are a family of cytotoxic marine natural products that have captured the attention of both synthetic and biological chemists due to their intricate molecular scaffolds and potent biological activities. Here we describe the identification of the gene cluster responsible for lomaiviticin biosynthesis in strains DPJ-0016 and DPJ-0019 using a combination of molecular approaches and genome sequencing. The link between the gene cluster and lomaiviticin production was confirmed using bacterial genetics, and subsequent analysis and annotation of this cluster revealed the biosynthetic basis for the core polyketide scaffold.

Image-based 384-well high-throughput screening method for the discovery of skyllamycins A to C as biofilm inhibitors and inducers of biofilm detachment in Pseudomonas aeruginosa.

To date, most antibiotics have primarily been developed to target bacteria in the planktonic state. However, biofilm formation allows bacteria to develop tolerance to antibiotics and provides a mechanism to evade innate immune systems. Therefore, there is a significant need to identify small molecules to prevent biofilm formation and, more importantly, to disperse or eradicate preattached biofilms, which are a major source of bacterial persistence in nosocomial infections.

Probing natural product biosynthetic pathways using Fourier transform ion cyclotron resonance mass spectrometry.

Two natural products, diazepinomicin (1) and dioxapyrrolomycin (2), containing stable isotopic labels of (15)N or deuterium, were used to demonstrate the utility of Fourier transform ion cyclotron resonance mass spectrometry for probing natural product biosynthetic pathways. The isotopic fine structures of significant ions were resolved and subsequently assigned elemental compositions on the basis of highly accurate mass measurements. In most instances the mass measurement accuracy is less than one part per million (ppm), which typically makes the identification of stable-isotope labeling unambiguous.

Investigating the biosynthetic origin of the nitro group in pyrrolomycins.

Feasible modes of introducing the nitro group into pyrrolomycin antibiotics were investigated based on incorporation of (15)N-labeled arginine and proline into dioxapyrrolomycin, produced by the actinomycete culture LL-F42248. Biosynthesis of nitrated pyrrolomycins was unaffected by the presence of nitric oxide synthase (NOS) inhibitors. The culture was able to grow in nitrogen-free (minimal) media and produce nitrated secondary metabolites.

Biosynthesis of diazepinomicin/ECO-4601, a Micromonospora secondary metabolite with a novel ring system.

The novel microbial metabolite diazepinomicin/ECO-4601 (1) has a unique tricyclic dibenzodiazepinone core, which was unprecedented among microbial metabolites. Labeled feeding experiments indicated that the carbocyclic ring and the ring nitrogen of tryptophan could be incorporated via degradation to the 3-hydroxyanthranilic acid, forming ring A and the nonamide nitrogen of 1. Genomic analysis of the biosynthetic locus indicated that the farnesyl side chain was mevalonate derived, the 3-hydroxyanthranilic acid moiety could be formed directly from chorismate, and the third ring was constructed via 3-amino-5-hydroxybenzoic acid.

Culicinin D, an antitumor peptaibol produced by the fungus Culicinomyces clavisporus, strain LL-12I252.

A group of new 10mer linear peptides, designated culicinins A-D (1-4), was isolated from the fermentation broth of the entomopathogenic fungus Culicinomyces clavisporus, strain LL-12I252. The structures of the culicinins were determined by a combination of 2D NMR and MS analysis. The major compound, culicinin D (4), exhibited selective inhibitory activity against PTEN-negative MDA468 tumor cells.

Dioxapyrrolomycin biosynthesis in Streptomyces fumanus.

Streptomyces fumanus, intramurally coded as culture LL-F42248, produces a series of pyrrolomycins including dioxapyrrolomycin (1) as the principal component. Our biosynthetic studies revealed that feeding labeled acetate to growing cultures of S. fumanus yielded pyrrolomycins labeled in the phenyl ring only.

Penicillium dravuni, a new marine-derived species from an alga in Fiji.

Penicillium dravuni is a new monoverticillate, sclerotium-forming species that was isolated from the alga Dictyosphaeria versluyii collected in Dravuni, Fiji. This species morphologically is similar to P. turbatum in the P.

Phaeochromycins A-E, anti-inflammatory polyketides isolated from the soil actinomycete Streptomyces phaeochromogenes LL-P018.

Five new polyketide metabolites, phaeochromycins A-E (1-5), were isolated from an actinomycete designated Streptomyces phaeochromogenes LL-P018, cultured from a soil sample collected from a riverbank in Westevenger, Germany. Phaeochromycins A and C were found to be weak inhibitors of MAPKAP kinase-2 (IC50 = 39 and 130 microM, respectively). The structures of the compounds were determined by spectroscopic analysis, primarily two-dimensional NMR, and revealed that phaeochromycins A, B, C, and E were octaketides, elaborated from a C4 starter unit, related to shunt products of the actinorhodin pathway, namely, mutactin, dehydromutactin, SEK34b, and BSM1.

Fumaquinone, a new prenylated naphthoquinone from Streptomyces fumanus.

A new prenylated naphthoquinone antibiotic, fumaquinone (5,7-dihydroxy-2-methoxy-3-methyl-6-(3-methyl-but-2-enyl)[1,4]naphthoquinone) was isolated from cultures of Streptomyces fumanus (LL-F42248). Its chemical structure was determined primarily by NMR spectroscopy. Preliminary feeding experiments indicated the naphthoquinone is of polyketide origin, while the O-methyl and aromatic C-methyl groups are derived from methionine.

Production of novel rapamycin analogs by precursor-directed biosynthesis.

The natural product rapamycin, produced during fermentation by Streptomyces hygroscopicus, is known for its potent antifungal, immunosuppressive, and anticancer activities. During rapamycin biosynthesis, the amino acid l-pipecolate is incorporated into the rapamycin molecule. We investigated the use of precursor-directed biosynthesis to create new rapamycin analogs by substitution of unusual l-pipecolate analogs in place of the normal amino acid.

Additional pyrrolomycins from cultures of Streptomyces fumanus.

Along with dioxapyrrolomycin (1), four new pyrrolomycin antibiotics, namely, pyrrolomycin G (3), pyrrolomycin H (4), pyrrolomycin I (5), and pyrrolomycin J (6), were produced in cultures of Streptomyces fumanus. Apart from dioxapyrrolomycin, pyrrolomycin G and pyrrolomycin H are the only other chiral members of the pyrrolomycin family of antibiotics, and their absolute stereochemistry was deduced to be 13S. Here, we report the isolation, structure elucidation, and antimicrobial activity of these new pyrrolomycins.

07H239-A, a new cytotoxic eremophilane sesquiterpene from the marine-derived Xylariaceous fungus LL-07H239.

07H239-A (1), a new eremophilane sesquiterpene from a marine-derived xylariaceous fungus, was isolated, characterized, and shown to be cytotoxic toward a variety of cancer cell lines, with some selectivity for a CCRFCEM leukemia line (IC(50) = 0.9 microg/mL).

Dictyosphaeric acids A and B: new decalactones from an undescribed Penicillium sp. obtained from the alga Dictyosphaeria versluyii.

Fungal isolate F01V25 was obtained from the alga Dictyosphaeria versluyii collected near Dravuni, Fiji, in 2001 and represented a previously undescribed Penicillium sp. Fermentation of isolate F01V25 resulted in the production of two new polyketides, dictyosphaeric acids A and B, along with the known anthraquinone carviolin. The relative stereochemistry of dictyosphaeric acids A and B was determined using the J-based configuration analysis method in conjunction with ROE and NOE correlations.

Novel alpha-pyrones produced by a marine Pseudomonas sp. F92S91: taxonomy and biological activities.

Inhibitors of the enzymes involved in fatty acid biosynthesis (FAB) have been reported as antibacterial agents. These include thiolactomycin, cerulenin, triclosan, diazoborine, naphthyridinones, aminopyridines and pyridoindoles. Our search for new FAB inhibitors, using a lacZ reporter cell-based screen, led to several confirmed hits.

Novel sulfur-containing rapamycin analogs prepared by precursor-directed biosynthesis.

[reaction: see text] Two novel sulfur-containing analogs of the immunosuppressive natural product rapamycin (1) were obtained by feeding cultures of Streptomyces hygroscopicus with l-nipecotic acid (4) and either (S)-1,3-thiazane-4-carboxylic acid (5) or (S)-1,4-thiazane-3-carboxylic acid (6). The structures of the two new compounds, 20-thiarapamycin (2) and 15-deoxo-19-sulfoxylrapamycin (3), were determined by spectroscopic methods.

Brocaenols A-C: novel polyketides from a marine derived Penicillium brocae.

Chemical investigation of a Penicillium brocae, obtained from a tissue sample of a Fijian Zyzyya sp. sponge, yielded two known diketopiperazines and three novel cytotoxic polyketides, brocaenols A-C. The brocaenols contain an unusual enolized oxepine lactone ring system that to the best of our knowledge is unprecedented in the literature.