Specific inhibition of candicidin biosynthesis by the lipogenic inhibitor cerulenin.

Cerulenin, an inhibitor of fatty acid synthesis, inhibits specifically the biosynthesis of the polyene macrolide candicidin by resting cells of Streptomyces. 50% inhibition was achieved with a cerulenin concentration of 1.5 mug/ml. Cells in which candicidin synthesis was inhibited for 10 h remained capable of candicidin synthesis after removal of the inhibitor. Cerulenin inhibits specifically the incorporation of [14C] propionate into candicidin but does not affect total protein or RNA synthesis. The uptake of [14C] propionate was not inhibited under conditions which totally prevented the incorporation of propionate into candicidin. Incorporation of p-amino[14C] benzoic acid NH2 [14C] BzO- into the aromatic moiety of candicidin was also inhibited by cerulenin. The inhibitory action of cerulenin was not reversed by exogenous fatty acids. Since cerulenin is known to block the condensation of malonyl-CoA subunits in the formation of fatty acids, it is concluded that the polyene macrolide candicidin is synthesized via the polyketide pathway by condensation steps similar to those occurring in fatty acid biosynthesis.

Comparative analysis of hexaene antibiotics.

A study of nine hexaene antibiotics resulted in their assignment to three subgroups on the basis of their bioactivities. Separation of individual components of the nine antibiotic complexes was accomplished by thin-layer chromatography. Similarities and differences among members of the subgroups were established by thin-layer chromatography, spectrophotometry and high performance liquid chromatography. Two antibiotics (endomycin and hexafungin) were found to be similar.

Hydroheptin: a water-soluble polyene macrolide. I. Taxonomy, fermentation and isolation.

A soil isolate of Streptomyces, which has been deposited in the culture collection of the Waksman Institute of Microbiology, Rutgers University as IMRU 3962, produces a new heptaene macrolide antifungal antibiotic, hydroheptin. The producing microorganism, which co-produces the antibiotic, chartreusin, has been identified as a strain of Streptomyces chartreusis. Fermentation and bioassay procedures were developed for the production and analysis of hydroheptin and chartreusin. Isolation and purification procedures based on solvent extraction and precipitation of an organic acid yielded a relatively pure product of hydroheptin.

Hydroheptin: a water-soluble polyene macrolide. II. Chemical and biological properties.

Hydroheptin, a new polyene macrolide antifungal antibiotic, is co-produced with the antibiotic, chartreusin, by a strain of Streptomyces chartreusis designated as IMRU 3962 isolated in our laboratory. The unique water-solubility of this antibiotic at neutrality, revealing in aqueous solution molecular dispersion and an ultraviolet-visible absorption spectrum characteristic of an all-trans heptaene chromophore, clearly distinguishes it from all previously-described and naturally-occurring heptaene macrolides. The isolation and identification of the amino sugar, mycosamine (3-amino-3,6-dideoxy-D-mannose), in acid hydrolysates of hydroheptin and the absence of an aromatic amine upon retrograde alkaline dealdolization of the molecule certainly characterize the antibiotic as a member of the non-aromatic heptaene macrolide group. Chromatographic and countercurrent distribution studies likewise support its novelty. With little or no demonstrable activity against bacteria, hydroheptin as compared to other non-aromatic heptaene macrolides exhibits excellent but somewhat less activity against a wide variety of yeasts and fungi. Likewise, its parenteral toxicity appears to be less than that of other heptaene macrolides.

New antibiotic pigments related to fusarubin from Fusarium solani (Mart.) Sacc. I. Fermentation, isolation, and antimicrobial activities.

A cholesterol-decomposing fungus, Fusarium solani (Mart.) SACC. strain PP 96, was found to produce several different naphthaquinone pigments in a glycerol-mineral salts medium. Three novel compounds structurally related to fusarubin were isolated by chloroform extration followed by silicic acid column chromatography and preparative thin-layer chromatography. The purified compounds were found to have relatively low activity against bacteria, yeasts and filamentous fungi.

Crisamicin A, a new antibiotic from Micromonospora. I. Taxonomy of the producing strain, fermentation, isolation, physico-chemical characterization and antimicrobial properties.

A microorganism, designated as RV-79-9-101 and now identified as Micromonospora purpureochromogenes subsp. halotolerans, isolated from a mud sample in the Philippines, has been shown to produce a complex of antibiotics called crisamicins. Thin-layer chromatography and bioautography, employing solvent extracts of whole fermentation broths, revealed a minimum of five antimicrobial components. The major biologically-active component of the antibiotic complex, crisamicin A, was obtained in pure form after preparative silica gel column chromatography followed by crystallization. Based on physico-chemical data crisamicin A has been identified as a novel member of the isochromanequinone group of antibiotics. It exhibits excellent in vitro activity against Gram-positive bacteria but little or no activity towards Gram-negative bacteria or fungi.

Studies on the biosynthesis of the antibiotic crisamicin A and carbon-13 magnetic resonance assignments.

The biosynthesis of crisamicin A, a novel dimeric isochromanequinone antibiotic from Micromonospora purpureochromogenes subsp. halotolerans has been investigated by [1-13C] and [2-13C] labeled acetate precursor feeding experiments. Analysis of the proton noise decoupled and off resonance 13C NMR spectra of 13C enriched and unenriched crisamicin A and their acetate derivatives indicated the biosynthesis via the polyketide pathway, as expected. Further analysis of the enriched spectra allowed the complete assignment of the carbon signals. Of particular interest was the establishment of the linkage between the two monomeric halves of the molecule and determination of the location of the phenolic hydroxyls.