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At low iron(III)-concentrations (<10 M) the fungus Aspergillus viridi-nutans Ducker & Thrower excretes desferri-ferricrocin as the main sideramine into the culture medium. While this compound accounts for 95% of the sideramines produced, small amounts of additional sidermines may also be detected. In a search for an inexpensive nutrient medium for optimum production of desferri-ferricrocin, experiments using shake flasks with good aeration were undertaken initially. The best medium conditions were then employed in a fermentor system. In a 20-1 fermentor with 'intensor' system, it was shown that at certain growth rates there was an inverse correlation between rate of growth and rate of sideramine production. A defined nutrient medium of glucose plus acetate as carbon sources, and urea or ammonium acetate as nitrogen sources was used. Two different feeding regimens were used in response to changes of pH or to changes of partial pressure of oxygen in the submerged culture: acetic acid/urea of acetic acid/ammonium acetate additions regulated these conditions. The rate of sideramine production under such feeding achieved a maximum of 20 mg l h over a period of several days. [ABSTRACT FROM AUTHOR]

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Rinamycin interfered with DNA-polymerase I of Escherichia coli in cell-free systems more effectively than actinomycin C. Its inhibitory action could be relieved by increasing the concentration of polymerase. The rinamycin concentrations that caused effective inhibition of the RNA-polymerase reaction in vitro were approximately 10 times higher than those required to inhibit the DNA-polymerase reaction in vitro. Derinamycin was as effective an inhibitor for the DNA-polymerase I reaction as actinomycin C, while having been stimulative for the RNA-polymerase reaction in cell-free systems of Escherichia coli. Its inhibitory action on DNA synthesis in vitro could be overcome by adding more DNA. In fact, spectral and antagonism studies suggested some sort of interaction between derinamycin and DNA. [ABSTRACT FROM AUTHOR]

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Copyright of Archives of Microbiology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The clavams valclavam and hydroxyethylclavam were both bacteriostatic and fungistatic. The molecular basis for growth inhibition of Escherichia coli was a non-competitive inhibition of homoserine-O-succinyltransferase (EC 2.3.1.46), thus blocking methionine biosynthesis. Eucaryotes such as Saccharomyces cerevisiae were inhibited by a different mode of action. Instead of interfering with methionine biosynthesis, the clavams inhibited the formation of RNA in living cells, although the RNA-polymerases of isolated yeast nuclei were not inhibited. The action of valclavam on E. coli was dependent on functional peptide transport systems. [ABSTRACT FROM AUTHOR]

The production of EDDS (ethylene-diamine-disuccinic acid), a potential substitute for EDTA, has been optimized up to a product concentration of 20 grams per litre in fermentations of Amycolatopsis orientalis. Decisive steps for the increase in productivity were variation of the synthetic medium composition, investigation of the influence of metal ions on product formation, controlled feeding of carbon and nitrogen sources in fed-batch fermentations and improvement of the downstream processing steps. [ABSTRACT FROM AUTHOR]

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The Zygomycete Cunninghamella elegans produces the polycarboxylate siderophore rhizoferrin. Production depends mainly on iron concentration in the medium. With an optimized production medium the yield of rhizoferrin in a bioreactor could be increased to more than 4 g/l. Supplementation of the basic production medium with different precursors led to the formation of nine new rhizoferrins. Both the diaminobutane backbone and the citric acid side-chains of rhizoferrin could be substituted by appropriate analogues. These substitutions led to new siderophores either with a variable length of diamine bridge or with fewer or different functional groups. The proportion of the new diamine analogues relative to the total rhizoferrin could be markedly increased by the use of α-difluoromethylornithine, an inhibitor of the ornithine decarboxylase. [ABSTRACT FROM AUTHOR]

Streptomyces griseus TÜ 6 produces the sideromycin antibiotic albomycin δ in concentrations of approximately 1 mg/l. The production depends on the phosphate, iron, and ornithine concentrations in the medium. In optimized conditions, the production of albomycin could be increased to 25 mg/l in a fedbatch fermentation. Isolation and purification could be achieved by reversed-phase and size-exclusion chromatography and preparative high-performance liquid chromatography (HPLC). The detection limit in quantitative determination of albomycin by HPLC was reached at a concentration of 1 μg/ml, which was 100 times less sensitive than biological testing, but this method, although time-consuming, was more selective. [ABSTRACT FROM AUTHOR]

A new group of iron-containing metabolites, with growth stimulating properties for a number of microorganisms, has been isolated from streptomycetes and named ferrioxamines. It is proposed to include them, together with some known substances, like ferrichrome, coprogen and the terregens factor, which either contain or bind iron, in a new class of growth factors, the sideramines. The biological property of the sideramines is counteracted by iron-containing antibiotics from streptomycetes, the sideromycins. They comprise, besides known products like grisein and albomycin, two new groups of antibiotics, among them the highly potent ferrimycins. [ABSTRACT FROM AUTHOR]

Alkaline degradation of fusigen, a sideramine from fungi, yields the known monohydroxamic acid fusarinine. L-Ornithine and cis-5-hydroxy-3-methylpentenoic-2-acid occur in fusigen in equal amounts, and ornithine is the only amino acid. Amino group(s) with pK 7,1, but no free carboxyl group can be found in fusigen. The calculated equivalent weight is 280, which again points to fusarinine as a structural subunit. By acetylation of fusigen three products are obtained, which can be separated by electrophoresis or chromatography. The titration data of the partially acetylated fusigen and the molecular weight estimation by vapour pressure osmometry of the desferriform of the fully acetylated fusigen show that fusigen is a trimeric fusarinine. These data together with those obtained from IR- and NMR-absorption spectra lead to the proposed structure: three fusarinine molecules are esterified head-to-tail to build a 36-membered ring. The quantitative estimation of all hydroxamic acids in the culture fluid of Fusarium cubense from the 2nd to the 9th day of fermentation and structural studies on some of these compounds revealed the spontaneous degradation of fusigen by ring opening and sequential split-off of fusarinine units. An analogous degradation pathway starts from N-acetyl-fusigen. The Δ2-anhydromevalonic lactone, found in the cultures of several fungi, seems to stem from the degradation of fusarinine. The total yield of Δ2-anhydromevalonic lactone can be increased severalfold by treatment of the culture fluid with hydrochloric acid prior to extraction. [ABSTRACT FROM AUTHOR]

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Boromycin, at a concentration of 0.05 μg/ml inhibits the synthesis of protein, RNA and DNA in whole cells of Bacillus subtilis. It is being antagonised by surface active compounds and is being bound to lipoprotein. Binding of the boromycin within the cell especially takes place at the cytoplasmic membrane. The inhibitory effect to Bacillus subtilis is being reversed by high concentration of potassium salts (e.g. 0.2 m KCl). The reversion is specific of potassium salts. After the adding of boromycin a discharge of potassium ions from the cells can be observed. The K-Na-activated ATP-ase of the cytoplasmic membrane is not influenced by boromycin. On an artificial membrane of carbon tetrachloride boromycin shows a low selectivity for potassium ions compared with sodium and lithium ions. The degradation of boromycin through alkaline and acid hydrolysis leads to a loss of antibiotic activity, due to the splitting off the boric acid from the molecule. [ABSTRACT FROM AUTHOR]

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The macrolide-antibiotics are discussed in respect to their chemistry and biology. The single substances are listed. An investigation and classification of the streptomycetes producing macrolides, is added; the single species are critically revised. Relations are established between the producers and their products. [ABSTRACT FROM AUTHOR]

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