The effect of ten naturally occurring and two synthetic inhibitors of NADH :ubiquinone oxidoreductase (complex I) of bovine heart, Neurosporu crassa and Escherichia coli and g1ucose:ubiquinone oxidoreductase (glucose dehydrogenase) of Gluconobacter oxidans was investigated. These inhibitors could be divided into two classes with regard to their specifity and mode of action. Class I inhibitors, including the naturally occuring piericidin A, annonin VI, phenalamid A2, aurachins A and B, thiangazole and the synthetic fenpyroximate, inhibit complex I from all three species in a partially competitive manner and glucose dehydrogenase in a competitive manner, both with regard to ubiquinone. Class I1 inhibitors including the naturally occuring rotenone, phenoxan, aureothin and the synthetic benzimidazole inhibit complex I from all species in an non-competitive manner, but have no effect on the glucose dehydrogenase. Myxalamid PI could not be classified as above because it inhibits only the mitochondrial complex I and in a competitive manner. All inhibitors affect the electron-transfer step from the high-potential iron-sulphur cluster to ubiquinone. Class I inhibitors appear to act directly at the ubiquinone-catalytic site which is related in complex I and glucose dehydrogenase.NADH : ubiquinone oxidoreductase, also known as respiratory complex I of mitochondria, transfers electrons from NADH to ubiquinone and links this process with translocation of protons across the inner membrane.

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Novel citrate-hydroxamate siderophores, named nannochelins A, B and C, were isolated from the culture broth of the myxobacteriumNannocystis exedens strain Nae485. Thenewsubstances showed weak growth-inhibitory activity against some bacteria and fungi.

Antibiotics From Gliding Bacteria, LV. – Myxochromide A: A Highly Unsaturated Lipopetide from Myxococcus virescens The isolation and structure elucidation of a new family of pigments, the myxochromides, are described. Myxochromide A was determined as a hexapeptide lactone out of: L‐Methyl‐Thr, D‐ or L‐Ala, L‐Leu, L‐Pro, D‐ or L‐Ala and L‐Glu, respectively. Its lactone formation was observed between the γ‐carboxyl of Glu and the OH group of the Me‐Thr residue. The chromophore, a heptaenoic acid, was found to bind as an amide to the N‐atom of the Thr moiety. Myxococcus flavescens produces the same pigments with myxochromide B as the main compounds.

Two groups of 3-substituted indole 1,6-9 as well as 4-substituted quinoline derivatives 2-5 and harman (10) were isolated from various species and genera of myxobacteria. They were identified by their spectroscopic data. Some of the metabolites show moderate antifungal activity. Their biosynthetic origin in myxobacteria was demonstrated for 1, 2, and 3 by incorporation of ~-[l'-'~C]tryptophan.In a screening program the myxobacterium Archangium gephyra, strain Ar T205, was noted because of its antifungal properties. The activity of the crude culture extract could be correlated with several UV-absorbing spots on TLC by bioautography with Mucor hiemalis and Pythium deburyanurn. For the isolation of the compounds responsible for the activity a 60-1 fermentation was performed in the presence of 600 ml of adsorber resin amberlite XAD-16. After standard work-up[21 the products were eluted from the resin with methanol and isolated according to Scheme 1 by two liquidhiquid partitions followed by several chromatographic steps. Thus, five compounds 1-5, besides a larger amount of Tyr-Pro dioxopipera~ine [~], were obtained in pure state. Compounds 1, 2, and 3 show moderate activity. against a variety of yeasts and fungi (Table 1). No antibacterial properties could be observed. 'H-NMR data suggest that all compounds contain a heteroaromatic and a small aliphatic moiety. 2D-NMR spectroscopy in combination with mass spectrometry immediately revealed the structures: 3-indolylacetaldoxime (l), 4-quinolylaldoxime (2), 4-(hydroxymethy1)quinoline (3), 4-quinolinecarbaldehyde (4), and 4-quinolinecarboxylic acid (5). Of these 4 and 5 were isolated in only very small yield and possibly may be artefacts formed during isolation.During our work with myxobacteria 1-3 and several other indole and quinoline derivatives were repeatedly isolated from various species and genera. They typically were detected as minor constituents during the isolation of other metabolites from selected production strains. Thus, Angiococcus disciformis, strain An d30, the producer of angiolam, myxochelin, and myxothiazol[41, also forms small amounts of 1. In addition, 3-(cyanomethy1)indole (6) and 3-hydroxyacetylindole (7)' were isolated and identified by their spec-