Uffe Anthoni

How Delisea pulchra furanones affect quorum sensing and swarming motility in Serratia liquefaciens MG1

Halogenated furanones produced by the benthic marine macroalga Delisea pulchra inhibit swarming motility of Serratia liquefaciens MG1. This study demonstrates that exogenously added furanones control transcription of the quorum sensing regulated gene swrA in competition with the cognate signal molecule N:-butanoyl-L-homoserine lactone. This in turn results in reduced production of the surface-active compound serrawettin W2, which is crucial for surface translocation of the differentiated swarm cells. It is demonstrated that furanones interfere with interspecies communication during swarming of mixed cultures and that the mode of interference in quorum-sensing control and interspecies communication is not through inhibition of autoinducer synthesis.

Viscosinamide, a new cyclic depsipeptide with surfactant and antifungal properties produced by Pseudomonas fluorescens DR54

Pseudomonas fluorescens DR54 showed antagonistic properties against plant pathogenic Pythium ultimum and Rhizoctonia solani both in vitro and in planta. Antifungal activity was extractable from spent growth media, and fractionation by semi‐preparative HPLC resulted in isolation of an active compound, which was identified as a new bacterial cyclic lipodepsipeptide, viscosinamide, using 1D and 2D 1H‐, 13C‐NMR and mass spectrometry. The new antibiotic has biosurfactant properties but differs from the known biosurfactant, viscosin, by containing glutamine rather than glutamate at the amino acid position 2 (AA2). No viscosin production was observed, however, when Ps. fluorescens DR54 was cultured in media enriched with glutamate. In vitro tests showed that purified viscosinamide also reduced fungal growth and aerial mycelium development of both P. ultimum and R. solani. Viscosinamide production by Ps. fluorescens DR54 was tightly coupled to cell proliferation in the batch cultures, as the viscosinamide produced per cell mass unit approached a constant value. In batch cultures with variable initial C, N or P nutrient levels, there were no indications of elevated viscosinamide production during starvation or maintenance of the cultures in stationary phase. Analysis of cellular fractions and spent growth media showed that a major fraction of the viscosinamide produced remained bound to the cell membrane of Ps. fluorescens DR54. The isolation, determination of structure and production characteristics of the new compound with both biosurfactant and antibiotic properties have promising perspectives for the application of Ps. fluorescens DR54 in biological control.

Structure, production characteristics and fungal antagonism of tensin – a new antifungal cyclic lipopeptide from Pseudomonas fluorescens strain 96.578

Aim: To study the antagonistic activity by Pseudomonas fluorescens strain 96.578 on the plant pathogenic fungus Rhizoctonia solani.

Structure of red and orange fluorescein

The structures of colorless, red, and yellow-orange fluorescein have been investigated by a combination of solution and solid state13C NMR. It is demonstrated that the three forms have lactonic, zwitterionic, and quinoid structures, respectively. Conflicting X-ray, NMR, and IR structural evidence is discussed for samples of red fluorescein which cannot readily be obtained in definite crystalline form. It is concluded that solid-state13C NMR spectroscopy is superior by revealing primarily the molecular structure but being fairly insensitive toward lattice variations.

Elemental sulphur, a possible allelopathic compound from Ceratophyllum demersum☆

Abstract Elemental sulphur has been isolated from the freshwater macrophyte Ceratophyllum demersum . Release of sulphur could explain the very low amount of

Antitumor cyclic peroxides from the sponge plakortis lita

Abstract Four new cyclic peroxides (5–8) along with known chondrillin (4) have been isolated as antitumor constituents of the sponge Plakortis lita. These are methyl-(3S*, 6S*)-3, 6-epidioxy- 6-methoxyoctadec-4-enoate (5), methyl( 3S*, 6S*, 16E)-3, 6-epidoxy- 6-methoxyoctadeca-4,16-dienoate (6), methyl( 3S*, 6S*, 14E, 16E)- 3, 6-epidioxy-6-methoxyoctadeca-4, 14, 16-trienoate (7), and methyl-( 3S*, 6S*, 16E, 18E)-3, 6-epidioxy-6-methoxyeicosa-4 ,16 ,18- trinoate (8). All of them are epimeric to 4 and exhibit higher antitumor potency than 4.

Seasonal variation and distribution of two phenolic compounds, rosmarinic acid and caffeic acid, in leaves and roots-rhizomes of eelgrass (Zostera Marina L.)

Abstract The seasonal variation and distribution of rosmarinic acid and caffeic acid in leaves and roots-rhizomes of eelgrass (Zostera marina L.) were examined by using an isocratic high-performance liquid chromatography (HPLC) method developed for separation and quantification of the two phenolic compounds in crude plant extracts. The variation in phenolic content was compared to variations in tissue concentrations of nitrogen and phosphorus, in order to test a proposed relationship between nutrient status of the plant and biosynthesis of the secondary metabolites. The concentration of rosmarinic acid (not previously found in a monocotyledon) plus caffeic acid ranged from 0.4 to 19.2 mg (g dw)-1 with rosmarinic acid being the quantitatively most important component. The figures represent low estimates due to loss of phenolics during sample preparation. High phenolic concentrations occurred in spring and low concentrations during summer and fall, and the highest concentrations were most often found in the...

Bryozoan secondary metabolites : a chemotaxonomical challenge

Abstract 1. 1. A survey of the literature shows that microorganisms are found to be present in several species of unrelated bryozoans (syn. ectoprocts). 2. 2. The occurrence and chemical structure of secondary metabolites in bryozoans are discussed. 3. 3. The possibility of a dietary vs a microbial origin of the secondary metabolites is discussed. 4. 4. A hypothesis is proposed that some of the secondary metabolites isolated from bryozoans are synthesized by associated microorganisms.

Standardized extraction method for paralytic shellfish toxins in phytoplankton

The optimal conditions were established for extraction of paralytic shellfish toxins from a Danish clone of Alexandrium tamarense using extraction with acetic acid and HCl in the concentration range 0.01–1.0 N. Physical destruction of the cells was investigated microscopically to select the most efficient extraction procedure.The toxin content was quantitated by an automized isocratic reversed-phase high-performance liquid chromatography (HPLC) method. The best results as judged from the total amount of toxins and the toxin profile were obtained using 0.05–1.0 N acetic acid and 0.01–0.02 N HCl. Hydrochloric acid in the concentration range 0.03–1.0 N caused the amount of C1 and C2 toxins to decrease sharply and concomitant increase of gonyautoxins 2 and 3.The phytoplankton extracts with 0.1 to 0.5 N acetic acid or 0.01 N HCl were stable during 6 months at −20 °C, but the extracts with HCl 0.02 N underwent a change in toxin profile, although the total amount of toxins was constant.

A revised structure of tyriverdin: The precursor of tyrian purple

Abstract The structure of tyriverdin, a precursor of Tyrian purple, has been revised by comparison of data obtained from synthetic and naturally derived samples. Model studies with indigotin, the debromoanalogue, are described and it is shown that the light induced transformations of precursors to pigments are chain reactions.