S-adenosylmethionine and morphogenesis inMucor racemosus

The intracellular concentration of S-adenosylmethionine (SAM) and the specific activity of S-adenosylmethionine synthetase (ATP:l-methionine S-adenosyltransferase, EC 2.5.1.6) were examined in wild-typeMucor racemosus, as well as a morphological mutant termedcoy, under conditions designed to prevent the morphogenesis of yeasts to hyphae. When the mutant was grown in a defined medium supplemented with methionine and induced to shift by exposure to air, there was an increase in intracellular SAM analogous to that previously reported with the wild type. However, when thecoy mutant was grown in the absence of methionine, the intracellular concentration decreased dramatically and the mutant failed to undergo the yeast to hypha transition. An inhibitor of SAM synthetase activity, cycloserine, was used to lower the intracellular concentration of SAM in the wild-type organisms. Under these conditions, wild-typeM. racemosus failed to undergo the transition from yeasts to hyphae when exposed to air.     

Detection of 3-nitropropionic acid and cytotoxicity inMucor circinelloides

Mucorales are regarded as the aetiological agents of Mucormycosis. Their capabilities to produce mycotoxins are not profoundly investigated, in contrast to those of the fungi from the generaPenicillium, Aspergillus, orFusarium. The aim of this study was to isolate and identify fungi of the order Mucorales and investigate mycotoxins production. Twelve samples of visibly moulded grass silage and eight samples of damaged whole crop maize silage were analysed. Malt extract agar plates were used for sub cultivation. Three fungal species of the order Mucorales were isolated from grass silage, which were identified by their macro-and micro-morphology asAbsidia corymbifera, Mucor circinelloides andRhizopus stolonifer. The cytotoxicity ofMucor circinelloides extract was analysed using the cytotoxicity test (MTT assay) and the result, showed a low cytotoxicity. Additionally extracts fromAbsidia corymbifera, Mucor circinelloides andRhizopus stolonifer were tested for mycotoxin-production using an LC/MS/MS-based multimycotoxin method. 3-nitropropionic acid was detected in the culture extract ofMucor circinelloides. Presented at the 30^th Mykotoxin Workshop Utrecht, Netherlands, April 28–30, 2008.     

In situ study of the localization and regulation of chitin synthetase inMucor rouxii

Synthesis of chitin inMucor rouxii was studied comparatively in whole cells, spheroplasts, toluene-treated cells, and cell-free extracts in order to determine the cellular location and regulation of chitin synthetase. Our data indicated that most of the enzyme is located inside the permeability barrier of the cell in the form of an inactive precursor. Apparently the enzyme and its destroying factor (protease?) are located in separate compartments of the cell. The role of proteases as the natural activating factors was questioned.     

Presence of carotenoids in Gordius aquaticus (Nematomorpha,Nemathelminthes) specimens from deep wells

By means of columnar and thin-layer chromatography, the presence of carotenoids in Gordius aquaticus L. (Nematomorpha, Nemathelminthes) from deep wells was studied.The investigations revealed the presence of the following carotenoids: -carotene, mutatochrome, -cryptoxanthin, ,-carotene epoxide,lutein, zeaxanthin and astaxanthin ester.     

Biosynthesis of polyuronides inMucor rouxii: Partial characterization of fucosyl transferase

Most of the fucosyl transferase activity fromMucor rouxii was detected in a crude membrane fraction. The enzyme transferredl-fucose from GDP-fucose to endogenous and exogenous acceptors. When crude membrane fractions were treated with neutral detergents such as Trition X-100 or Brij 36 T enzyme activity became dependent on exogenous acceptors such as mucoric acid or mucoran. Brij-treated membrane fractions showed maximum fucosyl transferase activity at pH 6.5, and at a temperature between 22 and 28°C. The cations Mn²⁺, Mg²⁺, Co²⁺, Zn²⁺, Fe²⁺, and Ca²⁺ activated the enzyme about twofold. The former was slightly more stimulatory at 4 mM. Km for GDP-fucose was 10 μM. Evidence was obtained that mucoric acid serves as acceptor for fucosyl moieties. Acid hydrolysis of the product synthesized from GDP-fuc by Brij-treated membrane fractions revealed fucose as the major radioactive sugar.     

Isolation of ergosterol peroxide and its reversion to ergosterol in the pathogenic fungus Sporothrix schenckii

Ergosterol peroxide, a presumed product of the H_{_2}O_{_2}-dependent enzymatic oxidation of ergosterol, has been isolated from yeast forms of the pathogenic fungus Sporothrix schenckii. The substance, which may have a role in fungal virulence, has been characterized mainly using spectroscopic methods (¹H and ¹³C nuclear magnetic resonance and high resolution mass spectra). The purified compound showed a molecular formula of C_{_28}H_{_44}O_{_3}, displaying characteristic features of epidioxy sterols and was reverted to ergosterol when submitted to S. schenckii enzymatic extract. This revised version was published online in June 2006 with corrections to the Cover Date.     

Algal carotenoids and chemotaxonomy

A qualitative and quantitative examination of the carotenoids of pure cultures of four marine microalgae, including Chroomonas salina, Vaucheria sessilis and Coccolithus huxleyi is reported. The latter contained a new, major carotenoid, and not fucoxanthin.     

Bacterial carotenoids

Zeaxanthin dirhamnoside is the major carotenoid of Corynebacterium autotrophicum. The absolute configuration 3R,3R followed from CD-properties of its hexaacetate, -L-assignment and ¹C₄ conformation were concluded from ¹H NMR data by comparison with model compounds.No. XLIX: Acta chem. scand. (in press)Dedicated to Professor R. Y. Stanier on his 60th birthday in appreciation of his studies on the function and biosynthesis of carotenoids and influence on the scientific development of his co-workers     

Fungal carotenoids

The Botanical Review -     

Determination of free and bound ergosterol in microorganisms

A method for the quantitative determination of free and esterified ergosterol in lipid fractions from biomasses grown on hydrocarbons as sole carbon source is described. Column chromatography was used for the fractionation of lipids. Esterified ergosterol was determined in the benzene fraction and free ergosterol in the methanol fraction by known methods.