Mapping the distribution of 3-hydroxy oxylipins in the ascomycetous yeast Saturnispora saitoi

The distribution of 3-hydroxy oxylipins in Saturnispora saitoi was mapped using immunofluorescence microscopy. Fluorescence was observed on aggregating ascospores, indicating the presence of 3-hydroxy oxylipins on the surface or between ascospores. The oxylipin was identified as 3-hydroxy 9:1 using gas chromatography mass spectrometry. Furthermore, ultrastructural studies using scanning and transmission electron microscopy on ascospores revealed a clear equatorial ledge surrounding oval-shaped ascospores.     

Oxylipins and ascospore morphology in the ascomycetous yeast genus Dipodascus

Immunofluorescence microscopy was used to assess members of the yeast genus Dipodascus for the presence of 3-hydroxy oxylipins. Fluorescence was associated with the aggregating ascospores in all species tested, thus suggesting the association of 3-hydroxy oxylipins with these cells, especially the surrounding slime sheaths. An ultrastructural study of the ascospores revealed sheaths with indentations, probably caused by the close packing of the ascospores to form clusters. In addition, an increase in the neutral and glycolipid fractions as well as a decrease in the phospholipid fraction during ascosporogenesis in D. ambrosiae was found. This revised version was published online in June 2006 with corrections to the Cover Date.     

Ascospore aggregation and oxylipin distribution in the yeast Dipodascopsis tothii

Upon cultivation of the yeast Dipodascopsis tothii in its sexual stage, small ascospores are released individually from the ascus tip, which then assemble in sheathed cluster balls. In contrast to Dipodascopsis uninucleata, this yeast produced smooth bean shaped ascospores with sheath-like appendages that assemble in a disordered sheathed ball of ascospores outside the ascus. Strikingly, upon release, the ascus tip contained 3-hydroxy oxylipins, while the released ascospore clusters contained little or no 3-hydroxy oxylipins as indicated by immunofluorescence microscopy. In D. uninucleata, these oxylipins are concentrated on the spore surface and interspore matrix, but not on the ascus tip.     

Acetylsalicylic acid as antifungal in <Emphasis Type="Italic">Eremothecium</Emphasis> and other yeasts

Interesting distribution patterns of acetylsalicylic acid (ASA, aspirin) sensitive 3-hydroxy (OH) oxylipins were previously reported in some representatives of the yeast genus Eremothecium—an important group of plant pathogens. Using immunofluorescence microscopy and 3-OH oxylipin specific antibodies in this study, we were able to map the presence of these compounds also in other Eremothecium species. In Eremothecium cymbalariae, these oxylipins were found to cover mostly the spiky tips of narrowly triangular ascospores while in Eremothecium gossypii, oxylipins covered the whole spindle-shaped ascospore with terminal appendages. The presence of these oxylipins was confirmed by chemical analysis. When ASA, a 3-OH oxylipin inhibitor, was added to these yeasts in increasing concentrations, the sexual stage was found to be the most sensitive. Our results suggest that 3-OH oxylipins, produced by mitochondria through incomplete β-oxidation, are associated with the development of the sexual stages in both yeasts. Strikingly, preliminary studies on yeast growth suggest that yeasts, characterized by mainly an aerobic respiration rather than a fermentative pathway, are more sensitive to ASA than yeasts characterized by both pathways. These data further support the role of mitochondria in sexual as well as asexual reproduction of yeasts and its role to serve as a target for ASA antifungal action.     

Mapping 3-hydroxy oxylipins on ascospores of <Emphasis Type="Italic">Eremothecium sinecaudum</Emphasis>

3-Hydroxy oxylipins were uncovered on ascospores of Eremothecium sinecaudum using immunofluorescence microscopy. This was confirmed by gas chromatography mass spectrometry. These oxylipins were observed only on ascospore parts characterised by nano-scale surface ornamentations simulating a corkscrew as demonstrated by scanning electron microscopy. Conventional ascospore staining further confirms its hydrophobic nature. Using confocal laser scanning microscopy we found that the corkscrew part with spiky tip of needle-shaped ascospores may play a role in rupturing the ascus in order to affect its release. Through oxylipin inhibition studies we hypothesise a possible role for 3-hydroxy oxylipins in facilitating the rupturing process.     

Cytology of Thamnidium elegans link

The resting nuclei in hyphae, sporangiophores and sporangiospores of sporangia and sporangiola of Thamnidium elegans consist of a large centrals nucleolus and a shell of chromatin surrounding the nucleolus. Division of the nucleus in hyphae and sporangiospores is achieved by elongation and constriction.     

Biologically active oxylipins from seaweeds

Our previous research has shown that many red algae metabolize polyunsaturated fatty acids to oxidized products resembling the eicosanoid hormones from mammals. We have extended these studies to members of the Phaeophyceae and Chlorophyta and find they also possess similar biosynthetic pathways. From several we have identified novel prostaglandin-like substances. Studies of the molecular mechanisms by which some of these marine oxylipins are formed have revealed that novel oxidative reactions are utilized. Understanding of these biosynthetic pathways in detail has allowed their utilization to produce research biochemicals of high value, such as 12S-hydroperoxyeicosatetraenoic acid (12S-HPETE). Because of their biological properties, seaweed-derived oxylipins have potential utility as pharmaceuticals and research biochemicals.     

Volatile and non-volatile fungal oxylipins in fungus-invertebrate interactions

Eight-carbon volatiles are characteristic of the odour profile of many filamentous fungi. They derive from enzymatic or non-enzymatic lipid oxidation and are thus termed volatile oxylipins. Collectively, non-volatile and volatile fungal oxylipins are important hormone-like factors that regulate the phenotypic status of a fungus, i.e. growth, morphological differentiation and secondary metabolite production. Given this intimate link between oxylipin formation and phenotypic change, we propose that the release of volatile oxylipins is an important means by which fungi may influence the course and outcome of interactions with animals. Such invertebrate – fungus interactions are intricate inter–kingdom relationships where either one depends on the other, or both on each other, where one is to the others benefit or detriment – eventually having even consequences on third parties and thus influencing whole foodwebs. In this review, we first highlight the connections between oxylipin formation and fungal phenotypic changes, how they affect invertebrate interactions and vice versa. We then expand this by implementing eight-carbon volatiles as infochemicals. Infochemicals are cues or signals perceived by the invertebrates' chemical senses, that are to the invertebrates' or the fungus’ benefit or detriment, through the behavioural responses they elicit. We point out, with various examples, that there is a strong analogy between fungus-invertebrate interactions mediated by fungal eight-carbon volatiles and plant-herbivore interactions mediated by six-carbon green-leaf volatiles released from wounded or stressed plants.     

Distribution of 3-hydroxy oxylipins and acetylsalicylic acid sensitivity in Cryptococcus species

Using a well tested antibody specific for 3-hydroxy oxylipins, we mapped the presence of these oxylipins in selected Cryptococcus (Filobasidiella) species. Immunofluorescence microscopy studies revealed that these compounds are deposited on cell wall surfaces, appendages, and collarettes. In vitro studies revealed that growth of Cryptococcus species was inhibited by acetylsalicylic acid (which is known to inhibit mitochondrial function, including the production of 3-hydroxy oxylipins) at concentrations as low as 1 mmol/L. The results suggest that acetylsalicylic acid is effective in controlling the growth of tested pathogens, probably by targeting their mitochondria. This study further expands the known function of this anti-inflammatory drug as anti-fungal agent.     

The presence of 3-hydroxy oxylipins in pathogenic microbes

There is a sufficient body of work documenting the distribution of 3-hydroxy oxylipins in microbes. However, there is limited information on the role of these compounds in microbial pathogenesis. When derived from mammalian cells, these compounds regulate patho-biological processes, thus an understanding of 3-hydroxy oxylipin function and metabolism could prove important in shedding light on how these compounds mediate cellular pathology and physiology. This could present 3-hydroxy oxylipin biosynthetic pathways as targets for drug development. In this minireview, we interrogate the relevant yeast and bacterial 3-hydroxy oxylipin literature in order to appreciate how these compounds may influence the inflammatory response leading to disease development.     

In vitro production of specialized reproductive torulose hyphae byFrankia strain ORS 021001 isolated fromCasuarina junghuhniana root nodules

Summary AFrankia strain (ORS 021001) isolated fromCasuarina junghuhniana root nodules was shown to produce four type of structuresin vitro: vegetative hyphae, sporangiospores within sporangia, N₂-fixing vesicles, and a fourth type of structure which is described in detail in this report. Structures of this latter type which we propose to call reproductive torulose hyphae: (RTH) result from enlargement and multiple segmentation of vegetative hyphae into torulose chaions of spore-like cells. RTH differ from sporangia in three major aspects: morphology, morphogenesis and outgrowth. RTH play an important role in survival and reproduction ofFrankia strain ORS 021001. Adding activated charcoal to the nutrient medium promotes the formation ofFrankia colonies orginating from RTH.     

Oxylipin covered ascospores of Eremothecium coryli

Eremothecium coryli is known to produce intriguing spindle-shaped ascospores with long and thin whip-like appendages. Here, ultra structural studies using scanning electron microscopy, indicate that these appendages serve to coil around themselves and around ascospores causing spore aggregation. Furthermore, using immunofluorescence confocal laser scanning microscopy it was found that hydrophobic 3-hydroxy oxylipins cover the surfaces of these ascospores. Using gas chromatography–mass spectrometry, only the oxylipin 3-hydroxy 9:1 (a monounsaturated fatty acid containing a hydroxyl group on carbon 3) could be identified. Sequential digital imaging suggests that oxylipin-coated spindle-shaped ascospores are released from enclosed asci probably by protruding through an already disintegrating ascus wall.     

Oxylipin and mitochondrion probes to track yeast sexual cells

When oxylipin and mitochondrion probes, i.e., fluorescing antibodies specific for 3-hydroxy fatty acids (3-OH oxylipins) and rhodamine 123 (Rh123), were added to yeast cells, these probes accumulated mainly in the sexual cells (i.e., both associated with ascospores) and not in the vegetative cells. This suggests increased mitochondrial activity in asci, since 3-OH oxylipins are mitochondrially produced and it is known that Rh123 accumulates selectively in functional mitochondria that maintain a high transmembrane potential (Delta Psi m). This increased activity may be necessary for the production and effective release of the many spores found in single-celled asci. These results may be useful in the rapid identification of asci and in yeast sexual spore mechanics, which may find application in yeast systematics as well as hydro-, aero-, and nano-technologies.     

Diastereoselective hydroxylation and reduction of derivatised tetrahydrofurans by Beauveria bassiana

The filamentous fungus, Beauveria bassiana ATCC 7159, catalyses the regio- and diastereoselective biohydroxylation of trans-2-methyl-5-benzyloxymethyl-tetrahydrofuran to the cis-3-hydroxy derivative. When incubated with cis-2-methyl-3-keto-5-benzyloxymethyltetrahydrofuran, the same fungus performs a reduction to give the cis- and trans-alcohols in a 4:1 ratio.     

Pinnaticoemansia, a new genus of Kickxellales, with a revised key to the genera of Kickxellales

Pinnaticoemansia coronantispora gen. sp. nov. (Kickxellaceae, Kickxellales) is described and illustrated. This species is characterized by imparipinnate sporocladia (sporocladia arranged in pairs), sporangiospores with a three-lobed corona, and the germination pattern of sporangiospores with downward hyphal growth and repeated dichotomy. The key to the genera of Kickxellales by Kurihara et al. (2001) is revised based on the observation of the germination pattern of this fungus in comparison with that of Asellariales.     

The distribution of 3-hydroxy oxylipins in fungi

One of the best-kept secrets by fungi especially yeast is the function of the different shapes and surface structures of their vegetative and sexual cells. They definitely do not produce these shapes (e.g. round, elongated, kidney, needle, hat, saturnoid, etc.) and surfaces (e.g. smooth, rough, hairy, warty, etc.) for our curiosity or to be classified, but surely produce these for their own benefit. This mini-review will show that a large variety of 3-hydroxy oxylipins are widely distributed in the fungal domain and closely associated with these surface ornamentations. In concert with nano-scale surface structures, they probably play a role in cell aggregation as well as spore release from sexual structures such as asci.     

Extracellular Tremella polysaccharides: structure, properties and applications

Tremella sp. is a yeast-like fungus from which polysaccharides can be isolated from either the yeast or the fungus phase, depending on the species. All of the polymers synthesized by these organisms consist of a mannan backbone to which small xylose side chains and glucuronic acid are attached. The main interest in these glucuronoxylomannans is their application in medicine to enhance the immune system.     

Metabolic products of microorganisms

The effect of the nucleoside-peptide antibiotics nikkomycin Z, nikkomycin X, and polyoxin A was tested on chitosomal chitin synthetase from yeast cells of the dimorphic fungus Mucor rouxii. The K _i was 0.6 M for polyoxin A and 0.5 M for nikkomycin X; nikkomycin Z was slightly less inhibitory (K _i=3.5M). Whereas the minimum inhibitory concentrations of the nikkomycins for growth and germination were quite low (about 1M, or lower), polyoxin A displayed no antifungal activity against yeast cells and sporangiospores of the test organism, even when present in high concentrations. These results are discussed with respect to structure/activity relationships.Abbreviations MIC minimum inhibitory concentration (i.e. concentration required to completely suppress growth: cf. Drews, 1979) - GlcNAc N-acetyl-d-glucosamine - UDP-GlcNAc uridine 5-diphospho-N-acetyl-d-glucosamine Metabolic products of microorganisms. 202. H. P. Kaiser and W. Keller-Schierlein: Strukturaufklärung von Elaiophylin: Spektroskopische Untersuchungen und Abbau. Helv. Chim. Acta 64: 407–424 (1981)     

Changes in the Lipid Composition of Mucor hiemalis Sporangiospores Related to the Age of the Spore-Forming Culture

Analysis of sporangiospore lipids of the fungus Mucor hiemalis F-1156 showed that alterations occur in the content of fatty acids and individual classes of lipids during long-term cultivation (for about 20 days). The changes in the lipid composition related to the age of the spore-forming mycelium suggest an important role of sporangiospore lipids in spore germination and in further development of the spherical cells formed in this processes. The M. hiemalis F-1156 sporangiospores with a lipid pool exhausted during long-term cultivation can give rise to both mycelial and yeastlike growth.