Mycelium

About: Mycelium is a research topic. Over the lifetime, 8923 publications have been published within this topic receiving 170993 citations.

Transcriptomic Analysis of Streptomyces coelicolor Differentiation in Solid Sporulating Cultures: First Compartmentalized and Second Multinucleated Mycelia Have Different and Distinctive Transcriptomes

Abstract: Streptomycetes are very important industrial bacteria, which produce two thirds of all clinically relevant secondary metabolites. They have a complex developmental-cycle in which an early compartmentalized mycelium (MI) differentiates to a multinucleated mycelium (MII) that grows inside the culture medium (substrate mycelium) until it starts to growth into the air (aerial mycelium) and ends up forming spores. Streptomyces developmental studies have focused mainly on the later stages of MII differentiation (aerial mycelium and sporulation), with regulation of pre-sporulation stages (MI/MII transition) essentially unknown. This work represents the first study of the Streptomyces MI transcriptome, analyzing how it differs from the MII transcriptome. We have used a very conservative experimental approach to fractionate MI from MII and quantify gene expressions. The expression of well characterized key developmental/metabolic genes involved in bioactive compound production (actinorhodin, undecylprodigiosin, calcium-dependent antibiotic, cpk, geosmin) or hydrophobic cover formation-sporulation (bld, whi, wbl, rdl, chp, ram) was correlated with MII differentiation. Additionally, 122 genes conserved in the Streptomyces genus, whose biological function had not been previously characterized, were found to be differentially expressed (more than 4-fold) in MI or MII. These genes encoded for putative regulatory proteins (transcriptional regulators, kinases), as well as hypothetical proteins. Knowledge about differences between the MI (vegetative) and MII (reproductive) transcriptomes represents a huge advance in Streptomyces biology that will make future experiments possible aimed at characterizing the biochemical pathways controlling pre-sporulation developmental stages and activation of secondary metabolism in Streptomyces.

Ectomycorrhizins - symbiosis-specific or artifactual polypeptides from ectomycorrhizas?

Abstract: Fungal mycelium of the fly agaric (Amanita muscaria [L. ex Fr.] Hooker), and inoculated or noninoculated seedlings of Norway spruce (Picea abies [L.] Karst.) were grown aseptically under controlled conditions. In order to detect symbiosis-specific polypeptides (‘ectomycorrhizins’, see Hubert and Martin, 1988, New Phytol.110, 339–346) the protein patterns of (i) fungal mycelium, (ii) mycorrhizal, and (iii) non-mycorrhizal root tips were compared by means of one- and twodimensional electrophoresis on a microscale. Because of the sensitivity of these micromethods (50 and 200 ng of protein, respectively), single mycorrhizal root tips and even the minute quantities of extramatrical mycelium growing between the roots of inoculated plants could be analysed. Differences in the protein patterns of root tips could be shown within the root system of an individual plant (mycorrhizal as well as non-mycorrhizal). In addition, the protein pattern of fungal mycelium grown on a complex medium (malt extract and casein hydrolysate) differed from that of extramatrical mycelium collected from the mycorrhiza culture (pure mineral medium). Such differences in protein patterns are obviously due to the composition of the media and/or different developmental stages. Consequently, conventional analyses which use extracts of a large number of root tips, are not suitable for differentiating between these effects and symbiosis-specific differences in protein patterns. In order to detect ectomycorrhizins, it is suggested that roots and mycelium from individual, inoculated plants should be analysed. This approach eliminates the influence of differing media, and at the same time allows a correct discrimination between developmental and symbiosisspecific changes. In our gels we could only detect changes in spot intensity but could not detect any ectomycorrhizins or the phenomenon of polypeptide ‘cleansing’, which both characterize theEucalyptus-Pisolithus symbiosis (Martin and Hubert, 1991, Experientia47, 321–331). We thus suggest that these reported effects either are specific for theEucalyptus-Pisolithus symbiosis or simply represent artifacts. The latter point of view is strengthened by a comparison of the experimental approaches.

Volatile terpenoids of endophyte-free and infected peppermint (Mentha piperita L.): chemical partitioning of a symbiosis.

Abstract: The study reports the effects on volatiles of an endophytic fungus inhabiting asymptomatically the leaves of peppermint. By means of headspace solid-phase microextraction (HS-SPME) and gaschromatography-mass spectrometry (GC-MS) terpenoids were sampled in time course from the head space of peppermint leaves and roots. After removal of the mycelium from peppermint tissues, fungal volatiles were analyzed and compared with those of pure fungal cultures. In the presence of the endophyte, the relative amount of all main compounds increased in leaves. Starting from the first 14 d of culture, (−)-menthone and (+)-neomenthol were consistently higher than in control plants. On the contrary, (+)-menthofuran increased only by 28 d of culture. Root volatiles were also dramatically altered by the presence of the fungus, with (+)-pulegone accounting for at least 44% of the total volatile emission. (+)-Pulegone was also the main compound of PGP-HSF mycelium isolated from peppermint roots. The sesquiterpenoid cuparene was found as a novel compound of peppermint leaf headspace and was a main volatile of ex planta and pure culture mycelia. The chemical spectrum of terpenoids and their distribution among peppermint roots, leaves, and mycelia are likely to account for a fine regulation of the mutualism in planta and for the acquisition by the fungus of novel metabolic competences.

Interactions between a mycophagous Collembola, dry yeast and the external mycelium of an arbuscular mycorrhizal fungus

Abstract: A plant growth system with root-free hyphal compartments was used to examine the interactions between a mycophagous Collembola (Folsomia candida Willem), dry yeast and an arbuscular mycorrhizal (AM) fungus [Glomus caledonium (Nicol. & Gerd.) Trappe and Gerdemann] in terms of Collembola reproduction, AM-hyphal length and AM-hyphal P transport. Collembola reproduction was unaffected by AM mycelium, but a supplement of dry yeast increased the Collembola population size. The addition of dry yeast increased AM-hyphal P transport by increasing hyphal length. Collembola without yeast affected neither AM-hyphal growth nor AM-hyphal P transport, whereas Collembola with yeast decreased AM-hyphal P transport by 75% after 8 weeks. The hyphal density of G. caledonium remained unaffected by Collembola except after 4 weeks in combination with yeast, when a 33% reduction was observed. The results of this experiment show that the interaction between F. candida and the external mycelium of G. caledonium is limited under the conditions imposed.

Accumulation of heavy metals by some wood-rotting fungi

Abstract: Accumulation of aluminum, cadmium, lead and calcium was studied in the wood-roting fungiDaedalea quercina, Ganoderma applanatum, Stereum hirsutum andSchizophyllum commune. The heavy metal content was measured in mycelia cultured in liquid media in the presence of either individual Al, Cd, Pb and Ca salts or of their mixtures. After 8-d cultivations in media containing 1 mmol/L concentration of individual heavy metals, the lead content was maximal in the mycelium ofStereum hirsutum (90.6 mmol/g) while the mycelium ofGanoderna applanatum contained maximal values of cadmium (272 mmol/g), aluminum (600 mmol/g) and calcium (602 mmol/g). When the mycelia were grown on mixtures of all metal salts, lead was the preferentially accumulated ion except inG. applanatum which had a higher affinity for aluminum.