Mycelium

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

Immunolocalization of hydrophobin HYDPt-1 from the ectomycorrhizal basidiomycete Pisolithus tinctorius during colonization of Eucalyptus globulus roots

Abstract: • The immunolocalization of one of the hydrophobins of Pisolithustinctorius (HYDPt-1) is reported. Hydrophobin proteins play key roles in adhesion and aggregation of fungal hyphae, and it is already known that formation of ectomycorrhizas on eucalypt roots enhances the accumulation of hydrophobin mRNAs in the mycelium of Pisolithus tinctorius. • Purification of SDS-insoluble proteins from the mycelium of P. tinctorius showed the presence of a 13 kDa polypeptide with properties of class I hydrophobin. • Polyconal antibodies were raised against a recombinant HYDPt-1 polypeptide, and these were used for immunofluorescence-coupled transmission electron microscopy. • HYDPt-1 is a cell wall protein located at the surface of the hyphae with no preferential accumulation in the fungal cells of the different tissues of the ectomycorrhiza (i.e. extraradical hyphae, mantle or Hartig net).

Impact of growth and uptake patterns of arbuscular mycorrhizal fungi on plant phosphorus uptake—a modelling study

Abstract: In this paper we present a mathematical model for estimating external mycelium growth of arbuscular mycorrhizal fungi and its effect on root uptake of phosphate (P). The model describes P transport in soil and P uptake by both root and fungi on the single root scale. We investigate differences in soil P depletion and overall P influx into a mycorrhizal root by assuming that different spatial regions of mycelia are active in P uptake. When all external hyphae contribute to P uptake, overall uptake is dominated by the fungus and the most effective growth pattern appears to be the one using a high level of anastomosis. The same is true when only the proportion of external hyphae assumed to be active contributes to uptake. When uptake is restricted to the tips, hyphal contribution to overall P uptake is less dominant; the most effective growth pattern appears to be the one characterised by nonlinear branching where branching stops at a given maximal hyphal tip density. Comparison to measured P depletion in the literature suggests that the scenario where active hyphae are contributing to P uptake is likely to fit the data best. These quantitative predictions promote our understanding of the mycorrhizal symbiosis and its role in plant P nutrition.

Enzyme activity and cell differentiation in neurospora

Abstract: ZALOKAR, MARKO. (Yale U., New Haven, Conn.) Enzyme activity and cell differentiation in Neurospora. Amer. Jour. Bot, 46(7): 555-559. Illus. 1959.-Morphological differences were observed in vegetative cells of Neurospora of different ages and in different parts of the mycelium. The surface layer of mycelium grown in standing cultures could be separated from the deep layer. The first contained most of the growing hyphae rich in protoplasm, while the second containecl heavily vacuolated hyphae laden with fat droplets. Specific activities of several enzymes were studied in conidia, young hyphae, and the surface and deep layers of mature mycelium. Succinic dehydrogenase was low in conidia and about 10 times more active in mature mycelium. The surface layer had twice the activity of the deep layer. Aldolase increased about 3 times after the germination of conidia; it was slightly lower in the surface than in the deep layer of mycelium. Tryptophan synthetase exhibited only small differences between conidia and mycelium and was slightly lower in the surface than in the deep layer. f-galactosidase was formed in appreciable amounts only after prolonged growth and had a much higher specific activity in the deep layer. The results were discussed in connection with cell differentiation and aging. IT HAS BEEN generally observed that there are progressive changes in the activity of enzymes in developing cultures of microorganisms, but such changes have seldom been correlated with concurrent changes in cell morphology. In Neurospora, B8-galactosidase has been found to increase with the age of the culture (Landman, 1951), while tryptophan synthetase decreases (Yanofsky, 1952a). It was not clear whether these changes were due to the aging of the entire culture or to the differentiation of cells which are endowed with different levels of enzyme activities. The latter assumption was suggested by the fact that the proportion of growing hyphal tips to old hyphae decreased with the age of the mycelium. The purpose of the present study was to investigate whether morphologically distinct types of hyphae in Neurospora mycelia show differences in enzymatic activities. Four enzymes, chosen to represent a variety of functions in metabolism, have been studied: (1) succinic dehydrogenase as a key enzyme in the citric acid cycle and for its localization in mitochondria; (2) aldolase as an essential enzyme in glycolysis; (3) 8-galactosidase as an induced enzyme; and (4) tryptophan synthetase as a constitutive enzyme under direct control of a particular gene (Yanofsky, 1952a). Enzymes which require either DPN or TPN as a co-factor could not be considered, since they could not be studied in conidial extracts which are rich in diphosphopyridine nucleotidase (Zalokar and Cochrane, 1956). MATERIAL AND METHODS.-Wild-type Neurospora crassa, E 5297, was used for all experiments. In order to obtain large quantities of conidia, Neurospora was grown on 500 ml. of nitrate medium (Zalokar and Cochrane, 1956) with 2% agar in 'Received for publication March 2, 1959. Fernbach flasks. It was found that conidiation was stimulated if cultures were kept for 3 days at 30?C. and subsequently moved to room temperature (20?-25?C.) for the next 4 days. Conidiation was further stimulated by replacing cotton plugs with several layers of gauze in order to increase aeration. The yield was as great as 5 g. fresh wt. of conidia per flask. Uniform growth of short, separate young hyphae was obtained on 200 ml. of minimal medium (Beadle and Tatum 1945) in 500-ml. Erlenmeyer flasks, vigorously shaken on a reciprocating shaker at 30?C. The cultures were inoculated with a heavy suspension of conidia (ca. 10 mg. fresh wt. per 100 ml. of medium) to provide enough material for chemical determinations. Older mycelia, free of conidia, were grown on a Fries minimal medium containing Tween 80 (Zalokar, 1954), in standing cultures. Large mycelial mats were grown in Roux' flasks in 200 ml. of media by incubation at 30?C. for 4 days. Layers of old and young parts of the mycelium could be separated in these mats after filtration on a Buchner funnel, as described below. It would, of course, have been desirable to work with material of various ages grown under similar conditions. This was not possible, because standing cultures were not appropriate for obtaining young hyphae in large amounts and shaken cultures were not suitable for obtaining older mycelia of uniform quality. In old, shaken cultures, hyphae coalesce into masses of mycelium of different sizes and unequal structure. The size of such masses limits the amount of tissue which has free access to the surrounding medium. This ambiguity could be avoided in standing cultures where the exposure of all the surface layer to the air and nutrients is uniform. Standing and shaking probably result in