Showing papers on "Mycelium published in 1978"

Lipid physiology of vesicular‐arbuscular mycorrhiza

Abstract: SUMMARY A microscopic and biochemical comparison was made of the distribution, quantity and composition of lipid in roots of onion, clover and ryegrass infected with the VA mycorrhizal fungus, Glomus mosseae, in uninfected roots and in the external mycelium from infected, aseptically grown onion roots. Abundant oil-droplets were observed in the internal and external fungal mycelium, in the vesicles and chlamydospores, and adjacent to the appressoria at entry points. Mycorrhizal roots contained significantly more total lipid than uninfected roots. In estimations of separated lipid classes, the mycorrhizal roots consistently showed higher levels of triglyceride than non-inycorrhizal roots. External mycelium contained high levels of neutral lipids, especially triglyceride, diglyceride and free fatty acids. Compared with uninfected roots, mycorrhizal onion roots contained higher levels of diphosphatidyl glycerol, phosphatidyl serine, phosphatidyl ethanolamine, phosphatidy) choline, phosphatidyl glycerol, phosphatidic acid and phosphatidyl inositol. With the exception of phosphatidyl inositol and phosphatidic acid, these were all prominent components of G. mosseae mycelium.

Basidiospore germination in some mycorrhiza-forming hymenomycetes

Abstract: Basidiospores from five randomly selected species of mycorrhiza-forming Hymenomycetes, viz. Laccaria laccata, Amanita muscaria, Lactarius helvus, Paxillus involutus, and Leccinum scabrum, did not germinate on any agar media tested (except for very few and irregular germinations in A. muscaria), nor did an addition of activated charcoal or a living Rhodotorula glutinis colony induce spore germination. However, with these two supplements together on the same agar plate slight germination occurred in all five species. In P. involutus percentage germination was further increased by a volatile factor produced by the mycelium of P. involutus. In L. scabrum a non-volatile substance exuded from its own mycelium strongly promoted germ vesicle and germ tube formation in the presence of activated charcoal. In both of these mycelial germination-inducing factors a certain specificity was indicated.

Direct observation of fungal aggregates in sand dune soil.

Abstract: The mycorrhizal fungus Glomus in association with bean hosts, Phaseolus vulgaris L., growing in pot cultures and grass hosts, Calamovilfa longiflora (Hook.) Scribn and Andropogon sp. growing on Lake Huron sand dunes produced extensive external mycelium. This mycelium was the dominant factor in the aggregation of soil particles. Light and scanning electron microscope studies indicated that the sand grains were attached to the hyphae. An amorphous deposit was often present at the interfaces of sand grains and hyphae. It appeared to act as an adhesive. Staining procedures indicated that this material contained polysaccharide. Other microorganisms were observed in association with the Glomus hyphae and the amorphous deposits.

On the taxonomy of Monilia roreri, an important pathogen of Theobroma cacao in South America

Abstract: Monilia roreri Cif., the causal agent of an important pod rot of cocoa in South America, is redescribed and illustrated. The presence of dolipore septa in the vegetative mycelium indicating basidio...

The role of adsorption in the elimination of aflatoxin B1 from contaminated media

Abstract: The mechanism involved in the disappearance of aflatoxin B1 from liquid medium by fungus mycelium has been investigated.

Intracellular cyclic adenosine 3',5'-monophosphate levels and streptomycin production in cultures of Streptomyces griseus.

Abstract: Changes in the amount of cyclic 3′,5′-adenosine monophosphate within the mycelium of Streptomyces griseus were measured as cultures progressed through trophophase and idiophase in a complex medium ...

Eurotium (Aspergillus) repens metabolites and their biological activity.

Abstract: Eurotium repens mycelium cultivated under static conditions was used to isolate and identify metabolities—echinulin, physcion, erythroglaucin, flavoglaucin and asperentin; the filtrate of the culture yielded asperentin 8-methylether The broadest biological activity spectrum was displayed by asperentin which had antibacterial and antifungal effects and, at a concentration of 86 ώg/ml, caused 50 % mor7 tality inArtemia saline larvae The highest cytotoxicity towards HeLa cells was found in physcion which caused 50 % growth inhibition at a concentration of 01 ώg/ml

The effect of pH and amino acids on conidiation and pigment production of Monascus major ATCC 16362 and Monascus rubiginosus ATCC 16367 in submerged shaken culture.

Abstract: Monascus major ATCC 16362 and Monascus rubiginosus ATCC 16367 were cultivated aerobically on media containing nitrate or ammonium as nitrogen source to which the following modifications were made: (1) pH adjusted to 2.5 before sterilization; (2) addition of yeast extract; (3) addition of amino acids in identical proportions and concentrations to those found in yeast extract; (4) adjustment of pH to 2.5 after addition of amino acids.The addition of amino acids in the form of yeast extract increased mycelium formation and reduced conidiation and pigment production. The addition of an amino acid mixture did not increase mycelium formation to the same extent as yeast extract but increased the number of conidia, while pigment production was reduced, especially when nitrate was the nitrogen source. As the amino acids are taken up after conidial formation has started, it would appear that it is not the amino acids themselves which are directly responsible for the induction of conidiation. The addition of amino a...

Kineosporia, a New Genus of the Order Actinomycetales

Abstract: The morphological, cultural, physiological, and biochemical characteristics of a new actinomycete are described. The organism is distinctive because of the absence of aerial mycelium and the presence of glycine and LL-diaminopimelic acid in its cell wall. The mycelium bore numerous round-to-pyriform sporangia, each of which contained a single zoospore. The strain could not be classified in any of the previously named genera of the Actinomycetales, and it is therefore considered to be a member of a new genus, for which the name Kineosporia is proposed. The type species (monotype) of this genus is K. aurantiaca sp. nov., so named because of its orange color when grown on agar media. The type strain of K. aurantiaca is A/10312 (=ATCC 29727).

A Staining Technique for Nuclei of Rhizoctonia Solani and Related Fungi

Abstract: The species concept of Rhizoctonia solani Kuhn, as reviewed by Parmeter and Whitney (1), stipulates a multinucleate condition in young vegetative hyphae. Fungi resembling R. solani but possessing predominantly binucleate cells may be characterized readily as distinct species if the nuclear condition is ascertained (2). Nuclear-staining techniques previously available for R. solani and related fungi involve complex procedures and preparation times ranging from 30 min to more than 1 h (4, 6). Such methods may be prohibitive if a number of isolates are to be stained. Tu and Kimbrough (5) devised a rapid-staining technique using an acidified solution of aniline blue in 50% glycerine. We have found that this technique is satisfactory for some isolates but results in poor resolution with others. Therefore, the following rapid-nuclear-staining technique was developed. Fifty-four isolates of R. solani and 98 isolates of binucleate R. solanilike fungi, including Ceratobasidium cornigerum Rogers, C. anceps (Bres. & H. Syd.) Jacks., and C. ramicola Tu & Kimbr., were grown on 15 ml of Difco potato-dextrose agar (PDA) in 9-cm plastic Petri dishes for 4 d at 21 C. Seven-mm mycelial plugs were cut from the edges of the fungal colonies and transferred to the center of sterile Petri dishes containing 15 ml of 1.5% water agar (ICN Pharmaceuticals, Cleveland, Ohio). The fungi were incubated at 21 C until colonies were ca 1 cm from the edge of the dishes. A small drop of 0.5% aniline blue or trypan blue in lactophenol, prepared according to the methods of Phillips and Hayman (3), was placed directly on the mycelium midway between the center and the periphery of the fungal colony (FIG. 1). The stained area was affixed with a 18 x 18 mm cover slip. Hyphal cells were examined microscopically at 400x either by placing Petri dishes directly on the micro1281

Functions of Trisporic Acid

Abstract: Trisporic acid, the sex hormone of the Mucorales, elicits the formation of zygophores in (+) and (—) mycelia of Mucor mucedo . It can diffuse through the medium, from its site of synthesis, to affect mycelium a considerable distance away. There is no evidence for its translocation through hyphae. It causes an increase in content of (3-carotene and ergosterol in recipient mycelium, and such increases are also observed during mating

Distribution and Activation of Chitin Synthase in Protoplast Fractions Released during the Lytic Digestion of Aspergillus nidulans Hyphae

Abstract: SUMMARY: Protoplasts were produced from Aspergillus nidulans mycelium using Trichoderma lytic enzyme. The influence of KC1 and MgSO4as stabilizer systems on the morphological variation of protoplasts produced during digestion and the pattern of release from hyphae were compared. The results suggest that protoplast release in the presence of KC1 followed a sequential fractionation of the hyphae with ‘early’ protoplasts originating from the tip regions and ‘late’ protoplasts from the distal regions. In MgSO4-stabilized systems the hyphae were disrupted in a less ordered fashion. Between 12 and 16% of the mycelial protein was recovered in protoplast form using the systems described. The level of chitin synthase (EC 2.4.1.16) and the capacity for trypsin-activation of the enzyme in protoplast fractions was investigated. In KC1-stabilized systems, ‘early’ (1 h) fractions possessed higher specific activities than later fractions. Activatable enzyme was low in the early fraction but was present at high levels in later fractions. It is suggested that these observations are consistent with a model relating active and activatable enzyme to hyphal growth.

The production of toxic metabolites by Chaetomium spp. isolated from soils of permanent pasture

Abstract: One hundred and two isolates of Chaetomium spp. have been identified from 2563 soil samples collected from permanent pasture at Nappan, Nova Scotia. Chaetomium umbonatum was the Chaetomium species most commonly isolated. Fifty-six of the Chaetomium isolates were grown in the laboratory and the cultures examined for the production of toxic metabolites. The culture filtrates of 12, and extracts of mycelium of 18, of these isolates inhibited bacterial growth. Chetomin was detected in nine mycelium extracts and isolated from four of the mycelium extracts. Chaetoglobosins were isolated from three mycelium extracts.

Actinomycin Biosynthesis by Protoplasts Derived from Streptomyces parvulus

Abstract: Conditions are described for the formation of protoplasts from Streptomyces parvulus that are able to synthesize actinomycin D de novo. Antibiotic synthesis by protoplasts, in contrast to that by mycelium, was sensitive to inhibition by actinomycin D and to a decrease in sucrose concentration. On the other hand, synthesis by mycelium was much more sensitive to inhibition by amino acid analogs (d-valine, cis-3-methylproline, and α-methyl-dl-tryptophan). In addition, the uptake of amino acids (l-methionine, sarcosine, and l- and d-valine) by protoplasts was significantly lower than that by mycelium. The advantages and limitations of using protoplasts for studying in vivo actinomycin synthesis are discussed.

Evidence for the Production of Ethylene by the Mycelium of Agaricus bisporus and its Relationship to Sporocarp Development

Abstract: The increased production of ethylene that occurs during the development of sporocarps of Agaricus bisporus results from increased formation by the compost but not by the casing layer. The increase depends on the presence of sporocarps up to a critical point in their development. It is concluded that the mycelium of A. bisporus in the compost is responsible for this ethylene production because no significant bacterial flora was found in the compost from fruiting cultures, and the mycelium growing on complex agar media also liberated ethylene. Mycelium growing on defined synthetic medium also evolved ethylene if methionine was supplied. From the results of the different assays, there was no evidence for a regulatory role of ethylene in growth or development of A. bisporus.

The Fungus Flora of Compost During Mycelium Colonization by the Cultivated Mushroom, Agaricus Brunnescens

Abstract: Isolations were made of fungi from mushroom compost at the end of the colonization or growth phase (called spawn run in the mushroom industry) by mycelium of Agaricus brunnescens. Fifty species of ...

Growth of and trehalase activity in the thermophilic fungusThermomyces lanuginosus

Abstract: The thermophilic fungus,Thermomyces lanuginosus, was grown in a glucose-asparagine liquid medium. Optimal mycelial growth occurred at 50°C. The conditions for sporulation were different from those required for vegetative growth. the former being favoured by lower nitrogen level and temperature. Trehalase (α, α-glu coside-l-glucohydrolase, EC 3.2.1.28) was one of the most active glycosidases at 50°C. Non-sporulating mycelium had higher levels of this enzyme than the sporulating mycelium. Trehalase was synthesized constitutively and its activity appears to be controlled by catabolite repression.

Kinetics of vegetative growth of Thermoactinomyces vulgaris

Abstract: The growth of Thermoactinomyces vulgaris on solid media was studied by microculture technique. Starting from a germinating spore the further development was followed by phase contrast microscopy. From serially taken photographs the kinetics of growth and branching of the mycelium was calculated. Also some observations on morphological behaviour were made. Regarding the total mycelium developing from one spore the growth occurred with a constant exponential growth rate, at least for the time tested (about ten doublings). This constancy of the mycelial growth rate was not attributed to constant rates of hyphal growth or branching. The hyphal growth rate increased during the development of the mycelium, so that the length produced by a hypha within a given time was smallest after germination and largest at the end of the experiment. Between the first and the 10th doubling of the mycelium the mean hyphal growth rate increased by the factor 27, in some cultures even by the factor 40. While hyphal growth changed from exponential to linear, branching was first linear and then approached exponential kinetics. Under different conditions of cultivation mycelia could have identical doubling times, but different hyphal growth rates and vice versa. Yeast extract caused a reduction of the hyphal growth rate and an enhancement of branching. Likewise the diminution of the supply of oxygen did not reduce the mycelial growth rate, but markedly decreased the hyphal growth rate, especially of the germ tube. The data obtained concerning the kinetics of growth and branching can be explained by a special form of cooperation of cytoplasmic and cell wall synthesis. With respect to the synthesis of cytoplasm a T. vulgaris mycelium behaves as one individual, which is not differentiated into replicating and non replicating areas (as recently was shown to be likely for Streptomyces hygroscopicus by SCHUHMANN and BERGTER 1976). The mycelial growth rate thus reflects the rate of the synthesis of cytoplasm. The hyphal growth rate is moreover determined by the rate of cell wall synthesis at the tip of each hypha. The observed increase of the hyphal growth rate is explainable by an acceleration of the cell wall synthesis during the development of the mycelium. Probably the branching is regulated indirectly. According to the different manner of cytoplasmic and cell wall synthesis, within a hypha a balance between both processes is maintainable only for a limited time. As soon as the momentary apical capacity for cell wall synthesis is exhausted, the balance is attained anew by originating a new site for wall synthesis, i.e. by branching. Branching was often defective. Especially in the absence of yeast extract a lot of lateral branches arose, which ceased further growth at an average length of 2.5 μm. It is suggested that yeast extract supports the transport of the nucleoids into the lateral branches, which otherwise is often infeasible. Reduction of the supply of oxygen favoured apical branching, so that dichotomous forms resulted.

The use of fungal protoplasts in the study of aflatoxin biosynthesis

Abstract: Protoplasts derived fromAspergillus flavus are shown to be capable of synthesizing aflatoxins when incubated in a chemically defined medium.14C-Acetate and14C-Versicolorin A, added to protoplasts from 3-day-old mycelium, are incorporated into aflatoxin B1.

Streptoalloteichus, a new genus of the family actinoplanaceae

Abstract: A new genus Streptoalloteichus is proposed in the family Actinoplanaceae to distinguish species of actinomycetes which form short or long spore-chains on aerial mycelium, bears oval sporangia with motile spores and has a characteristic cell-wall composition of strain C677-91 type. Strain C677-91 (ATCC 31217, FERM-P No. 4070) was named Streptoalloteichus hindustanus gen. nov. and sp. nov. The actinomycete strain C677-91 produces spore-chain clusters and sclerotia in the aerial mycelium which are morphologically similar to those found in some species of Streptomyces. The cultural characteristics of the strain on agar media also resemble those of Streptomyces species and the colonies have no distinct color. Strain C677-91 produces sporangia or sporangia-like vesicles which contain one to several spores in the vegetative mycelium. The sporangiospores possess a single long polar flagellum and are motile. The cell wall of strain C677-91 contains meso-alpha,epsilon-diaminopimelic acid, alanine, glutamic acid, galactose, mannose, rhamnose and glucosamine. Strain C677-91 has several important characteristics in common with Streptomyces tenebrarius including the production of nebramycin factors but the latter strain does not produce sporangia.

Interaction of atrazine with soil microorganisms: population changes and accumulation.

Abstract: A loam soil treated with atrazine at rates of 10, 30, and 100 μg/g soil resulted in increased populations of actinomycetes, bacteria, and fungi over those in non-treated soil. The increases were in proportion to the amount of atrazine and persisted for at least 2 months. Living actinomycete and fungal mycelia were incubated for 48 h in distilled water, nutrient broth, or soil containing 5 μg/ml (g) of the herbicide. Actinomycete and fungal mycelia accumulated atrazine from water to concentrations up to 87-fold and 132-fold, respectively, over that in the ambient medium. The maximum accumulation from soil by actinomycete mycelia was 26-fold and by fungal mycelia 13-fold. Fungi accumulated little or no atrazine from a nutrient medium whereas actinomycetes accumulated up to 13-fold. Dead mycelia usually did not accumulate atrazine in excess of the ambient concentration. Mycelium of Sclerotium rolfsii growing in a nutrient medium containing 20 μg atrazine/ml accumulated 157 μg/g wet weight after 8 days. Scler...

Localization of beta-(1,3)-glucanase in the mycelium of Sclerotium rolfsii.

Abstract: The role of the lytic enzyme beta-(1,3)-glucanase in cell wall synthesis and its distribution in the mycelium of the fungus Sclerotium rolfsii were studied. Enzyme activity was determined after enzyme extraction with Triton X-100 from a cell wall preparation. Specific zones of immunofluorescence appeared in the hyphal tips, clamp connections, new septa, and lateral branching when a specific antiserum was used with the indirect method of the fluorescent antibody staining. Enzymatic activity in the cell wall preparation was inactivated by diethylpyrocarbonate. However, 69% of the total enzymatic activity was present in a latent form which was not affected by the ester. This result suggests that most of the beta-(1,3)-glucanase was present along the hyphal cell walls in a "masked" form. An active enzyme appeared only in those regions which showed immunofluorescence. The activity of glucan synthetase, an enzyme essential for wall formation, was higher in the branching funus grown on L-threonine-supplemented synthetic medium than in the synthetic medium-grown fungus. Images

Aflatoxin is degraded by heated and unheated mycelia, filtrates of homogenized mycelia and filtrates of broth cultures of Aspergillus parasiticus

Abstract: Steaming one-half of a lot of 9-day-old mycelia of Aspergillus parasiticus NRRL 2999 for 6 min resulted in little or no subsequent degradation of aflatoxin B1 or G1 by these mycelia. The other half of these mycelia was not heat-treated and degraded aflatoxins B1 and G1 Filtrates of the growth substrate which remained after the mycelium was removed from 8- to 15-day old cultures of A. parasiticus NRRL 2999 did not degrade substantial amounts of aflatoxin B1 or G1, whereas mycelia originally produced on these filtrates degraded substantial amounts of both aflatoxins. The supernatant fluid from homogenates of 9-day-old mycelia of A. parasiticus NRRL 2999 degraded aflatoxins B1 and G1 when 0.1 M or 1.0 M phosphate buffer, pH 6.5, was used to suspend the homogenate. These data support the hypothesis that the aflatoxin degrading factor(s) present in the mycelium of A. purasiticus is/are enzyme(s) or at least influenced by enzyme(s).

Characterization and classification of mycorrhizae of Douglas-fir. III. Pseudotsuga menziesii + Byssoporia (Poria) terrestris vars. lilacinorosea, parksii, and sublutea

Abstract: Three distinct Douglas-fir (Pseudotsuga menziesii) ectomycorrhizae formed by newly recognized varieties of Byssoporia (Poria) terrestris are described. They are named according to tree species and fungus as follows: P. menziesii + B. terrestris var. lilacinorosea. P. menziesii + B. terrestris var. parksii, and P. menziesii + B. terrestris var. sublutea. Each mycorrhiza is macroscopically and microscopically defined, including surrounding mycelium and attached rhizomorphs. Cultural characteristics of the three fungal symbionts grown on potato dextrose agar medium are briefly noted.

Uptake of 14C photosynthates from Pisum sativum by haustoria of Erysiphe pisi

Abstract: The technique for isolating haustorial complexes from leaves of Pisum sativum infected with Erysiphe pisi has been used to investigate the nutritional physiology of the host-parasite interface. The numerical efficiency of the extraction procedure was 4 to 5%. The haustorial complexes showed oxygen uptake in vitro which was unaffected by exogenous glucose, sucrose or mannitol. Haustorial complexes were isolated from leaves exposed to [14C]O2 where the mycelium was either left attached or separated from the leaves prior to the exposure. In each case, 14C assimilates soluble in boiling 95% ethanol were found in the haustorial complexes even after they were treated with Triton X-100 (1%). When the mycelium was attached large quantities of soluble and insoluble label accumulated in it. In isolations from leaves where the mycelium had been separated prior to 1 to 12 h exposures the quantity of soluble 14C assimilates in the haustorial complexes increased linearly. Subsequent in vitro incubation for 6 to 12 h had little effect on the amount of soluble label in the complexes, but [14C]O2 was released indicating that assimilates had passed across the host interface into the haustorial cytoplasm. Controls using uninfected leaves and infected leaves exposed in the dark showed that the contribution of host contamination and [14Q]O2 02 fixation by the haustorium was small. The quantity of label resident in the haustorial complexes was only a small proportion of label found in the mycelial and host fractions within the same area of leaf. These results are discussed in relation to the role of the haustorium in nutrient transfer from the host to parasite.

Citrate Regulation of NADP+-Specific Isocitrate Dehydrogenase of Aspergillus niger

Abstract: Many theories have been proposed to account for the accumulation of citrate in selected strains of Aspergillus niger (Berry et al., 1977). Citrate accumulation was attributed by Ramakrishnan et al. (1955) to loss of aconitase and isocitrate dehydrogenase activity, but the presence of these enzymes was clearly demonstrated by La Nauze (1966). The presence of tricarboxylic acid-cycle enzymes throughout the fermentation was further demonstrated by Ahmed et al. (1972), using intact mitochondria. Mattey (1977) reported the presence of an NADP+-specific isocitrate dehydrogenase in mitochondria of an A . niger strain during the phase of growth in which citrate was produced, which was inhibited by citrate, but was not affected by other tricarboxylic acid-cycle intermediates. He postulated that the regulation of isocitrate dehydrogenase activity by citrate could form the basis for the control of citrate production. If this is correct, then citrate inhibition of isocitrate dehydrogenase should be found in other strains of A. niger. In the present communication we report on the effect of citrate on NADP+-specific isocitrate dehydrogenase enzymes from two strains, one of which (72-4) can yield commercially useful quantities of citrate under suitable conditions, the other normally cultured for cellulolytic enzymes (50-565 ii). Stock cultures of A. niger strain 72-4 of Shu & Johnson (1947) and A . niger Van Tieghem strain C.M.I.50-565 ii (Commonwealth Mycological Institute, Kew, Surrey, U.K.) were maintained on Czapek-Dox agar. The organisms were grown in a highsucrose medium (Ahmed et al., 1972) in shake culture from an inoculum of 5 x lo7 conidia. Changes in mycelial weight, medium pH and citrate concentrations in the medium and mycelium were determined over an incubation period of 14 days. Citrate was determined by the method of Saffran & Denstedt (1948), modified by Spencer & Lowenstein (1967). Both strains showed similar batch culture growth kinetics. A . niger strain 72-4 showed a marked increase in citrate concentration in the mycelium from an initial value of 0.5mM to a maximum of 4 . 6 6 m ~ by the fifth day of cultivation, when citrate accumulation in the medium became significant. A. niger strain C.M.I. 50-565 ii showed no significant variation in citrate concentration in the mycelium, reaching 0.55 mM by the seventh day of cultivation. There is thus an 8-fold difference in internal citrate concentrations between the two strains. The pH of the medium fell from 3.1 to 1.9 during the first 4 says in both strains. The internal pH of the mycelium did not seem to be affected by the external pH under these conditions. Strain 72-4 produced 2.5g of citrate per g of dry mycelium by day 10 of cultivation, and strain C.M.I. 50-565 ii produced 0.609g of citrate per g of dry mycelium at this time. It would therefore appear that citrate concentrations in the medium and the mycelium are related. Mitochondria were isolated and disrupted as previously described (Mattey, 1977). Isocitrate dehydrogenase activity was assayed by the method of Ochoa (1948), with NADP+ and D,-threo-isocitrate as substrates. The NADP+-specific isocitrate dehydrogenase activity from mitochondria, isolated from day-6 mycelia, was inhibited by citrate, but was not affected by malate, fumarate, succinate, a-oxoglutarate or pyruvate. Fig. 1 shows a double-reciprocal (LineweaverBurk) plot of NADP+-specific isocitrate dehydrogenase activity versus substrate concentration, in the presence and absence of citrate, from both strains. It was previously reported that citrate inhibition of the NADP+-specific isocitrate dehydrogenase appeared to be competitive, but it is apparent that at higher isocitrate concentrations the enzyme does not obey conventional Michaelis-Menten kinetics. The kinetic data suggested that two similar enzymes were acting on the same substrate, but

The control of fruiting body formation in the ascomycete Sordaria macrospora Auersw. by regulation of hyphal development : An analysis based on scanning electron and light microscopic observations.

Abstract: The morphological effects of biotin and L-arginine on fruiting body formation of the ascomycete Sordaria macrospora are investigated by scanning electron and light microscopy. Biotin is recognized as an elongation factor and arginine as a branching factor in vegetative and reproductive hyphae. In the absence of exogenous biotin, development is blocked after the ascogonium-core hypha stage of protoperithecial morphogenesis, whereas linear growth of the myceliar front is maintained. The addition of exogenous arginine to a biotin deficient culture induces the formation of numerous side branches even in the older mycelium. Fruiting body formation, however, remains blocked at the protoperithecial stage as before, because of the inability of the side branches to elongate. When biotin and arginine are administered simultaneously, a most vigorous branching and growth are induced in the older mycelium, accompanied by a rapid and maximal formation of fruiting bodies. The results are summarized in a model of the exogenous control of hyphal morphogenesis. The model is designed to explain the relationship between fruiting and hyphal density as well as the edge effect on fruiting body formation.

Continuous fermentation to produce fungal protein. Effect of growth rate on the biomass yield and chemical composition of Fusarium moniliforme

Abstract: Fusarium moniliforme was grown on a carob aqueous extract in a chemostat for fungal protein production. The substrate was adjusted to provide 0.5 percent carob sugars supplemented with inorganic salts. The dilution rate varied from 0.086 to 0.227 hr/sup -1/ under constant conditions of temperature (30/sup 0/C), pH (4.5), and oxygen saturation (60 to 80 percent). A yield of 0.709 g dry mycelium/g consumed carob sugar and a productivity value of 0.687 g dry mycelium/liter hr/sup -1/ were obtained at ..mu.. = 0.205 hr/sup -1/. The maintenance coefficient was 0.077 g carob sugar/g dry mycelium hr/sup -1/. While the carbohydrate and purine content of dry mycelium increased at ..mu.. values from 0.114 to 0.205 hr/sup -1/, both true (Lowry) and crude (N x 6.25) protein contents decreased at the same ..mu.. range. Maximum values of 36.3 percent true and 47.9 percent crude protein of dry mycelium were obtained at ..mu.. = 0.114 hr/sup -1/, whereas a minimum purine content of 99.8 ..mu..mol/g corresponding to 6.42 percent nucleic acids was recorded at ..mu.. = 0.086 hr/sup -1/. It was concluded that a continuous fermentation of carob aqueous extract using F. moniliforme should be operated at growth rates of approximately 0.205 hr/supmore » -1/ in order to maximize protein production.« less