Phycomyces Blakesleeanus Burgeff Research Articles

Role of nitric oxide synthase in the light-induced development of sporangiophores in Phycomyces blakesleeanus.

Blue light controls the development of sporangiophores in the zygomycete Phycomyces blakesleeanus Burgeff. Light represses the production of microsporangiophores and enhances the development of macrosporangiophores. Inhibition of the biosynthesis of tetrahydrobiopterin, a cofactor of NO synthase, inhibits this photomorphogenesis. Light induces production of citrulline from arginine in the mycelium and in sporangiophores. The citrulline-forming activity is dependent on NADPH, independent of calcium, and inhibited by NO synthase inhibitors. It is reduced in tetrahydrobiopterin-depleted mycelium. Light induces emission of NO from the developing fungus in the same order of magnitude as citrulline formation from arginine. The NO donor sodium nitroprusside can replace the light effect on sporangiophore development, and inhibitors of NO synthase repress it. We suggest that a fungal NO synthase is involved in sporangiophore development and propose its participation in light signaling.

Effect of the Urtica dioica agglutinin on germination and cell wall formation of Phycomyces blakesleeanus Burgeff

The lectin from stinging nettle rhizomes, Urtica dioica agglutinin (UDA), did not affect the evolution of wet and dry weight, protein, nucleic acid, ATP, cAMP and glycerol content during early germination of Phycomyces blakesleeanus spores. However, earlier investigations established a strongly reduced mycelial growth of several phytopathogenic fungi by this small plant lectin. Total uptake and incorporation of radioactive precursors showed no differences between UDA or control hyphae, but UDA significantly altered the distribution patterns of [14C]-glucose incorporated into the walls of Phycomyces blakesleeanus (more label was recovered in the chitin fraction). Moreover, a small but significant stimulation of chitin synthase and a similar inhibition of chitin deacetylase was found in cell wall preparations. These observations could lead to a better understanding of plant-pathogen interrelationships and to a further elucidation of cell wall structure in fungi.

Nutritional evaluation of the fungus Phycomyces blakesleeanus as a protein source

AbstractThe quality of the protein of the carotenogenic fungus Phycomyces blakesleeanus Burgeff, strain NRRL 1555 ( ‐ ), was evaluated with rats and observed to have a protein efficiency ratio of 1.4. The limiting amino acids were tryptophan, sulphur‐containing amino acids, lysine and isoleucine. Upon incorporation into diets containing 100 g kg−1 protein the proportions of the above mentioned amino acids of the optimal recommended dietary allowances for growing rats were 33.0%, 57.4%, 74.5% and 87.2% respectively. Furthermore, the fungal protein was found to contain an excess of histidine about eight fold more than the recommended dietary allowance for growing rats. Some safety aspects were examined and, although the fungus was consumed in high dietary concentrations, 242 g kg−1 of the diet, no pronounced toxicological effects were observed.

High-and low-intensity photosystems in Phycomyces phototropism: Effects of mutations in genes madA, madB, and madC

Sporangiophores of Phycomyces blakesleeanus Burgeff that have been grown in darkness and are then suddenly exposed to unilateral light show a two-step bending response rather than a smooth, monotonic response found in light-adapted specimens (Galland and Lipson, 1987, Proc. Natl. Acad. Sci. USA 84, 104-108). The stepwise bending is controlled by two photosystems optimized for the low-and high-intensity ranges. These two photosystems have now been studied in phototropism mutants with defects in genes madA, madB, and madC. All three mutations raise the threshold of the low-intensity (low-fluence) photosystem by about 10(6)-fold and that of the high-intensity (high-fluence) system by about 10(3)-fold. Estimates for the light-adaptation time constants of the low-and high-intensity photosystems show that the mutants are affected in adaptation. In the mutants, the light-adaptation kinetics are only slightly affected in the low-intensity photosystem but, for the high-intensity photosystem, the kinetics are considerably slower than in the wild type.

Synthesis and proteolytic activation of chitin synthetase in Phycomyces blakesleeanus Burgeff

The chitin synthetase of Phycomyces blakesleeanus mycelium is a particulate enzyme sedimenting mostly at 1000xg. The activity in crude extracts or cellular fractions can be increased more than tenfold by mild trypsin treatment. Plotting the reaction velocity versus UDP-N-acetylglucosamine concentration yields a sigmoidal curve. N-acetylglucosamine, which greatly stimulates the enzyme, changes the kinetics to an almost normal hyperbolic relationship.

Decarboxylation of Gluconic Acid and Fructose by Dormant and Activated Spores of Phycomyces blakesleeanus Burgeff

Summary Dormant spores of Phycomyces blakesleeanus can metabolize glucose but not gluconic acid nor fructose. Both the latter substrates can be utilized by activated spores after 4 h of germination; for gluconic acid decarboxylation, however, glucose has to be present in the germination medium. Cycloheximide prevents utilization of both substrates. 5-Fluorouracil is also inhibitory for both substrates, but inhibition is only effective for fructose in the presence of glucose. This suggests that fructose is metabolized along the glucose metabolising systems or by a more specific mechanism in the presence of glucose.

Zygosporogenesis in Phycomyces blakesleeanus

Zygosporogenesis in Phycomyces blakesleeanus Burgeff was observed via scanning and transmission electron microscopy. The surface architecture of the initial stages of conjugation up to mature whole and longitudinally cryofractured zygospores was described and illustrated. The development and structure of the fusion wall, gametangial septum, appendages, and the lateral wall layers of the developing zygospore were investigated with the transmission electron microscope.

Glucose metabolism of dormant and heat-activated spores of Phycomyces blakesleeanus burgeff

The metabolism of [(14)C]glucose has been studied in Phycomyces spores during dormancy, activation, and the initial stages of germination. Dormant spores are able to take up and metabolize exogenous glucose into different products; the major part of it goes to trehalose synthesis (up to 60% when the external glucose concentration exceeds 10(-3) M). During activation itself (i.e. a prolonged treatment at 50°) there is a general increase of glucose uptake and metabolism, without major changes in the relative rates of (14)C-label distribution in the different fractions (as compared to the metabolism of dormant spores), except for a drop in material insoluble in 80% ethanol and a still higher percentage (73%) going to trehalose synthesis. In the early hours of germination we find an enhancement of the uptake and metabolism of glucose. Trehalose synthesis is practically switched off within 2 h whereas the major part of glucose (65%) is metabolized to CO2 and ethanol-insoluble proteinaceous material.

New Photoresponses of Phycomyces

The influence of light on asexual fruiting and mycelial growth of Phycomyces blakesleeanus Burgeff was studied by means of fruiting body counts and size measurements in cultures on solid media under varied incubation conditions. Five types of photoresponses were shown by ATCC Strain 8743a: (a) photoinduction of giant sporangiophores; (b) interference by light with an endogenous system that otherwise induces fruiting when the mycelium approaches the rim of the Petri dish; (c) inhibition of mycelial growth rates by light; (d) inhibition of dwarf sporangiophore induction by light; and (e) postponement by light of death in clones maintained by serial transfer at low temperature. A second strain, designated G5, showed responses comparable to (a), (b), and (d). The magnitudes of the responses were greatly affected by temperature of incubation and available nitrogen (asparagine) supply. The photoinduction of giant sporangiophores could be demonstrated with light of wavelengths between 380 and 480 nanometers but not with 520 nanometers or above. At 480 nanometers, light doses as small as 40 ergs per square centimeter were effective in inducing giant sporangiophores in strain 8743a.

Mechanism of translocation of potassium in sporangiophores of Phycomyces blakesleeanus in an aqueous environment

In sporangiophores of Phycomyces blakesleeanus Burgeff bridging aqueous phases of different potassium concentration, gradients of potassium concentration and electrical potential were generated intracellularly and caused movement of potassium in a direction towards the aqueous phase of lower potassium concentration. Measured rates of potassium movement agreed closely with rates predicted from the Nernst-Planck diffusion equation. It appears that bulk flow of cytoplasm does not make a significant contribution to the translocation of potassium under the experimental conditions.

Crystalloids of Phycomyces Sporangiophores: Nature and Photosensitive Accumulation

Crystalloids accumulate in the vacuoles of the giant sporangiophores of Phycomyces blakesleeanus Burgeff during growth. On the basis of solubility in alkaline solutions, cytochemical staining reactions, trypsin sensitivity, optical absorption and response in the Lowry protein test, the crystalloids have been judged to consist principally of an acidic protein. In assays by Lowry test and by reference to optical absorption at 280 mmu, dark-grown sporangiophores were consistently found to contain from 2 to 4 times as much crystalloid material as light-grown counterparts. Concurrent assays of soluble phenolic materials revealed no significant effect of culture illumination, while carotene content of sporangiophores and mycelium was found to be raised from 2 to 4-fold by illumination during growth.

Zygospore initiation, development and germination in Phycomyces blakesleeanus

The effects of low temperature, light and starvation upon zygospore initiation and development in Phycomyces blakesleeanus Burgeff were studied. Sexual structures were initiated, but did not mature, and partially developed game-tangia matured slowly, but normally, at 1°C. Continuous diffuse or feeble light was optimum for initiation and development, but continuous intense light was nearly completely inhibitory. The result of starvation was production of fewer and smaller but otherwise normal zygospores. The influence upon germination of growth factors, heat and cold treatments, the state of maturity, and of short and long-term ageing were studied. Indole-actic acid and gibberellic acid were ineffective in pretreatments or as substrate adjuncts. Germinations were obtained from 70% of immature zygospores forthwith and from 30% of mature zygospores following at least 8 months ageing at 1°. Any one germ sporangium contained exclusively spores of one mating type, either plus or minus. Mycelial germinations frequently occurred; in a single instance such a germination appeared to be heterocaryotic for sexual reaction. Evidence is submitted for transgressive genetic segregation for quantitative mating capacity.

VITAMIN B1 OR ITS INTERMEDIATES AND GROWTH OF CERTAIN FUNGI

SCHOPFER (1934a, 1934b) reported that Phycomyces Blakesleeanus Burgeff does not grow upon a medium of mineral salts, pure dextrose, asparagine, and water, but grows normally on the same medium to which a minute quantitv of crystalline vitamin B, is added. Schopfer's discovery resulted from a suggestion made to him by Burgeff (Schopfer, 1934c) based on the latter's observation of the effect of crystalline vitamin B1 on the growth of Phycomyces. Other fungi found by Schopfer (1935) to require vitamin B1 include Absidia ranosa, Parasitella simplex, Mucor Ramanmnianus, Dicranophora fulva, Chaetocladium Brefeldi, Choanephora cucurbita, Choan,ephora persicaria, and Pilaria anomala. Earlier reports on the importance of vitamin B1 as a growth factor for the lower plants have been published by various investigators including R. J. Williams (1920, 1930), Lepeschkin (19'24), and others. The conclusive evidence of the importance of vitamin B, (aneurin or thiamin) for the growth of plants depended upon a supply of the pure vitamin, which became available in 1934. We have confirmed Schopfer's report of the effect of vitamin B1 on the growth of Phycomyces BRakcesleeanus, and since there are many organisms which do not grow, or grow poorly, on the common synthetic media (those lacking some natural organic supplement), we have determined the effect of vitamin B1 on a number of fungi. MATERIALS AND METHODS.-In addition to Ph ycomyces Blakesleeanus, a plus strain kindly furnished by A. F. Blakeslee, we have used other organisms secured through the courtesy of W. E. Maneval, J. T. Middleton, or C. M. Tucker. Those furnished by Maneval were Absidia glauca Hagem, Basidiobolus ranarum Eidam, Mortierella sp. no. 11, Mortierella candelabrum v. Tiegham and le Monnier, Mucor circinelloides v. Tiegham, Mucor griseolilacinus Povah, Mucor sp. no. 103, Mucor sp. no. 115, Circinella aspera Lendner, Cunninghamella sp. no. 102, Thamnidium elegans Link, Zygorhynchus Moelleri Vuill, Zygorhynchus sp. no. 111, Rhizopus nigricans Ehrenberg, + and -, Phycomyces nitens (Agardh) Kunze and Schmidt, +, Sphaerulina trifolii Rostr. From Tucker we secured cultures of Phytophthora Boehmeriae Saw., P. cactoram (L. and C.) Schwet, P. cambivora (Petri) Buis, P. capsici Leon., P. cinnamoni Rands, P. colocasiae Racib., P. cryptogea Pethyb. and Laff., P. Drechsleri Tuck., P. palmivora Butler, P. parasitica Dast., P. fagopyri Takimoto; Agaricus campestris Linn., Schizophyllum commune Fr., Sclerotium delphinii Welch, and S. Rolfsii Sac. Middleton furnished cultures of Pythium arrhenomanes Drechsler, P. polycladon Sideris, P.