Ascospore Germination Research Articles

Physiology of the Cell Surface of Neurospora Ascospores. III. Distinction between the Adsorptive and Entrance Phases of Cation Uptake

SUMMARYThe germination of ascospores of Neurospora tetrasperma has been shown to be inhibited by continual incubation in very small amounts of metal cations. Of these, Ag+, and p-chloromercuribenzoic acid (PCB) are the most toxic. Furthermore, these cations were shown to be adsorbed to the surface of the dormant ascospore from where they can penetrate to affect sensitive loci within or upon the surface of the cell. Cations like Ag+, Cu++ and UO2++ can be taken up in sufficient quantity by the dormant cell so that germination is inhibited, even when the activated cells are incubated in distilled water. On the other hand, cations like Th++++ and Al+++ do not inhibit under the latter conditions despite the fact that they are bound to the cell surface and are quite toxic when continually incubated with the germinating ascospore. These experiments support the idea that the dormant cell is impermeable to cations whereas this barrier is raised when germination is induced. Although, in a general way, the toxicity of some of the metals tested varies directly as a function of the insolubility of their mercaptide, the slope of the curve does not agree with that found by Shaw for other organisms.

Physiology of the cell surface of Neurospora ascospores. II. Interference with dye adsorption by polymyxin

Polymyxin B prevents the germination of ascospores of Neurospora tetrasperma with an LD 50 of 3–4 p.p.m. The toxic effect of polymyxin is partially reversed by calcium and magnesium ions. The effect of polymyxin on the respiration of activated ascospores does not become apparent until after 2 hr. The effect upon respiration is reversed by calcium ions. Dormant and activated ascospores remove about the same amount of polymyxin from solution almost immediately upon exposure to the antibiotic. After 90 min. the apparent uptake of activated cells is markedly diminished while that of the dormant spores increases slightly. Polymyxin competes noncompetitively with methylene blue for sites on the surface of the cells when added simultaneously with the dye. However, if the antibiotic is added before methylene blue, dye uptake is almost entirely suppressed and an uncompetitive type of inhibition results. These data, in conjunction with those showing polymyxin uptake by cell-wall fragments, suggest that the antibiotic occupies sites on the surface of the ascospore and that these sites differ from those binding methylene blue.

Lysozyme-Induced Sensitivity of Neurospora Ascospores to Furfural

The precise nature of the permeability barriers of plant cells has eluded analysis although their physiological effects have been exhaustively studied. Contributing most to the difficulties encountered in these studies has been the complexity of their chemical constituents and or? ganization. However, an excellent approach to this problem exists in the use of enzymes as specific reagents in the analysis of cell wall and membrane constituents. Apart from their specificity, these substances act under mild (physiological) conditions and are large enough in size so that it may be assumed that their effect would be localized on the outside of the cell. Weibull (1953) has shown that the ability of a bacterial cell to retain certain cellular constituents is greatly altered by the use of lysozyme. In addition, Tomcsik (1954) reported that prolongations of bacterial cross walls may extend into the capsule on the basis of enzymatic digestion of antibody-treated cells. With these facts in mind, studies were undertaken on the effect of enzymatic treatment upon the ascospores of Neurospora tetrasperma. These cells exist in at least two different physiological conditions, the durations of which are under the control of the investigator. Thus, in the dormant state, the cell metabolizes at a low rate, is impermeable to some poisons, and is resistant to drying and other physical treatments. Two means exist for breaking dormancy and these include heat-treatment (Goddard, 1935) and treatment with furfural and related heterocyclic compounds (Emerson, 1948; Sussman, 1953). Upon such activation a twenty to thirty-fold increase in metabolic rate ensues, accompanied by other changes in permeability and resistance to chemical and physical treatments. Using these facts as a basis, the effect of lysozyme and other enzymes upon the activation and germination of ascospores of N. tetrasperma was investigated. By this means it was hoped to learn

Physiology of the cell surface on Neurospora ascospores. I. Cation binding properties of the cell surface.

Acids like hydrogen fluoride, hydrazoic and fluoroacetic have been shown to prevent the germination of ascospores of N. tetrasperma when dormant spores are treated. On the other hand, propionate, cysteine and others are ineffective when used in this way. When activated ascospores were treated, much lower concentrations of the acids were sufficient to poison the spores. As in other systems, these substances are most effective at a pH below their pKa.

The Effect of Temperature and Nutrients Upon Spore Germination of the Oak Wilt Fungus

The optimum temperature for the germination of ascospores and endoconidia of E. fagacearum is within the range of 21° to 32° C; the maximum is between 33° and 36° C; and the minimum is below 3° C. ...

The Effect of Furfural Upon the Germination and Respiration of Ascospores of Neurospora tetrasperma

American Journal of BotanyVolume 40, Issue 6 p. 401-404 Article THE EFFECT OF FURFURAL UPON THE GERMINATION AND RESPIRATION OF ASCOSPORES OF NEUROSPORA TETRASPERMA Alfred S. Sussman, Alfred S. Sussman Department of Botany, University of Michigan, Ann Arbor, MichiganSearch for more papers by this author Alfred S. Sussman, Alfred S. Sussman Department of Botany, University of Michigan, Ann Arbor, MichiganSearch for more papers by this author First published: 01 June 1953 https://doi.org/10.1002/j.1537-2197.1953.tb06499.xCitations: 14AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume40, Issue6June 1953Pages 401-404 RelatedInformation

The effect of heterocyclic and other compounds upon the germination of ascospores of Neurospora tetrasperma.

SUMMARY: Eleven 5-membered heterocyclic compounds, in addition to furfural and furfuryl alcohol, were effective in overcoming the dormancy of ascospores of Neurospora tetrasperma. The substitution of a nitro group in the 5-position imparted fungistatic properties to otherwise innocuous furans and pyrroles; carboxylic acid derivatives of these heterocyclic compounds likewise were toxic. From data on the time-course of furfural activation, it is shown that the Q 10 for this process is 4.1 over the temperature range from 20 to 30°.

Morphological and physiological studies on Sordaria destruens (Shear) comb.nov. (syn. Melanospora destruens), Sordaria fimicola and Melanospora zamiae

Three strains of Melanospora destruens were compared with three of Sordaria fimicola and one of Melanospora zamiae. The strains of M. destruens and Sordaria fimicola resemble each other in size and shape of perithecia, size and general shape of asci, and size, shape and method of germination of ascospores, but differ in shape of the tip of the ascus which is slightly flatter in Melanospora destruens than in Sordaria fimicola, and in the greater frequency of the presence of a wide gelatinous sheath surrounding the ascospores of S. fimicola. Melanospora zamiae differs from both M. destruens and Sordaria fimicola in possessing a long perithecial neck with a fringe of bristles surrounding the ostiole, pyriform evanescent asci, and spindle-shaped ascospores with two polar germ-pores and in the mode of germination. S. fimicola shows a greater tendency to a ‘staled’ type of growth than does Melanospora destruens or M. zamiae. The strains of Sordaria fimicola and Melanospora destruens all show higher cardinal points for temperature than does M. zamiae. The reaction of M. zamiae to different sources of carbon and growth substances also differed from that of the M. destruens and Sordaria fimicola strains which show only minor differences among themselves. It is suggested that Melanospora destruens should be transferred to Sordaria as S. destruens (Shear) Hawker, comb.nov. Fertile strains of Melanospora destruens grow relatively more quickly at temperatures of 30° C. and over than do sterile strains, and incubation of new subcultures for several days at 30° C. prevents loss of fertility in culture.

STUDY OF BYSSOCHLAMYS FULVA AND CONTROL MEASURES IN PROCESSED FRUITS

Summary A survey of various fruit‐producing areas in England showed that fruit and foliage were liable to be contaminated with ascospores of Byssochlamys fulva. Contamination was most pronounced on mummified plums and on certain fruit refuse. The thermal death point of ascospores is about 96°C., but only a small proportion of spores show this maximum heat resistance. Conidia are killed by exposure to relatively low temperatures. The reaction and the sucrose concentration of the heating medium, and the strain of the fungus, are factors influencing the heat resistance of ascospores. Ascospores germinate slowly and irregularly, but their germination is stimulated by previous heating to about 70°C. Ascospore germination and mycelial growth take place at relatively high temperatures, in high sucrose concentrations, in acid media, and in very high concentrations of carbon dioxide. Ascospores are relatively insensitive to antiseptics and to desiccation. Growth is accompanied by the production of a pectin‐destroying enzyme. The results of laboratory experiments were applied to canning experiments and good agreement was obtained. Natural contamination on fruits could be overcome in cans by heating the contents to 195°F. The amount of mycelial growth developing in an infected can depends upon the size of head space and the storage temperature.

OBSERVATIONS ON APPLE CANKER

Summary The fungus causing apple canker is described and its identity with Nectria galligena Bres. is confirmed. The methods of dispersal of the spores of Ngalligena have been examined. The ascospores are discharged forcibly from the perithecium, the eight spores of each ascus typically being ejected simultaneously. Field investigations have shown that spores are discharged during wet periods at all times of the year. Ascospore discharge reaches its maximum in January‐February and falls to a minimum in the summer months. The dispersal of conidia occurs during wet periods in the spring and autumn. Germination both of ascospores and conidia occurs over a range of temperature from 2 to 30°C, the optimum being at 20°C.

The Conidial Stage of Peziza Pustulata

Heat treatment which is so effective in inducing germination of ascospores of some species has been found indispensable in connection with genetic work with species of Neurospora, Gelasinospora and certain other forms. While the method is very effective in growing Ascobolus carbonarius, it is of practically no value to induce germination of spores of Ascobolus magnificus. It is very desirable that a method be discovered for germinating the spores of this species as well as those of other Ascomycetes where it has been reported that the primary ascus nucleus is tetraploid, while the nuclei of the vegetative hyphae are haploid. If this can be supported genetically it will settle once for all the controversy over double fertilization in the Ascomycetes. Ascobolus magnificus varies sufficiently to be adaptable for genetic work if the eight spores of an ascus could be made to germinate. It is now twenty-five years since the writer published that note on Artificial cultures of Ascobolus and (Mycologia 4: 218-222. 1912). Heat treatment was found to be effective in bringing about germination of the ascospores of the form reported as Aleuria umbrina. Fruiting bodies for that work had been found in the first weeks of June of that year on a spot where

Gibberella Saubinetii (Mont.) Sacc. on British Cereals: II. Physiological AKD Pathological Studies

Summary G. Saubinetii (Mont.) Sacc., the conidial stage of which is known as Fusarium graminearum Schwabe, produces mature perithecia on natural and artificial substrata, given ample moisture and a uniform temperature of 21° to 22°C. British summer shade temperature does not suffice for this.The minimum temperature for the germination of conidia and ascospores is about 6°C. Between 5° and 10°C. both kinds of spores develop mycelia, and the fungus can infect cereal seedlings. The optimum temperature for vegetative growth of the fungus and the production of mature perithecia is about 24° C.; the maximum temperature for growth is about 37°C.In its vegetative and perithecial stages this fungus can withstand prolonged exposure to a temperature range of — 1° to — 20°C. and in its vegetative stage it persists through the winter in this country.Under storage conditions it retains its vitality for at least two years in its vegetative stage, and for at least one year (probably much longer) in its perithecial stage.Heating to 100°C. for five minutes under dry conditions kills G. Saubinetii on or in diseased grains, but this treatment of seed grain is not a practicable way of controlling the disease. G. Saubinetii causes “seedling blight” and “foot rot” of cereals, but is much less virulent than .F. culmorum and F. avenaceum in this respect. All three fungi attack the ears in a similar way, with similar virulence and with similar results. G. Saubinetii occurs throughout England and in Ireland, but full details of its frequency of occurrence in the British Isles have not yet been obtained.

Germination of Ascospores

Germination of Ascospores