Studies on the mechanism of action of sulfanilamide on mycelial felts of Rhizoctonia solani

Summary Sulfanilamide induced strong inhibitory effects on the growth, respiration and carbohydrate synthesis by mycelial felts of Rhizoctonia solani. The possible reasons for such inhibitory effects are discussed.The inhibitory effects of sulfanilamide were almost completely alleviated by the inclusion of p-aminobenzoic (PABA) acid in the culture medium of the fungal mats. R. solani normally produces certain amounts of PABA and its growth and metabolism is inhibited in presence of excess of it.     

Effect of colchicine on the nitrogen metabolism and fate of phosphates absorbed during the formation of fungal felts of cunninghamella sp.

Summary During formation of fungal mats of Cunninghamella sp., colchicine seemed to have no effect on the mycelial dry weight but increased the phosphorus and nitrate uptake only when present in 20 p.p.m. All treatments increased the organic phosphorus content and peptide fraction of the tissue medium systems. These phenomena were furthered by raising the concentration of the drug. Colchicine showed its inhibitory effects on protein synthesis only when administered in the high concentration. The mechanism of nitrate utilisation in presence of colchicine was also discussed.     

Utilization of Methionine by Mycelial Felts of Fusarium Culmorum

When the amino-acid L-methionine was used as the sole sourceof nitrogen in the culture medium it induced appreciable inhibitionof growth, respiration, and protein synthesis by mycelial matsof Fusarium culmorum. Such inhibitory effects increased with(a) lapse of time and (b) increase in concentration of methioninein the culture medium. The results of the experiments presented below support the viewthat methionine is first oxidatively deaminated before it istaken up by the mycelial mats of the fungus being tested.     

A preliminary study of the applicability of sweet potatoes for mycological fat production

Summary For mycological fat production,Aspergillus nidulans andPenicillium lilacinum were grown on media made up of crushed and boiled sweet potatoes. Mycelial mats containing a fair amount of fat were obtained, namely, 15 % in case ofAspergillus and 24 % in case ofPenicillium. Media containing an external supply of glucose gave rise to increase in percentage fat in mycelium, but the amount of mycelium and consequently the total fat content decreased.Addition of sodium nitrate gave heavier mycelial mats but the total fat content could not be raised.Addition of potassium phosphate or magnesium sulphate or both to the sweet potato medium gave rise to heavier mycelial mats but with lower fat content.     

Effect of metabolic inhibitors on growth and brefeldin A formation inCurvularia lunata

Arsenite as opposed to azide exerted a stronger inhibitory effect on brefeldin A production than on mycelial growth of cultures ofCurvularia lunata. However, azide was a more potent inhibitor of mycelial growth than arsenite at 0.5 mn and 1.0 mm. The inhibitory effects of iodoacetate on growth and brefeldin A formation were significantly less potent than those of iosoacetamide. Increases in the levels of fluoride elicited a variable inhibitory effect on brefeldin A production and a corresponding deorease in biomass.     

A preliminary study on the effects of salicylic and jasmonic acids on Ganoderma boninense growth,mycelial hydrophobicity,and media pH under in vitro assays

Potato dextrose agar amended with salicylic acid (SA) suppressed growth of all Ganoderma boninense isolates. However, mycelial growth inhibitory effects varied with times, SA concentrations and G. boninense isolates. At 150 ppm of SA or higher, growth suppression diminished with time and mycelial growth recovery was observed. In contrast, jasmonic acid (JA) unexpectedly improved growth of G. boninense. At 21 day-after-inoculation, pH changes and hydrophobicity for the melanised mycelia were lower compared to non-melanised mycelia. The degree of inhibitory or promotional effects on the growth of G. boninense and the level of G. boninense mycelial hydrophobicity by SA and JA were isolate-dependent.     

Compatability of Metarhizium anisopliae var. anisopliae with chemical pesticides

The effects of various insecticides on the mycelial growth, sporulation and conidial germination of Metarhizium anisopliae var. anisopliae isolate E₉ were studied in the laboratory. Chlorpyrifos was the most toxic organophosphate to mycelial growth and sporulation at all concentrations. Temephos, malathion and leptophos were highly toxic to sporulation while malathion was the most inhibitory to germination. The carbamates, carbofuran, methomyl and oxamyl were moderately toxic to mycelial growth and sporulation while oxamyl had an adverse effect on germination. The pyrethroids (pyrethrin, permethrin and resmethrin) and the insect growth regulators (diflubenzuron and methoprene) were not inhibitory to the various developmental stages of isolate E₉. The chlorinated hydrocarbons (chlordane, lindane and toxaphene) were more deleterious than all other insecticide groups tested. Among the fungicides, benomyl and maneb produced the greatest inhibition.     

Synchronous Conidiation of Piricularia oryzae by the Replacement Culture

For the purpose of studying the mechanism of conidiogenesis in Piricularia oryzae, methods were developed to separate the phase of mycelial growth from that of conidiation and also to evaluate them quantitatively.

When P. oryzae was grown on media with low carbon : nitrogen ratio and high nitrogen concentration, conidiation did not take place, in spite of its vegetative growth. Conidiation occurred in a very short period of time when the above mycelia were replaced on nutritionally poor media. Cellophane membrane was overlaid on solid medium and conidia were spread uniformly. Evenly grown mycelial mat which could be easily transferred onto the post-culture medium was obtained. As the preculture medium, MSA medium with carbon: nitrogen ratio of 6.3 and nitrogen concentration of 1.5 g/liter was used. The evenly grown mycelial mat was cut into small square mats of 1.44 cm² each and the small square mycelial mats were transferred onto the post-culture medium together with the cellophane membrane. The conidiation took place in the post-culture and the vegetative growth in the preculture and the conidiation in the post-culture could be observed separately and quantitatively.

Conidiation did not occur at all in the preculture and the degree of conidiation which took place in the post-culture varied according to the precultural conditions. This means that it is a certain state of physiological condition in the preculture which determines the degree of conidiation in the post-culture. The authers designated this state of physiological condition as the “latent activity of conidiation” (LAC). For the purpose of the quantitative estimation of this activity, we expressed LAC in terms of the degree of conidiation in the post-culture under a defined cultural condition. The LAC was subject to change very easily, declined rapidly and disappeared upon prolonged preculture. Only young mycelia showed to have this activity.

The influences of the precultural condition on the development of the LAC and vegetative growth were generally parallel. However, the LAC was generally more sensitive to the environmental condition than the vegetative growth, especially to the temperature change.

The conidia formed were uniform in size and had high rate of germination. Several strains of P. oryzae tested showed very similar behavior.     

Effect of proteolytic and glycolytic enzymes on a factor inSorghum bicolor that induces mycelial growth in the smut fungus,Sporisorium reilianum

Proteins obtained from seedling shoots and floral meristems ofSorghum bicolor (L.) Moench cv. NK 1210 induced mycelial growth in the smut fungus,Sporisorium reilianum in vitro. Proteins precipitated with trichloroacetic acid and ammonium sulfate were equally effective as inducers, although there were minor variations in the pattern of mycelial growth. Hydrolysis of the protein fraction with the proteolytic enzyme pronase E resulted in considerable reduction in the proteins' ability to induce mycelial growth. Digestion of the protein fraction with driselase, resulted in a slight enhancement of biological activity. The results suggest that amino sugar moieties in glycoproteins may act as inducers of mycelial growth inSporisorium reilianum.     

Aviglycine and propargylglycine inhibit conidial germination and mycelial growth of <Emphasis Type="Italic">Fusarium oxysporum</Emphasis>f. sp. <Emphasis Type="Italic">luffae</Emphasis>

Two inhibitors, aviglycine and propargylglycine, were tested for their ability to suppress methionine synthesis thus inhibit conidial germination and mycelial growth of Czapek-Dox liquid medium grown Fusarium oxysporum f. sp. luffae μM. The linear inhibition range for mycelial growth was about 7.6–762.9 μM. Although aviglycine did not completely inhibit both conidial germination and mycelial growth, it showed significant inhibitory effect at 1.5 μM. The inhibition range for propargylglycine against conidial germination and mycelial growth were from 0.08 to 8841 μM and from 0.8 to 884.1 μM, respectively. Propargylglycine inhibited conidial germination and mycelial growth at a concentration of 8841 μM. The EC₅₀ values of aviglycine were 1 μM for conidial growth and 122 μM for mycelial growth, and the EC₅₀ values of propargylglycine were 47.7 μM for conidial growth and 55.6 μM for mycelial growth. Supplement of methionine released inhibition of aviglycine or propargylglycine to conidial germination. In addition, a mixture of aviglycine (1.5 μM) and propargylglycine (8841 μM) showed additive inhibitive effect than applied alone on 10 isolates. From these results, both aviglycine and propargylglycine exhibited inhibitory activity, and suggest that they can provide potential tools to design novel fungicide against fungal pathogens.     

Studies on the Metabolism of Aspergillii

Endogenous respiration of Aspergillus sojae K.S. was studied in terms of biochemical analysis. It was found that the different kind of substrates was utilized for the endogenous respiratoin according to C:N ratio of the agar medium on which the mold was grown. In the mycelial mats grown on the medium of low C:N value, pool amino acids, protein, and nucleic acids were mainly utilized from the beginning while carbohydrate or lipid displayed a minor role. The corresponding amount of ammonia was formed. On the other hand, in the mycelial mats grown on the medium of rather high C:N value, carbohydrate or lipid was the major substrate of endogenous respiration in the early stages of incubation. The utilization of the nitrogenous materials and the accompanying formation of ammonia got to start only after the lapse of several hours of incubation.     

Studies on the mechanism of fungicidal action of crystal violet on mycelial felts of fusarium culmorum

Summary Crystal violet, when incorporated in culture media of mycelial felts of Fusarium culmorum, reduced, or in certain cases stopped, the uptake of nitrate-nitrogen, protein and peptide synthesis, and carbon dioxide output by the mycelial mats.Addition of cysteine hydrochloride or sodium glutamate to the culture media did not alleviate the toxicity of crystal violet.The possible mode of fungicidal action of crystal violet is discussed.     

Studies on the mechanism of fungicidal action of mercuric chloride on mycelial felts of Rhizoctonia solani

Summary Mercuric chloride induced strong inhibitory effect on the growth, respiration and carbohydrate synthesis by mycelial felts of R. solani. Such inhibitory effects can be antagonised by the amino acid cysteine when mixed with the toxin in the nutritive medium. Methionine failed to do so. The possible explanations for the inhibitory actions of mercuric chloride are thoroughly discussed.     

The use of acetate in the metabolism of penicillium lilacinum thom

Summary The effects of adding sodium acetate to a sucrose-salts medium favorable for fat formation by Penicillium lilacinum on growth and metabolism of the fungus were studied. The presence of acetate suppressed the rate of growth during the early period of incubation, but this effect almost disappeared towards the end of the experiment. The acetate also suppressed the rate of accumulation of the carbohydrates, the nitrogenous compounds, and fats in the mycelial mats, during the logarithmic period of growth. By the end of the incubation period the amounts of these substances in the acetate-fed cultures were not much less than those of the controls. It is suggested that training the fungus on acetate may help it to utilize the acetate for fat synthesis.     

Antagonism of Chaetomium globosum, Gliocladium virens and Trichoderma viride to four soil-borne Phytophthora species

Chaetomium globosum, Gliocladium virens and Trichoderma viride, isolated from soil samples from the Kivu-region of Zaire, are antagonistic and mycoparasitic to four soil-borne Phytophthora spp. Radial growth of Phytophthora cinnamomi, P. cactorum, P. fragariae or P. nicotianae mycelia was inhibited in all antagonist-pathogen combinations; mycelial mats of Phytophthora colonies were overgrown by the antagonists and hyphae lysed. Samples of mycoparasited mycelium, plated on benlateamended PDA to inhibit the development of antagonists, showed severely reduced vitality after 77 days of dual culture.     

The effect of pH value on the toxicity of culture filtrates ofHelminthosporium Sativum and on its possible correlation to extracellular nitrogen accumulation

Summary Helminthosporium sativum P.K. & B. was grown on modified Fries No. 3 medium buffered at pH 4.7, 5.5, 6.7, and 7.8. The nitrogen content of the culture filtrate, mycelial growth and the toxicity of the filtrate (as measured by its wilt inducing capacity to lupin seedlings) were traced over 24 days. The correlation between nitrogen accumulation and the toxicity of the filtrates was clear in case of media originally buffered at 4.7, 5.5 and 7.8. On the other hand, there was no correlation between growth of the mycelial mats and toxin production. The toxicity of the filtrate was attributed to two substances at least, one of unknown composition produced during the accelerated growth phase, while the other is nitrogenous and produced during the decline growth phase i.e. autolytic in nature. Acidity of the medium favoured toxin production during the first two weeks of incubation. The toxicity of the filtrate remained stable within a wide range of pH between pH 3–9.4.     

Cyclic adenosine 3′,5′-monophosphate as “first messenger” inStreptomyces hygroscopicus—Bimodal regulation of germination and growth

The effect of different cyclic AMP concentrations on spore germination and mycelial growth was studied with light and electron microscopy. Cyclic AMP inhibited the transition from spores to vegetative cells inStreptomyces hygroscopicus but stimulated growth of outgrown mycelia. The optimum inhibitory concentrations for germination (5–10 mM) were also the optimum concentrations for stimulation of mycelial growth. Concentrations between 10 mM and 20 mM resulted in a rapid shift from stimulation to strong inhibition of growth. Both electron microscope observations and other data indicate that cyclic AMP may be a first messenger of communication between different cells of this microorganism.     

In vitro inhibitory effects of rosemary and sage extracts on mycelial growth and sclerotial formation and germination of Sclerotinia sclerotiorum

The anti-fungal efficacy for two Labiate plants, rosemary (Rosmarinus officinalis L.) and Greek sage (Salvia fructicosa Mill.), against Sclerotinia sclerotiorum fungus (Lib.) de Bary has been investigated. The inhibitory effect of these plants as crude leaf ethanolic extract on the radial mycelial growth as well as on sclerotial production and germination was measured in vitro at various concentrations (stock?=?0.5?g dry leaf powder/ml ddH₂O) in the growth medium. In general, rosemary extract revealed a remarkable anti-fungal effect against the fungus, being more inhibitory than Greek sage in this respect. This was evident as total inhibition of radial mycelial growth by rosemary occurred at 10% extract concentration, while sage was half as potent producing such an effect at double the concentration (20%). Both rosemary and sage extracts were more inhibitory to sclerotial formation than to mycelial growth as the fungus ceased to produce any sclerotia at the lower concentrations of 5 and 5–10%, respectively. In addition, rosemary was highly effective in inhibiting sclerotia germination as total inhibition of germination occurred at 20% extract concentration at three?days and onward after incubation. Moreover, at this level, the survival of sclerotia was totally lost when examined after 12?days of incubation. For sage, inhibition of sclerotial germination/death was only 20% at 12th day of incubation. The results of this study indicate that the extracts of rosemary and Greek sage leaves could become natural alternatives to synthetic fungicides to manage diseases of S. sclerotiorum.     

Dibutyryl c-AMP as an inducer of sporidia formation: Biochemical and antigenic changes during morphological differentiation of Karnal bunt (<Emphasis Type="Italic">Tilletia indica</Emphasis>) pathogen in axenic culture

Effect of dibutyryl adenosine 3′,5′-cyclic monophosphate (dbc-AMP), an analogue of c-AMP, was investigated on growth and morphological differentiation ofTilletia indica. Exponential growth was observed up to 21 days in both presence and absence of dbc-AMP; however, increasing concentration of dbc-AMP was deleterious to mycelial growth in liquid culture. A slow increase of mycelial biomass up to 21 days and decline at 30 days in the presence of 2.5 mM dbc-AMP was observed, therefore, this concentration was chosen in subsequent investigations. The inhibitory influence of dbc-AMP was further substantiated by decrease in soluble protein. The fungus on exposure to dbc-AMP experienced morphological differentiation from vegetative mycelial phase to sporogenous mycelial phase, and was induced to produce filiform sporidia. Use of quantitative ELISA further suggested that sporidia formation took more than 21 days in the presence of dbc-AMP. Variations of proteins during different stages ofT. indica grown in the presence and absence of dbc-AMP suggested the expression of stage-specific proteins or differential expression of proteins induced by dbc-AMP. The changes in expression of cell surface antigens as evidenced from decrease and increase binding of anti-mycelial and anti-sporidial antibodies in dbc-AMP treated culture by ELISA was further interpreted on the basis of morphological differentiation from mycelial to sporidial phase     

Antifungal activity of some plant extracts on some pathogenic fungi

The inhibitory activity of five plant extracts viz. Artemisia absinthium L., Rumex obtusifolius L., Taraxacum officinale Weber ex Wiggers, Plantago lanceolata L. and Malva sylvestris L. were evaluated against the mycelial growth of three fungi Alternaria alternata (Fr.) Keissler, Penicillium expansum Link ex Thom. and Mucor piriformis Fisher that cause rot diseases in fruits and vegetables resulting in low yield and quality of fruits and vegetables. Results revealed that all the concentrations of plant extracts brought about significant inhibition in the mycelial growth of these pathogenic fungi. However, the highest concentration caused maximum inhibition in the mycelial growth followed by lower concentrations of plant extracts. The extract of A. absinthium leaves at highest concentration (S) proved highly effective in inhibiting the mycelial growth of all these pathogenic fungi followed by other plant extracts. These plants thus may have potential as the new natural fungicide for management of fungal rot diseases.