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At least 19 recordsLinked to original sources
PubMed1976

Physiology and characterization of a fungal milk-clotting enzyme from Aspergillus flavus.

Aspergillus flavus produced extracellularly an active rennin-like enzyme when grown aerobically in whey media. The enzyme was detected at early stages of growth reaching a maximum after three to four days at 25 degrees. The activity was destroyed by heating to temperatures higher than 50 degrees, whereas the presence of skim milk during heating preserved the enzyme activity, at least, up to 70 degrees. Calcium chloride significantly stimulated the milk-clotting activity up to 1% final concentration. The clotting time was inversely proportional to protein concentration in the range 0.2-0.6 mg/ml and the enzyme exhibited marked stability when stored at 37 degrees at pH 6.

Animals↗
PubMed1979

Biosynthesis of fat in surface culture of a local strain of Aspergillus flavus.

An Aspergillus flavus strain isolated from Egyptian soil produced fat in appreciable amounts. General evidence for the operation of the tricarboxylic acid cycle in this organism has been ascertained by the detection of citric, malic and fumaric acids in the metabolized culture solution. Maximum fat yield was attained after seven days of incubation. The lower intial pH value of the media favoured the fat obtained from the felts and raised its acid value. When the felts were sterilized in their acidic metabolism solutions increased the acid values of the fats over those of fats extracted from felts sterilized in distilled water. The felts autoclaved for the longest time produced the highest yields of fat with the highest free acidity. The employment of calcium carbonate in the nutrient solutions raised appreciably the acid values of the fats and suppressed the other metabolic activities.

Aspergillus flavus↗
PubMed2026

Genetic diversity and antifungal susceptibility among ecological niche populations of Aspergillus flavus in Yaoundé, Cameroon.

Aspergillus flavus is a ubiquitous fungus commonly found in a variety of ecological niches including soil, crops, the air, and humans. In humans, it is the second leading cause of invasive aspergillosis (IA) and is linked to other illnesses through contamination of agricultural products with aflatoxins. As such, A. flavus threatens food safety, economic wellbeing, and human health, particularly in less developed regions and countries such as Cameroon. To mitigate these effects, farmers and clinicians rely on triazoles to reduce aflatoxin contamination and treat IA. However, a consequence of increasing triazole use is the emergence and spread of triazole resistance in both agriculture and clinics. To identify the prevalence of triazole resistance and the potential genetic relationships among triazole resistant and susceptible strains, this study investigated antifungal susceptibility to both clinical and agricultural triazoles and analyzed genetic variation among various ecological niche populations of A. flavus in Cameroon. Strain genotypes were obtained through analysis of six polymorphic microsatellite markers. Our analyses revealed that 30.3% (17/56) of the strains were resistant to at least one of the four triazoles, with increased minimum inhibitory concentrations found among crop-isolated strains. A Permutational Multivariate Analysis of Variance suggested limited ecological niche-based clustering of genotypes, consistent with frequent gene flow and dispersal among ecological niches. A multilocus linkage disequilibrium analysis revealed evidence of non-random recombination in A. flavus. Overall, this study elucidates the interplay between ecological pressures, antifungal resistance, and genetic differentiation, and invites alternative methods to control aflatoxin contamination in foods without the use of agricultural fungicides.

Aspergillus flavus↗
PubMed1978

Aspergillus flavus keratitis.

Corneal infection due to the species Aspergillus flavus is rare and often destructive. This report describes a case of Aspergillus flavus corneal ulcer that failed to respond to amphotericin B, pimaricin, and clotrimazole. The eye subsequently became phthisical. The rational approach to the management of fungal corneal infection is to culture or perform sensitivity tests on the isolated organism. Early surgical intervention should be done if the infection fails to respond to medical treatment, and if the disease process extends deep into the stromal tissue and anterior chamber. Fungal malignant glaucoma requires excisional keratoplasty, lens extraction, and anterior vitrectomy.

Aspergillosis↗
PubMed1976

Synthesis of chitin by particulate preparations from Aspergillus flavus.

Cell-free extracts from Aspergillus flavus catalyzed the synthesis of chitin from UDP-GlcNAc. Most of the activity was associated with membrane-rich fractions whereas no activity was detected in the cell walls. Chitin synthetase was activated by fungal acid proteases; animal and plant proteases destroyed it. Upon incubation at 0 C and 28 C chitin synthetase was inactivated, probably by the action of proteases present in the particulate preparations. Maximal activity was obtained at pH 6.6-7.1 and 15 C. Arrhenius plot showed a biphasic curve with the transition at 7 C. E values were 3300 Kcal/mole above this temperature and 15500 Kcal/mole below it. The enzyme was activated by GlcNAc and required a divalent metal, the most active being Mg++. By plotting v vs UDP-GlcNAc concentration a sigmoidal curve was obtained. Km calculated at high substrate concentrations was 20 mM. Chitin synthetase was competitively inhibited by polyoxin D (Ki 6.5 muM) and (Ki 1.35 mM), the latter giving complex kinetics.

Anti-Bacterial Agents↗
PubMed1977

Production of cyclopiazonic acid by Aspergillus flavus Link.

Production of cyclopiazonic acid by Aspergillus flavus is reported for the first time. A procedure for its production by agitated solid substrate fermentation on red wheat is described along with the isolation procedure and physical and chemical properties of this indole derivative. The compound has been found to exert antibacterial activity.

Aspergillus flavus↗
PubMedDate not supplied

[Dynamics of B1 aflatoxin and Aspergillus flavus spore formation on rye and wheat grain].

Rye and wheat grain was infected with Aspergillus flavus spores. The dynamics of B1 aflatoxin and spore formation was studied. The synthesis of B1 aflatoxin in the mold-affected grain started simultaneously with the emergence of fungal spores; its further accumulation in the grain correlated with an increase in the spore number till the stage of maximum spore formation. The highest level of aflatoxin synthesis was inversely proportional to the number of Aspergillus flavus spores which infected the grain before its molding.

Aflatoxins↗
PubMed1978

Cyclopiazonic acid production by aflatoxigenic and non-aflatoxigenic strains of Aspergillus flavus.

Twenty-eight of 54 isolates of Aspergillus flavus grown on autoclaved agricultural commodities such as wheat, rice and corn were found to produce the mycotoxin cyclopiazonic acid. Eighteen of the A. flavus isolates produced aflatoxin, and fourteen isolates produced both cyclopiazonic acid and aflatoxin. A preliminary screening of some aflatoxin-contaminated corn samples revealed for the first time the natural occurrence of cyclopiazonic acid in agricultural commodities.

Aflatoxins↗
PubMed1975

Inhibition of growth of Aspergillus flavus and Trichoderma viride by peanut embryos.

Growth of Aspergillus flavus and Trichoderma viride on agar media was inhibited around embryos of green peanut seeds but not around embryos of cured seeds, intact peanut seeds, or testae. Both fungi were able to colonize intact seeds and testae. Substances inhibitory to A. flavus and T. viride were extracted with acetone from cotyledons of freshly harvested peanut seeds. Four compounds inhibitory to A. flavus were detected in crude acetone extracts. Three of the compounds demonstrated properties of phenolics. Results of this study suggest that inhibitory compounds in peanut cotyledons may play a role in protecting the peanut embryo from fungal infection.

Antifungal Agents↗
PubMed1979

[Effect of the fungal metabolites of Aspergillus flavus and A. niger on the tissue sorptive capacity of the large intestine].

Effects of metabolites of the tiny fungi of Aspergillus flavus and A. niger on the ability of mucuos membrane cells of the large intestine to absorb and exterminate certain dyes has been studied experimentally on guinea-pigs. It has been shown that under these influences, a violation of the cell and tissue metabolism in the large intestine occurs, namely, the absorbtion of the neutral red increased by 1.7 and 1.4 times, respectively, and the processes of extermination of the cells were inhibited by 1.5--1.6 times.

Animals↗
PubMed1977

Modification of the radiation resistance of Aspergillus flavus mycelial units by some chemicals.

Survival curves for the mycleium of Aspergillus flavus Link var. columnaris Raper and Fennell were constructed after irradiation with gamma rays in the presence of NaCl, NaBr, NaI, KCl, KBr, KI, CaCl2, CaBr2, CaI2, Ca(NO3)2, NaNO2, NaNO3, KNO2, iodoacetic acid, iodoacetamide and vitamin K5. In addition iodized salt was also tested. All the chemicals tested exhibited initial toxicity at zero dose. However, most of the chemicals demonstrated a synergism when present during irradiation. Compounds containing iodine were invariably the strongest radiosensitizers. The iodine present as an admixture in salt also retained its radiosensitizing character. Sodium bromide and calcium bromide behaved in a different way. The initial toxicity was reduced along with an increase in radiation dose resulting in more survival.

Aspergillus flavus↗
PubMed1979

Multiple toxin production by an isolate of Aspergillus flavus.

Three toxins were recovered from rice and wheat cultures of an isolate of Aspergillus flavus. The toxins were present simultaneously in the cultures after one or two weeks incubation and were identified as aflatoxin, cyclopiazonic acid and aflatrem, a recently identified indole-mevalonate metabolite.

Aflatoxins↗
PubMed1979

[Effect of sterigmatocystin on the toxinogenesis of the Aspergillus flavus group].

The aflatoxinogenesis of Aspergillus parasiticus is significantly enhanced by the presence, in the medium, of sterigmatocystin at a high level (35--50 microgram/ml); low concentrations, in the order of 175 microgram/ml, have no effect on the production of aflatoxins. During the period where the aflatoxinogenesis of the culture is high, no variation of the sterigmatocystin level is noted, Experiments with 14C-sterigmatocystin indicate that the mold does not utilize the metabolite itself as a precursor of aflatoxins.

Aflatoxins↗
PubMed1977

Regulation of aflatoxin biosynthesis. 2 Comparative study of tricarboxylic acid cycle in aflatoxigenic and non-aflatoxigenic strains of Aspergillus flavus.

The presence of a functional TCA cycle and its intermediates has been shown in Aspergillus parasiticus and Aspergillus flavus. The role of the TCA cycle in aflatoxin biosynthesis has been studied. In A. parasiticus the TCA cycle was activated on the second day of growth (exponential growth phase) resulting in the onset of aflatoxin biosynthesis. Pyruvate accumulation to toxic levels in A. parasiticus is suggested to shift the growth phase from exponential to stationary with the onset of aflatoxin biosynthesis. In A. flavus, a non-aflatoxigenic strain, no pyruvate accumulation was observed. Moreover, the onset of aflatoxin production in A. parasiticus was followed by a decline in the levels of TCA cycle intermediates indicating their possible utilization in secondary metabolite synthesis. Accumulation of TCA cycle intermediates in A. flavus is suggested to be due to non-diversion to aflatoxin biosynthesis.

Aflatoxins↗