SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
The echinocandin caspofungin is a potent inhibitor of the activity of 1,3-beta-D-glucan synthase from Aspergillus flavus, Aspergillus terreus, and Aspergillus nidulans. In murine models of disseminated infection, caspofungin prolonged survival and reduced the kidney fungal burden. Caspofungin was at least as effective as amphotericin B against these filamentous fungi in vivo.
Fungicidal activity of wild plants Larrea tridentata, Karwinskia humboldtiana, Ricinus communis, Eucalyptus globulus, Ambrosia ambrosioides, Nicotiana glauca, Ambrosia confertiflora, Datura discolor, Baccharis glutinosa, Proboscidea parviflora, Solanum rostratum, Jatropha cinerea, Salpianthus macrodonthus y Sarcostemma cynanchoides was evaluated against the moulds species Aspergillus flavus, Aspergillus niger, Penicillium chrysogenum, Penicillium expansum, Fusarium poae y Fusarium moniliforme moulds species. Alcoholic extracts 6% (w/v) were prepared using six grams of dried plant powders (leaves and stems) and alcohol (70% ethanol or 70% methanol). A spore suspension (1x10(6); ufc/ml) of each mould was prepared by adding saline solution (0.85%) and 0.1% tween 80. The extracts were mixed with Czapeck yeast agar (CYA) at 45-50 degrees C in 1:10 relation on Petri dishes. Triplicate Petri dishes of each treatment and for each mould were centrally inoculated and three Petri dishes were used without treatment as controls. The inoculated dishes and controls were incubated at 25 +/- 2 degrees C for eight days. The incubated dishes were examined each 48 h and after the colony diameter (radial growth) was measured. Two mould species were controlled by L. tridentata, B. glutinosa and P. parviflora. Extracts of L. tridentata in methanol or ethanol at 41.5-100% inhibited all six species of moulds.
Cu,Zn superoxide dismutases (SODs) have been purified to homogeneity from Aspergillus flavus and A. niger, which are significant causative agents of aspergillosis, and from A. nidulans and A. terreus, which are much rarer causative agents of disease, using a combination of isoelectric focusing and gel filtration fast protein liquid chromatography. The purified enzymes have been compared with the previously described SOD from the most important pathogen in the genus, A. fumigatus (M. D. Holdom, R. J. Hay, and A. J. Hamilton, Free Radical Res. 22:519-531, 1995). The N-terminal amino acid sequences of the four newly purified enzymes were almost identical and demonstrated homology to known Cu,Zn SODs from a range of organisms including that from the previously described SOD from A. fumigatus. SOD activity was detectable in the culture filtrates of all species, and intracellular Cu,Zn SOD activity as a proportion of total protein was highest in early-log-phase cultures. The specific activities of the purified enzymes were similar, and all four of the newly described enzymes were inhibited by potassium cyanide and diethyldithiocarbamate, known Cu,Zn SOD inhibitors. Sodium azide and o-phenanthroline demonstrated inhibition at concentrations from 5 to 30 mM, and EDTA also exhibited a varying degree of inhibition of SOD activity. However, there were differences in the nonreduced molecular masses, the reduced molecular masses, and the isoelectric points of the four newly described SODs and the A. fumigatus enzyme; these varied from 55 to 123 kDa, 17.5 to 19.5 kDa, and 5.0 to 5.9, respectively. Of particular note was the observation that the A. fumigatus enzyme was thermostable compared with the SODs from the other species; in addition, the A.fiumigatus enzyme retained all of its activity at 37 degrees C relative to 20 degrees C, whereas the SODs of A. nidulans and A. terreus lost significant activity at the higher temperature. Aspergillus Cu,Zn SOD plays a hypothetical role in the avoidance of oxidative killing mechanisms, and our data suggest that the thermotolerant A. fumigatus Cu,Zn SOD would be more effective in such a protective system than, for example, the equivalent enzyme from the more rarely pathogenic A. nidulans.
Aspergillus spp. cause disease in a broad range of organisms, but it is unknown if strains are specialized for particular hosts. We evaluated isolates of Aspergillus flavus, Aspergillus fumigatus, and Aspergillus nidulans for their ability to infect bean leaves, corn kernels, and insects (Galleria mellonella). Strains of A. flavus did not affect nonwounded bean leaves, corn kernels, or insects at 22 degrees C, but they killed insects following hemocoelic challenge and caused symptoms ranging from moderate to severe in corn kernels and bean leaves injured during inoculation. The pectinase P2c, implicated in aggressive colonization of cotton balls, is produced by most A. flavus isolates, but its absence did not prevent colonization of bean leaves. Proteases have been implicated in colonization of animal hosts. All A. flavus strains produced very similar patterns of protease isozymes when cultured on horse lung polymers. Quantitative differences in protease levels did not correlate with the ability to colonize insects. In contrast to A. flavus, strains of A. nidulans and A. fumigatus could not invade living insect or plant tissues or resist digestion by insect hemocytes. Our results indicate that A. flavus has parasitic attributes that are lacking in A. fumigatus and A. nidulans but that individual strains of A. flavus are not specialized to particular hosts.
Aspergillus flavus utilized gallic acid as sole carbon source and increased in presence of glucose and sucrose. The enzymes were inducible in nature and during degradation of gallic acid. 4-carboxy, 2-hydroxy cis, cis-muconic acid and pyruvic acid were detected. The estradiol (meta) fission of gallic acid by A. flavus was postulated.
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.
Aspergillus flavus grown in a liquid medium containing pectin as the sole carbon source produced extracellular enzymes which degraded the 1,4-alpha-D-glycosidic bonds of pectin. The products of degradation were characteristic of substances produced by transeliminase. Synthesis of this enzyme was repressed by the addition of sucrose, glucose, fructose and maltose. The crude enzyme was partially purified by a combination of ultrafiltration and ammonium sulfate precipitation. The partially purified enzyme was separated by molecular exclusion chromatography into three components A, B and C, with molar masses ranging from 13.2 to 64 kDa. Only fraction B exhibited enzymic activity and further fractionated by ion-exchange chromatography into four components I-IV. Among these components, only fractions I and II possessed transeliminase activity. Both fractions had an optimum activity at pH 8.5 and 35 degrees C, and were stimulated by Ca2+, Mg2+, Na+ and K+ but inhibited by EDTA and DNP. The apparent Km for the degradation of pectin by fractions I and II were 6.2 and 8.0 g/L, respectively.
Aspergillus flavus produced approximately 50 U/mL of amylolytic activity when grown in liquid medium with raw low-grade tapioca starch as substrate. Electrophoretic analysis of the culture filtrate showed the presence of only one amylolytic enzyme, identified as an alpha-amylase as evidenced by (i) rapid loss of color in iodine-stained starch and (ii) production of a mixture of glucose, maltose, maltotriose and maltotetraose as starch digestion products. The enzyme was purified by ammonium sulfate precipitation and ion-exchange chromatography and was found to be homogeneous on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified enzyme had a molar mass of 52.5 +/- 2.5 kDa with an isoelectric point at pH 3.5. The enzyme was found to have maximum activity at pH 6.0 and was stable in a pH range from 5.0 to 8.5. The optimum temperature for the enzyme was 55 degrees C and it was stable for 1 h up to 50 degrees C. The Km and V for gelatinized tapioca starch were 0.5 g/L and 108.67 mumol reducing sugars per mg protein per min, respectively.
This research examines the distribution of aflatoxins among conidia and sclerotia of toxigenic strains of Aspergillus flavus Link and Aspergillus parasiticus Speare cultured on Czapek agar (21 days, 28 degrees C). Total aflatoxin levels in conidia and sclerotia varied considerably both within (intrafungal) and among strains. Aspergillus flavus NRRL 6554 accumulated the highest levels of aflatoxin (conidia: B1, 84000 ppb; G1, 566000 ppb; sclerotia: B1, 135000 ppb; G1, 968000 ppb). Substantial aflatoxin levels in conidia could place at risk those agricultural workers exposed to dust containing large numbers of A. flavus conidia. Cellular ratios of aflatoxin B1 to aflatoxin G1 were nearly identical in conidia and sclerotia even though levels of total aflatoxins in these propagule types may have differed greatly. Aflatoxin G1 was detected in sclerotia of all A. flavus strains but in the conidia of only one strain. Each of the A. parasiticus strains examined accumulated aflatoxin G1 in both sclerotia and conidia. These results are examined in the context of current evolutionary theory predicting an increase in the chemical defense systems of fungal sclerotia, propagules critical to the survival of these organisms.
Aspergillus flavus, like approximately one-third of ascomycete fungi, is thought to be cosmopolitan and clonal because it has uniform asexual morphology. A. flavus produces aflatoxin on nuts, grains, and cotton, and assumptions about its life history are being used to develop strategies for its biological control. We tested the assumptions of clonality and conspecificity in a sample of 31 Australian isolates by assaying restriction site polymorphisms from 11 protein encoding genes and DNA sequences from five of those genes. A. flavus isolates fell into two reproductively isolated clades (groups I and II). The lack of concordance among gene genealogies among isolates in one of the clades (group I) was consistent with a history of recombination. Our analysis included five strains of the closely related industrial fungus A. oryzae, all of which proved to be clonally related to group I.
The aim of this study was to test the suitability of the RT-PCR (reverse transcription-polymerase chain reaction) technique to differentiate aflatoxin-producing from aflatoxin-non-producing strains of Aspergillus flavus and Aspergillus parasiticus. Total RNAs of 13 strains grown under inducing yeast extract-sucrose (YES) and non-inducing yeast extract-peptone (YEP) media, respectively, were analyzed by using specific primers based on the conserved regions of nine structural genes (aflD, aflG, aflH, aflI, aflK, aflM, aflO, aflP, and aflQ) and two regulatory genes aflS and aflR of the aflatoxin B1 biosynthetic pathway. Transcription was confirmed by the expression of the beta-tubulin gene. The expression of the majority aflatoxin biosynthetic genes including aflR and aflS of all strains varied with regard to the aflatoxin-producing ability and the growth conditions. Nonetheless, we found that the expression profile of the three genes aflD, aflO, and aflP was consistently correlated with a strain's ability to produce aflatoxins or not in YES as well as the inability to produce aflatoxins in YEP. The devised RT-PCR profiling method reflects aflatoxin concentrations ranging from 0.1 to 60 microg/ml of the culture filtrates as determined by fluorescence HPLC. The results are discussed in relation to the suitability of RT-PCR as well as cDNA-based array techniques in diagnostic laboratory settings where individual isolates are being tested for potential toxin production to identify toxigenic isolates of Aspergillus species.
Aspergillus flavus and Aspergillus parasiticus produced ethylene during early growth. However, the onset of toxin biosynthesis was marked by the absence of ethylene evolution. 2-Chloroethyl phosphonic acid, an ethylene-generating compound, inhibited aflatoxin biosynthesis in vivo. The reciprocal relationship between the production of aflatoxin and ethylene by the organism may indicate the involvement of the latter in the regulation of aflatoxin biogenesis.
Contamination of food and feedstuffs by Aspergillus species and their toxic metabolites is a serious problem as they have adverse effects on human and animal health. Hence, food contamination monitoring is an important activity, which gives information on the level and type of contamination. A PCR-based method of detection of Aspergillus species was developed in spiked samples of sterile maize flour. Gene-specific primers were designed to target aflR gene, and restriction fragment length polymorphism (RFLP) of the PCR product was done to differentiate Aspergillus flavus and Aspergillus parasiticus. Sterile maize flour was inoculated separately with A. flavus and A. parasiticus, each at several spore concentrations. Positive results were obtained only after 12-h incubation in enriched media, with extracts of maize inoculated with A. flavus (101 spores/g) and A. parasiticus (104 spores/g). PCR products were subjected to restriction endonuclease (HincII and PvuII) analysis to look for RFLPs. PCR-RFLP patterns obtained with these two enzymes showed enough differences to distinguish A. flavus and A. parasiticus. This approach of differentiating these two species would be simpler, less costly and quicker than conventional sequencing of PCR products.
This study examined the potential for controlling toxigenic Aspergillus flavus and Aspergillus parasiticus by biological means using a myxobacterium commonly found in soil. The ability of Nannocystis exedens to antagonize A. flavus ATCC 16875, A. flavus ATCC 26946, and A. parasiticus NRRL 3145 was discovered. Cultures of aflatoxigenic fungi were grown on 0.3% Trypticase peptone yeast extract agar for 14 days at 28 degrees C. When N. exedens was grown in close proximity with an aflatoxigenic mold, zones of inhibition (10 to 20 mm) developed between the bacterium and mold colony. A flattening of the mold colony on the sides nearest N. exedens and general stunting of growth of the mold colony were also observed. When N. exedens was added to the center of the cross-streak of a mold colony, lysis of the colony by the bacterium was observed after 24 h. Microscopic observations revealed that N. exedens grew on spores, germinating spores, hyphae, and sclerotia of the molds. These results indicate that N. exedens may be a potential biocontrol agent against A. flavus and A. parasiticus.
The distribution of Aspergillus flavus and Aspergillus parasiticus in sugarcane field soils and on harvested sugarcane stems was studied on seven islands of Okinawa and Kagoshima Prefectures, the southernmost prefectures in Japan. With the use of a combination of dilution plate and plant debris plate techniques, the fungi were detected on all seven islands studied and in 74% of 53 soil samples. The fungi were also found on the cut surfaces of sugarcane stems from one of the islands. A. parasiticus was the predominant fungus, although many atypical A. parasiticus isolates that produced metulated conidial heads were also obtained. The proportions of isolates testing positive for aflatoxin production were ca. 89% (146 of 164) of all isolates and ca. 69% of A. flavus isolates. More than 40% of A. flavus isolates also produced G aflatoxins. Scanning electron microscopic observation of conidial wall texture was useful in distinguishing A. parasiticus from A. flavus. Cyclopiazonic acid, an indole mycotoxin, was never synthesized by any of the A. parasiticus or G aflatoxin-producing A. flavus isolates tested.
This study aimed to determine the effect of bread making steps on the stability of aflatoxin. Sakha 8 wheat and Gemaiza 5 wheat cultivars, were used in the present study. They were inoculated with a dense spore suspension of toxigenic fungal species of Aspergillus flavus and a non toxigenic species of Aspergillus ochraceus singly and combined. Aflatoxin concentration was determined in the whole wheat grain, after milling, after fermentation, and after bread-baking process. Results showed that the highest reduction percentage for the total aflatoxins (81, G1 and G2), was in Sakha 8 (32.96%) (single treatment), Gemaiza 5 (19.54%) (single treatment ), Gemaiza 5 (18.65%) (combined treatment), and finally in Sakha 8 (16.49%) (combined treatment). There was no significant difference (p < 0.05) in aflatoxins content between Sakha 8 and Gemaiza 5 treated singly and in a combined way before and after milling process. In the mean time, the percentage of AFB1, AFG1 and AFG2 were reduced by 31.98%, 44.53% and 35.35%, respectively, while the total aflatoxins concentration were reduced by 41.17% after baking. Results also showed the presence of a significant difference at p < 0.05 among the whole grain, after milling and after baking concerning AFG1, AFG2 and the total aflatoxins content. No significant difference was found in case of AFB1.
Elastolytic and elastase inhibitory activities were investigated for 13 strains of Aspergillus fumigatus, three strains of Aspergillus flavus and three strains of Aspergillus niger. Nine of the 13 strains of A. fumigatus and all strains of A. flavus demonstrated elastase activity (more than 1 unit ml(-1)). Six of the 13 strains of A. fumigatus and all strains of A. flavus expressed elastase inhibitory activity (more than 2 units ml(-1)). However, no elastase or elastase inhibitory activities were observed with A. niger. It was also found that crude elastase inhibitors from six strains of A. fumigatus and two strains of A. flavus were stable to heat treatment at 100 degrees C for 10 min. In addition, human leukocyte elastases were inhibited by crude elastase inhibitors from A. fumigatus and A. flavus; however, no effect was observed on the elastase derived from porcine pancreas.
A mixed culture of Aspergillus nidulans (GH79) and Aspergillus flavus (CMI 91019B) produced two antibiotics, designated VI and VII, which were not elaborated when either fungus was grown alone. Chemical and spectroscopic analysis of VI, the major component, indicated that this compound was identical to hydroxyaspergillic acid. The minor component, VII, was produced in too low a yield for its identity to be established. However, partial characterization suggests that this antibiotic also belongs to the aspergillic acid group of mycotoxins.