Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Aspergillus”

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.

At least 109 records · Page 6Linked to original sources
PubMed1983

Aspects of genetic interaction in hybrids of Aspergillus nidulans and Aspergillus rugulosus obtained by protoplast fusion.

Hybrids were produced by protoplast fusion between strains of Aspergillus rugulosus and mitotic master strains of Aspergillus nidulans with a genetic marker on each linkage group. Analysis of segregants induced by growth on benomyl revealed recombination between every pair of unlinked markers. Parental combinations of markers were often recovered at significantly higher frequencies than expected. This aberrant segregation was not correlated with any particular pair of linkage-groups and was attributed to inter-species incompatibility. The segregation of genetic markers of A. rugulosus from the hybrids suggested that A. nidulans and A. rugulosus may differ in haploid chromosome number and chromosome size. In sexual crosses between A. nidulans and strains containing chromosomes of mixed parental origin recombinants were recovered. The results support the classification of A. nidulans and A. rugulosus as separate species.

Aspergillus↗
PubMed1984

Aspergillic acids produced by mixed cultures of Aspergillus flavus and Aspergillus nidulans.

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.

Anti-Bacterial Agents↗
PubMed1993

Purification and characterization of glucose-6-phosphate dehydrogenase from Aspergillus niger and Aspergillus nidulans.

Glucose-6-phosphate dehydrogenase (G6PD; D-glucose 6-phosphate:NADP+ oxidoreductase, EC 1.1.1.49) has been purified from Aspergillus nidulans and Aspergillus niger by a combination of affinity and anion exchange chromatography. A 500-1000-fold purification was obtained and the final enzyme preparations were shown to be pure but not homogeneous. For both fungi the purified enzyme preparation gave two bands on native and denaturing gels. The catalytically active form is a multimer. The molecular mass of the monomers is 60 and 57 kDa for A. nidulans and 55 and 53 kDa for A. niger. Both enzymes exhibited strict specificity towards both substrates glucose 6-phosphate and NADP+. The A. nidulans and A. niger G6PD enzymes catalyse the conversion of glucose 6-phosphate via a random order mechanism. Inhibition studies provided evidence for the physiological role of G6PD as producer of NADPH in both fungi.

Aspergillus nidulans↗
PubMed2000

Landmarks in the early duplication cycles of Aspergillus fumigatus and Aspergillus nidulans: polarity, germ tube emergence and septation.

When the spores of filamentous fungi break dormancy, nuclear division is accompanied by a series of ordered morphological events including the switch from isotropic to polar growth, the emergence of a second germ tube from the conidium and septation. Correlation of these morphological events with nuclear number allows them to serve as duplication cycle landmarks. Early duplication cycle landmarks have been characterized in Aspergillus nidulans, but not in other filamentous fungi. To learn more about duplication cycle control in filamentous fungi, a study was undertaken to compare the timing of landmarks in Aspergillus fumigatus and A. nidulans. Nuclear duplication took approximately 45 min in A. fumigatus, with mitosis occupying roughly 5% of this period. Under the same conditions, nuclear duplication in A. nidulans took approximately 60 min, with mitosis occupying roughly 4% of this period. In A. fumigatus the isotropic to polar switch preceded the first mitosis in 22% of cells, while in A. nidulans the isotropic to polar switch did not occur until after the first mitosis. In both A. fumigatus and A. nidulans the earliest emergence of a second germ tube from the conidium occurred after the third mitotic division. However, by the fifth mitosis only 19% of A. fumigatus conidia had a second germ tube, compared to 98% of A. nidulans conidia. In both A. fumigatus and A. nidulans, formation of the first septum occurred after the fourth mitotic division. In all experiments a few cells lagged behind the others in nuclear number. In this delayed group, it was common to see landmark events at an earlier mitotic division. Differences in nuclear number when identical landmarks occur in A. fumigatus versus A. nidulans, and uncoupling of mitotic division and landmarks in delayed cells suggest that nuclear division and morphogenesis lie in parallel pathways, perhaps coordinated by checkpoints.

Aspergillus fumigatus↗
PubMed2002

cAMP alteration of growth rate of Aspergillus fumigatus and Aspergillus niger is carbon-source dependent.

cAMP signalling has been shown to be essential for normal growth, morphology and virulence in fungal pathogens of both plants and animals. The effects of exogenous cAMP on the growth of the opportunistic pathogen Aspergillus fumigatus were compared to those of Aspergillus niger, which has previously been demonstrated to respond to extracellular cAMP. Both cAMP and phosphodiesterase inhibitors markedly reduced the radial growth rate of A. niger after 48 h on minimal medium with glucose as the carbon source, whereas the growth of A. fumigatus was not affected by cAMP. However, when glycerol, which does not initiate carbon catabolite repression, was used as a carbon source, cAMP inhibited the radial growth rate of only A. fumigatus (P<0.05). The addition of cAMP to glycerol-minimal medium resulted in a fourfold increase in protein kinase A activity in A. fumigatus cell extracts when compared with pre-treatment samples. The protein kinase A activity in A. fumigatus cell extracts from cultures grown in glucose did not change significantly with the addition of cAMP. These studies demonstrate that although the growth rates of both A. fumigatus and A. niger are sensitive to the addition of exogenous cAMP, the response of each organism is distinct and dependent on the carbon source used.

Aspergillus fumigatus↗
PubMed1975

Hybridization and selection for increased penicillin titre in wild-type isolates of Aspergillus nidulans.

Repeated hybridization and selection among wild-type isolates produced strains of Aspergillus nidulans with increased penicillin titre. Four independent selection lines were established, each originating from a sexual cross between two different heterokaryon-incompatible wild-type isolates. In each generation, two selected high-titre sister strains were crossed to produce the next generation. An initial increase in titre was obtained in each line, but after four or five generations of selection the genetic variation was considerably reduced and the rate of response to selection had decreased. From a base population of wild-type isolates with a mean titre of 8-6 units/ml the progeny mean titre was raised to between 16 and 20 units/ml in each line. The gradual nature of the response suggests that a number of genes determine penicillin titre in the wild-type isolates used. The gene action throughout the selection programme was predominantly additive.

Aspergillus nidulans↗
PubMed1999

Aspergillus fumigatus catalases: cloning of an Aspergillus nidulans catalase B homologue and evidence for at least three catalases.

The presence of catalases in the water soluble fractions of three Aspergillus fumigatus strains was investigated using non-denaturing and denaturing polyacrylamide gel electrophoresis and Western analysis. Using non-denaturing polyacrylamide gel electrophoresis and staining for catalase activity, three separate catalases were identified. An A. fumigatus catalase gene (catB) was cloned from genomic DNA using the Aspergillus niger catR gene as a probe. Polyclonal antibodies were raised to a glutathione S-transferase-CatB fusion product expressed in Escherichia coli. Western analysis indicated that, under denaturing conditions, the polyclonal antibody recognised a 90-kDa band and under non-denaturing conditions, two separate bands were identified. These results indicate that A. fumigatus in addition to CatB, produces at least two other catalases, one of which is similar in size to CatB. The polyclonal antibody was also used to observe catalase expression in mice, experimentally infected with A. fumigatus. Staining was observed heterogeneously throughout the fungal hyphae. This result indicates that catalase is produced by A. fumigatus during invasive aspergillosis.

Animals↗
PubMed1998

Transcript of a homolog of aflR, a regulatory gene for aflatoxin synthesis in Aspergillus parasiticus, was not detected in Aspergillus oryzae strains.

Some strains of Aspergillus oryzae were shown to have homologs of aflR, a regulatory gene for aflatoxin synthesis in Aspergillus parasiticus. Transcription of an aflR homolog was examined in six strains of A. oryzae having the homologs, using polymerase chain reaction (PCR) coupled with reverse transcription. No PCR product was obtained when the RNA prepared from the A. oryzae strains cultivated under aflatoxin-producing condition was used as template for amplification of the aflR cDNA. By contrast, a PCR product of the expected size was obtained with RNA from A. parasiticus NIAH-26 processed by the same procedure. From genomic DNA of these strains, PCR products of the same size as above were obtained. Possible degradation of the aflR mRNA in the RNA preparation of the A. oryzae strains was negligible, because the calmodulin transcript was detected by PCR from the same RNA samples. Thus, the aflR homologs in the non-aflatoxigenic A. oryzae strains examined are not expressed even under aflatoxin-producing condition.

Aflatoxins↗
PubMed1999

The Aspergillus niger acuA and acuB genes correspond to the facA and facB genes in Aspergillus nidulans.

Mutants in Aspergillus niger unable to grow on acetate as a sole carbon source were previously isolated by resistance to 1.2% propionate medium containing 0.1% glucose. AcuA mutants lacked acetyl-CoA synthetase (ACS) activity and acuB mutants lacked both ACS and isocitrate lyase activity. An acuA mutant was transformed to the acu+ phenotype with a clone of ACS (facA) from Aspergillus nidulans. The acuB mutant was transformed with the A. niger facB clone which has been identified by cross-hybridisation of an A. nidulans facB clone. These results confirm that acuA in A. niger is the gene for ACS and acuB is analogous to the A. nidulans facB regulatory gene.

Acetate-CoA Ligase↗
PubMed2000

Aspergillus fumigatus alb1 encodes naphthopyrone synthase when expressed in Aspergillus oryzae.

Conidial pigment biosynthesis is an important virulence factor in Aspergillus fumigatus, a human fungal pathogen. Involvement of DHN-melanin pathway in the biosynthesis of A. fumigatus conidial pigment implies that the Alb1p polyketide synthase (PKS) is a 1,3,6, 8-tetrahydroxynaphthalene (T4HN) synthase. The Alb1p, however, shows higher sequence similarity to a naphthopyrone synthase than to a T4HN synthase. To clarify the function of Alb1p, the alb1 gene was overexpressed in a heterologous host Aspergillus oryzae. The Alb1p PKS product in this heterologous expression system was identified as heptaketide naphthopyrone instead of pentaketide T4HN. The data suggest that Alb1p is a naphthopyrone synthase.

Aspergillus fumigatus↗
PubMed2004

In vitro evaluation of double and triple combinations of antifungal drugs against Aspergillus fumigatus and Aspergillus terreus.

Microdilution broth checkerboard techniques based on the National Committee for Clinical Laboratory Standards methodology were used to study double and triple antifungal combinations against clinical isolates of Aspergillus fumigatus and A. terreus. The influences of the end-point definition (partial or complete inhibition) and the mode of reading (visually or spectrophotometrically) were determined. Interactions between antifungal drugs were also evaluated by agar diffusion tests. Combinations of caspofungin with either amphotericin B or voriconazole were additive for all the isolates, and antagonism was not observed. The interaction between caspofungin and flucytosine was synergistic for 62% of the isolates. In contrast, the interaction between voriconazole and flucytosine was never synergistic and antagonism was noted for 93% of the isolates. The triple combination of caspofungin with flucytosine and amphotericin B was synergistic for all the isolates tested. The triple combination of caspofungin with flucytosine and voriconazole was also mostly synergistic; but complex interactions were obtained for some isolates, with synergy or antagonism depending on the concentrations of caspofungin and voriconazole. Analysis of the influence of the reading technique on the results showed that spectrophotometric reading was a good alternative to the recommended visual reading. The results of these in vitro tests suggest that the activity of flucytosine as part of a double combination with caspofungin and as part of a triple combination with caspofungin and amphotericin B against Aspergillus spp. warrants further investigations. Animal studies are needed to evaluate the in vivo efficacies of these combinations.

Antifungal Agents↗
PubMed1983

Effect of specific amino acids on growth and aflatoxin production by Aspergillus parasiticus and Aspergillus flavus in defined media.

Four amino acids were used as sole nitrogen sources or as supplements to ammonium sulfate, and casein and ammonium sulfate were used as sole nitrogen sources to examine their effects on aflatoxin production by Aspergillus parasiticus NRRL 2999 and Aspergillus flavus 3357 grown on synthetic liquid media. In general, when proline, asparagine, casein, and ammonium sulfate were used as sole nitrogen sources, they supported more growth and toxin production than tryptophan or methionine. However, proline stimulated more toxin production per gram of mycelium in stationary cultures than the other nitrogen sources, including the amino acid asparagine, which is generally recognized as supporting good aflatoxin production. The exact responses to individual nitrogen sources were influenced by the species of fungus and whether cultures were stationary or shaken. In shake cultures, but not in stationary cultures, increased growth was generally associated with increased toxin production.

Aflatoxins↗
PubMed1985

Possible implications of reciprocity between ethylene and aflatoxin biogenesis in Aspergillus flavus and Aspergillus parasiticus.

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.

Aflatoxins↗
PubMed1997

The faeA genes from Aspergillus niger and Aspergillus tubingensis encode ferulic acid esterases involved in degradation of complex cell wall polysaccharides.

We report the cloning and characterization of a gene encoding a ferulic acid esterase, faeA, from Aspergillus niger and Aspergillus tubingensis. The A. niger and A. tubingensis genes have a high degree of sequence identity and contain one conserved intron. The gene product, FAEA, was overexpressed in wild-type A. tubingensis and a protease-deficient A. niger mutant. Overexpression of both genes in wild-type A. tubingensis and an A. niger protease-deficient mutant showed that the A. tubingensis gene product is more sensitive to degradation than the equivalent gene product from A. niger. FAEA from A. niger was identical to A. niger FAE-III (C. B. Faulds and G. Williamson, Microbiology 140:779-787, 1994), as assessed by molecular mass, pH and temperature optima, pI, N-terminal sequence, and activity on methyl ferulate. The faeA gene was induced by growth on wheat arabinoxylan and sugar beet pectin, and its gene product (FAEA) released ferulic acid from wheat arabinoxylan. The rate of release was enhanced by the presence of a xylanase. FAEA also hydrolyzed smaller amounts of ferulic acid from sugar beet pectin, but the rate was hardly affected by addition of an endo-pectin lyase.

Amino Acid Sequence↗
PubMed1994

HYP1, a hydrophobin gene from Aspergillus fumigatus, complements the rodletless phenotype in Aspergillus nidulans.

Aspergillus fumigatus produces conidia that are highly dispersable and resistant to degradation. We have sought to analyze these properties by studying the rodlets which form the outer spore coat protein. Degenerate primers based on hydrophobins in other fungi were applied to genomic DNA from A. fumigatus in PCR. A product of this reaction with similarity to an Aspergillus nidulans gene as judged by Southern hybridization was chosen for further study. Cloning and sequencing revealed a gene with two introns which encodes a protein of 159 amino acids. Structural characteristics consistent with those of other fungal hydrophobin genes, especially conserved cysteine residues, are present. The expression of the gene is limited to the developmental stages in which maturing conidiophores are present. This A. fumigatus gene, HYP1, was used to transform a mutant strain of A. nidulans that lacks rodlets. Transformants with a single copy of HYP1 expressed a rodlet layer on their conidia as observed by freeze-fracture electron microscopy.

Amino Acid Sequence↗
PubMed1977

Distribution and conformation of crystalline nigeran in hyphal walls of Aspergillus niger and Aspergillus awamori.

Hyphal walls of Aspergillus awamori containing increased amount of the alpha-glucan, nigeran, became correspondingly more opaque when viewed in the electron microscope as shadowed preparations. However, increased polymer deposition was not accompanied by any significant change in wall thickness. The nigeran of both A. awamori and Aspergillus niger occurred in situ in a crystalline conformation identical to that of single crystals prepared with pure polysaccharide. Furthermore, this polymer was the dominant crystalline material in the hyphae whether or not they were enriched in nigeran. Enzymic digestion of nigeran in A. niger and A. awamori revealed that the bulk of the polymer was exposed to the cell's exterior. However, a certain fraction was accessible to enzymic attack only after the wall was treated with boiling water. A third portion, detectable only by x-ray diffraction, was associated with other components and could not be extracted, even with prolonged boiling. It was removed by hot, dilute alkali and was associated in the wall with another glucan fraction. Dry heating of A. niger walls altered their susceptibility to enzymic digestion of nigeran in situ. It is proposed that this treatment introduces interstices in the crystal surface that facilitate attack.

Aspergillus↗
PubMed1999

Biotransformation of hinesol isolated from the crude drug Atractylodes lancea by Aspergillus niger and Aspergillus cellulosae.

Biotransformation of the sesquiterpene alcohol hinesol (1) with spasmolytic activity, which was prepared from the rhizome of Atractylodes lancea, was carried out by Aspergillus niger and Aspergillus cellulosae IFO 4040. Compound 1 was easily converted to compounds 2-9 by A. niger, and compounds 10 and 11 by A. cellulosae, respectively. Their stereostructures were established by a combination of high-resolution NMR spectral analysis, X-ray crystallographic analysis, and chemical reactions such as epoxydation.

Aspergillus↗
PubMed2002

Cloning and characterization of the nagA gene that encodes beta-n-acetylglucosaminidase from Aspergillus nidulans and its expression in Aspergillus oryzae.

We isolated a beta-N-acetylglucosaminidase encoding gene and its cDNA from the filamentous fungus Aspergillus nidulans, and designated it nagA. The nagA gene contained no intron and encoded a polypeptide of 603 amino acids with a putative 19-amino acid signal sequence. The deduced amino acid sequence was very similar to the sequence of Candida albicans Hex1 and Trichoderma harzianum Nag1. Yeast cells containing the nagA cDNA under the control of the GAL1 promoter expressed beta-N-acetylglucosaminidase activity. The chromosomal nagA gene of A. nidulans was disrupted by replacement with the argB marker gene. The disruptant strains expressed low levels of beta-N-acetylglucosaminidase activity and showed poor growth on a medium containing chitobiose as a carbon source. Aspergillus oryzae strain carrying the nagA gene under the control of the improved glaA promoter produced large amounts of beta-N-acetylglucosaminidase in a wheat bran solid culture.

Acetylglucosaminidase↗