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PubMed1997

Arabinoxylan degradation by fungi: characterization of the arabinoxylan-arabinofuranohydrolase encoding genes from Aspergillus niger and Aspergillus tubingensis.

The genes encoding the enzyme arabinoxylan arabinofuranohydrolase, which releases L-arabinose from arabinoxylan, have been cloned from the closely related fungi Aspergillus niger and Aspergillus tubingensis and were shown to be functional in A. niger. Integration of multiple copies in the genome resulted in over-expression of the enzymes. The arabinofuranohydrolases encoded comprise 332 amino acids and have 94% amino acid identity. Their primary structure is not related to those of other alpha-L-arabinofuranosidases, except for a low similarity with XYLC, a bacterial alpha-L-arabinofuranosidase from Pseudomonas fluorescens which acts on oat spelt xylan. The axhA expression pattern in A. niger differed from that of abfB, since it was strongly induced by birchwood xylan and much less by L-arabitol or L-arabinose. Furthermore, Northern analysis revealed that axhA expression was de repressed in creAd mutants and carbon catabolite repressed by D-glucose.

Amino Acid Sequence↗
PubMed2006

Sugarcane molasses and yeast powder used in the Fructooligosaccharides production by Aspergillus japonicus-FCL 119T and Aspergillus niger ATCC 20611.

Different concentrations of sucrose (3-25% w/v) and peptone (2-5% w/v) were studied in the formulation of media during the cultivation of Aspergillus japonicus-FCL 119T and Aspergillus niger ATCC 20611. Moreover, cane molasses (3.5-17.5% w/v total sugar) and yeast powder (1.5-5% w/v) were used as alternative nutrients for both strains' cultivation. These media were formulated for analysis of cellular growth, beta-Fructosyltransferase and Fructooligosaccharides (FOS) production. Transfructosylating activity (U ( t )) and FOS production were analyzed by HPLC. The highest enzyme production by both the strains was 3% (w/v) sucrose and 3% (w/v) peptone, or 3.5% (w/v) total sugars present in cane molasses and 1.5% (w/v) yeast powder. Cane molasses and yeast powder were as good as sucrose and peptone in the enzyme and FOS (around 60% w/w) production by studied strains.

Aspergillus↗
PubMed1991

Intracellular and extracellular production of proteins in Aspergillus under the control of expression signals of the highly expressed Aspergillus nidulans gpdA gene.

The expression in Aspergillus is described of genes, coding for intracellular and extracellular proteins controlled by the promoter region of the constitutively and efficiently expressed glyceraldehyde-3-phosphate dehydrogenase gene (gpdA) of Aspergillus nidulans. Both the homologous gpdA and the heterologous Escherichia coli beta-galactosidase (lacZ) and beta-glucuronidase (uidA) genes could be expressed intracellularly at levels as high as 10-25% of total soluble protein. Efficient extracellular production of A. niger glucoamylase could be achieved with a fusion-gene containing the region of the glucoamylase gene coding for the mature protein preceded by a synthetic fungal signal sequence. Extracellular production of a heterologous protein, E. coli beta-glucuronidase, with such a fusion was much less efficient. Only very low levels of beta-glucuronidase were detected in the culture fluid, whereas considerable enzyme activity was detected in the mycelium.

Amino Acid Sequence↗
PubMed1992

Isolation of an Aspergillus terreus mutant impaired in arginine biosynthesis and its complementation with the argB gene from Aspergillus nidulans.

Using filtration enrichment techniques, an Aspergillus terreus arginine auxotrophic strain which contains a mutation that abolishes ornithine transcarbamylase (OTCase) activity has been isolated. This mutant has been genetically transformed with the cloned Aspergillus nidulans OTCase gene. Prototrophic transformants arose at a frequency of about 50 transformants per microgram of plasmid DNA. Southern blot analysis of DNA from the transformants showed that the transforming DNA was ectopically integrated at different locations in the A. terreus genome, often in multiple tandem copies. The transformants were phenotypically stable for several mitotic divisions and retained their capacity to produce extracellular enzymes.

Arginine↗
PubMed2004

Mitochondrial DNA organisation of the mtDNA type 2b of Aspergillus tubingensis compared to the Aspergillus niger mtDNA type 1a.

A physical and functional map of Aspergillus tubingensis mtDNA type 2b was constructed and compared to Aspergillus niger typeI a mtDNA. The gene content and order, as well as the patterns of restriction sites, were similar. Two unidentified ORFs and several repeat elements were found in the region between the ndhl and ndh4 genes on both mtDNAs. The sizes of the A. niger and A. tubingensis mtDNAs were 31.23 and 33.06 kb. respectively, the difference was principally attributed to the altered intron content of their coxl genes.

Aspergillus↗
PubMed2004

Production of toxic metabolites in Aspergillus niger, Aspergillus oryzae, and Trichoderma reesei: justification of mycotoxin testing in food grade enzyme preparations derived from the three fungi.

Aspergillus niger, Aspergillus oryzae, and Trichoderma reesei are three important production organisms used in industrial fermentations. Several of the fungal secondary metabolites produced by selected strains of these three fungi are capable of eliciting toxicity in animals. Among those toxic substances are the well-known mycotoxins 3-nitropropionic acid and ochratoxin A. However, many others, such as kojic acid, may not be true mycotoxins. The production, extraction, chemical structure, and the toxicity (expressed as LD(50)) of these substances are reviewed. Production of toxic secondary metabolites in A. niger, A. oryzae, and T. reesei is strain-specific and environment-dependent. Considering all of the safety measures taken in the industrial production process, these three fungal species are safe to use. The recently revised JECFA specification for mycotoxins in food enzyme preparations is also discussed. The extent of mycotoxin tests in food enzyme preparations should be judged on a case-by-case basis, through a careful evaluation based on knowledge of taxonomy, biochemistry, and genetics. In many cases, the testing scope at the level of genus should be sufficient. In other cases, the scope can even be further narrowed based on scientific knowledge and assessment.

Animals↗
PubMed1997

Action patterns and mapping of the substrate-binding regions of endo-(1-->5)-alpha-L-arabinanases from Aspergillus niger and Aspergillus aculeatus.

The substrate binding sites of endo-(1-->5)-alpha-L-arabinanases (EC 3.2.1.99) from Aspergillus niger and Aspergillus aculeatus were investigated using reduced and regular (1-->5)-alpha-L-arabino-oligosaccharides and high performance anion exchange chromatographic analysis. Calculation of bond cleavage frequencies and kcat/K(m) parameters for these substrates enabled the determination of the number of arabinofuranosyl binding subsites and the estimation of the binding affinities of each subsite. The A. aculeatus endo-arabinanase has six subsites arranged symmetrically around the catalytic site, while the A. niger endo-arabinanase has five subsites; two from the catalytic site towards the non-reducing end of the bound substrate and three toward the reducing end. The two subsites directly adjacent to the catalytic sites in both the A. niger and A. aculeatus endo-arabinanase have near-zero net free energy of binding. These results are unlike most glycopyranosyl endo-hydrolases studied which have net negative (unfavourable) energies of interaction at these two subsites, and may be related to the greater conformational flexibility of arabinofuranosyl residues than glycopyranosyl residues. The complete subsite maps are also rationalized with regard to the observed action patterns of these enzymes on linear (1-->5)-alpha-L-arabinan.

Aspergillus↗
PubMed2000

Invertase production of common storage moulds in food and feed grains as a possibility for rapid detection of Aspergillus flavus group and Aspergillus fumigatus.

Invertase production of grain storage moulds was studied. Aspergillus spp. and Penicillium spp. were grown in a sucrose based liquid medium, at 37 degrees C. The A. flavus group (A. flavus, A. parasiticus, A. nomius, A. oryzae) and A. fumigatus showed a fast growth and intense invertase activity, while other Aspergillus spp. and Penicillium spp. grew slower and produced less invertase. The pattern of accumulated reducing sugar after 20 and 48 h of incubation was characteristic to the species studied. From inoculation studies the detection limit was calculated as: 1-10 conidia of A. flavus group and A. fumigatus, as compared to 10(3)-10(4) for the other species studied. The method may be recommended as a rapid test for the detection of A. flavus group and A. fumigatus in food and feed grains.

Animal Feed↗
PubMed1997

Genes encoding multiple drug resistance-like proteins in Aspergillus fumigatus and Aspergillus flavus.

Polymerase chain reaction using degenerate primers was used to identify genes encoding proteins of the ATP-binding cassette superfamily in Aspergillus fumigatus and Aspergillus flavus. In A. fumigatus, two genes (AfuMDR1 and AfuMDR2) encoding proteins of the ATP-binding cassette superfamily were identified. One gene (AflMDR1) was isolated from A. flavus and is the apparent homologue to AfuMDR1. AfuMDR1 and AflMDR1 encode proteins of molecular weights 148,000 and 143,000, respectively, each containing 12 putative transmembrane regions and two ATP-binding sites. These proteins are arranged in two homologous halves, each half consisting of a hydrophobic region (encoding six putative transmembrane domains) and an ATP-binding site. The AfuMDR1 and AflMDR1-encoded proteins bear a high degree of similarity to the Schizosaccharomyces pombe leptomycin B resistance protein and to human MDR1. The second gene identified in A. fumigatus, AfuMDR2, encodes a protein of molecular weight 85,000, containing four putative transmembrane domains and an ATP binding domain. The encoded protein is similar to those encoded by MDL1 and MDL2, two MDR-like genes of Saccharomyces cerevisiae. Expression of AFUMDR1 in S. cerevisiae conferred increased resistance to the antifungal agent cilofungin (LY121019), an echinocandin B analog.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2002

Heterologous expression of the Aspergillus nidulans alcR-alcA system in Aspergillus niger.

The inducible and strongly expressed alcA gene encoding alcohol dehydrogenase I from Aspergillus nidulans was transferred together with the activator gene alcR, in the industrial fungus Aspergillus niger. This latter organism does not possess an inducible alc system but has an endogenously constitutive lowly expressed alcohol dehydrogenase activity. The overall induced expression of the alcA gene was of the same order in both fungi, as monitored by alcA transcription, alcohol dehydrogenase activity and heterologous expression of the reporter enzyme, beta-glucuronidase. However, important differences in the pattern of alcA regulation were observed between the two fungi. A high basal level of alcA transcription was observed in A. niger resulting in a lower ratio of alcA inducibility. This may be due to higher levels of the physiological inducer of the alc regulon, acetaldehyde, from general metabolism in A. niger which differs from that of A. nidulans.

Alcohol Dehydrogenase↗
PubMed2003

Identification of genes differentially expressed during aflatoxin biosynthesis in Aspergillus flavus and Aspergillus parasiticus.

A complex regulatory network governs the biosynthesis of aflatoxin. While several genes involved in aflatoxin production are known, their action alone cannot account for its regulation. Arrays of clones from an Aspergillus flavus cDNA library and glass slide microarrays of ESTs were screened to identify additional genes. An initial screen of the cDNA clone arrays lead to the identification of 753 unique ESTs. Many showed sequence similarity to known metabolic and regulatory genes; however, no function could be ascribed to over 50% of the ESTs. Gene expression analysis of Aspergillus parasiticus grown under conditions conducive and non-conductive for aflatoxin production was evaluated using glass slide microarrays containing the 753 ESTs. Twenty-four genes were more highly expressed during aflatoxin biosynthesis and 18 genes were more highly expressed prior to aflatoxin biosynthesis. No predicted function could be ascribed to 18 of the 24 genes whose elevated expression was associated with aflatoxin biosynthesis.

Aflatoxins↗
PubMed2003

The Aspergillus nidulans alcA promoter drives tightly regulated conditional gene expression in Aspergillus fumigatus permitting validation of essential genes in this human pathogen.

Aspergillus fumigatus causes invasive aspergillosis, a mycosis that is usually fatal in immunocompromised patients. Functional genomics in this fungus will aid the discovery of novel antifungal drugs to treat invasive aspergillosis. However, there is still a need for appropriate molecular genetic tools to facilitate such functional studies. Here, we describe the use of a conditional gene expression system allowing the identification of novel therapeutic targets through validation of essential genes in A. fumigatus. This system is based on the capacity of the Aspergillus nidulans alcA promoter (alcA(p)) to tightly regulate gene expression in this fungus. Conditionally regulated gene expression in A. fumigatus was demonstrated by transcriptional and phenotypic analyses of strains expressing a nuclear migration gene with a terminal phenotype, the A. fumigatus nudC gene, under control of this promoter. This conditional expression system, the first one described in A. fumigatus, will also be useful for investigating the function of essential genes by altering the threonine/glucose ratio in the growth medium.

Alcohol Dehydrogenase↗
PubMedDate not supplied

Production of aflatoxins B1, B2, G1, and G2 in pure and mixed cultures of Aspergillus parasiticus and Aspergillus flavus.

Production of aflatoxins B1, B2, G1, and G2 in pure and mixed cultures of Aspergillus parasiticus and aspergillus flavus were compared. Differing percentages of A. parasiticus (NRRL 2999) and A. flavus (NRRL 5520) conidia were used as inoculum and allowed to grow in static liquid culture for 10 days. The pure and mixed cultures of A. parasiticus/A. flavus were extracted and the aflatoxins partially purified. High-performance liquid chromatography was then used to determine aflatoxin concentrations. The maximal decreases of G1 and G2 production occurred when the inocula went from 0 to 12.5% or 25% A. flavus. Aflatoxins G1 and G2 comprised less than 10% of the total aflatoxins when the A. parasiticus/A. flavus inocula contained greater than 25% A. flavus. Production of aflatoxins B1 and B2 increased slightly as the percentage of A. flavus in the A. parasiticus/A. flavus mixed inoculum increased. A. flavus is apparently capable of suppressing accumulation of aflatoxins G1 and G2 by A. parasiticus when these fungi are grown in mixed culture.

Aflatoxin B1↗
PubMed1992

Effect of methotrexate on the germination and growth of Aspergillus fumigatus and Aspergillus flavus strains.

Methotrexate at concentrations of greater than or equal to 10(-5) M caused a significant reduction in the rate of germ tube formation of spores of Aspergillus fumigatus, but not of Aspergillus flavus, after 7 h incubation. At 10(-3) M the drug caused a significant reduction in germ tube elongation of A. fumigatus and A. flavus strains during the first 7 h of germination. After 18 h incubation, drug concentrations of greater than or equal to 4 x 10(-4) M produced greater than 80% reduction in growth of all strains tested. Potentiation of the antifungal effect against A. fumigatus was detected in tests in which methotrexate at 10(-4) M was used in combination with amphotericin B at 5 x 10(-7) M.

Amphotericin B↗
PubMed2001

Resistance to itraconazole in Aspergillus nidulans and Aspergillus fumigatus is conferred by extra copies of the A. nidulans P-450 14alpha-demethylase gene, pdmA.

Triazoles selectively inhibit the cytochrome P-450-dependent C-14 lanosterol alpha-demethylase (P-450 14 alpha DM), a key enzyme in ergosterol biosynthesis in fungi. To investigate mechanisms of triazole resistance in a mould, we used Aspergillus nidulans, a genetically amenable model fungus closely related to more pathogenic members of the genus. We selected for genes that would give resistance to itraconazole following transformation with a high copy genomic library of A. nidulans. In all the resistant colonies that we isolated, resistance was conferred by extra copies of the A. nidulans P-450 14 alpha DM gene, pdmA. We determined that in A. nidulans, extra copies of pdmA increase the MIC for itraconazole 36 times over wild-type controls. Similarly, transformation of an Aspergillus fumigatus strain with pITZR1 resulted in increased resistance to itraconazole. Our results indicate that triazole resistance in clinical isolates of moulds may result from amplification or overexpression of the P-450 14 alpha DM and demonstrate the utility of A. nidulans as a promising model fungus for the analysis of drug resistance and susceptibility in the pathogenic fungus A. fumigatus.

Amino Acid Sequence↗
PubMed2003

Activity of micafungin (FK463) against an itraconazole-resistant strain of Aspergillus fumigatus and a strain of Aspergillus terreus demonstrating in vivo resistance to amphotericin B.

We compared the activity of four doses of micafungin (FK463) with that of amphotericin B, liposomal amphotericin B and itraconazole in a murine model of disseminated aspergillosis. Temporarily neutropenic mice were infected with a lethal dose of either an itraconazole-resistant Aspergillus fumigatus isolate or Aspergillus terreus, a species that is less susceptible to amphotericin B. Treatment was started 24 h after infection and lasted for 7 days. Mice were treated with either amphotericin B (0.5 or 5 mg/kg), liposomal amphotericin (5 or 25 mg/kg), itraconazole (25 or 75 mg/kg) or FK463 (either 1, 2, 5 or 10 mg/kg). Treatment of the A. fumigatus model with either amphotericin B, liposomal amphotericin or FK463 prolonged survival. Doses of FK463 5 and 10 mg/kg had a 100% survival. Treatment of A. terreus infection with either itraconazole or FK463, but not amphotericin B, also prolonged survival. Doses of liposomal amphotericin of 5 and 25 mg/kg were ineffective against A. terreus infection. No treatment regime was able to totally clear the liver or kidneys in either model. The data indicate that FK463 may have a clinical role in the treatment of life-threatening invasive aspergillosis.

Amphotericin B↗
PubMed1991

Isolation and nucleotide sequence of the Aspergillus restrictus gene coding for the ribonucleolytic toxin restrictocin and its expression in Aspergillus nidulans: the leader sequence protects producing strains from suicide.

We describe the cloning and characterization of the gene coding for the ribotoxin restrictocin, from Aspergillus restrictus (gene res, EMBL accession Number X56176). This toxin is a potent inhibitor of protein synthesis in eucaryotes and is of potential interest as a component of immunotoxins. To analyze the mechanism of self-protection in the producing organism, the res gene was cloned into the vector pFB39 and introduced into Aspergillus nidulans. The secretion of active restrictocin from transformants suggests that the pro-toxin is not an active nuclease but is activated during the process of secretion.

Allergens↗
PubMed2001

Maize ribosome-inactivating protein inhibits normal development of Aspergillus nidulans and Aspergillus flavus.

The abundant maize kernel ribosome-inactivating protein 1 (RIP1) was tested for antifungal activity against Aspergillus nidulans and Aspergillus flavus. A microculture assay was developed to monitor fungal growth and development after treatment of conidia with RIP1 or control proteins. A striking decrease in hyphal proliferation was observed when conidia of A. nidulans, a genetically well-characterized nonpathogenic species, were treated with RIP1 protein. Treatment with a RIP1 mutant protein that lacked enzymatic ribosome-inactivating activity caused no observable effects. RIP1 treatment of conidia from the maize pathogen A. flavus resulted in increased hyphal branching. Examination of the branched hyphae after Congo red staining revealed only one growing hyphal tip per conidium. These results indicate that both fungi were affected by RIP1 treatment, but the lysis seen with treatment of A. nidulans was apparently avoided by A. flavus. A developmental time course revealed that both fungal species were affected by RIP1 at the postdivisional growth stage. The inhibitory activity of RIP1 against normal fungal growth is consistent with a biological function to protect the seed from fungal invasion.

Aspergillus flavus↗