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1.
V. Vivekanand Pallavi Dwivedi Amit Sharma Nidhi Sabharwal Rajesh P. Singh 《World journal of microbiology & biotechnology》2008,24(12):2799-2804
An environmentally sound biobleaching to get high quality paper pulp from mixed wood pulp was attempted employing laccase
from Aspergillus fumigatus VkJ2.4.5 for lignin removal. Laccase treatment was performed in the presence of a mediator N-hydroxybenzotriazole (HBT, 1.5% w/w), resulting into notably higher level of delignification of the pulp. Enzyme at 10 Ug−1 of pulp at 50°C, pH 6.0, for 2 h with a pulp consistency of 10% was found suitable for enabling maximum decrease in the kappa
number. The kappa number and yellowness decreased by 14 and 4% whereas ISO brightness improved by 7%. The presence of a characteristic
peak at 280 nm indicated the presence of lignin in the effluent during biobleaching. Analysis of FTIR spectra of residual
lignin revealed characteristic modifications following enzymatic bleaching by laccase mediator system (LMS). Variations in
morphology and crystallinity of pulp were evaluated by scanning electron microscopy and X-ray diffraction analysis. 相似文献
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K. Parvathi R. Naresh Kumar R. Nagendran 《World journal of microbiology & biotechnology》2007,23(5):671-676
Summary Biosorption of manganese from its aqueous solution using yeast biomass Saccharomyces cerevisiae and fungal biomass Aspergillus niger was carried out. Manganese biosorption equilibration time for A. niger and S. cerevisiae were found to be 60 and 20 min, with uptakes of 19.34 and 18.95 mg/g, respectively. Biosorption increased with rise in pH,
biomass, and manganese concentration. The biosorption equilibrium data fitted with the Freundlich isotherm model revealed
that A. niger was a better biosorbent of manganese than S. cerevisiae. 相似文献
4.
The aim of the present work was to observe microbial decolorization and biodegradation of the Direct Violet 51 azo dye by
Candida albicans isolated from industrial effluents and study the metabolites formed after degradation. C. albicans was used in the removal of the dye in order to further biosorption and biodegradation at different pH values in aqueous solutions.
A comparative study of biodegradation analysis was carried out using UV–vis and FTIR spectroscopy, which revealed significant
changes in peak positions when compared to the dye spectrum. Theses changes in dye structure appeared after 72 h at pH 2.50;
after 240 h at pH 4.50; and after 280 h at pH 6.50, indicating the different by-products formed during the biodegradation
process. Hence, the yeast C. albicans was able to remove the color substance, demonstrating a potential enzymatic capacity to modify the chemical structure of
pigments found in industrial effluents. 相似文献
5.
Family 18 chitinases hydrolyze chitin through a substrate-assisted catalytic mechanism and are to a variable extent able to
catalyze transglycosylation reactions. Previously Aspergillus fumigatus AfChiB1 was found to be able to catalyze transglycosylation reactions. Structural analysis reveals that AfChiB1 consists
of an eight-stranded β/α-barrel. Like other members of the family 18 hydrolases, AfChiB1 has conserved substrate binding site
and catalytic acid, while a suitable nucleophile is missing. In this study, Trp137, Asp246, and Met243, which are close to
the glycosidic cleavage site, were mutated to glutamate individually. As a result, the W137E remained its hydrolytic activity
and was completely devoid of transglycosyl activity, while the D246E reduced its chitinolytic activity and increased its transglycosyl
activity. And the M243E showed a remarkable reduction of chitinolytic activity and complete loss of transglycosyl activity.
These results suggested that the transglycosyl reaction catalyzed by the AfChiB1 is due to lacking of nucleophile.
Enzymes: exochitinases (EC 3.2.1.14) 相似文献
6.
We provide the first indication of the extent of the complex chitinolytic system of a filamentous fungus. Phylogenetic analysis
of the 14 apparent chitinases of the opportunistic fungal pathogen Aspergillus fumigatus identified four and ten enzymes related to plant and bacterial chitinases, respectively. Further, real time-RT-PCR studies
revealed distinct patterns of gene expression, consistent with morphogenetic or nutritional roles, for members of the fungal/plant
or fungal/bacterial sub-families, respectively. Our results provide a basis for future studies with A. fumigatus chitinases, which may lead to the exploitation of these enzymes, or their regulators, in the development of novel drug strategies. 相似文献
7.
Mota Júnior AO Malavazi I Soriani FM Heinekamp T Jacobsen I Brakhage AA Savoldi M Goldman MH da Silva Ferreira ME Goldman GH 《Molecular genetics and genomics : MGG》2008,280(6):483-495
Here, we characterize the Aspergillus fumigatus homologue ncsA Neuronal Calcium Sensor. We showed that ncsA is not an essential gene and ?ncsA growth was decreased in the presence of EGTA and SDS. Furthermore, the ?ncsA mutant is more resistant to calcium chloride. NcsA:mRFP localizes to the cytoplasm and its cellular localization is not affected by the cellular response to either calcium chloride or EGTA. The ?ncsA mutant strain is more sensitive to voriconazole, itraconazole, and amphotericin. Polar growth in the ΔncsA mutant was also considerably more affected by lovastatin than in the wild type strain. The Spitzenkörper can be visualized in both strains and although the vacuolar system does not seem to be very different, there is an increase in the staining intensity on the germling surface of the ?ncsA strain. NcsA promotes pmcA and pmcB expression and therefore there is a reduced expression of these ion pumps in the ΔncsA mutant background, and also of other genes involved in the response to calcium in A. fumigatus. The ncsA inactivation mutation is not causing loss of virulence in a low dose murine infection when compared to the corresponding wild type strain. 相似文献
8.
Liebmann B Mühleisen TW Müller M Hecht M Weidner G Braun A Brock M Brakhage AA 《Archives of microbiology》2004,181(5):378-383
Aspergillus fumigatus is an important pathogen of the immunocompromised host, causing pneumonia and invasive disseminated disease with high mortality. In order to determine the importance of lysine biosynthesis for growth and pathogenicity, the A. fumigatus lysF gene, encoding a homologue of the A. nidulans homoaconitase LysF, was cloned and characterized. Cosmid cosGTM encoding lysF complemented a lysF mutant of Aspergillus nidulans. A. fumigatus lysF was deleted, resulting in a lysine-auxotroph. This phenotype was complemented to the wild-type by supplementation of the medium with both L-lysine and -aminoadipic acid, or transformation using cosmid cosGTM. To study the virulence of the lysF deletion mutant of A. fumigatus, a low-dose intranasal mouse infection model of invasive aspergillosis was optimized for immunosuppressed BALB/c mice, allowing the application of an infection dose as low as 5×103 conidia per mouse. In this murine model, the lysF mutant was avirulent, suggesting that lysine biosynthesis, or at least a functional homoaconitase, is important for survival of A. fumigatus in vivo and a potential target for antifungal drugs. 相似文献
9.
Y. P. Vinetsky A. M. Rozhkova A. M. Chulkin A. D. Satrutdinov O. A. Sinitsyna E. A. Fedorova A. O. Bekkarevich O. N. Okunev A. P. Sinitsyn 《Biochemistry. Biokhimii?a》2009,74(8):882-887
The gene encoding the xlnR xylanolytic activator of the heterologous fungus Aspergillus niger was incorporated into the Penicillium canescens genome. Integration of the xlnR gene resulted in the increase in a number of activities, i.e. endoxylanase, β-xylosidase, α-L-arabinofuranosidase, α-galactosidase, and feruloyl esterase, compared to the host P. canescens PCA 10 strain, while β-galactosidase, β-glucosidase, endoglucanase, and CMCase activities remained constant. Two different expression constructs were developed. The first consisted of the nucleotide sequence containing the mature P. canescens phytase gene under control of the axhA promoter region gene encoding A. niger (1,4)-β-D-arabinoxylan-arabinofuranohydrolase. The second construct combined the P. canescens phytase gene and the bgaS promoter region encoding homologous β-galactosidase. Both expression cassettes were transformed into P. canescens host strain containing xlnR. Phytase synthesis was observed only for strains with the bgaS promoter on arabinose-containing culture media. In conclusion, the bgaS and axhA promoters were regulated by different inducers and activators in the P. canescens strain containing a structural tandem of the axhA promoter and the gene of the xlnR xylanolytic activator. 相似文献
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Taisa Magnani Frederico Marianetti Soriani Vicente de Paulo Martins Anna Carolina de Freitas Policarpo Carlos Artério Sorgi Lúcia Helena Faccioli Carlos Curti Sérgio Akira Uyemura 《Journal of bioenergetics and biomembranes》2008,40(6):631-636
We previously demonstrated that conidia from Aspergillus fumigatus incubated with menadione and paraquat increases activity and expression of cyanide-insensitive alternative oxidase (AOX).
Here, we employed the RNA silencing technique in A. fumigatus using the vector pALB1/aoxAf in order to down-regulate the aox gene. Positive transformants for aox gene silencing of A. fumigatus were more susceptible both to an imposed in vitro oxidative stress condition and to macrophages killing, suggesting that AOX is required for the A. fumigatus pathogenicity, mainly for the survival of the fungus conidia during host infection and resistance to reactive oxygen species
generated by macrophages. 相似文献
12.
Exposure to Aspergillus fumigatus is linked with respiratory diseases such as asthma, invasive aspergillosis, hypersensitivity pneumonitis, and allergic bronchopulmonary
aspergillosis. Molecular methods using quantitative PCR (qPCR) offer advantages over culture and optical methods for estimating
human exposures to microbiological agents such as fungi. We describe an assay that uses lyticase to digest A. fumigatus conidia followed by TaqMan™ qPCR to quantify released DNA. This method will allow analysis of airborne A. fumigatus samples collected over extended time periods and provide a more representative assessment of chronic exposure. The method
was optimized for environmental samples and incorporates: single tube sample preparation to reduce sample loss, maintain simplicity,
and avoid contamination; hot start amplification to reduce non-specific primer/probe annealing; and uracil-N-glycosylase to prevent carryover contamination. An A. fumigatus internal standard was developed and used to detect PCR inhibitors potentially found in air samples. The assay detected fewer
than 10 A. fumigatus conidia per qPCR reaction and quantified conidia over a 4−log10 range with high linearity (R
2 > 0.99) and low variability among replicate standards (CV=2.0%) in less than 4 h. The sensitivity and linearity of qPCR for
conidia deposited on filters was equivalent to conidia calibration standards. A. fumigatus DNA from 8 isolates was consistently quantified using this method, while non-specific DNA from 14 common environmental fungi,
including 6 other Aspergillus species, was not detected. This method provides a means of analyzing long term air samples collected on filters which may
enable investigators to correlate airborne environmental A. fumigatus conidia concentrations with adverse health effects. 相似文献
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The maT clade of transposons is a group of transposable elements intermediate in sequence and predicted protein structure to mariner and Tc transposons, with a distribution thus far limited to a few invertebrate species. We present evidence, based on searches of publicly available databases, that the nematode Caenorhabditis briggsae has several maT-like transposons, which we have designated as CbmaT elements, dispersed throughout its genome. We also describe two additional transposon sequences that probably share their evolutionary history with the CbmaT transposons. One resembles a fold back variant of a CbmaT element, with long (380-bp) inverted terminal repeats (ITRs) that show a high degree (71%) of identity to CbmaT1. The other, which shares only the 26-bp ITR sequences with one of the CbmaT variants, is present in eight nearly identical copies, but does not have a transposase gene and may therefore be cross mobilised by a CbmaT transposase. Using PCR-based mobility assays, we show that CbmaT1 transposons are capable of excising from the C. briggsae genome. CbmaT1 excised approximately 500 times less frequently than Tcb1 in the reference strain AF16, but both CbmaT1 and Tcb1 excised at extremely high frequencies in the HK105 strain. The HK105 strain also exhibited a high frequency of spontaneous induction of unc-22 mutants, suggesting that it may be a mutator strain of C. briggsae. 相似文献
15.
Fungi of the genus Aspergillus can infect all tissues and organs, causing invasive mycosis (aspergillosis). This disease can be fatal, especially in immunocompromised patients. Microbiological monitoring of these infectious agents is obligatory in modern medical facilities. Mobile elements can be used as markers to identify the Aspergillus species and strains found indoors as well as to diagnose aspergillosis. Genomic sequences of two Aspergillus species, A. fumigatus and A. nidulans, were analyzed in silico in order to detect LTR retrotransposons. These species were found to considerably differ in the composition of retrotransposon families. One of the families, present in both Aspergillus species, was phylogenetically quite different from all known fungal retrotransposons. The majority of its elements were damaged copies. Nevertheless, allegedly undamaged LTR retrotransposon copies were described that contained intact ORFs and might be active. 相似文献
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Notocactus scopa cv. Soonjung was subjected to in planta Agrobacterium tumefaciens-mediated transformation with vacuum infiltration, pin-pricking, and a combination of the two methods. The pin-pricking combined with vacuum infiltration (20-30 cmHg for 15 min) resulted in a transformation efficiency of 67-100%, and the expression of the uidA and nptII genes was detected in transformed cactus. The established in planta transformation technique generated a transgenic cactus with higher transformation efficiency, shortened selection process, and stable gene expression via asexual reproduction. All of the results showed that the in planta transformation method utilized in the current study provided an efficient and time-saving procedure for the delivery of genes into the cactus genome, and that this technique can be applied to other asexually reproducing succulent plant species. 相似文献
18.
Cary JW OBrian GR Nielsen DM Nierman W Harris-Coward P Yu J Bhatnagar D Cleveland TE Payne GA Calvo AM 《Applied microbiology and biotechnology》2007,76(5):1107-1118
The aflatoxin-producing fungi, Aspergillus flavus and A. parasiticus, form structures called sclerotia that allow for survival under adverse conditions. Deletion of the veA gene in A. flavus and A. parasiticus blocks production of aflatoxin as well as sclerotial formation. We used microarray technology to identify genes differentially
expressed in wild-type veA and veA mutant strains that could be involved in aflatoxin production and sclerotial development in A. flavus. The DNA microarray analysis revealed 684 genes whose expression changed significantly over time; 136 of these were differentially
expressed between the two strains including 27 genes that demonstrated a significant difference in expression both between
strains and over time. A group of 115 genes showed greater expression in the wild-type than in the veA mutant strain. We identified a subgroup of veA-dependent genes that exhibited time-dependent expression profiles similar to those of known aflatoxin biosynthetic genes
or that were candidates for involvement in sclerotial production in the wild type. 相似文献
19.
Ola M. Gomaa John E. Linz C. A. Reddy 《World journal of microbiology & biotechnology》2008,24(10):2349-2356
Synthetic textile dyes are among the most dangerous chemical pollutants released in industrial wastewater streams. Recognizing
the importance of reducing the environmental impact of these dyes, the ability of the white rot fungus Phanerochaete chrysosporium to decolorize various textile dyes was investigated. This fungus decolorized 6 of the 14 structurally diverse dyes with varying
efficiency (between 14% and 52%). There was no discernable pattern of decolorization even among dyes of the same chemical
class, suggesting that attack on the dyes is relatively non-specific. Among the three dyes which showed >40% decolorization,
Victoria Blue B (VB) was chosen for further analysis because the ability of the fungus to decolorize VB was nearly independent
over a relatively broad concentration range. Blocking lignin peroxidase (LiP) and manganese peroxidase (MnP) production by
the fungus did not substantially affect VB decolorization. Inhibition of laccase production by adding various inhibitors to
shaken cultures reduced VB decolorization significantly suggesting a role for laccase in VB decolorization. When sodium azide
and aminotriazole were used to inhibit endogenous catalase and cytochrome P-450 oxygenase activities, there was 100% and 70%
reduction in VB decolorization, respectively. Adding benzoate to trap hydrogen peroxide-derived hydroxyl radicals resulted
in 50% decolorization of VB. Boiling the extracellular fluid (ECF) for 30 min resulted in approximately 50% reduction in VB
decolorization. Collectively, these data suggest that laccase, and/or oxygenase/oxidase and a heat-stable non-enzymatic factor,
but not Lip and MnP, play a role in VB decolorization by P. chrysosporium. 相似文献
20.
Qingxin Zhao Sheng Yuan Yuling Zhang Hong Zhu Chuanchao Dai Fang Yang Fengmin Han 《World journal of microbiology & biotechnology》2007,23(8):1057-1064
Pectate lyase A (PelA) of Aspergillus nidulans was successfully expressed in Escherichia coli and effectively purified using a Ni2+-nitrilotriacetate-agarose column. Enzyme activity of the recombinant PelA could reach 360 U ml−1 medium. The expressed PelA exhibited its optimum level of activity over the range of pH 7.5–10 at 50°C. Mn2+, Ca2+, Fe2+, Mg2+ and Fe3+ ions stimulated the pectate lyase activity, but Cu2+ and Zn2+ inhibited it. The recombinant PelA had a V
max of 77 μmol min−1 mg−1 and an apparent K
m of 0.50 mg ml−1 for polygalacturonic acid. Low-esterified pectin was the optimum substrate for the PelA, whereas higher-esterified pectin
was hardly cleaved by it. PelA efficiently macerated mung bean hypocotyls and potato tuber tissues into single cells. 相似文献