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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
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Stable mutants of Aspergillus nidulans, resistant to 1 mM Ni were developed by step-by-step repeated culturing of the fungus on the medium containing increasing
concentrations of nickel chloride. Characterization of mutants could differentiate them into two categories NiR I and NiR II. Each category of mutants exhibited alterations in growth, conidial germination and melanin secretion both in Ni-free
and Ni-containing media. NiR II mutants were little slow in growth with sparse mycelia and conidiation but showed high melanin secretion and higher Ni-uptake
in comparison to NiR I mutant. Studies involving metabolic and translational inhibitors could prove that Ni-accumulation was biphasic. The initial
energy independent surface accumulation was found to be followed by energy dependent intarcellular uptake. Increase in the
concentration of the metal in the medium or the time of exposure did not proportionately increase the metal uptake by the
mutants. Ni-uptake followed Michaelis-Menton saturation kinetics, which was enhanced under optimum pH of 6.5–7.5 and reduced
complexity of the medium due to free availability of ions. Resistance to Ni was found to be constitutive in NiRI mutant, and could be induced in NiRII mutant. 相似文献
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Aspergillus nidulans senses red and blue-light and employs a phytochrome and a Neurospora crassa White Collar (WC) homologous system for light perception and transmits this information into developmental decisions. Under
light conditions it undergoes asexual development and in the dark it develops sexually. The phytochrome FphA consists of a
light sensory domain and a signal output domain, consisting of a histidine kinase and a response regulator domain. Previously
it was shown that the phytochrome FphA directly interacts with the WC-2 homologue, LreB and another regulator, VeA. In this
paper we mapped the interaction of FphA with LreB to the histidine kinase and the response regulator domain at the C-terminus
in vivo using the bimolecular fluorescence complementation assay and in vitro by co-immunoprecipitation. In comparison, VeA
interacted with FphA only at the histidine kinase domain. We present evidence that VeA occurs as a phosphorylated and a non-phosphorylated
form in the cell. The phosphorylation status of the protein was independent of the light receptors FphA, LreB and the WC-1
homologue LreA. 相似文献
6.
A hypothetical protein AN1772.2 of Aspergillus nidulans was found to have a 56% identity with a known type C ferulic acid esterase (FAE) from Talaromyces stipitatus. In addition, it contained a 13-amino acid conserved region flanking the characteristic G-X-S-X-G motif of a serine esterase,
suggesting a FAE function for the protein. The putative FAE was successfully cloned from the genomic DNA and expressed in
Saccharomyces cerevisiae. The recombinant protein exhibited high FAE activities. Therefore, its function as an FAE was unequivocally determined. About
86% of the enzyme activity was found in the growth medium, indicating that the native signal peptide was effective in the
yeast expression system. The recombinant FAE was purified to its homogeneity, and subsequently characterized. The FAE is stable
over an unusually wide range of pH (4.0–9.5), has a pH optimum of 7.0, and a temperature optimum of 45°C. A substrate specificity
profiling reveals that the enzyme is a type B FAE, despite its strong sequence homology with type C FAEs, raising an interesting
question on the role of the conserved region in substrate specificity. 相似文献
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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
9.
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
10.
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
11.
Genome sequence analysis of Xanthomonas
oryzae pv. oryzae has revealed a cluster of 12 ORFs that are closely related to the gum gene cluster of Xanthomonas campestris pv. campestris. The gum gene cluster of X. oryzae encodes proteins involved in xanthan production; however, there is little experimental evidence supporting this. In this
study, biochemical analyses of xanthan produced by a defined set of X. oryzae
gum mutant strains allowed us to preliminarily assign functions to most of the gum gene products: biosynthesis of the pentasaccharide repeating unit for GumD, GumM, GumH, GumK, and GumI, xanthan polymerization
and transport for GumB, GumC, GumE, and GumJ, and modification of the pentasaccharide repeating unit for GumF, GumG, and GumL.
In addition, we found that the exopolysaccharides are essential but not specific for the virulence of X. oryzae.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Sang-Yoon Kim and Jeong-Gu Kim contributed equally to this work. 相似文献
12.
Phytogenous Phenolic and benzene compounds have been described as being responsible for many biological activities including
antifungal effects. The effect of caffeine and cinnamic and caffeic acids on a model fungus, Aspergillus nidulans, was investigated at its initial stage of germination. Conidia did not germinate in the presence of cinnamic acid (1 mM).
Caffeine and caffeic acid exerted a negative effect on germination, on the nuclear duplication cycle and on first septum formation.
The effects of caffeine were dose-dependent; effects of caffeic acid (1 mM) were more intense than those of caffeine (10 mM). 相似文献
13.
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
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Fekete E Karaffa L Sándor E Bányai I Seiboth B Gyémánt G Sepsi A Szentirmai A Kubicek CP 《Archives of microbiology》2004,181(1):35-44
The catabolism of d-galactose in yeast depends on the enzymes of the Leloir pathway. In contrast, Aspergillus nidulans mutants in galactokinase (galE) can still grow on d-galactose in the presence of ammonium—but not nitrate—ions as nitrogen source. A. nidulans galE mutants transiently accumulate high (400 mM) intracellular concentrations of galactitol, indicating that the alternative d-galactose degrading pathway may proceed via this intermediate. The enzyme degrading galactitol was identified as l-arabitol dehydrogenase, because an A. nidulans loss-of-function mutant in this enzyme (araA1) did not show NAD+-dependent galactitol dehydrogenase activity, still accumulated galactitol but was unable to catabolize it thereafter, and a double galE/araA1 mutant was unable to grow on d-galactose or galactitol. The product of galactitol oxidation was identified as l-sorbose, which is a substrate for hexokinase, as evidenced by a loss of l-sorbose phosphorylating activity in an A. nidulans hexokinase (frA1) mutant. l-Sorbose catabolism involves a hexokinase step, indicated by the inability of the frA1 mutant to grow on galactitol or l-sorbose, and by the fact that a galE/frA1 double mutant of A. nidulans was unable to grow on d-galactose. The results therefore provide evidence for an alternative pathway of d-galactose catabolism in A. nidulans that involves reduction of the d-galactose to galactitol and NAD+-dependent oxidation of galactitol by l-arabitol dehydrogenase to l-sorbose. 相似文献
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Phylogenetic relations within the genus Gordonia were analyzed using partial gyrB and secA1 gene sequences of 23 type species in comparison with those of 16S rRNA gene. The gyrB and secA1 phylogenies showed agreement with that constructed using 16S rRNA gene sequences. The degrees of divergence of the gyrB and secA1 genes were approximately 3.4 and 1.7 times greater, respectively, than that of 16S rRNA gene. The gyrB gene showed more discriminatory power than either the secA1 or 16S rRNA gene, facilitating clear differentiation of any two Gordonia species using gyrB gene analysis. Our data indicate that gyrB and secA1 gene sequences are useful as markers for phylogenetic study and identification at the species level of the genus Gordonia. 相似文献
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Hong-Guan Xie Yong-Gang Bao Li-ping Bai Jun-Jie Shan Rong Jiang Yang Zhang Lian-Hong Guo Ren Zhang Yuan Li 《Journal of microbiology (Seoul, Korea)》2009,47(2):193-200
Streptomyces sp. 139 generates a novel exopolysaccharide (EPS) designated as Ebosin, which exerts an antagonistic effect on IL-1R in vitro and anti-rheumatic arthritis activity in vivo. A ste gene cluster for Ebosin biosynthesis consisting of 27 ORFs was previously identified in our laboratory. In this paper, ste16 was expressed in Escherichia coli BL21 and the recombinant protein was purified, which has the ability to catalyze the transfer of the methyl group from S-adenosylmethionine
(AdoMet) to dTDP-4-keto-6-deoxy-D-glucos, which was thus identified as a methyltransferase. In order to determine the function
of ste16 in Ebosin biosynthesis, the gene was disrupted with a double crossover via homologous recombination. The monosaccharide composition
of EPS-m generated by the mutant strain Streptomyces sp. 139 (ste16) was found to differ from that of Ebosin. The IL-1R antagonist activity of EPS-m was markedly lower than that of Ebosin.
These experimental results have shown that the ste16 gene codes for a methyltransferase which is involved in Ebosin biosynthesis.
These authors contributed equally to this work. 相似文献
18.
Zhang CL Zheng BQ Lao JP Mao LJ Chen SY Kubicek CP Lin FC 《Applied microbiology and biotechnology》2008,78(5):833-840
Many endophytic fungi are known to protect plants from plant pathogens, but the antagonistic mechanism has rarely been revealed.
In this study, we wished to learn whether an endophytic Aspergillus sp., isolated from Taxus mairei, would indeed produce bioactive components, and if so whether (a) they would antagonize plant pathogenic fungi; and (b) whether
this Aspergillus sp. would produce the compound also under conditions of confrontation with these fungi. The endophytic fungal strain from
T. mairei was identified as Aspergillus clavatonanicus by analysis of morphological characteristics and the sequence of the internal transcribed spacers (ITS rDNA) of rDNA. When
grown in surface culture, the fungus produced clavatol (2′,4′-dihydroxy-3′,5′-dimethylacetophenone) and patulin (2-hydroxy-3,7-dioxabicyclo
[4.3.0]nona-5,9-dien-8-one), as shown by shown by NMR, MS, X-ray, and EI-MS analysis. Both exhibited inhibitory activity in
vitro against several plant pathogenic fungi, i.e., Botrytis cinerea, Didymella bryoniae, Fusarium oxysporum f. sp. cucumerinum, Rhizoctonia solani, and Pythium ultimum. During confrontation with P. ultimum, A. clavatonanicus antagonized its growth of P. ultimum, and both clavatol as well as patulin were formed as the only bioactive components, albeit with different kinetics. We conclude
that A. clavatonanicus produces clavatol and patulin, and that these two polyketides may be involved in the protection of T. mairei against attack by plant pathogens by this Aspergillus sp. 相似文献
19.
Gene silencing using siRNA has been examined in the industrially-important fungus, Aspergillus niger. Protoplasts of an A. niger strain containing a single genomic copy of the Escherichia coli uidA gene, encoding β-glucuronidase (GUS), under control of the A. niger glaA promoter at the same genomic locus, were exposed to siRNA targeted against the uidA gene. Down-regulation of uidA mRNA
and GUS activity by siRNA was observed in mycelia that developed from the protoplasts. The down-regulation was transient and
was not carried over to conidiation. We concluded that gene silencing by siRNA provides a relatively quick method for analysis
of gene function in A. niger. 相似文献
20.
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