scholarly journals Unexpected Link between Metal Ion Deficiency and Autophagy in Aspergillus fumigatus

2007 ◽  
Vol 6 (12) ◽  
pp. 2437-2447 ◽  
Author(s):  
Daryl L. Richie ◽  
Kevin K. Fuller ◽  
Jarrod Fortwendel ◽  
Michael D. Miley ◽  
Jason W. McCarthy ◽  
...  
Keyword(s):  
Metal Ions ◽  
Aspergillus Fumigatus ◽  
Stress Responses ◽  
Metal Ion ◽  
Nitrogen Sources ◽  
Hyphal Growth ◽  
Wild Type ◽  
Serine Threonine Kinase ◽  
Gene Encoding ◽  
Carbon And Nitrogen

ABSTRACT Autophagy is the major cellular pathway for bulk degradation of cytosolic material and is required to maintain viability under starvation conditions. To determine the contribution of autophagy to starvation stress responses in the filamentous fungus Aspergillus fumigatus, we disrupted the A. fumigatus atg1 gene, encoding a serine/threonine kinase required for autophagy. The ΔAfatg1 mutant showed abnormal conidiophore development and reduced conidiation, but the defect could be bypassed by increasing the nitrogen content of the medium. When transferred to starvation medium, wild-type hyphae were able to undergo a limited amount of growth, resulting in radial expansion of the colony. In contrast, the ΔAfatg1 mutant was unable to grow under these conditions. However, supplementation of the medium with metal ions rescued the ability of the ΔAfatg1 mutant to grow in the absence of a carbon or nitrogen source. Depleting the medium of cations by using EDTA was sufficient to induce autophagy in wild-type A. fumigatus, even in the presence of abundant carbon and nitrogen, and the ΔAfatg1 mutant was severely growth impaired under these conditions. These findings establish a role for autophagy in the recycling of internal nitrogen sources to support conidiophore development and suggest that autophagy also contributes to the recycling of essential metal ions to sustain hyphal growth when exogenous nutrients are scarce.

scholarly journals Aspergillus fumigatus Calcipressin CbpA Is Involved in Hyphal Growth and Calcium Homeostasis

2009 ◽  
Vol 8 (4) ◽  
pp. 511-519 ◽  
Author(s):  
Nadthanan Pinchai ◽  
B. Zachary Perfect ◽  
Praveen Rao Juvvadi ◽  
Jarrod R. Fortwendel ◽  
Robert A. Cramer ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Stress Responses ◽  
Critical Role ◽  
Hyphal Growth ◽  
Wild Type ◽  
New Class ◽  
High Calcium ◽  
Feedback Inhibitor ◽  
Dependent Mechanism

ABSTRACT Calcineurin is a conserved protein phosphatase that plays a critical role in Ca2+ signaling and stress responses. Previously, a new class of conserved calcineurin-binding proteins, the calcipressins, was identified. However, the role of these proteins remains controversial, and both inhibitory and stimulatory effects on calcineurin were observed. In this study, we investigate the role of CbpA, the Aspergillus fumigatus member of the calcipressin family, and report that deletion of the cbpA gene resulted in reduced hyphal growth and limited attenuated virulence. Interestingly, under high-calcium-level conditions, the ΔcbpA strain displayed improved Ca2+ tolerance compared to the wild-type strain and revealed increased expression of vcxA, chsA, and cnaA, which encode the vacuolar Ca2+/H+ exchanger VcxA, chitin synthase A, and the calcineurin catalytic subunit CnaA, respectively. The increased transcript levels of these three genes were reversed in the presence of the calcineurin inhibitor FK506, indicating a calcineurin-dependent mechanism. Overexpression of cbpA resulted in decreased transcription of vcxA, chsA, and cnaA, associated with wild-type sensitivity to Ca2+. Taken together, our study highlights the importance of CbpA in the regulation of hyphal growth and calcium adaptation of A. fumigatus and provides evidence that CbpA may serve as a feedback inhibitor in some aspects of calcineurin functions.

scholarly journals Improved Cordycepin Production by Cordyceps militaris KYL05 Using Casein Hydrolysate in Submerged Conditions

Biomolecules ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 461 ◽  
Author(s):  
Soo Kweon Lee ◽  
Ju Hun Lee ◽  
Hyeong Ryeol Kim ◽  
Youngsang Chun ◽  
Ja Hyun Lee ◽  
...  
Keyword(s):  
Functional Foods ◽  
Casein Hydrolysate ◽  
Nitrogen Sources ◽  
Culture Conditions ◽  
Cordyceps Militaris ◽  
Wild Type ◽  
Carbon And Nitrogen Sources ◽  
Carbon And Nitrogen ◽  
Bioactive Product ◽  
Submerged Conditions

Cordycepin, a beneficial bioactive product specifically found in Cordyceps, has received attention in various bioindustrial applications such as in pharmaceuticals, functional foods, and cosmetics, due to its significant functions. However, low productivity of cordycepin is a barrier to commercialization. In this study, Cordyceps militaris was mutated by UV irradiation to improve the cordycepin production. The highest producer KYL05 strain was finally selected and its cordycepin production was increased about 1.5-fold compared to wild type. In addition, the effects of culture conditions were fundamentally investigated. Optimal conditions were as follows: pH 6, temperature of 25 °C, shaking speed of 150 rpm, and culture time of 6 days. Effects of medium component on cordycepin production were also investigated by using various carbon and nitrogen sources. It was found that glucose and casein hydrolysate (CH) were most effective as carbon and nitrogen sources in cordycepin production (2.3-fold improvement) with maximum cordycepin production of about 445 mg/L. In particular, production was significantly affected by CH. These results should be of value in improving the efficiency of mass production of cordycepin.

scholarly journals Amino Acid Transport and Metabolism in Mycobacteria: Cloning, Interruption, and Characterization of anl-Arginine/γ-Aminobutyric Acid Permease inMycobacterium bovis BCG

2000 ◽  
Vol 182 (4) ◽  
pp. 919-927 ◽  
Author(s):  
Anjali Seth ◽  
Nancy D. Connell
Keyword(s):  
Amino Acid ◽  
Mutant Strain ◽  
Nitrogen Sources ◽  
Single Copy ◽  
Aminobutyric Acid ◽  
Cosmid Library ◽  
Wild Type ◽  
Carbon And Nitrogen ◽  
Genes Encoding ◽  
Type Gene

ABSTRACT Genes encoding l-arginine biosynthetic and transport proteins have been shown in a number of pathogenic organisms to be important for metabolism within the host. In this study we describe the cloning of a gene (Rv0522) encoding an amino acid transporter fromMycobacterium bovis BCG and the effects of its deletion onl-arginine transport and metabolism. The Rv0522 gene of BCG was cloned from a cosmid library by using primers homologous to therocE gene of Bacillus subtilis, a putative arginine transporter. A deletion mutant strain was constructed by homologous recombination with the Rv0522 gene interrupted by a selectable marker. The mutant strain was complemented with the wild-type gene in single copy. Transport analysis of these strains was conducted using 14C-labeled substrates. Greatly reduced uptake of l-arginine and γ-aminobutyric acid (GABA) but not of lysine, ornithine, proline, or alanine was observed in the mutant strain compared to the wild type, grown in Middlebrook 7H9 medium. However, when the strains were starved for 24 h or incubated in a minimal salts medium containing 20 mM arginine (in which even the parent strain does not grow),l-[14C]arginine uptake by the mutant but not the wild-type strain increased strongly. Exogenousl-arginine but not GABA, lysine, ornithine, or alanine was shown to be toxic at concentrations of 20 mM and above to wild-type cells growing in optimal carbon and nitrogen sources such as glycerol and ammonium. l-Arginine supplied in the form of dipeptides showed no toxicity at concentrations as high as 30 mM. Finally, the permease mutant strain showed no defect in survival in unactivated cultured murine macrophages compared with wild-type BCG.

scholarly journals A Fungus-Specific Ras Homolog Contributes to the Hyphal Growth and Virulence of Aspergillus fumigatus

2005 ◽  
Vol 4 (12) ◽  
pp. 1982-1989 ◽  
Author(s):  
Jarrod R. Fortwendel ◽  
Wei Zhao ◽  
Ruchi Bhabhra ◽  
Steven Park ◽  
David S. Perlin ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Growth Control ◽  
Biomass Accumulation ◽  
Hyphal Growth ◽  
Pathogenic Fungi ◽  
Total Biomass ◽  
Gene Encoding ◽  
Directional Growth ◽  
Solid Media ◽  
Hyphal Morphology

ABSTRACT The Ras family of GTPase proteins has been shown to control morphogenesis in many organisms, including several species of pathogenic fungi. In a previous study, we identified a gene encoding a fungus-specific Ras subfamily homolog, rasB, in Aspergillus fumigatus. Here we report that deletion of A. fumigatus rasB caused decreased germination and growth rates on solid media but had no effect on total biomass accumulation after 24 h of growth in liquid culture. The ΔrasB mutant had an irregular hyphal morphology characterized by increased branching. Expression of rasBΔ113-135, a mutant transgene lacking the conserved rasB internal amino acid insertion, did not complement the deletion phenotype of delayed growth and germination rates and abnormal hyphal morphology. Virulence of the rasB deletion strain was diminished; mice infected with this strain exhibited ∼65% survival compared to ∼10% with wild-type and reconstituted strains. These data support the hypothesis that rasB homologs, which are highly conserved among fungi that undergo hyphal growth, control signaling modules important to the directional growth of fungal hyphae.

scholarly journals Regulation and Physiological Role of theDAS1 Gene, Encoding Dihydroxyacetone Synthase, in the Methylotrophic Yeast Candida boidinii

1998 ◽  
Vol 180 (22) ◽  
pp. 5885-5890 ◽  
Author(s):  
Yasuyoshi Sakai ◽  
Tomoyuki Nakagawa ◽  
Masayuki Shimase ◽  
Nobuo Kato
Keyword(s):  
Formate Dehydrogenase ◽  
Physiological Role ◽  
Nitrogen Sources ◽  
Host Genome ◽  
Candida Boidinii ◽  
Carbon And Nitrogen Sources ◽  
Gene Encoding ◽  
Carbon And Nitrogen ◽  
Dihydroxyacetone Synthase

ABSTRACT The physiological role of dihydroxyacetone synthase (DHAS) inCandida boidinii was evaluated at the molecular level. TheDAS1 gene, encoding DHAS, was cloned from the host genome, and regulation of its expression by various carbon and nitrogen sources was analyzed. Western and Northern analyses revealed thatDAS1 expression was regulated mainly at the mRNA level. The regulatory pattern of DHAS was similar to that of alcohol oxidase but distinct from that of two other enzymes in the formaldehyde dissimilation pathway, glutathione-dependent formaldehyde dehydrogenase and formate dehydrogenase. The DAS1 gene was disrupted in one step in the host genome (das1Δ strain), and the growth of the das1Δ strain in various carbon and nitrogen sources was compared with that of the wild-type strain. Thedas1Δ strain had completely lost the ability to grow on methanol, while the strain with a disruption of the formate dehydrogenase gene could survive (Y. Sakai et al., J. Bacteriol. 179:4480–4485, 1997). These and other experiments (e.g., those to determine the expression of the gene and the growth ability of thedas1Δ strain on media containing methylamine or choline as a nitrogen source) suggested that DAS1 is involved in assimilation rather than dissimilation or detoxification of formaldehyde in the cells.

scholarly journals Antioxidant Activity of Aspergillus fumigatus

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Daljit Singh Arora ◽  
Priyanka Chandra
Keyword(s):  
Antioxidant Activity ◽  
Aspergillus Fumigatus ◽  
Incubation Temperature ◽  
Reducing Power ◽  
Nitrogen Sources ◽  
Total Phenolic ◽  
Frap Assay ◽  
Carbon And Nitrogen ◽  
Phenolic Contents ◽  
Scavenging Effect

The antioxidant activity of Aspergillus fumigatus was assayed by different procedures and correlated with its extracellular total phenolic contents. Different physio-chemical parameters were optimized to enhance the activity. The culture grown under stationary conditions for 10 days at 25°C at pH 7 gave the best antioxidant activity. Statistical approaches demonstrated sucrose and NaNO3 to be the most suitable carbon and nitrogen sources, respectively. Response surface analysis showed 5% sucrose, 0.05% NaNO3, and incubation temperature of 35°C to be the optimal conditions for best expression of antioxidant activity. Under these conditions, the antioxidant potential assayed through different procedures was 89.8%, 70.1%, and 70.2% scavenging effect for DPPH radical, ferrous ion and nitric oxide ion, respectively. The reducing power showed an absorbance of 1.0 and FRAP assay revealed the activity of 60.5%. Extracellular total phenolic content and antioxidant activity as assayed by different procedures positively correlated.

scholarly journals Erg4A and Erg4B Are Required for Conidiation and Azole Resistance via Regulation of Ergosterol Biosynthesis in Aspergillus fumigatus

2016 ◽  
Vol 83 (4) ◽  
Author(s):  
Nanbiao Long ◽  
Xiaoling Xu ◽  
Qiuqiong Zeng ◽  
Hong Sang ◽  
Ling Lu
Keyword(s):  
Endoplasmic Reticulum ◽  
Aspergillus Fumigatus ◽  
Plasma Membranes ◽  
Current Knowledge ◽  
Hyphal Growth ◽  
Antifungal Drugs ◽  
Ergosterol Biosynthesis ◽  
Wild Type ◽  
Content Type ◽  
Ergosterol Synthesis

ABSTRACT Ergosterol, a fungus-specific sterol enriched in cell plasma membranes, is an effective antifungal drug target. However, current knowledge of the ergosterol biosynthesis process in the saprophytic human fungal pathogen Aspergillus fumigatus remains limited. In this study, we found that two endoplasmic reticulum-localized sterol C-24 reductases encoded by both erg4A and erg4B homologs are required to catalyze the reaction during the final step of ergosterol biosynthesis. Loss of one homolog of Erg4 induces the overexpression of the other one, accompanied by almost normal ergosterol synthesis and wild-type colony growth. However, double deletions of erg4A and erg4B completely block the last step of ergosterol synthesis, resulting in the accumulation of ergosta-5,7,22,24(28)-tetraenol, a precursor compound of ergosterol. Further studies indicate that erg4A and erg4B are required for conidiation but not for hyphal growth. Importantly, the Δerg4A Δerg4B mutant still demonstrates wild-type virulence in a compromised mouse model but displays remarkable increased susceptibility to antifungal azoles. Our data suggest that inhibitors of Erg4A and Erg4B may serve as effective candidates for adjunct antifungal agents with azoles. IMPORTANCE Knowledge of the ergosterol biosynthesis pathway in the human opportunistic pathogen A. fumigatus is useful for designing and finding new antifungal drugs. In this study, we demonstrated that the endoplasmic reticulum-localized sterol C-24 reductases Erg4A and Erg4B are required for conidiation via regulation of ergosterol biosynthesis. Moreover, inactivation of both Erg4A and Erg4B results in hypersensitivity to the clinical guideline-recommended antifungal drugs itraconazole and voriconazole. Therefore, our finding indicates that inhibition of Erg4A and Erg4B might be an effective approach for alleviating A. fumigatus infection.

Production and Optimization of Cellulase Activity of Thermomonospora Viridis Isolated From Rice Straw

2021 ◽  
Vol 50 (2) ◽  
pp. 395-404
Author(s):  
Faozia Faleha Sadida ◽  
Ma Manchur
Keyword(s):  
Enzyme Activity ◽  
Metal Ions ◽  
Rice Straw ◽  
Cellulase Activity ◽  
Nitrogen Sources ◽  
Cellulase Production ◽  
Tetraacetic Acid ◽  
Carbon And Nitrogen Sources ◽  
Carbon And Nitrogen ◽  
Optimum Ph

A highly cellulolytic actinomycete SR1 was locally isolated from rice straw and provisionally identified as Thermomonospora viridis. Optimum pH, temperature, carbon and nitrogen sources for its cellulase production were 6.5, 35°C, Carboxymethyl cellulase (CMC) and yeast extract, respectively whereas those of cellulase activity were 7.5, 40°C, CMC and peptone respectively. The effects of various metal ions and different reductant and inhibitors on its cellulase activity were investigated. Univalent Ag+ was found to decrease the enzyme activity whereas increased by bivalent Mg2+. Ethylene diamine tetraacetic acid (EDTA) caused remarkable decrease of cellulase activity but β-Mercaptoethanol stimulated its cellulase activity. Bangladesh J. Bot. 50(2): 395-404, 2021 (June)

Disruption of the gene encoding the ChiB1 chitinase of Aspergillus fumigatus and characterization of a recombinant gene product

Microbiology ◽  
2003 ◽  
Vol 149 (10) ◽  
pp. 2931-2939 ◽  
Author(s):  
Alex K. Jaques ◽  
Tamo Fukamizo ◽  
Diana Hall ◽  
Richard C. Barton ◽  
Gemma M. Escott ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Wild Type Strain ◽  
Chitinase Activity ◽  
Gene Replacement ◽  
Wild Type ◽  
Gene Encoding ◽  
Batch Cultures ◽  
Putative Active Site ◽  
Hydrolysis Of

The gene encoding a major, inducible 45 kDa chitinase of Aspergillus fumigatus was cloned and analysis of the deduced amino acid sequence identified a chitinase of the fungal/bacterial class which was designated ChiB1. Recombinant ChiB1, expressed in Pichia pastoris, was shown to function by a retaining mechanism of action. That is, the β-conformation of the chitin substrate linkage was preserved in the product in a manner typical of family 18 chitinases. Cleavage patterns with the N-acetylglucosamine (GlcNAc) oligosaccharide substrates GlcNAc4, GlcNAc5 and GlcNAc6 indicated that the predominant reaction involved hydrolysis of GlcNAc2 from the non-reducing end of each substrate. Products of transglycosylation were also identified in each incubation. Following disruption of chiB1 by gene replacement, growth and morphology of disruptants and of the wild-type strain were essentially identical. However, during the autolytic phase of batch cultures the level of chitinase activity in culture filtrate from a disruptant was much lower than the activity from the wild-type. The search for chitinases with morphogenetic roles in filamentous fungi should perhaps focus on chitinases of the fungal/plant class although such an investigation will be complicated by the identification of at least 11 putative active site domains for family 18 chitinases in the A. fumigatus TIGR database (http://www.tigr.org/).

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