-
Journal of Microbiology and... Apr 2023Exo-polygalacturonase (exo-PG) hydrolyzes pectin acids and liberates mono-galacturonate, which plays an important role in juice extraction, and has rarely been reported....
Exo-polygalacturonase (exo-PG) hydrolyzes pectin acids and liberates mono-galacturonate, which plays an important role in juice extraction, and has rarely been reported. Exo-PG (AfumExoPG28A) from belongs to the glycoside hydrolase 28 family. In this study, its gene was cloned and the protein was expressed and secreted in with a maximal activity of 4.44 U/ml. The optimal temperature and pH of AfumExoPG28A were 55°C and 4.0, respectively. The enzyme exhibited activity over almost the entire acidic pH range (>20.0% activity at pH 2.5-6.5) and remained stable at pH 2.5-10.0 for 24 h. The and values of AfumExoPG28A were calculated by the substrate of polygalacturonic acid as 25.4 mg/ml and 23.6 U/mg, respectively. Addition of AfumExoPG28A (0.8 U/mg) increased the light transmittance and juice yield of plantain pulp by 11.7% and 9%, respectively. Combining AfumExoPG28A (0.8 U/mg) with an endo-PG (0.8 U/mg) from our laboratory, the enzymes increased the light transmittance and juice yield of plantain pulp by 45.7% and 10%, respectively. Thus, the enzyme's potential value in juice production was revealed by the remarkable acidic properties and catalytic activity in fruit pulp.
Topics: Polygalacturonase; Aspergillus fumigatus; Enzyme Stability; Glycoside Hydrolases; Temperature; Hydrogen-Ion Concentration
PubMed: 36788465
DOI: 10.4014/jmb.2211.11003 -
Metallomics : Integrated Biometal... Mar 2017The devastating infections that fungal pathogens cause in humans are underappreciated relative to viral, bacterial and parasitic diseases. In recent years, the... (Review)
Review
The devastating infections that fungal pathogens cause in humans are underappreciated relative to viral, bacterial and parasitic diseases. In recent years, the contributions to virulence of reductive iron uptake, siderophore-mediated uptake and heme acquisition have been identified in the best studied and most life-threatening fungal pathogens: Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus. In particular, exciting new work illustrates the importance of iron acquisition from heme and hemoglobin in the virulence of pathogenic yeasts. However, the challenge of establishing how these fungi gain access to hemoglobin in blood and to other sources of heme remains to be fully addressed. Recent studies are also expanding our knowledge of iron uptake in less-well studied fungal pathogens, including dimorphic fungi where new information reveals an integration of iron acquisition with morphogenesis and cell-surface properties for adhesion to host cells. Overall, the accumulating information provides opportunities to exploit iron acquisition for antifungal therapy, and new work highlights the development of specific inhibitors of siderophore biosynthesis and metal chelators for therapeutic use alone or in conjunction with existing antifungal drugs. It is clear that iron-related therapies will need to be customized for specific diseases because the emerging view is that fungal pathogens use different combinations of strategies for iron acquisition in the varied niches of vertebrate hosts.
Topics: Animals; Aspergillosis; Aspergillus fumigatus; Cryptococcosis; Cryptococcus neoformans; Humans; Iron; Virulence
PubMed: 28217776
DOI: 10.1039/c6mt00301j -
Mycopathologia Dec 2014Pathogenic fungi employ numerous mechanisms to flourish in the stressful environment encountered within their mammalian hosts. Central to this arsenal for filamentous... (Review)
Review
Pathogenic fungi employ numerous mechanisms to flourish in the stressful environment encountered within their mammalian hosts. Central to this arsenal for filamentous fungi is invasive growth within the host microenvironment, mediated by establishment and maintenance of polarized hyphal morphogenesis. In Aspergillus fumigatus, the RasA signal transduction pathway has emerged as a significant regulator of hyphal morphogenesis and virulence, among other processes. The factors contributing to the regulation of RasA itself are not as thoroughly understood, although proper temporal activation of RasA and spatial localization of RasA to the plasma membrane are known to play major roles. Interference with RasA palmitoylation or prenylation results in mislocalization of RasA and is associated with severe growth deficits. In addition, dysregulation of RasA activation results in severe morphologic aberrancies and growth deficits. This review highlights the relationship between RasA signaling, hyphal morphogenesis, and virulence in A. fumigatus and focuses on potential determinants of spatial and temporal RasA regulation.
Topics: Aspergillus fumigatus; Gene Expression Regulation, Fungal; Hyphae; Lipoylation; Protein Prenylation; Signal Transduction; Virulence; ras Proteins
PubMed: 24952717
DOI: 10.1007/s11046-014-9765-1 -
Applied and Environmental Microbiology Oct 2021An efficient reactive oxygen species (ROS) detoxification system is vital for the survival of the pathogenic fungus Aspergillus fumigatus within the host high-ROS...
An efficient reactive oxygen species (ROS) detoxification system is vital for the survival of the pathogenic fungus Aspergillus fumigatus within the host high-ROS environment of the host. Therefore, identifying and targeting factors essential for oxidative stress response is one approach to developing novel treatments for fungal infections. The oxidation resistance 1 (Oxr1) protein is essential for protection against oxidative stress in mammals, but its functions in pathogenic fungi remain unknown. The present study aimed to characterize the role of an Oxr1 homolog in A. fumigatus. The results indicated that the OxrA protein plays an important role in oxidative stress resistance by regulating the catalase function in A. fumigatus, and overexpression of catalase can rescue the phenotype associated with OxrA deficiency. Importantly, the deficiency of decreased the virulence of A. fumigatus and altered the host immune response. Using the Aspergillus-induced lung infection model, we demonstrated that the mutant strain induced less tissue damage along with decreased levels of lactate dehydrogenase (LDH) and albumin release. Additionally, the mutant caused inflammation at a lower degree, along with a markedly reduced influx of neutrophils to the lungs and a decreased secretion of cytokine usually associated with recruitment of neutrophils in mice. These results characterize the role of OxrA in A. fumigatus as a core regulator of oxidative stress resistance and fungal pathogenesis. Knowledge of ROS detoxification in fungal pathogens is useful in the design of new antifungal drugs and could aid in the study of oxidative stress resistance mechanisms. In this study, we demonstrate that OxrA protein localizes to the mitochondria and functions to protect against oxidative damage. We demonstrate that OxrA contributes to oxidative stress resistance by regulating catalase function, and overexpression of catalase (CatA or CatB) can rescue the phenotype that is associated with OxrA deficiency. Remarkably, a loss of OxrA attenuated the fungal virulence in a mouse model of invasive pulmonary aspergillosis and altered the host immune response. Therefore, our finding indicates that inhibition of OxrA might be an effective approach for alleviating A. fumigatus infection. The present study is, to the best of our knowledge, a pioneer in reporting the vital role of Oxr1 protein in pathogenic fungi.
Topics: Animals; Aspergillosis; Aspergillus fumigatus; Catalase; Fungal Proteins; Mice; Oxidative Stress; Reactive Oxygen Species; Virulence
PubMed: 34524893
DOI: 10.1128/AEM.01120-21 -
Current Opinion in Microbiology Dec 2020The mammalian immune system can tune its inflammatory response to the threat level posed by an invading pathogen. It is well established that the host utilizes numerous... (Review)
Review
The mammalian immune system can tune its inflammatory response to the threat level posed by an invading pathogen. It is well established that the host utilizes numerous 'patterns of pathogenicity', such as microbial growth, invasion, and viability, to achieve this tuning during bacterial infections. This review discusses how this notion fits during fungal infection, particularly regarding Aspergillus fumigatus infection. Moreover, how the environmental niches filled by A. fumigatus may drive the evolution of the fungal traits responsible for inducing the strain-specific inflammatory responses that have been experimentally observed will be discussed. Moving forward understanding the mechanisms of the fungal strain-specific inflammatory response due to the initial interactions with the host innate immune system will be essential for enhancing our therapeutic options for the treatment of invasive fungal infections.
Topics: Animals; Aspergillosis; Aspergillus fumigatus; Fungal Proteins; Humans; Invasive Fungal Infections
PubMed: 32898768
DOI: 10.1016/j.mib.2020.08.004 -
Future Microbiology Jun 2009Aspergillus fumigatus is the most prevalent thermophilic inhabitants of decaying vegetation and one of the most important human opportunistic fungal pathogens. Like... (Review)
Review
Aspergillus fumigatus is the most prevalent thermophilic inhabitants of decaying vegetation and one of the most important human opportunistic fungal pathogens. Like other fungi, A. fumigatus cells are covered by a cell wall, which is both a protective, rigid exoskeleton and a dynamic structure, undergoing constant modification depending on its environment. The cell wall, in the majority of fungi, is composed of polysaccharides, and understanding the biochemical organization and biogenesis of an A. fumigatus cell wall is essential as this envelop is continuously in contact with the environment/host cell and acts as a sieve and reservoir for molecules, such as enzymes and toxins that play an active role during infection. This article is intended to give an overview of the biosynthesis of constituent cell wall polysaccharides and their postsynthetic modification in A. fumigatus, it also discusses the antifungal drugs that affect cell wall polysaccharide biosynthesis.
Topics: Antifungal Agents; Aspergillus fumigatus; Biosynthetic Pathways; Cell Wall; Polysaccharides
PubMed: 19492968
DOI: 10.2217/fmb.09.29 -
Current Opinion in Microbiology Aug 2011The opportunistic fungal pathogen Aspergillus fumigatus adapts to iron limitation by upregulation of iron uptake mechanisms including siderophore biosynthesis and... (Review)
Review
The opportunistic fungal pathogen Aspergillus fumigatus adapts to iron limitation by upregulation of iron uptake mechanisms including siderophore biosynthesis and downregulation of iron-consuming pathways to spare iron. These metabolic changes depend mainly on the transcription factor HapX. Consistent with the crucial role of iron in pathophysiology, genetic inactivation of either HapX or the siderophore system attenuates virulence of A. fumigatus in a murine model of aspergillosis. The differences in iron handling between mammals and fungi might serve to improve therapy and diagnosis of fungal infections.
Topics: Animals; Aspergillosis; Aspergillus fumigatus; Gene Expression Regulation, Fungal; Homeostasis; Host-Pathogen Interactions; Humans; Iron; Molecular Structure; Oxidative Stress; Siderophores; Spores, Fungal; Transcription, Genetic; Transcriptional Activation; Virulence
PubMed: 21724450
DOI: 10.1016/j.mib.2011.06.002 -
Microbiology (Reading, England) May 2007In fungi, nonribosomal peptide synthetases (NRP synthetases) are large multi-functional enzymes containing adenylation, thiolation (or peptidyl carrier protein, PCP) and... (Review)
Review
In fungi, nonribosomal peptide synthetases (NRP synthetases) are large multi-functional enzymes containing adenylation, thiolation (or peptidyl carrier protein, PCP) and condensation domains. These enzymes are often encoded within gene clusters. Multiple NRP synthetase ORFs have also been identified in fungi (14 in Aspergillus fumigatus). LeaA, a methyltransferase, is involved in secondary metabolite gene cluster regulation in Aspergillus spp. The NRP synthetases GliP and FtmA respectively direct the biosynthesis of the toxic metabolites gliotoxin and brevianamide F, a precursor of bioactive prenylated alkaloids. The NRP synthetase Pes1 has been shown to mediate resistance to oxidative stress, and in plant-pathogenic ascomycetes (e.g. Cochliobolus heterostrophus) an NRP synthetase, encoded by the NPS6 gene, significantly contributes to virulence and resistance to oxidative stress. Adenylation (A) domains within NRP synthetases govern the specificity of amino acid incorporation into nonribosomally synthesized peptides. To date there have only been limited demonstrations of A domain specificity (e.g. A. fumigatus GliP and in Beauveria bassiana) in fungi. Indeed, only in silico prediction data are available on A domain specificity of NRP synthetases from most fungi. NRP synthetases are activated by 4'-phosphopantetheinylation of serine residues within PCP domains by 4'-phosphopantetheinyl transferases (4'-PPTases). Coenzyme A acts as the 4'-phosphopantetheine donor, and labelled coenzyme A can be used to affinity-label apo-NRP synthetases. Emerging fungal gene disruption and gene cluster expression strategies, allied to proteomic strategies, are poised to facilitate a greater understanding of the coding potential of NRP synthetases in fungi.
Topics: Aspergillus fumigatus; Fungi; Peptide Biosynthesis, Nucleic Acid-Independent; Peptide Synthases
PubMed: 17464044
DOI: 10.1099/mic.0.2006/006908-0 -
Microbiology Spectrum Dec 2021In Aspergillus fumigatus, the repetitive region of the gene is one of the most frequently used loci for intraspecies typing of this human pathogenic mold. Using PCR...
In Aspergillus fumigatus, the repetitive region of the gene is one of the most frequently used loci for intraspecies typing of this human pathogenic mold. Using PCR amplification and Sanger sequencing of only a single marker, typing is readily available to most laboratories and highly reproducible. Here, I evaluate the usefulness of the marker for resistance detection and epidemiologic stratification among A. fumigatus isolates. After resolving nomenclature conflicts from published studies and adding novel types, the number of known types now adds up to 38. Their distribution mostly correlates with A. fumigatus population structure, and they are also meaningful for narrowly defined cases of azole resistance phenotypes. Isolates carrying the pandemic resistance allele TR/L98H show signs of interclade crossing of strains with t02 or t04A, into the t11 clade. Furthermore, absolute differences in voriconazole MIC values between t02/t04B versus t11 TR/L98H isolates indicate that the genetic background of resistance mutations may have a pivotal role in cross-resistance phenotypes and, thus, clinical outcome and environmental selection. Despite the general genetic similarity of isolates with identical types, outcrossing into other clades is also observed. The type alone, therefore, does not sufficiently discriminate genetic clades to be used as the sole marker in epidemiologic studies. Aspergillus fumigatus is a ubiquitously distributed saprophytic mold and a leading cause of invasive aspergillosis in human hosts. Pandemic azole-resistant strains have emerged on a global scale, which are thought to be propagated through use of azole-based fungicides in agriculture. To perform epidemiologic studies, genetic typing of large cohorts is key. Here, I evaluate the usefulness of the frequently used marker for resistance detection and epidemiologic stratification among A. fumigatus isolates. The phylogenetic distribution of types mostly correlates with A. fumigatus population structure and is also meaningful for narrowly defined cases of azole resistance phenotypes. Nevertheless, outcrossing of into other clades is also observed. The type alone, therefore, does not sufficiently discriminate genetic clades and should not be used as the sole marker in epidemiologic studies.
Topics: Antifungal Agents; Aspergillosis; Aspergillus fumigatus; Drug Resistance, Fungal; Fungal Proteins; Genetic Markers; Humans; Membrane Proteins; Microbial Sensitivity Tests; Molecular Typing; Mycological Typing Techniques; Polymorphism, Single Nucleotide; Voriconazole
PubMed: 34787484
DOI: 10.1128/Spectrum.01214-21 -
Microbiology Spectrum Feb 2022Aspergillus fumigatus is an important opportunistic pathogenic fungus that causes invasive aspergillosis in immunocompromised humans. Regulated fungal growth is...
Aspergillus fumigatus is an important opportunistic pathogenic fungus that causes invasive aspergillosis in immunocompromised humans. Regulated fungal growth is essential for disease development and progression. Thus, screening for genes that regulate fungal growth may lead to the identification of potential therapeutic targets for invasive aspergillosis (IA). Screening of the transfer DNA (T-DNA) random-insertion A. fumigatus mutants identified a severe growth deficiency mutant AFM2954 and featured as the mutated gene described as a putative intracellular protein transporter of unknown function. The deletion of exhibited severe growth defects and significantly increased the nematode and mouse survival rates and decreased the fungal loads and histopathological damages in mouse lungs. Transcriptomic analyses revealed expression changes associated with the cell wall synthesis, the tricarboxylic acid cycle (TCA cycle), and oxidative phosphorylation genes in the mutant. Deletion of the gene resulted in resistance to cell wall-perturbing agents and thickened cell wall as well as reduced ATP contents and mitochondrial membrane potential, suggested that affected the cell wall synthesis and mitochondrial function of A. fumigatus. All together, our study uncovered novel functions of in growth and virulence of A. fumigatus and provided a theoretical basis for the development of new therapeutic target for treating IA patients. Aspergillus fumigatus is the main causative agent of invasive aspergillosis in immunocompromised hosts, with up to 90% lethality. Nevertheless, the fungal factors that regulate the pathogenesis of A. fumigatus remain largely unknown. Better understanding of the mechanisms controlling growth of A. fumigatus may provide novel therapeutic targets. In the present study, we characterized in the opportunistic pathogen A. fumigatus. The function of remains unknown. We proved its important role in growth and virulence, likely because of its effects on cell wall synthesis and mitochondrial functions.
Topics: Amino Acid Sequence; Animals; Aspergillosis; Aspergillus fumigatus; Fungal Proteins; Gene Expression Regulation, Fungal; Humans; Male; Mice; Mice, Inbred BALB C; Sequence Alignment; Sequence Deletion; Virulence
PubMed: 35107385
DOI: 10.1128/spectrum.01558-21