Evaluation of antidiabetic, antioxidant, and cytotoxic potential of maize (zea mays l.) husk leaf extracts.

In current study, Maize (Zea mays L.) husk leave extracts were appraised for biological activities such as cytotoxicity, antidiabetic, antioxidant and antimicrobial. Maceration was performed to collect various fractions of husk leave extracts using a pool of solvents i.e., n-hexane, chloroform, ethyl acetate, butanol and methanol. Antioxidant potential was measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging, reducing power and linoleic acid oxidation assay, using butylated hydroxy toluene (BHT) as a positive control. Total phenolic and flavonoid contents were found to be 18.47-425.11 mg/100 g GAE and 5.83-16.72 mg/100 g CE, respectively. The DPPH scavenging assay was exhibited in the range of 76.36 to 88.53%. The percentage inhibition in linoleic acid oxidation was found from 10.16 to 79.51%. Significant antimicrobial activity was demonstrated by husk leaf extracts against bacterial strains and fungal strains using disc diffusion and minimum inhibitory concentration (MIC) method. Amylase alpha assay was employed to analyze the antidiabetic activity which ranged between 9.52-24.81%. Cytotoxicity was evaluated by % age lysis (0.35-9.54%), while thrombolytic activity ranged between 7.67 to 31.27%. The results presented in this study revealed that maize (Zea mays L.) husk leaf extracts can be a valuable source of biologically active compounds and may be consumed as a source of potent herbal medicine in pharmaceuticals.

Biomanagement of rice root-knot nematode Meloidogyne graminicola using five indigenous microbial isolates under pot and field trials.

AIMS: To ascertain the effectiveness of Aspergillus niger, Trichoderma harzianum, Pochonia chlamydosporia, Bacillus subtilis and Pseudomonas fluorescens against rice root-knot nematode, Meloidogyne graminicola, and to optimize their application methods. METHODS AND RESULTS: The relative effectiveness of five indigenous biocontrol agents (BCA) against M. graminicola on rice cv. PS-5 was tested initially in pot culture. The BCAs, A. niger, P. chlamydosporia and P. fluorescens proved more effective, and significantly reduced the nematode disease. It is hypothesized that success of a biocontrol module may vary with the BCA and application methods. Hence, the effectiveness of the above three BCAs as well as seven different treatment schemes were evaluated in naturally infested farmer's fields during 2 consecutive years. In nematode-infested plots without any BCA treatments, terminal galls formed on the roots, and plants suffered a 19-31% decrease in the growth and yield. The treatments with P. chlamydosporia or A. niger through root-dip (RD) plus one soil application (SA) at 15 days after planting were found to be highly effective against the nematode. CONCLUSIONS: Relatively greater nematode control was achieved with RD plus two SAs (15 + 30 DAP) but statistically the effect was on par with RD + one SA at 15 DAP. These treatments significantly reduced galling (22-25%), egg mass production (21-29%) and reproduction factor (63-70%) of M. graminicola, and subsequently increased the grain yield (11-21%). SIGNIFICANCE AND IMPACT OF THE STUDY: Application methods enhanced the effectiveness of BCAs against M. graminicola. The RD plus one SA at 15 DAP proved to be most effective treatment to control root-knot disease in rice. Use of multiple treatments (root dip and SA) appears cumbersome, but in view of effectiveness and limitation of chemical control in rice paddies, farmers may adopt the above module that may lead to 11-21% yield improvement.

Phytochemical screening and biological activities of Bromus pectinatus Thunb.

The present research study investigates the phytochemical and pharmacological importance of Bromus pectinatus. Qualitative phytochemical analysis of this plant was carried out to use standard method for the presence of various bioactive constituents. Results showed the ethanolic extract contain natural product such as steroids, alkaloids, tannins, coumarin, saponins, flavonoids and phenols. These compounds play a key role to reducing various disease and microbial inhibition. The ethanolic extract also showed the antimicrobial and antifugal activity against different pathogenic bacterial strains e.g Escherichia coli, Micrococus leutus, Protus vulgarus, and Kelebsela pneumona and three fungal strains Aspergillus fumigatus, Aspergillus flavous, Aspergillus niger. The antioxidant assay was performed as % inhibition of DPPH (1, 1-diphenyl-2-picryl-hydrazyl) free radicals. The plant extract has more antioxidant activity as compared to ascorbic acid. The maximum concentration (800µg/ml) is the most effective of all. The plant extract showed the high cytotoxicity activity against Brine shrimp. Moreover, the plant extract exhibited allelopathic effect on different growth parameters of wheat plant mostly at higher concentration. These results indicate that the BPEE have a potential broad-spectrum antimicrobial, cytotoxic, antioxidant and phytotoxic activity due to the presence of bioactive compounds.

Apical but not sub-apical hyphal compartments are self-sustaining in growth.

It was recently demonstrated that apical compartments of Aspergillus niger hyphae are self-sustaining in growth. This was shown by assessing the growth rate of individual hyphae before and after dissection of the second compartment. Using the same methodology, it is here demonstrated that single apical compartments of the septate fungi Penicillium chrysogenum and Schizophyllum commune as well as the 500-µm-apical region of the non-septate fungus Rhizopus stolonifer are also self-sustaining in growth. In contrast, single 2nd compartments (obtained by dissection of the first and third compartment) of the septate fungi or the region between 500 and 1000 µm from tips of R. stolonifer were severely impacted in their growth rate. In addition, it is shown that existing or newly formed branches originating from the 2nd compartments function as a backup system for hyphal growth when the apical part of the hypha of the three studied fungi is damaged. Together, it is concluded that the apical compartments/zones of the studied fungi are self-sustaining in growth. In contrast, the subapical region is not self-sustaining but functions as a backup once the apical zone is damaged. This back up system is relevant in nature because the apices of hyphae are the first to be exposed to (a)biotic stress conditions when entering an unexplored substrate.

Aspergillus niger α-1,3-glucan acts as a virulence factor by inhibiting the insect phenoloxidase system.

Phenoloxidase (PO) is a key enzyme in the melanization process involved in elimination of pathogens in insects. The PO system is rapidly activated in response to pathogen recognition. Inhibition of PO activity can be a way to avoid immune response and increase infection effectiveness. In this study, the effects of inoculation of Galleria mellonella larvae with Aspergillus niger α-1,3-glucan and conidia on PO activity in hemolymph are analyzed in comparison with the effects of ß-1,3/1,6-glucan inoculation. Our results indicate that α-1,3-glucan, a fungal cell wall polysaccharide, can play a role of a virulence factor involved in inhibition of the insect PO system.

Physical Properties, Chemical Analysis, and Evaluation of Antimicrobial Response of New Polylactide/Alginate/Copper Composite Materials.

In recent years, due to an expansion of antibiotic-resistant microorganisms, there has been growing interest in biodegradable and antibacterial polymers that can be used in selected biomedical applications. The present work describes the synthesis of antimicrobial polylactide-copper alginate (PLA-ALG-Cu2+) composite fibers and their characterization. The composites were prepared by immersing PLA fibers in aqueous solution of sodium alginate, followed by ionic cross-linking of alginate chains within the polylactide fibers with Cu(II) ions to yield PLA-ALG-Cu2+ composite fibers. The composites, so prepared, were characterized by scanning electron microscopy (SEM), UV/VIS transmittance and attenuated total reflection Fourier-transform infrared spectroscopy ATR-FTIR, and by determination of their specific surface area (SSA), total/average pore volumes (through application of the 5-point Brunauer-Emmett-Teller method (BET)), and ability to block UV radiation (determination of the ultraviolet protection factor (UPF) of samples). The composites were also subjected to in vitro antimicrobial activity evaluation tests against colonies of Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria and antifungal susceptibility tests against Aspergillus niger and Chaetomium globosum fungal mold species. All the results obtained in this work showed that the obtained composites were promising materials to be used as an antimicrobial wound dressing.

Developmental stages of biofilm and characterization of extracellular matrix of manglicolous fungus Aspergillus niger BSC-1.

Fungal biofilm is ubiquitous in natural environment. The major constituent of fungal biofilm other than biomass is the extracellular matrix (ECM), in which fungal hyphae are embedded. Physical properties of biofilms such as attachment, mechanical strength, and antibiotic resistance can be attributed to ECM. The present work probes various stages of biofilm formation by filamentous manglicolous fungus Aspergillus niger BSC-1. The spectroscopic analysis revealed that with an increase in incubation time the biofilm formation was significantly increased (p < .0001) up to 36 h. Scanning electron micrograph and confocal micrograph depicted the development of fungal biofilm comprising of six stages, that is, (a) adsorption, (b) active attachment, (c) germling and monolayer formation, (d) hyphal development and formation of ECM, (e) maturation of ECM, and (f) dispersal of spores. At maturation stage, thickness of biofilm was observed upto approximately 15 µm. Approximately, 8.1 mg of ECM materials were extracted from 20 ml of broth culture using ethanol precipitation method. Furthermore, attenuated total reflectance Fourier-transformed infrared spectroscopic analysis exhibited peaks at 3,398, 2,930, 1,571, 1,391, 1,092, 977 cm-1 which confirmed the presence of protein, carbohydrate, and lipid in the biofilm-associated matrix.

FlbA-Regulated Gene rpnR Is Involved in Stress Resistance and Impacts Protein Secretion when Aspergillus niger Is Grown on Xylose.

Proteins are secreted throughout the mycelium of Aspergillus niger except for the sporulating zone. A link between sporulation and repression of protein secretion was underlined by the finding that inactivation of the sporulation gene flbA results in mycelial colonies that secrete proteins throughout the colony. However, ΔflbA strain hyphae also lyse and have thinner cell walls. This pleiotropic phenotype is associated with differential expression of 36 predicted transcription factor genes, one of which, rpnR, was inactivated in this study. Sporulation, biomass, and secretome complexity were not affected in the ΔrpnR deletion strain of the fungus. In contrast, ribosomal subunit expression and protein secretion into the medium were reduced when A. niger was grown on xylose. Moreover, the ΔrpnR strain showed decreased resistance to H2O2 and the proteotoxic stress-inducing agent dithiothreitol. Taking the data together, RpnR is involved in proteotoxic stress resistance and impacts protein secretion when A. niger is grown on xylose.IMPORTANCEAspergillus niger secretes a large amount and diversity of industrially relevant enzymes into the culture medium. This makes the fungus a widely used industrial cell factory. For instance, carbohydrate-active enzymes of A. niger are used in biofuel production from lignocellulosic feedstock. These enzymes represent a major cost factor in this process. Higher production yields could substantially reduce these costs and therefore contribute to a more sustainable economy and less dependence on fossil fuels. Enzyme secretion is inhibited in A. niger by asexual reproduction. The sporulation protein FlbA is involved in this process by impacting the expression of 36 predicted transcription factor genes. Here, we show that one of these predicted transcriptional regulators, RpnR, regulates protein secretion and proteotoxic stress resistance. The gene is thus an interesting target to improve enzyme production in A. niger.

Signal pattern plot: a simple tool for time-dependent metabolomics studies by 1H NMR spectroscopy.

We show an alternative way to visualize time course NMR data without the application of multivariate data analysis, based on the temporal change of the metabolome of hazelnuts after mold infestation. Fresh hazelnuts were inoculated with eight different natural mold species and the growth was studied over a period of 14 days. The data were plotted in a color-coded scheme showing metabolic changes as a function of chemical shift, which we named signal pattern plot. This plot graphically displays alteration (trend) of a respected signal over time and allows visual interpretation in a simple manner. Changes are compared with a reference sample stored under identical conditions as the infected nuts. The plot allows, at a glance, the recognition of individual landmarks specific to a sample group as well as common features of the spectra. Each sample reveals an individual signal pattern. The plot facilitates the recognition of signals that belong to biological relevant metabolites. Betaine and five signals were identified that specifically changed upon mold infestation. Graphical abstract.

The study of intracellular and secreted high-molecular-mass protease(s) of Trichoderma spp., and their responses to conidiation stimuli.

We continued our study of high-molecular-mass proteases (HMMPs) using several strains of the genus Trichoderma, and other filamentous fungi (Botrytis cinerea, Aspergillus niger, Fusarium culmorum, and Penicillium purpurogenum). We found that five Trichoderma strains secreted HMMPs into the media after induction with bovine serum albumin. Botrytis cinerea and F. culmorum secreted proteases in the absence of inducer, while A. niger or P. purpurogenum did not secrete proteolytic activity (PA). The activity of HMMPs secreted by or intracellularly located in Trichoderma spp. represents the predominant part of cellular PA, according to zymogram patterns. This observation allowed the study of HMMPs' physiological role(s) independent from the secretion. In studying conidiation, we found that illumination significantly stimulated PA in Trichoderma strains. In the T. atroviride IMI 206040 strain, we demonstrated that this stimulation is dependent on the BLR1 and BLR2 receptors. No stimulation of PA was observed when mechanical injury was used as an elicitor of conidiation. Compounds used as inhibitors or activators of conidiation exerted no congruent effects on both PA and conidiation. These results do not favour a direct role of HMMPs in conidiation. Probably, HMMP activity may be involved in the process of the activation of metabolism during vegetative growth, differentiation, and aging-related processes.

Effects of partial dietary substitution of groundnut meal by defatted, Aspergillus niger-fermented and heated Jatropha curcas kernel meal on feed intake and growth performance of broiler chicks.

This study was conducted to determine intake and growth performance of broiler chicks fed with Jatropha curcas kernel meal physico-chemically and biologically processed. The feed experiment lasted for 7 days with 20-day-old Ross 308 strain unsexed broiler chicks. Two dietary treatments were given each to ten animals, according to a complete randomized design. Kernels, manually obtained from J. curcas seed, were defatted, heated, and fermented with a strain of Aspergillus niger and oven-dried, in order to obtain the treated jatropha kernel meal. This latter was used to replace one third of a groundnut meal premix which was then incorporated in a commercial diet to warrant iso-nitrogenous and iso-caloric characteristics of the diets. Data collected were analyzed according to ANOVA procedure. The results revealed that the animals that received the diet incorporating jatropha kernel meal had numerically higher live weight (156.1 vs. 152.7 g/animal) (P > 0.05) and average daily weight gain (12.3 vs. 11.7 g/day/animal) (P > 0.05) than the control ones, at the end of experiment. The average daily feed intake was the same for the two groups of animals (23.2 g/day/animal) (P > 0.05) with a similar feed conversion ratio (2.0 vs. 2.1 respectively for the jatropha group and the control group). The survival rate, at the end of the experiment, was 100% for the two groups of animals. Physico-chemically and biologically processed Jatropha curcas kernel could be an interesting by-product for poultry feeding.

Induced accumulation of Au, Ag and Cu in Brassica napus grown in a mine tailings with the inoculation of Aspergillus niger and the application of two chemical compounds.

This study evaluated the ability of Brassica napus for extracting gold (Au), silver (Ag) and copper (Cu) from a mine tailings, with the inoculation of two Aspergillus niger strains, and the application of ammonium thiocyanate (NH4SCN) or ammonium thiosulfate [(NH4)2S2O3]. After seven weeks of growth inoculated or non-inoculated plants were applied with 1 or 2 g kg-1 of either NH4SCN or (NH4)2S2O3, respectively. Eight days after the application of the chemical compounds, plants were harvested for determining the total dry biomass, and the content of Au, Ag, and Cu in plant organs. Application of (NH4)2S2O3 or NH4SCN resulted in enhanced Au-accumulation in stems (447% and 507%, respectively), while either (NH4)2S2O3+Aspergillus, or NH4SCN increased the Au-accumulation in roots (198.5% and 404%, respectively) when compared to the control. Treatments with (NH4)2S2O3 or (NH4)2S2O3+Aspergillus significantly increased (P ≤ 0.001) the accumulation of Ag in leaves (677% and 1376%, respectively), while NH4SCN + Aspergillus, and (NH4)2S2O3 enhanced the accumulation in stems (7153% and 6717.5%). The Ag-accumulation in roots was stimulated by NH4SCN+ Aspergillus, and (NH4)2S2O3+ Aspergillus (132.5% and 178%, respectively), when compared to the control. The combination of NH4SCN+Aspergillus significantly enhanced the Cu-accumulation in leaves (228%); whereas NH4SCN+ Aspergillus, or (NH4)2S2O3+ Aspergillus resulted in greater accumulation of Cu in stems (1233.5% and 1580%, respectively) than the control. Results suggest that either NH4SCN or (NH4)2S2O3 (with or without Aspergillus) improved the accumulation of Au and Ag by B. napus. Accumulation of Au and Ag in plant organs overpassed the hyperaccumulation criterion (> 1 mg kg-1 of plant biomass); whereas Cu-accumulation in stems and roots also overpassed such criterion (> 1000 mg kg-1) by applying either NH4SCN or (NH4)2S2O3 + A. niger.

Comparative transcriptome analysis reveals different strategies for degradation of steam-exploded sugarcane bagasse by Aspergillus niger and Trichoderma reesei.

BACKGROUND: Second generation (2G) ethanol is produced by breaking down lignocellulosic biomass into fermentable sugars. In Brazil, sugarcane bagasse has been proposed as the lignocellulosic residue for this biofuel production. The enzymatic cocktails for the degradation of biomass-derived polysaccharides are mostly produced by fungi, such as Aspergillus niger and Trichoderma reesei. However, it is not yet fully understood how these microorganisms degrade plant biomass. In order to identify transcriptomic changes during steam-exploded bagasse (SEB) breakdown, we conducted a RNA-seq comparative transcriptome profiling of both fungi growing on SEB as carbon source. RESULTS: Particular attention was focused on CAZymes, sugar transporters, transcription factors (TFs) and other proteins related to lignocellulose degradation. Although genes coding for the main enzymes involved in biomass deconstruction were expressed by both fungal strains since the beginning of the growth in SEB, significant differences were found in their expression profiles. The expression of these enzymes is mainly regulated at the transcription level, and A. niger and T. reesei also showed differences in TFs content and in their expression. Several sugar transporters that were induced in both fungal strains could be new players on biomass degradation besides their role in sugar uptake. Interestingly, our findings revealed that in both strains several genes that code for proteins of unknown function and pro-oxidant, antioxidant, and detoxification enzymes were induced during growth in SEB as carbon source, but their specific roles on lignocellulose degradation remain to be elucidated. CONCLUSIONS: This is the first report of a time-course experiment monitoring the degradation of pretreated bagasse by two important fungi using the RNA-seq technology. It was possible to identify a set of genes that might be applied in several biotechnology fields. The data suggest that these two microorganisms employ different strategies for biomass breakdown. This knowledge can be exploited for the rational design of enzymatic cocktails and 2G ethanol production improvement.

Identification and genomic analysis of antifungal property of a tomato root endophyte Pseudomonas sp. p21.

Pseudomonas sp., which occupy a variety of ecological niches, have been widely studied for their versatile metabolic capacity to promote plant growth, suppress microbial pathogens, and induce systemic resistance in plants. In this study, a Pseudomonas sp. strain p21, which was isolated from tomato root endophytes, was identified as having antagonism against Aspergillus niger. Further analysis showed that this strain had the ability to biosynthesise siderophores and was less effective in inhibiting the growth of A. niger with the supplementation of Fe3+ in the agar medium. Genomic sequencing and the secondary metabolite cluster analysis demonstrated that Pseudomonas sp. p21 harboured 2 pyoverdine biosynthetic gene clusters, which encode compounds with predicted core structures and two variable tetra-peptide or eleven-peptide chains. The results indicated that siderophore-mediated competition for iron might be an important mechanism in Pseudomonas suppression of the fungal pathogen A. niger and in microbe-pathogen-plant interactions.

Antioxidant defense response induced by Trichoderma viride against Aspergillus niger Van Tieghem causing collar rot in groundnut (Arachis hypogaea L.).

The study was conducted to examine the antioxidant enzymes induced by Trichoderma viride JAU60 as initial defense response during invasion of rot pathogen Aspergillus niger Van Tieghem in five groundnut varieties under pot culture. Seed treatment of T. viride JAU60 reduced 51-58% collar rot disease incidence in different groundnut varieties under pathogen infected soil culture. The activities of the antioxidant enzymes, viz., superoxide dismutase (SOD, EC 1.15.1.1), guaiacol peroxidase (GPX, EC 1.11.1.7) and ascorbate peroxidase (APX, EC 1.11.1.11), elevated in response to pathogen infection, in higher rate by tolerant varieties (J-11 and GG-2) compared with susceptible (GAUG-10, GG-13, GG-20) and further induced by T. viride treatment. Trichoderma treatment remarkably increased the 2.3 fold SOD, 5 fold GPX and 2.5 fold APX activities during disease development in tolerant varieties and the same was found about 1.2, 1.5 and 2.0 folds, respectively, in susceptible varieties. Overall, T. viride JAU60 treated seedlings (T3) witnessed higher activities of SOD (1.5 fold), GPX (3.25 fold) and APX (1.25 fold) than pathogen treatment (T2) possibly suggest the induction of antioxidant defense response by Trichoderma bio-controller to combat oxidative burst produced by invading pathogen.

Common airborne fungi induce species-specific effects on upper airway inflammatory and remodelling responses.

OBJECTIVE: Whilst the exact cause of chronic rhinosinusitis (CRS) remains elusive, it is clear that both inflammation and remodelling are key disease processes. Environmental fungi have been linked to airway inflammation in CRS; however, their role in the pathogenesis of this condition remains controversial. The current consensus suggests that whilst fungi may not be directly causative, it is likely that CRS patients have deficits in their innate and potentially acquired immunity, which in turn may modify their ability to react to fungi. This study used a nasal polyp explant tissue stimulation model to study the inflammatory and remodelling responses related to challenge with common airborne fungal species. METHODS: Ex vivo nasal polyp tissue from six well phenotyped CRSwNP patients undergoing functional endoscopic sinus surgery was stimulated with 1, 10 and 100 µg/ml of Alternaria alternata, Aspergillus niger, Cladosporium sphaerospermum and Penicillium notatum and compared with unchallenged polyp tissue as control. Enzyme-linked immunosorbent assay (ELISA) was used to measure the levels of pro-inflammatory cytokines interleukin-6 (IL-6), granulocyte macrophage colony stimulating factor (GM-CSF) and tumour necrosis factor-α (TNF-α); and pro-remodelling cytokines transforming growth factor-b1 (TGF-b1), and basic fibroblast growth factor (bFGF) in the polyp supernatant. RESULTS: Aspergillus niger stimulation increased pro-inflammatory cytokines TNF-α, GM-CSF and IL-6 whilst having little effect on the remodelling cytokines bFGF and TGF-b1. In contrast, stimulation with Cladosporium sphaerospermum, Alternaria alternata and Penicillium notatum reduced pro-inflammatory cytokines TNF-α and IL-6, but induced a dose-dependent increase in remodelling cytokines TGF-b1 and bFGF. CONCLUSIONS: This study shows that common airborne fungi induce species-specific effects on the upper airway inflammatory and remodelling responses. These findings provide further immunological evidence of a disease-modifying role for fungi in CRS.

Fungal quorum sensing molecules: Role in fungal morphogenesis and pathogenicity.

When microorganisms live together in high numbers, they need to communicate with each other. To achieve cell-cell communication, microorganisms secrete molecules called quorum-sensing molecules (QSMs) that control their biological activities and behaviors. Fungi secrete QSMs such as farnesol, tyrosol, phenylethanol, and tryptophol. The role of QSMs in fungi has been widely studied in both yeasts and filamentous fungi, for example in Candida albicans, C. dubliniensis, Aspergillus niger, A. nidulans, and Fusarium graminearum. QSMs impact fungal morphogenesis (yeast-to-hypha formation) and also play a role in the germination of macroconidia. QSMs cause fungal cells to initiate programmed cell death, or apoptosis, and play a role in fungal pathogenicity. Several types of QSMs are produced during stages of biofilm development to control cell population or morphology in biofilm communities. This review article emphasizes the role of fungal QSMs, especially in fungal morphogenesis, biofilm formation, and pathogenicity. Information about QSMs may lead to improved measures for controlling fungal infection.

Selective transport between heterogeneous hyphal compartments via the plasma membrane lining septal walls of Aspergillus niger.

Hyphae of ascomycetes are compartmentalized by septa. The central pore in these septa allows for cytoplasmic streaming. However, many of these pores are closed by Woronin bodies in Aspergillus, which prevents cytoplasmic mixing and thus maintains hyphal heterogeneity. Here, glucose uptake and transport was studied in Aspergillus niger. Glucose uptake was higher in the hyphal population with high transcriptional activity when compared to the population with low transcriptional activity. Glucose was transported from the colony center to the periphery, but not vice versa. This unidirectional flow was similar in the wild-type and the ΔhexA strain that does not form Woronin bodies. This indicated that septal plugging by Woronin bodies does not impact long distance glucose transport. Indeed, the glucose analogue 2-NBDG (2-(N-[7-nitrobenz-2-oxa-1,3-diazol-4-yl]amino)-2-deoxyglucose) translocated to neighboring hyphal compartments despite Woronin body mediated plugging of the septum that separated these compartments. Notably, 2-NBDG accumulated in septal cross walls, indicating that intercompartmental glucose transport is mediated by transporters that reside in the plasma membrane lining the septal cross-wall. The presence of such transporters would thus enable selective transport between heterogeneous compartments.

Inhibition of oxidative phosphorylation for enhancing citric acid production by Aspergillus niger.

BACKGROUND: The spore germination rate and growth characteristics were compared between the citric acid high-yield strain Aspergillus niger CGMCC 5751 and A. niger ATCC 1015 in media containing antimycin A or DNP. We inferred that differences in citric acid yield might be due to differences in energy metabolism between these strains. To explore the impact of energy metabolism on citric acid production, the changes in intracellular ATP, NADH and NADH/NAD+ were measured at various fermentation stages. In addition, the effects of antimycin A or DNP on energy metabolism and citric acid production was investigated by CGMCC 5751. RESULTS: By comparing the spore germination rate and the extent of growth on PDA plates containing antimycin A or DNP, CGMCC 5751 was shown to be more sensitive to antimycin A than ATCC 1015. The substrate-level phosphorylation of CGMCC 5751 was greater than that of ATCC 1015 on PDA plates with DNP. DNP at tested concentrations had no apparent effect on the growth of CGMCC 5751. There were no apparent effects on the mycelial morphology, the growth of mycelial pellets or the dry cell mass when 0.2 mg L(-1) antimycin A or 0.1 mg L(-1) DNP was added to medium at the 24-h time point. The concentrations of intracellular ATP, NADH and NADH/NAD+ of CGMCC 5751 were notably lower than those of ATCC 1015 at several fermentation stages. Moreover, at 96 h of fermentation, the citric acid production of CGMCC 5751 reached up to 151.67 g L(-1) and 135.78 g L(-1) by adding 0.2 mg L(-1) antimycin A or 0.1 mg L(-1) DNP, respectively, at the 24-h time point of fermentation. Thus, the citric acid production of CGMCC 5751 was increased by 19.89% and 7.32%, respectively. CONCLUSIONS: The concentrations of intracellular ATP, NADH and NADH/NAD+ of the citric acid high-yield strain CGMCC 5751 were notably lower than those of ATCC 1015. The excessive ATP has a strong inhibitory effect on citric acid accumulation by A. niger. Increasing NADH oxidation and appropriately reducing the concentration of intracellular ATP can accelerate glycolysis and the TCA cycle to enhance citric acid yield.

Morphological transitions under oxidative stress in response to metabolite formation in Aspergillus niger.

Oxidative stress is associated with metabolite formation in fungi. In contrast to an Aspergillus niger wild-type strain, a sclerotia-formation regulator ansclR deletion strain demonstrated increased susceptibility to oxidative stress and reduced transcription of the catalase gene, catB, while an ansclR overexpression strain showed enhanced resistance to oxidative stress and increased expression of catB. In addition, ansclR complementation strain expressed a wild-type level of catB. The ansclR overexpression strain also produced the same metabolites as the wild type strain treated with H2O2. Furthermore, LC-MS, NMR, and IR analyses showed that the main metabolite was a steroid analog. Our study adds new clues to oxidative stress-related factors and metabolite formation in A. niger.