Aspergillus Flavus (aspergillus + flavu)

Distribution by Scientific Domains
Distribution within Chemistry

Selected Abstracts

Substrate specificity of a maize ribosome-inactivating protein differs across diverse taxa

FEBS JOURNAL, Issue 7 2000
Julie E. Krawetz
The superfamily of ribosome-inactivating proteins (RIPs) consists of toxins that catalytically inactivate ribosomes at a universally conserved region of the large ribosomal RNA. RIPs carry out a single N-glycosidation event that alters the binding site of the translational elongational factor eEF1A and causes a cessation of protein synthesis that leads to subsequent cell death. Maize RIP1 is a kernel-specific RIP with the unusual property of being produced as a zymogen, proRIP1. ProRIP1 accumulates during seed development and becomes active during germination when cellular proteases remove acidic residues from a central domain and both termini. These deletions also result in RIP activation in vitro. However, the effectiveness of RIP1 activity against target ribosomes remains species-dependent. To determine the potential efficiency of maize RIP1 as a plant defense protein, we used quantitative RNA gel blots to detect products of RIP activity against intact ribosomal substrates from various species. We determined the enzyme specificity of recombinant maize proRIP1 (rproRIP1), papain-activated rproRIP1 and MOD1 (an active deletion mutant of rproRIP1) against ribosomal substrates with differing levels of RIP sensitivity. The rproRIP1 had no detectable enzymatic activity against ribosomes from any of the species assayed. The papain-activated rproRIP1 was more active than MOD1 against ribosomes from either rabbit or the corn pathogen, Aspergillus flavus, but the difference was much more marked when rabbit ribosomes were used as a substrate. The papain-activated rproRIP1 was much more active against rabbit ribosomes than homologous Zea mays ribosomes and had no detectable effect on Escherichia coli ribosomes. [source]

Utilization of essential oil as natural antifungal against nail-infective fungi

Mamta Patra
Abstract During antifungal screening of some essential oils, Foeniculum vulgare exhibited the strongest activity, completely inhibiting the mycelial growth of the nail-infective fungi, Trichophyton rubrum, T. mentagrophytes and Scytalidium dimidiatum. The essential oil was found to be fungicidal at 0.2, 0.4 and 0.5 µl/ml concentrations. The oil was efficiently active against heavy doses of inoculum at minimum fungicidal concentrations. The fungicidal activity of the oil was found to be thermostable up to 80 °C, with no descramble decrease in activity after 48 months of storage. The oil also showed a broad fungitoxic spectrum, inhibiting the mycelial growth of other nail-infective fungi, viz. Aspergillus flavus, A. fumigatus, A. niger,A. ustus, Candida albicans, Epidermophyton floccosum, Microporum audouinii, M. canis, M. gypseum, M. nanum, Rhizopus nigricans, Trichophyton tonsurans and T. violaceum. Moreover, it did not exhibit any adverse effects on mammalian skin and nails up to 5% concentration. As such, the oil has a potential use as an effective herbal chemotherapeutic after undergoing successful clinical trials. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Solitary embolic cutaneous aspergillosis in the immunocompromised patient with acute myelogenous leukemia , a propos another case caused by Aspergillus flavus

Aleksandar L. Krunic MD
A 68-year-old male with acute myelogenous leukemia was admitted for consolidation chemotherapy. The in-hospital course was complicated by neutropenia, fever and nodular pulmonary opacities suggestive of multifocal pneumonia. The patient subsequently developed a single, solitary necrotic crusted nodule on the right cheek. Skin biopsy demonstrated embolic vascular invasion with septate hyphae, dichotomous branching and minimal inflammation. Tissue culture revealed Aspergillus flavus. Despite systemic antifungal therapy with amphotericin B and granulocyte transfusions, the patient developed respiratory failure and died of disseminated aspergillosis, sepsis and renal failure. The clinical presentation of disseminated infection with Aspergillus flavus as a solitary embolic cutaneous lesion is extremely rare. We have reviewed other cases described in the literature and suggest this pattern of cutaneous involvement as more typical of disseminated infection with Aspergillus flavus. [source]

Original article: Antifungal activities of cinnamon oil against Rhizopus nigricans, Aspergillus flavus and Penicillium expansum in vitro and in vivo fruit test

Yage Xing
Summary The postharvest pathogens such as R. nigricans, A. flavas and P. expansum are the causal agents of jujube or orange fruit, therefore, in vitro and in vivo antifungal activities of cinnamon oil to inactivate these fungi were investigated. Cinnamaldehyde is the main constituent of cinnamon oil. The minimum inhibitory concentrations of cinnamon oil against Rhizopus nigricans, Aspergillus flavus and Penicillium expansum were 0.64% (v/v), 0.16% (v/v) and 0.16% (v/v), respectively. The antifungal activity of cinnamon oil against A. flavus and P. expansum was stronger than that against R. nigricans and the activity was improved with increasing its concentration. In an in vivo study, cinnamon oil with concentrations of 2.0% (v/v) and 3.0% (v/v) showed complete control the growth of fungi in wound-inoculated Lingwu Long Jujube and Sand Sugar Orange fruits. These results revealed that cinnamon oil has a good potential to be as a natural antifungal agent for fruit applications. [source]

Moisture sorption isotherm and xerophilic moulds associated with dried cocoyam chips in storage in Nigeria

J. Obeta Ugwuanyi
Summary Extended storage of cocoyams (Colocasia antiquorum and Colocasia esculenta) is achieved in parts of Nigeria by processing them into smoked and dried chips. In this study, cocoyam chips were collected from parts of Nigeria at the end of drying, at various periods of storage and from markets, and analysed for moisture content, moisture sorption characteristics and xerophilic moulds. Moisture content of chips ranged from 7.07 ± 1.1% for freshly dried samples to 16 ± 2.2% for samples stored up to 8 months. Six mould species from four groups of the genus Aspergillus (including five xerophiles) identified as Aspergillus fumigatus, Eurotium repens, Eurotium amstelodami, Eurotium chevalieri and Aspergillus flavus and Aspergillus niger and Mucor sp. were isolated. The variety of moulds increased with storage and moisture content of samples. Moisture sorption in dried chips showed type II sigmoidal behaviour. Wood smoke significantly protected chips from mould colonization, but in cooperation with reduced water activity. Simple and inexpensive storage of freshly dried samples in airtight bags led to prolonged storage of up to 14 months without deterioration. [source]

Control of Aspergillus section Flavi growth and aflatoxin accumulation by plant essential oils

R. Bluma
Abstract Aims:, The antifungal effect of Pimpinella anisum (anise), Pėumus boldus (boldus), Mentha piperita (peppermint), Origanum vulgare (oregano) and Minthosthachys verticillata (peperina) essential oils against Aspergillus section Flavi (two isolates of Aspergillus parasiticus and two isolates of Aspergillus flavus) was evaluated in maize meal extract agar at 0·982 and 0·955 water activities, at 25°C. Methods and Results:, The percentage of germination, germ-tube elongation rate, growth rate and aflatoxin B1 (AFB1) accumulation at different essential oils concentrations were evaluated. Anise and boldus essential oils were the most inhibitory at 500 mg kg,1 to all growth parameters of the fungus. These essential oils inhibited the percentage of germination, germ-tube elongation rate and fungal growth. AFB1 accumulation was completely inhibited by anise, boldus and oregano essential oils. Peperina and peppermint essential oils inhibited AFB1 production by 85,90% in all concentrations assayed. Conclusions:, Anise and boldus essential oils could be considered as effective fungitoxicans for Aspergillus section flavi. Significance and Impact of the Study:, Our results suggest that these phytochemical compounds could be used alone or in conjunction with other substances to control the presence of aflatoxigenic fungi in stored maize. [source]

Metal ion enhancement of fungal growth, gene expression and aflatoxin synthesis in Aspergillus flavus: RT-PCR characterization

R. Cuero
Abstract Aims: To determine the effect of mineral ions (e.g., Zn2+, Cu2+, and Fe2+) on the enhancement of fungal growth, total RNA, aflatoxin pathway gene expression, and production of aflatoxin and its precursor O -methylsterigmatocystin (OMST). Methods and Results: The influence of the metal ions, as a single or mixed treatments, was observed in submerged cultures of toxigenic Aspergillus flavus through changes in the fungal RNA or aflatoxin pathway gene (omtA) by reverse transcription-polymerase chain reaction (RT-PCR) levels, and also in fungal dry-weight accumulation, aflatoxin and OMST production. Conclusions: The ion treatments induced changes of fungal total RNA, mRNA levels, associate fungal growth, biosynthesis of aflatoxin and OMST, and enhanced expression of RT-PCR. Significance and Impact of Study: Demonstrates at the cellular and molecular level, the significant effects of metal ions on both fungal growth and production of aflatoxin. [source]

The use of powder and essential oil of Cymbopogon citratus against mould deterioration and aflatoxin contamination of ,egusi' melon seeds

S. A. Bankole Dr.
Experiments were carried out to determine the potential of using the powder and essential oil from dried ground leaves of Cymbopogon citratus (lemon grass) to control storage deterioration and aflatoxin contamination of melon seeds. Four mould species: Aspergillus flavus, A. niger, A. tamarii and Penicillium citrinum were inoculated in the form of conidia suspension (approx. 106 conidia per ml) unto shelled melon seeds. The powdered dry leaves and essential oil from lemon grass were mixed with the inoculated seeds at levels ranging from 1,10 g/100 g seeds and 0.1 to 1.0 ml/100 g seeds respectively. The ground leaves significantly reduced the extent of deterioration in melon seeds inoculated with different fungi compared to the untreated inoculated seeds. The essential oil at 0.1 and 0.25 ml/100 g seeds and ground leaves at 10 g/100 g seeds significantly reduced deterioration and aflatoxin production in shelled melon seeds inoculated with toxigenic A. flavus. At higher dosages (0.5 and 1.0 ml/100 g seeds), the essential oil completely prevented aflatoxin production. After 6 months in farmers' stores, unshelled melon seeds treated with 0.5 ml/ 100 g seeds of essential oil and 10 g/100 g seeds of powdered leaves of C. citratus had significantly lower proportion of visibly diseased seeds and Aspergillus spp. infestation levels and significantly higher seed germination compared to the untreated seeds. The oil content, free fatty acid and peroxide values in seeds protected with essential oil after 6 months did not significantly differ from the values in seeds before storage. The efficacy of the essential oil in preserving the quality of melon seeds in stores was statistically at par with that of fungicide (iprodione) treatment. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


ABSTRACT Essential oils (EOs) and extracts (methanol, acetone and diethyl ether) of fresh and dried oregano (Origanum onites L.) were used to determine the antifungal effect on Alternaria alternata, Aspergillus flavus (two strains), Aspergillus niger (two strains), Aspergillus parasiticus, Fusarium semitectum, Fusarium oxysporum, Mucor racemosus and Penicillium roqueforti by disk diffusion methods. Minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of all samples were determined. The antifungal activity of the fresh herb was greater than that of the dried herb. MIC values for fresh and dried methanol extracts were 150,950 µg/mL and 750,950 µg/mL, respectively. MFC values for methanol extracts were determined between 300 and 1200 µg/mL for fresh oregano and between 750 and 1100 µg/mL for dried oregano. The EOs of fresh and dried oregano totally inhibited test fungi. EOs produced the lowest MIC and MFC values: 8.5 µg/mL and 9.0 µg/mL, respectively (P < 0.005). The highest extract activity was exhibited by fresh oregano against A. alternata (24 mm) followed by P. roqueforti (20 mm). The greatest total antifungal effect was observed from methanol extracts. The chemical composition of fresh oregano EO and extracts was examined using gas chromatography-mass spectrometry (GC-MS). Over 80 volatiles were detected, of which 42 were positively identified by matching both MS fragmentation patterns with standardized retention characteristics. p-Cymene, thymol and carvacrol were the most prominent, followed by ,-pinene, camphor and borneol. PRACTICAL APPLICATIONS In the past decade interest in natural antimicrobial plant extracts has been growing. Various plants have historically been used for the purposes of food preservation and flavor enhancement as well as medicinal purposes. An example is oregano, the leafy part of the plant belonging to the Labiatae family. It has been used to improve the flavor and the organoleptic properties of many foods from numerous cultures. It has also been used to prolong the storage life of foods probably because of antifungal properties. The preservative nature of fresh oregano has been employed in many food applications, including meat and fish products, as well as in pharmaceuticals, alternative medicines and natural therapies. [source]


ABSTRACT Ninety random grain samples were collected and analyzed for mycotoxins, and the effect of gamma irradiation on the production of mycotoxins in grains was studied. Aspergillus, Penicillium, Mucor, Rhizopus, Fusarium, Alternaria, Scopulariopsis and Cladosporium were the most common fungal genera isolated from grains. Aspergillus flavus, Aspergillus niger, Aspergillus candidus, Aspergillus ochraceus, Penicillium citrinum, Penicillium expansum, Penicillium citreonigrum, Penicillium purpurogenum, Penicillium griseofulvum and Penicillium verrucosumwere the most common Aspergillus and Penicillium species in grains. Out of 120 Aspergillus and Penicillium isolates, 80 were mycotoxin producers. Analysis of grains revealed the occurrence of aflatoxin B1 ochratoxin A, cycolopiazonic acid and citrinin. Of the 90 samples, 67 were positive for one or more mycotoxin. Irradiation of grains at dose of 2.0 and 4.0 kGy decreased significantly the total fungal counts compared with unirradiated controls. After 100 days of storage at room temperature, the unirradiated grains were contaminated with high concentrations of mycotoxins as compared with irradiated 4.0-kGy samples. Mycotoxin production in grains decreased with increasing irradiation doses and was not detected at 6.0 kGy over 100 days of storage. [source]

Effect of Calcium Propionate and Water Activity on Growth and Aflatoxins Production by,Aspergillus flavus

Sahib Alam
ABSTRACT:, The efficacy of calcium propionate at 2 different doses (0.5% and 1%) against growth and aflatoxins production by,Aspergillus flavus,(A-2092) was investigated,in vitro,on Czapek yeast extract agar at different levels of water activity (aw) in the range of 0.94 to 0.996aw.,A. flavus,spores germinated on all calcium propionate and aw,treatments; however, 1% calcium propionate at 0.94 aw,delayed the germination process for up to 10 d. The growing rate of mycelia was slower (0.28 mm/d) at 1% calcium propionate and 0.94 aw. Aflatoxins (B1, B2, G1, and G2) were also produced minimally (36.1, 1, 1.86, and 1.01 ng/g of media, respectively) at the aforementioned dose rate of calcium propionate and water activity. It was concluded that addition of calcium propionate and aw,amelioration can prove effective tools for suppressing the germination, growth rate, and aflatoxins production by,A. flavus,in substrate. [source]

Essential Oil of,Aegle marmelos,as a Safe Plant-Based Antimicrobial Against Postharvest Microbial Infestations and Aflatoxin Contamination of Food Commodities

Priyanka Singh
ABSTRACT:, The essential oil of,Aegle marmelos,L. Correa (Rutaceae) showed strong fungitoxicity against some storage fungi-causing contamination of foodstuffs. The oil also showed efficacy as aflatoxin suppressor at 500 ,L/L as it completely arrested the aflatoxin B1 production by the toxigenic strains (Navjot 4NSt and Saktiman 3NSt) of,Aspergillus flavus,Link. Keeping in view the side effects of synthetic fungicides,,A. marmelos,oil may be recommended as an antimicrobial of plant origin to enhance the shelf life of stored food commodities by controlling the fungal growth as well as aflatoxin secretion. This is the 1st report on aflatoxin B1 inhibitory nature of this oil.,A. marmelos,oil may be recommended as a novel plant-based antimicrobial in food protection over synthetic preservatives, most of which are reported to incite environmental problems because of their nonbiodegradable nature and side effects on mammals. The LD50 of,Aegle,oil was found to be 23659.93 mg/kg body weight in mice (Mus musculus,L.) when administered for acute oral toxicity showing nonmammalian toxicity of the oil. GC-MS analysis of the oil found DL-Limonene to be major component. [source]

Fungistatic Activity of Heat-Treated Flaxseed Determined by Response Surface Methodology

Y. Xu
ABSTRACT:, The objective of this study was to evaluate the effect of heat treatment on the fungistatic activity of flaxseed (Linum usitatissimum) in potato dextrose agar (PDA) medium and a fresh noodle system. The radial growth of Penicillium chrysogenum, Aspergillus flavus, and a Penicillium sp. isolated from moldy noodles, as well as the mold count of fresh noodle enriched with heat treated flaxseed, were used to assess antifungal activity. A central composite design in the response surface methodology was used to predict the effect of heating temperature and time on antifungal activity of flaxseed flour (FF). Statistical analysis determined that the linear terms of both variables (that is, heating temperature and time) and the quadratic terms of the heating temperature had significant (P < 0.05) effects on the radial growth of all 3 test fungi and the mold count log-cycle reduction of fresh noodle. The interactions between the temperature and time were significant for all dependent variables (P < 0.05). Significant reductions in antifungal activities were found when FF was subjected to high temperatures, regardless of heating time. In contrast, prolonging the heating time did not substantially affect the antifungal activities of FF at low temperature. However, 60% of the antifungal activity was retained after FF was heated at 100 °C for 15 min, which suggests a potential use of FF as an antifungal additive in food products subjected to low to mild heat treatments. [source]

Antifungal Activity Stability of Flaxseed Protein Extract Using Response Surface Methodology

Y. Xu
ABSTRACT:, The stability of the antifungal activity of flaxseed (Linum usitatissimum) protein extract was evaluated in this study. Response surface methodology (RSM) using Box,Behnken factorial design was used to evaluate the effects of treatment variables, that is, temperature (50 to 90 °C), time (1 to 29 min), and pH (2 to 8), on the residual antifungal activity (RAA) against Penicillium chrysogenum, Fusarium graminearum, Aspergillus flavus, and a Penicillium sp. isolated from moldy noodles. Regression analyses suggested that the linear terms of the temperature and time had significant (P < 0.05) negative effects on the RAA against all test fungi, whereas that of pH had a significant (P < 0.1) positive role on the RAA of all 3 fungi. In addition, the RAA was significantly (P < 0.05) affected by the quadratic terms of time for all fungi, and the quadratic term of temperature played a significant (P < 0.1) role on RAA against F. graminearum. One interaction term (temperature-pH) was found to significantly (P < 0.1) affect the RAA against both Penicillium strains tested. The results indicated that , 90% antifungal activity was lost after the protein extracts were heated at 90 °C for 8 min except for F. graminearum. At pasteurization condition, , 50% activity was retained except for P. chrysogenum. The results also suggested that neutral and alkaline pH favored the antifungal activity stability of the protein extracts. Thus, flaxseed protein might be promising if used as a preservative in foods with neutral or alkaline pH requiring mild heat treatments. [source]

Promising antimicrobial agents: Synthetic approaches to novel tricyclic and tetracyclic pyrimidinones with antimicrobial properties

Hatem M. Gaber
New tricyclic pyrimidinone derivatives were obtained from the corresponding thiazolopyrimidinone or hydrazino systems. The annelation of tricyclic hydrazino compound with 1,2,4-triazole and tetrazole moieties gave novel tetracyclic condensed pyrimidinones. The investigation of the antimicrobial properties of tricyclic and tetracyclic pyrimidinones, by agar-well diffusion assay, was carried out against six pathogenic bacteria (Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Klebsiella spp, and Salmonella typhyrium) and four pathogenic fungi (Aspergillus flavus, Aspergillus niger, Aspergillus fumigatus, and Trichderma horozianum). Most of the compounds tested exhibited some degree of antimicrobial activity against microorganisms. Among these compounds, 4-benzylidenhydrazino-8-cyano-7-(furan-2-yl)thiazolo[3,2- a:4,5- d,]dipyrimidin-9-one (12) showed the most favorable antibacterial activity, while compound 17 showed the highest effect on fungi. Interestingly, tetrazole derivative 19 displayed a remarkable effect on fungi much more than the corresponding 3-substituted triazole derivatives on the one hand, whereas the lowest effect on bacteria on the other. J. Heterocyclic Chem., (2010). [source]

AFLP Analysis of Trichoderma spp. from India Compared with Sequence and Morphological-based Diagnostics

H. K. Buhariwalla
Abstract Trichoderma species offer considerable potential for controlling aflatoxin contamination in groundnut and other crops. Initial classification of 48 Trichoderma isolates, derived from four different groundnut cultivation sites in India was based on alignment of 28S rDNA sequences to GenBank sequences of ex-type strains. This was found to be substantially more reliable than our routine morphological characterization, but did not provide a comprehensive diagnostic solution, as unique single nucleotide polymorphism (SNP) haplotypes could not be identified for all species. However, all the Trichoderma isolates could be readily distinguished by amplified fragment length polymorphism (AFLP) analysis, based on six primer pair combinations, which generated 234 polymorphic bands. In addition, individual AFLP bands were identified which differentiate closely related species. Similarly, AFLP bands were identified that correlated with different types of antagonism to Aspergillus flavus. The implications of these results for the development of simple polymerase chain reaction (PCR)-based diagnostic assays for antagonistic isolates of Trichoderma is discussed. [source]

Characterization of Aspergillus flavus strains from Brazilian Brazil nuts and cashew by RAPD and ribosomal DNA analysis

G.E.O. Midorikawa
Abstract Aims:, The aim of this study was to determine the genetic variability in Aspergillus flavus populations from Brazil nut and cashew and develop a polymerase chain reaction (PCR) detection method. Methods and Results:, Chomatography analysis of 48 isolates identified 36 as aflatoxigenic (75%). One hundred and forty-one DNA bands were generated with 11 random amplified polymorphic DNA (RAPD) primers and analysed via unweighted pair group analysis, using arithmetic means (UPGMA). Isolates grouped according to host, with differentiation of those from A. occidentale also according to geographical origin. Aspergillus flavus -specific PCR primers ASPITSF2 and ASPITSR3 were designed from ribosomal DNA internal transcribed spacers (ITS 1 and 2), and an internal amplification control was developed, to prevent false negative results. Specificity to only A. flavus was confirmed against DNA from additional aspergilli and other fungi. Conclusions:, RAPD-based characterization differentiated isolates according to plant host. The PCR primer pair developed showed specificity to A. flavus, with a detection limit of 10 fg. Significance and Impact of the Study:, Genetic variability observed in A. flavus isolates from two Brazilian agroecosystems suggested reproductive isolation. The PCR detection method developed for A. flavus represents progress towards multiplex PCR detection of aflatoxigenic and nonaflatoxigenic strains in Hazard Analysis Critical Control Point systems. [source]

Inhibition of aflatoxin B1 production of Aspergillus flavus, isolated from soybean seeds by certain natural plant products

Y.L. Krishnamurthy
Abstract Aims:, The inhibitory effect of cowdung fumes, Captan, leaf powder of Withania somnifera, Hyptis suaveolens, Eucalyptus citriodora, peel powder of Citrus sinensis, Citrus medica and Punica granatum, neem cake and pongamia cake and spore suspension of Trichoderma harzianum and Aspergillus niger on aflatoxin B1 production by toxigenic strain of Aspergillus flavus isolated from soybean seeds was investigated. Methods and Results:, Soybean seed was treated with different natural products and fungicide captan and was inoculated with toxigenic strain of A. flavus and incubated for different periods. The results showed that all the treatments were effective in controlling aflatoxin B1 production. Captan, neem cake, spore suspension of T. harzianum, A. niger and combination of both reduced the level of aflatoxin B1 to a great extent. Leaf powder of W. somnifera, H. suaveolens, peel powder of C. sinensis, C. medica and pongamia cake also controlled the aflatoxin B1 production. Conclusions:, All the natural product treatments applied were significantly effective in inhibiting aflatoxin B1 production on soybean seeds by A. flavus. Significance and Impact of the Study:, These natural plant products may successfully replace chemical fungicides and provide an alternative method to protect soybean and other agricultural commodities from aflatoxin B1 production by A. flavus. [source]

Effect of trans -2-hexenal on the growth of Aspergillus flavus in relation to its concentration, temperature and water activity

F. Gardini
Aims:,The antifungal activity of trans -2-hexenal on Aspergillus flavus in a model system in relation to its concentration, incubation temperature and aw was assessed. Methods and Results:,A model describing the antifungal activity of the aldehyde in relation to these variables was obtained. Conclusions:,According to this model, the inhibition of A. flavus was weakly dependent on the incubation temperature (at least within the range of values considered) and strongly affected by the trans -2-hexenal concentration and aw, which showed a remarkable synergistic effect. Significance and Impact of the Study:,Trans -2-hexenal proved to be a molecule with remarkable antimicrobial properties, even when added in closed systems at low concentration. [source]

Scanning electron microscopy applied to seed-borne fungi examination

Marcelo De Carvalho Alves
Abstract The aim of this study was to test the standard scanning electron microscopy (SEM) as a potential alternative to study seed-borne fungi in seeds, by two different conditions of blotter test and water restriction treatment. In the blotter test, seeds were subjected to conditions that enabled pathogen growth and expression, whereas the water restriction method consisted in preventing seed germination during the incubation period, resulting in the artificial inoculation of fungi. In the first condition, seeds of common bean (Phaseolus vulgaris L.), maize (Zea mays L.), and cotton (Gossypium hirsutum L.) were submitted to the standard blotter test and then prepared and observed with SEM. In the second condition, seeds of cotton (G. hirsutum), soybean (Glycine max L.), and common bean (P. vulgaris L.) were, respectively, inoculated with Colletotrichum gossypii var. cephalosporioides, Colletotrichum truncatum, and Colletotrichum lindemuthianum by the water restriction technique, followed by preparation and observation with SEM. The standard SEM methodology was adopted to prepare the specimens. Considering the seeds submitted to the blotter test, it was possible to identify Fusarium sp. on maize, C. gossypii var. cephalosporioides, and Fusarium oxysporum on cotton, Aspergillus flavus, Penicillium sp., Rhizopus sp., and Mucor sp. on common bean. Structures of C. gossypii var. cephalosporioides, C. truncatum, and C. lindemuthianum were observed in the surface of inoculated seeds. Microsc. Res. Tech., 2009. © 2009 Wiley-Liss, Inc. [source]

Recombination and lineage-specific gene loss in the aflatoxin gene cluster of Aspergillus flavus

Abstract Aflatoxins produced by Aspergillus flavus are potent carcinogens that contaminate agricultural crops. Recent efforts to reduce aflatoxin concentrations in crops have focused on biological control using nonaflatoxigenic A. flavus strains AF36 (=NRRL 18543) and NRRL 21882 (the active component of afla-guard®). However, the evolutionary potential of these strains to remain nonaflatoxigenic in nature is unknown. To elucidate the underlying population processes that influence aflatoxigenicity, we examined patterns of linkage disequilibrium (LD) spanning 21 regions in the aflatoxin gene cluster of A. flavus. We show that recombination events are unevenly distributed across the cluster in A. flavus. Six distinct LD blocks separate late pathway genes aflE, aflM, aflN, aflG, aflL, aflI and aflO, and there is no discernable evidence of recombination among early pathway genes aflA, aflB, aflC, aflD, aflR and aflS. The discordance in phylogenies inferred for the aflW/aflX intergenic region and two noncluster regions, tryptophan synthase and acetamidase, is indicative of trans-species evolution in the cluster. Additionally, polymorphisms in aflW/aflX divide A. flavus strains into two distinct clades, each harbouring only one of the two approved biocontrol strains. The clade with AF36 includes both aflatoxigenic and nonaflatoxigenic strains, whereas the clade with NRRL 21882 comprises only nonaflatoxigenic strains and includes all strains of A. flavus missing the entire gene cluster or with partial gene clusters. Our detection of LD blocks in partial clusters indicates that recombination may have played an important role in cluster disassembly, and multilocus coalescent analyses of cluster and noncluster regions indicate lineage-specific gene loss in A. flavus. These results have important implications in assessing the stability of biocontrol strains in nature. [source]

Characterization of microsatellite loci in the aflatoxigenic fungi Aspergillus flavus and Aspergillus parasiticus

Nai Tran-Dinh

Comparative pharmacodynamic interaction analysis of triple combinations of caspofungin and voriconazole or ravuconazole with subinhibitory concentrations of amphotericin B against Aspergillus spp.

MYCOSES, Issue 3 2010
Joanne P. Demchok
Summary Triple combination therapy with an antifungal triazole, echinocandin and amphotericin B (AmB) is used in some centres to treat refractory aspergillosis. The objective of this study was to investigate the effect of subinhibitory concentrations of AmB on the double combinations of caspofungin (CAS) + voriconazole (VOR) or ravuconazole (RAV) against Aspergillus fumigatus, Aspergillus flavus and Aspergillus terreus. Isolates were studied in triplicate against CAS/VOR and CAS/RAV combinations by chequerboard broth microdilution. AmB was added to each double combination at concentrations of 0, 0.1 and 0.2 ,g ml,1. The fractional inhibitory concentration (FIC) index was calculated for the double and triple combinations. Comparative analysis was performed by repeated measures analysis followed by Dunnett's post-test. The double combinations of CAS/RAV and CAS/VOR were synergistic or additive in most conditions. Addition of AmB to the double combinations resulted in increased FIC indices for A. fumigatus and A. flavus. By contrast, AmB increased the synergism of the double combinations decreasing FIC indices for A. terreus (P < 0.05). RAV and VOR displayed similar synergistic activity with CAS. The addition of sub-inhibitory amphotericin B concentrations reduced but did not eliminate the synergistic interaction between the echinocandin and triazole against A. fumigatus and A. flavus, while it increased the synergy against A. terreus. [source]

Aspergillus flavus: an emerging non- fumigatus Aspergillus species of significance

MYCOSES, Issue 3 2009
Suganthini Krishnan
Summary Invasive aspergillosis is rare in immunocompetent people but contributes to significant morbidity and mortality in immunosuppressed patients. The majority (approximately 80%) of invasive Aspergillus infections is caused by Aspergillus fumigatus. The second most frequent (approximately 15,20%) pathogenic species is Aspergillus flavus and to a lesser extent, Aspergillus niger and Aspergillus terreus. Aspergillus flavus has emerged as a predominant pathogen in patients with fungal sinusitis and fungal keratitis in several institutions worldwide. To date, there has not been any publication exclusively reviewing the topic of A. flavus in the literature. This article reviews the microbiology, toxigenicity and epidemiology of A. flavus as well as describes the clinical characteristics, diagnosis and management of infections caused by this organism. [source]

Identification of medically important Aspergillus species by single strand conformational polymorphism (SSCP) of the PCR-amplified intergenic spacer region Identifizierung humanmedizinisch relevanter Aspergillus-Arten durch Analyse der Einzelstrang-Konformations-Polymorphismen der amplifizierten Intergenic-Spacer-Region

MYCOSES, Issue 11-12 2000
P.-M. Rath
Aspergillus; Identifizierung; ITS-Region; PCR; SSCP Summary., The amplified 5.8S RNA coding DNA with the neighbouring internal transcribed spacers ITS I and ITS II (ITS I,5.8S rDNA , ITS II) of 27 culture collection strains of Aspergillus fumigatus, Aspergillus flavus, Aspergillus nidulans, Aspergillus niger, and Aspergillus terreus were investigated by single strand conformational polymorphism (SSCP) analysis. All strains showed a polymerase gel electrophoresis (PCR) product of 0.6 kb. Separation of DNA single strands of the PCR product in an acrylamide-bisacrylamide gel containing formamide SSCP resulted in individual patterns for each of the species. A minor variability within the species A. fumigatus and A. flavus did not affect the correct species identification. The results were confirmed when investigating 55 wild strains from patients and the environment. It is concluded that the analysis of the amplified ITS I,5.8S rDNA , ITS II region by SSCP allows the differentiation of the medically most relevant aspergilli. As the method does not require morphologically fully developed fungal colonies, it yields species diagnosis faster than the conventional macroscopic and microscopic identification. Zusammenfassung., Die amplifizierte 5,8S RNA kodierende DNA mit den benachbarten Internal Transcribed Spacern ITS I und ITS II (ITS I,5,8S rDNA , ITS II) von 27 Referenzstämmen der Spezies Aspergillus fumigatus, A. flavus, A. nidulans, A. niger und A. terreus wurde durch Analyse der Einzelstrang-Konformations-Polymorphismen (SSCP) untersucht. Alle Stämme zeigten ein PCR-Produkt mit einer Größe von 0,6 kb. Die SSCP-Muster nach Auftrennung der DNA-Einzelstränge dieses Produktes in einem Acrylamid-Bisacrylamid Gel mit Formamid waren für jede der untersuchten Spezies charakteristisch. Eine geringfügige Variabilität der Muster bei den Spezies A. fumigatus und A. flavus schränkte die Interpretation nicht ein. Die Ergebnisse wurden bei der Analyse von 55 Isolaten von Patienten und aus der Umwelt bestätigt. Die SSCP-Analyse der amplifizierten ITS I,5,8S rDNA , ITS II Region erlaubt somit eine Differenzierung der humanmedizinisch wichtigsten Aspergillus -Spezies vor der Ausbildung charakteristischer makro- und mikromorphologischer Strukturen. [source]

In Vitro antifungal activity of extract and plumbagin from the stem bark of Diospyros crassiflora Hiern (Ebenaceae)

J. P. Dzoyem
Abstract In this study the methanol/dichloromethane (1:1) extract and plumbagin isolated from extract of stem barks of Diospyros crassiflora were tested for their antifungal activity against 12 strains of yeast pathogens and filamentous fungi: Candida albicans, Candida glabrata, Candida krusei, Candida tropicalis, Cryptococcus neoformans, Aspergillus niger, Aspergillus flavus, Alternaria sp., Cladosporium sp., Geotrichum candidum, Fusarium sp. and Penicillium sp. The growth of all fungi strains tested was inhibited by the extract and plumbagin. The diameter of inhibition zones varied from 12 to 18 mm and from 21 to 35 mm for the extract and plumbagin, respectively. The MIC values ranged from 12.5 to 25 mg/mL for the extract and 0.78,3.12 µg/mL for plumbagin. It is therefore suggested that extracts from the stem bark of Diospyros crassiflora could be used traditionally in the treatment of fungal infections. Compared with ketoconazole used as a standard antifungal, plumbagin could be considered as a promising antifungal agent. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Disease resistance conferred by the expression of a gene encoding a synthetic peptide in transgenic cotton (Gossypium hirsutum L.) plants

Kanniah Rajasekaran
Summary Fertile, transgenic cotton plants expressing the synthetic antimicrobial peptide, D4E1, were produced through Agrobacterium -mediated transformation. PCR products and Southern blots confirmed integration of the D4E1 gene, while RT-PCR of cotton RNA confirmed the presence of D4E1 transcripts. In vitro assays with crude leaf protein extracts from T0 and T1 plants confirmed that D4E1 was expressed at sufficient levels to inhibit the growth of Fusarium verticillioides and Verticillium dahliae compared to extracts from negative control plants transformed with pBI-d35S,- uidA-nos (CGUS). Although in vitro assays did not show control of pre-germinated spores of Aspergillus flavus, bioassays with cotton seeds in situ or in planta, inoculated with a GFP-expressing A. flavus, indicated that the transgenic cotton seeds inhibited extensive colonization and spread by the fungus in cotyledons and seed coats. In planta assays with the fungal pathogen, Thielaviopsis basicola, which causes black root rot in cotton, showed typical symptoms such as black discoloration and constriction on hypocotyls, reduced branching of roots in CGUS negative control T1 seedlings, while transgenic T1 seedlings showed a significant reduction in disease symptoms and increased seedling fresh weight, demonstrating tolerance to the fungal pathogen. Significant advantages of synthetic peptides in developing transgenic crop plants that are resistant to diseases and mycotoxin-causing fungal pathogens are highlighted in this report. [source]

Synthesis of antibacterial and antifungal cobalt(II), copper(II), nickel(II) and zinc(II) complexes with bis-(1,1,-disubstituted ferrocenyl)thiocarbohydrazone and bis-(1,1,-disubstituted ferrocenyl)carbohydrazone

Zahid H. Chohan
Abstract The condensation reaction of 1,1,-diacetylferrocene with thiocarbohydrazide and carbohydrazide to form bis-(1,1,-disubstituted ferrocenyl)thiocarbohydrazone and bis-(1,1,-disubstituted ferrocenyl)carbohydrazone has been studied. The compounds obtained have been further used as ligands for their ligand and antimicrobial properties with cobalt(II), copper(II), nickel(II) and zinc(II) metal ions. The compounds synthesized have been characterized by physical, spectral and analytical methods and have been screened for antibacterial activity against Escherichia coli, Bacillus subtillis, Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella typhi, and for antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glaberata using the agar well-diffusion method. All the compounds synthesized have shown good affinity as antibacterial and antifungal agents, which increased in most of the cases on complexation with the metal ions. Copyright © 2004 John Wiley & Sons, Ltd. [source]

A multicriteria ranking of organotin(IV) compounds with fungicidal properties

Godwin A. Ayoko
Abstract The application of multicriteria decision-making methods to the results of in vitro antifungal properties of organotin compounds of the type PhxSnXz (x = 2 or 3; X = O2CC6H4OH, O2CC6H4OCOCH3, Cl or O2CCH3; z = 1 or 2) and of free 2-hydroxybenzoic and 2-acetoxybenzoic acids against Aspergillus niger, Aspergillus flavus, Candida albicans, Penicillium citrinum, Trichophyton rubrum and Trichophyton violaceum have been described. Ranking information necessary to select one toxicant in preference to others and to assess the properties influencing the preference has been obtained. Patterns in the multivariate analyses suggest that cationic and anionic moieties of the toxicant play some roles in their fungicidal activities. The triphenyltin compounds were generally more active than their diphenyltin analogues, but the acetoxybenzoates were more active than the corresponding hydroxybenzoates, acetates or chlorides. Thus, triphenyltin acetoxybenzoate is up to 7.5 times as active as the corresponding acetate, which is commercially marketed as a fungicide. The results of the analyses have been discussed in the light of the mechanism of antifungal activity of organotin compounds and the potential of multivariate data analysis techniques to facilitate the screening and ranking of antifungal agents. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Synthesis and Antifungal Activity of 1-Aryl-3-phenethylamino-1-propanone Hydrochlorides and 3-Aroyl-4-aryl-1-phenethyl-4-piperidinols

Ebru Mete
Abstract Mono-Mannich bases, 1-aryl-3-phenethylamino-1-propanone hydrochlorides, 1a, 2a, 3a, 4a, 5a, 6a, 7a, 8a, 9a, and semi-cyclic mono-Mannich bases, 3-aroyl-4-aryl-1-phenethyl-4-piperidinols, 1b, 2b, 3b, 4b, 5b, 6b, 7b, 8b, 9b, were synthesized by a non-classical Mannich reaction. The aryl part was: C6H5 for 1a, 1b; 4-CH3C6H4 for 2a, 2b; 4-CH3OC6H4 for 3a, 3b; 4-ClC6H4 for 4a, 4b; 4-FC6H4 for 5a, 5b; 4-BrC6H4 for 6a, 6b; 2,4-(Cl)2C6H3 for 7a, 7b; 4-NO2C6H4 for 8a, 8b; and C4H3S(2-yl) i. e., 2-thienyl for 9a, 9b. Piperidinol compounds 2b, 3b, 4b, 5b, 7b, 8b, and 9b are reported here for the first time. The synthesized compounds were tested against seven types of plant pathogenic fungi and three types of human pathogenic fungi using the agar dilution assay. Itraconazole was tested against Candida parapsilosis as the reference compound, while Nystatin was tested as the reference compound against the other fungi. Compounds 1a, 1b, 2a, 4a, 4b, 5a, 5b, 6a, 7a, 8a, 9a, and 9b can be selected as model compounds to develop new antifungal agents against the human pathogen Microsporum canis. Compounds 8a and 8b, which had a similar antifungal activity compared with the reference compound Nystatin against the plant pathogen Aspergillus flavus, can serve as model compounds to develop new antifungal agents to solve agricultural problems. [source]