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Wilkinson JR Yu J Bland JM Nierman WC Bhatnagar D Cleveland TE 《Applied microbiology and biotechnology》2007,74(6):1308-1319
Aflatoxins are toxic and carcinogenic secondary metabolites produced by the fungi Aspergillus flavus and Aspergillus parasiticus. To better understand the molecular mechanisms that regulate aflatoxin production, the biosynthesis of the toxin in A. flavus and A. parasticus grown in yeast extract sucrose media supplemented with 50 mM tryptophan (Trp) were examined. Aspergillus flavus grown in the presence of 50 mM tryptophan was found to have significantly reduced aflatoxin B1 and B2 biosynthesis, while A. parasiticus cultures had significantly increased B1 and G1 biosynthesis. Microarray analysis of RNA extracted from fungi grown under these conditions revealed 77 genes that are expressed
significantly different between A. flavus and A. parasiticus, including the aflatoxin biosynthetic genes aflD (nor-1), aflE (norA), and aflO (omtB). It is clear that the regulatory mechanisms of aflatoxin biosynthesis in response to Trp in A. flavus and A. parasiticus are different. These candidate genes may serve as regulatory factors of aflatoxin biosynthesis. 相似文献
3.
K. R. N. Reddy Ch. Surendhar Reddy P. Nataraj Kumar C. S. Reddy K. Muralidharan 《World journal of microbiology & biotechnology》2009,25(1):33-39
Twenty-two aflatoxin B1 (AFB1) producing Aspergillus flavus strains were isolated from 1,200 discolored rice grain samples collected from 20 states across India and tested their potential
to produce AFB1 on different agar media. Further these isolates were characterized through randomly amplified polymorphic
DNA method. All the strains of A. flavus were produced AFB1 on yeast extract sucrose agar media and none of the strains on A. flavus and A. parasiticus agar. Among the 22 strains, two strains from Tamil Nadu (DRAf 009) and Maharashtra (DRAf 015) produced high amount of AFB1
in all the media tested. To assess the genetic variability in A. flavus, the isolates were analyzed by using random amplified polymorphic DNA markers. Isolates showed 17–80% similarity with standard
culture of A. flavus (MTCC 2799). 相似文献
4.
Doris Hartinger Stefan Heinl Heidi Elisabeth Schwartz Reingard Grabherr Gerd Schatzmayr Dietmar Haltrich Wulf-Dieter Moll 《Microbial cell factories》2010,9(1):62
Background
Fumonisin B1 is a cancerogenic mycotoxin produced by Fusarium verticillioides and other fungi. Sphingopyxis sp. MTA144 can degrade fumonisin B1, and a key enzyme in the catabolic pathway is an aminotransferase which removes the C2-amino group from hydrolyzed fumonisin B1. In order to study this aminotransferase with respect to a possible future application in enzymatic fumonisin detoxification, we attempted expression of the corresponding fumI gene in E. coli and purification of the enzyme. Since the aminotransferase initially accumulated in inclusion bodies, we compared the effects of induction level, host strain, expression temperature, solubility enhancers and a fusion partner on enzyme solubility and activity. 相似文献5.
Ema Carina Rosas-Burgos Mario O. Cortez-Rocha Francisco J. Cinco-Moroyoqui Ramón E. Robles-Zepeda Jaime López-Cervantes Dalia I. Sánchez-Machado Fernando Lares-Villa 《World journal of microbiology & biotechnology》2009,25(12):2257-2261
The aims of this study were to evaluate the antifungal properties of Baccharis glutinosa and Ambrosia confertiflora extracts against Aspergillus flavus, A. parasiticus and Fusarium verticillioides, and to isolate the group of compounds that are responsible for the antifungal activity. Samples of aerial parts from each
plant were extracted with 70% methanol and sequentially partitioned with hexane, ethyl acetate, and n-butanol. The partitioned fractions were evaluated in their capacity to inhibit the radial growth of the three species of
fungi. The active fraction was used for an assay-guided chromatography of antifungal extracts. The results showed that the
extract from B. glutinosa partitioned in ethyl acetate (Bea) showed the highest antifungal activity against the three fungi. Bea completely inhibited
the growth of F. verticillioides at 0.8 mg/ml, whereas the radial growth of A. flavus and A. parasiticus was inhibited 70% at 1.5 mg/ml. The purified antifungal fraction from Bea showed 72, 54, and 52% of antifungal activity,
respectively. 相似文献
6.
María Guillermina Fernández-Juri Julián A. Muzzolón Ana María Dalcero Carina E. Magnoli 《Mycotoxin Research》2011,27(4):273-280
The aim of the present study was to evaluate the inhibitory effect of Enterococcus faecium and Lactococcus lactis subsp. lactis isolated from faeces of healthy dogs on (i) lag phase, (ii) growth rate, and (iii) aflatoxin B1 production by Aspergillus section Flavi on in vitro assays. Thirteen lactic acid bacteria (LAB) isolates were used as antagonist microorganisms. Antagonistic activity
was assayed against four potentially aflatoxigenic Aspergillus section Flavi isolates: A. flavus (AF210 and AF281), A. parasiticus (AP245) and A. parasiticus (NRRL 2999). In general, the longest lag phases of Aspergillus isolates were obtained with E. faecium GJ40. Respecting the growth rate, no significant reduction was found in this parameter in the interaction assays with A. flavus and antagonist isolates respecting the control. While in A. parasiticus a significant reduction in growth rate was only observed in the interaction among reference strain and E. faecium MF5 isolate (p < 0.05). In general, AFB1 production was reduced by most of the LAB isolates assayed, except for E. faecium GJ18, GJ20, MF3 and MF4. This study provides the first data about the antiaflatoxigenic activity of autochthonous LAB isolated
from dog faeces. 相似文献
7.
Brewing and consumption of traditional beer have social–economic significance in most African countries including Botswana.
Traditional sorghum malt, wort, and beer samples were collected from three villages around Gaborone, Botswana. Forty-six malt
samples were analyzed for fungi on three different media and developing colonies were subcultured for identification. Rhizopus, Fusarium, Mucor, and Aspergillus were the most common genera isolated. Out of the 46 malt samples, 72% contained Rhizopus stolonifer, 63% Fusarium verticillioides (syn. Fusarium moniliforme), and 37% Aspergillus flavus. Although Aspergillus flavus was isolated from malt samples, aflatoxins (B1, B2, G1, and G2) were not detected in any of the samples analyzed. When the malt, wort, and beer samples were analyzed for fumonisin Bl and zearalenone, fumonisin B1 was detected in 3 malt samples, with concentrations ranging from 47 to 1316 μg/kg, while zearalenone was detected in 56%,
48% and 48% of the malt, wort and beer samples, respectively. Zearalenone concentration in samples ranged from 102 to 2213 μg/kg
in malt, 26 to 285 μg/l in wort and 20 to 201 μg/l, in beer. Zearalenone carry-over from wort to beer ranged from 23 to 403%.
Therefore, although aflatoxins and fumonisin B1 do not appear to be major contaminants, zearalenone is common and could pose a potential problem in traditional beer in Botswana. 相似文献
8.
Freshly harvested soybean, rice and corn from farms and corn-based pelleted feeds were collected from ranches from the coastal and mountain regions in Ecuador during 1998, and assessed for fungal contamination. The most prevalent fungi on pelleted feed were Aspergillus flavus and Fusarium graminearum. The prevalent fungi recovered from soybean were F. verticillioides, F. semitectum, Aspergillus flavus and A. ochraceus. In rice, F. oxysporum was the most prevalent toxigenic fungal species recorded, followed by F. verticillioides and A. flavus. In corn, F. verticillioides was the most prevalent fungus isolated in both the coastal and mountain regions, with high isolation frequencies of A. flavus and A. parasiticus at the coast. Based on the toxigenic species recovered, ochratoxin A may pose a contamination risk for soybean. A higher probability of aflatoxin contamination of corn was found in the coastal samples compared to those of the mountain region, while a risk of fumonisin contamination of corn exists in both regions.This revised version was published online in October 2005 with corrections to the Cover Date. 相似文献
9.
During hot and humid seasons, extensive rot of sour lime was observed to be caused by Aspergillus flavus. In view of this, investigations were undertaken to obtain data on the production of various toxins by A. flavus during post harvest pathogenesis of sour lime. Sixty percent of the pathogenic A. flavus isolates were detected to be aflatoxin B1 producers in sour lime tissue. It was also noted that thirty three percent of aflatoxigenic A. flavus isolates had the potential to coproduce cyclopiazonic acid (CPA). Such aflatoxigenic isolates produced quantitatively more CPA (ranging from 250.0 to 2501.3 g/kg) than aflatoxin B1 (ranging from 141.3 to 811.7 g/kg) in the affected sour lime. This study demonstrates for the first time that sour lime are a favourable substrate for aflatoxin B1 and cyclopiazonic acid production by A. flavus isolates. This is of great concern to the health of consumers. 相似文献
10.
Fusarium verticillioides is the most important seed transmitted pathogen that infects maize. It produces fumonisins, toxins that have potential toxicity for humans and animals. Control of F. verticillioides colonisation and systemic contamination of maize has become a priority area in food safety research. The aims of this research were (1) to characterise the maize endorhizosphere and rhizoplane inhabitant bacteria and Fusarium spp., (2) to select bacterial strains with impact on F. verticillioides growth and fumonisin B1 production in vitro, (3) to examine the effects of bacterial inoculum levels on F. verticillioides root colonisation under greenhouse conditions. Arthrobacter spp. and Azotobacter spp. were the predominant genera isolated from maize endorhizosphere and rhizoplane at the first sampling period, whilst F. verticillioides strains showed the greatest counts at the same isolation period. All F. verticillioides strains were able to produce fumonisin B1 in maize cultures. Arthrobacter globiformis RC5 and Azotobacter armeniacus RC2, used alone or in a mix, demonstrated important effects on F. verticillioides growth and fumonisin B1 suppression in vitro. Only Azotobacter armeniacus RC2 significantly reduced the F. verticillioides root colonisation at 106 and 107 CFU g–1 levels under greenhouse conditions. 相似文献
11.
Occurrence of Fumonisin B<Subscript>1</Subscript> in Corn from the Main Corn-Producing Areas of China 总被引:1,自引:0,他引:1
Fumonisin B1 (FB1) is the most abundant of the fumonisin mycotoxins, mainly produced in maize by F. verticillioides and F. proliferatum. A total of 282 corn samples harvested in 2005 from six provinces, the main corn-producing areas of China, were analyzed
for FB1 using high-performance liquid chromatography. All samples except one were (99.6%) positive for FB1 at levels varying from 3 to 71,121 ng/g with mean and median levels for all samples of 6,662 and 1,569 ng/g, respectively.
During an analysis of the distribution pattern for FB1, it became apparent that 43.6% of tested samples had FB1 concentrations below 1,000 ng/g, while 25.2% contained in excess of 5,000 ng/g. The average exposure to FB1 (1.1 μg/kg body weight/day) is within the provisional maximum tolerable daily intake of 2 μg/kg body weight/day set by the
Joint FAO/WHO Expert Committee on Food Additives. 相似文献
12.
Maren A. Klich 《Mycoscience》2007,48(2):71-80
Aflatoxins are carcinogenic mycotoxins formed by a number of fungi in the genus Aspergillus. The major fungi responsible for aflatoxin formation in crop seeds in the field and in storage are Aspergillus flavus and A. parasiticus. This review emphasizes developmental, environmental, biological, and chemical factors that influence aflatoxin formation
by A. flavus and A. parasiticus. 相似文献
13.
Jürgen Reiß 《Archives of microbiology》1982,133(3):236-238
The influence of various inhibitors of hyphal growth, sporulation and biosynthesis of aflatoxin B1 in Aspergillus parasiticus NRRL 2999 was studied. 6-Thioguanine, dl-ethionine, fluoroacetic acid and phenylboric acid, inhibitors of maturation of fungal conidiophores and of conidiogenesis, were added at various concentrations to malt extract agar. Lower concentrations of 6-thioguanine and dl-ethionine did not inhibit the growth of hyphae and the sporulation. Phenylboric acid reduced conidiogenesis more than hyphal growth. The yields of aflatoxin B1 were significantly reduced. Additions of fluoroacetic acid did not greatly affect the growth of hyphae but totally inhibited the production of conidia and concurrently significantly reduced the formation of aflatoxin B1. An interrelation between conidiogenesis and onset of secondary metabolism in A. parasiticus is evident. 相似文献
14.
Stefan Heinl Doris Hartinger Michaela Thamhesl Gerd Schatzmayr Wulf-Dieter Moll Reingard Grabherr 《Biodegradation》2011,22(1):25-30
Previous research identified several microorganisms and pathways capable of degrading the mycotoxin fumonisin B1 (FB1). Degradation of FB1 by microorganisms seems to comprise two essential steps: hydrolysis to hydrolyzed fumonisin B1 (HFB1) and deamination of the hydrolysis product. One of the previously studied microorganisms was the Gram negative bacterium
ATCC 55552. The gene corresponding to the first step of FB1 degradation in this bacterium was identified, but the genetic basis for deamination of the hydrolyzed intermediate remained
unexplained (Duvick et al. 2000, PCT patent application WO200004158). Here we report the sequence and HFB1-deaminating activity of a novel aminotransferase encoded by the bacterium ATCC 55552. The corresponding gene was identified,
sequenced, and over-expressed in Escherichia coli. Cell lysates of the recombinant E. coli strain showed distinct HFB1-deaminating activity in the presence of pyridoxal phosphate and pyruvate, as was demonstrated by liquid chromatography–mass
spectrometry. Thus, we suggest the novel enzyme to be part of the fumonisin catabolic pathway of the bacterium ATCC 55552. 相似文献
15.
Mohammed Aiyaz Shetty Thimmappa Divakara Siddaiah Chandra Nayaka Puttaswamy Hariprasad 《Biocontrol Science and Technology》2015,25(10):1105-1119
In the present investigation, seven rhizobacteria and nine Trichoderma spp. were evaluated to suppress seed-borne mycotoxigenic fungi (Aspergillus flavus and Fusarium verticillioides) and mycotoxin (aflatoxin and fumonisin) and to improve planting value of maize. Under in vitro conditions, these beneficial microorganisms suppressed the growth of A. flavus and F. verticillioides to various extents. Bacillus sp. (Bsp 3/aM), Pseudomonas putida (Has 1/c), Trichoderma asperellum (M5) and T. asperellum (T2) exhibited the greatest antagonistic effect on seed-borne mycotoxigenic fungi, and subsequently reduced mycotoxin concentrations in seeds. Under greenhouse conditions, these four biocontrol strains were also found to increase root length, shoot length, % germination, vigour index, fresh weight and dry weight of seedlings. Considering their overall performances, strains Bsp 3/aM, Has 1/c, M5 and T2 were selected for field studies as microbial talcum formulations. Among the tested microbial formulations, strain Bsp 3/aM significantly increased yield by 9.4% and 6.2% over the control in two maize cultivars Hema and Pearl, respectively. Increased plant growth and yield was also correlated with nutrient uptake in both the tested cultivars. All microbial formulation recorded significantly (p ≤ 0.05) reduced A. flavus infection and aflatoxin contamination in harvested seeds. But, none of the microbial formulations were found significant (p ≤ 0.05) in reducing F. verticilliodes incidence and fumonisin contamination. Our findings indicate that these microbial antagonists indirectly improve host health by suppressing seed-borne incidence of mycotoxigenic fungi and directly by facilitating nutrient uptake, thereby revealing their potential as both biofertilisers and biopesticides for maize production. 相似文献
16.
Intraspecific competition is the basis for biological control of aflatoxins, but there is little understanding of the mechanism(s)
by which competing strains inhibit toxin production. Evidence is presented that demonstrates a relationship between strength
of the vegetative compatibility reaction and aflatoxin production in Aspergillus flavus and A. parasiticus using the suspended disk culture method. Combining wild-type aflatoxin-producing isolates belonging to different vegetative
compatibility groups (VCGs) resulted in a substantial reduction in aflatoxin yield. Pairs of aflatoxin-producing isolates
within the same VCG, but showing weak compatibility reactions using complementary nitrate-nonutilizing mutants, also were
associated with reduced levels of aflatoxin B1. In contrast, pairings of isolates displaying a strong compatibility reaction typically produced high levels of aflatoxins.
These results suggest that interactions between vegetatively compatible wild-type isolates of A. flavus and A. parasiticus are cooperative and result in more aflatoxin B1 than pairings between isolates that are incompatible. Successful hyphal fusions among spore germlings produce a common mycelial
network with a larger resource base to support aflatoxin biosynthesis. By comparison, vegetative incompatibility reactions
might result in the death of those heterokaryotic cells composed of incompatible nuclei and thereby disrupt the formation
of mycelial networks at the expense of aflatoxin biosynthesis.
The content of this paper was presented at the 50th Anniversary Meeting of the Mycological Society of Japan, June 3–4, 2006,
Chiba, Japan 相似文献
17.
Aspergillus flavus and Aspergillus parasiticus cause perennial infection of agriculturally important crops in tropical and subtropical areas. Invasion of crops by these
fungi may result in contamination of food and feed by potent carcinogenic aflatoxins. Consumption of aflatoxin contaminated
foods is a recognised risk factor for human hepatocellular carcinoma (HCC) and may contribute to the high incidence of HCC
in Southeast Asia. This study conducted a survey of Vietnamese crops (peanuts and corn) and soil for the presence of aflatoxigenic
fungi and used microsatellite markers to investigate the genetic diversity of Vietnamese Aspergillus strains. From a total of 85 samples comprising peanut (25), corn (45) and soil (15), 106 strains were isolated. Identification
of strains by colony morphology and aflatoxin production found all Vietnamese strains to be A. flavus with no A. parasiticus isolated. A. flavus was present in 36.0% of peanut samples, 31.1% of corn samples, 27.3% of farmed soil samples and was not found in virgin soil
samples. Twenty-five per cent of the strains produced aflatoxins. Microsatellite analysis revealed a high level of genetic
diversity in the Vietnamese A. flavus population. Clustering, based on microsatellite genotype, was unrelated to aflatoxin production, geographic origin or substrate
origin. 相似文献
18.
Mogensen JM Møller KA von Freiesleben P Labuda R Varga E Sulyok M Kubátová A Thrane U Andersen B Nielsen KF 《Journal of industrial microbiology & biotechnology》2011,38(9):1329-1335
Tolypocladium inflatum is known primarily for its production of the cyclosporines that are used as an immunosuppressive drug. However, we report
here the production of the carcinogenic fumonisins B2 and B4 by this biotechnologically relevant fungal genus. These mycotoxins were detected in 11 strains tested from three species:
Tolypocladium inflatum, T. cylindrosporum, and T. geodes. Production of fumonisins by Fusarium spp. and Aspergillus niger is highly medium- and temperature-dependent, so the effect of these parameters on fumonisin production by three T. inflatum strains was studied. Maximum production was achieved on media with high sugar content incubated at 25–30°C. Since these results
demonstrate that fumonisin production could be widespread within the genus Tolypocladium, the potential contamination of commercial cyclosporine preparations with fumonisins needs to be investigated. 相似文献
19.
The minimum inhibitory concentration (MIC) of Origanum vulgare, Aloysia triphylla, Aloysia polystachya and Mentha piperita essential oils (EOs) against Fusarium verticillioides M 7075 (F. moniliforme, Sheldon) were assessed, using the semisolid agar antifungal susceptibility (SAAS) technique. O. vulgare, A. triphylla, A. polystachya and M. piperita EOs were evaluated at final concentrations of 10, 20, 40, 50, 100, 200, 250, 500, 1000 and 1500 εl per litre (εl/l) of culture medium. A. triphylla and O. vulgare EOs showed the highest inhibitory effects on F. verticillioides mycelial development. This inhibition was observed at 250 and 500 εl/l for EOs coming from Aloysia triphylla and O. vulgare, respectively. Thus, the effects of EOs on FB1 production were evaluated using corn grain (Zea mays) as substrate. The EOs were inserted on the 5th, 10th, 15th and 20th day of maize postinoculation with a conidia suspension
of F. verticillioides. O. vulgare and A. triphylla were applied to give final concentrations of 30 ppm and 45 ppm, respectively. Different effects were observed in the toxicogenicity
at the 20th day treatment. The O. vulgare EO decreased the production level of FB1 (P < 0.01) while A. triphyla EO increased it (P < 0.001) with respect to those obtained in the inoculated maize, not EOs treated. Results obtained in the present work indicate
that fumonisin production could be inhibited or stimulated by some constituents of EOs coming from aromatic plants. Further
studies should be performed to identify the components of EOs with modulatory activity on the growth and fumonisins production
of Fusarium verticillioides. 相似文献
20.
Chiou CH Lee LW Owens SA Whallon JH Klomparens KL Townsend CA Linz JE 《Archives of microbiology》2004,182(1):67-79
Aflatoxins are highly toxic and carcinogenic fungal secondary metabolites. At least 18 enzyme activities are required for aflatoxin biosynthesis in the filamentous fungus Aspergillus parasiticus. One of these enzymes, versicolorin B synthase (VBS), catalyzes bisfuran ring closure in versiconal hemiacetal (a reaction near the middle of the pathway) to form versicolorin B. This reaction is required for the subsequent activation to aflatoxin B1-8,9 epoxide, a highly reactive and toxic aflatoxin metabolite, and is important for aflatoxin toxicity. We analyzed the localization of VBS in the aflatoxin-producing strain A. parasiticus SU-1 grown on solid media using a colony fractionation technique developed previously. A highly specific polyclonal antibody, raised against a maltose-binding protein–VBS fusion protein synthesized in Escherichia coli, was used to detect VBS in SU-1 grown on a rich solid medium via immunofluorescence confocal laser scanning microscopy (CLSM) and immunogold transmission electron microscopy (TEM). VBS was detected in both vegetative hyphae and in asexual developmental structures, called conidiophores. Western blot and CLSM analyses demonstrated the highest abundance of VBS in colony fraction S2 consisting of cells that had grown for 24–48 h; this fraction also contained the highest levels of newly developed conidiophores and the highest abundance of aflatoxin B1, consistent with VBS abundance. At the subcellular level, CLSM and TEM detected VBS distributed throughout the cytoplasm and concentrated in ring-like structures surrounding nuclei. It is uncertain whether enzymatically active VBS is present in either or both locations. 相似文献