The Experts below are selected from a list of 768 Experts worldwide ranked by ideXlab platform
Brett M Tyler - One of the best experts on this subject based on the ideXlab platform.
-
restriction enzyme analysis of mitochondrial dna of the aspergillus flavus group a flavus a parasiticus and a Nomius
Applied and Environmental Microbiology, 1990Co-Authors: S F Moody, Brett M TylerAbstract:Mitochondrial DNA restriction fragment length polymorphisms were identified that clearly distinguish Aspergillus flavus, A. parasiticus, and A. Nomius. Mitochondrial DNAs of A. flavus and A. parasiticus were found to be circular, and their size was estimated size to be 32 kilobases. A restriction map was constructed for the mitochondrial genome of an A. parasiticus isolate by using four restriction endonucleases. Four genes tested were found to have the same order as in the mitochondrial genome of A. nidulans. The mitochondrial genome of A. Nomius was estimated to be 33 kilobases.
-
use of nuclear dna restriction fragment length polymorphisms to analyze the diversity of the aspergillus flavus group a flavus a parasiticus and a Nomius
Applied and Environmental Microbiology, 1990Co-Authors: S F Moody, Brett M TylerAbstract:Abstract Recombinant DNA clones carrying high-copy or low-copy sequences from Aspergillus nidulans and Neurospora crassa were used to identify restriction fragment length polymorphisms (RFLPs) diagnostic for members of the A. flavus group: A. flavus, A. parasiticus, and A. Nomius. These fungi were resolved into three distinct categories when they were grouped according to RFLP patterns. Subgroups within these categories were also evident. This limited RFLP analysis of nuclear DNA of members of the A. flavus group did not identify any RFLPs that differentiate these isolates on the basis of toxin production, but limited correlation with geographic location was observed.
Peter J Cotty - One of the best experts on this subject based on the ideXlab platform.
-
description of a distinctive aflatoxin producing strain of aspergillus Nomius that produces submerged sclerotia
Mycopathologia, 2009Co-Authors: M A Doster, Peter J Cotty, Themis J MichailidesAbstract:A new distinctive strain of Aspergillus Nomius that produces the potent mycotoxins, aflatoxins, is described from pistachio, pecan, and fig orchards in California. Similar to the typical strain of A. Nomius (as represented by the ex-type), the O strain produced both B and G aflatoxins but not cyclopiazonic acid, had similar conidial ornamentation, and grew poorly at 42°C. Furthermore, previous published DNA sequence supports that the new strain is very closely related to the ex-type of A. Nomius. However, the O strain differs from the ex-type in several morphological characters. The ex-type was initially described as producing “indeterminate sclerotia” that appear as large (up to 3 mm long) elongated sclerotia on surfaces of media. The O strain produces only small spherical sclerotia (mean diameter <0.3 mm) submerged in the medium. In addition, the O strain has predominantly uniseriate conidial heads, whereas the typical strain of A. Nomius has predominantly biseriate heads. The O strain colony color on both Czapek solution agar and Czapek yeast extract agar was more yellowish than the ex-type of A. Nomius and other common aflatoxin-producing fungi. Isolates of the O strain reported here from several orchards represent the first report of A. Nomius in California.
-
Description of a Distinctive Aflatoxin-Producing Strain of Aspergillus Nomius that Produces Submerged Sclerotia
Mycopathologia, 2009Co-Authors: M A Doster, Peter J Cotty, Themis J MichailidesAbstract:A new distinctive strain of Aspergillus Nomius that produces the potent mycotoxins, aflatoxins, is described from pistachio, pecan, and fig orchards in California. Similar to the typical strain of A. Nomius (as represented by the ex-type), the O strain produced both B and G aflatoxins but not cyclopiazonic acid, had similar conidial ornamentation, and grew poorly at 42°C. Furthermore, previous published DNA sequence supports that the new strain is very closely related to the ex-type of A. Nomius . However, the O strain differs from the ex-type in several morphological characters. The ex-type was initially described as producing “indeterminate sclerotia” that appear as large (up to 3 mm long) elongated sclerotia on surfaces of media. The O strain produces only small spherical sclerotia (mean diameter
-
Aflatoxin-producing Aspergillus species from Thailand
International Journal of Food Microbiology, 2006Co-Authors: Kenneth C. Ehrlich, Kerri Kobbeman, Beverly G. Montalbano, Peter J CottyAbstract:Aflatoxin-producing Aspergillus species were isolated from soil samples from ten different regions within Thailand. Aspergillus flavus was present in all of the soil samples. Unlike previous studies, we found no A. parasiticus or A. flavus capable of both B- and G-type aflatoxin production in any of the samples. A. pseudotamarii, which had not been previously reported from Thailand, was found in four soil samples. In two of the samples A. Nomius was determined to be the most abundant aflatoxin-producing species. Based on sequence alignments for three DNA regions (Taka-amylase A (taa), the rRNA internal transcribed spacer (ITS), and the intergenic region for the aflatoxin biosynthesis genes aflJ and aflR) the A. Nomius isolates separated into three well-supported clades. Isolates from one of the A. Nomius clades had morphological properties similar to those found for S-type isolates capable of B and G aflatoxin production and could easily be mistaken for these isolates. Our results suggest that such unusual A. Nomius isolates could be a previously unrecognized agent for aflatoxin contamination in Thailand. Published by Elsevier B.V.
-
Aflatoxin biosynthesis cluster gene cypA is required for G aflatoxin formation.
Applied and Environmental Microbiology, 2004Co-Authors: Kenneth C. Ehrlich, Perng-kuang Chang, Jiujiang Yu, Peter J CottyAbstract:Aspergillus flavus isolates produce only aflatoxins B1 and B2, while Aspergillus parasiticus and Aspergillus Nomius produce aflatoxins B1, B2, G1, and G2. Sequence comparison of the aflatoxin biosynthesis pathway gene cluster upstream from the polyketide synthase gene, pksA, revealed that A. flavus isolates are missing portions of genes (cypA and norB) predicted to encode, respectively, a cytochrome P450 monooxygenase and an aryl alcohol dehydrogenase. Insertional disruption of cypA in A. parasiticus yielded transformants that lack the ability to produce G aflatoxins but not B aflatoxins. The enzyme encoded by cypA has highest amino acid identity to Gibberella zeae Tri4 (38%), a P450 monooxygenase previously shown to be involved in trichodiene epoxidation. The substrate for CypA may be an intermediate formed by oxidative cleavage of the A ring of O-methylsterigmatocystin by OrdA, the P450 monooxygenase required for formation of aflatoxins B1 and B2.
-
Sequence comparison of aflR from different Aspergillus species provides evidence for variability in regulation of aflatoxin production.
Fungal Genetics and Biology, 2003Co-Authors: Kenneth C. Ehrlich, Beverly G. Montalbano, Peter J CottyAbstract:Aflatoxin contamination of foods and feeds is a world-wide agricultural problem. Aflatoxin production requires expression of the biosynthetic pathway regulatory gene, aflR, which encodes a Cys6Zn2-type DNA-binding protein. Homologs of aflR from Aspergillus Nomius, bombycis, parasiticus, flavus, and pseudotamarii were compared to investigate the molecular basis for variation among aflatoxin-producing taxa in the regulation of aflatoxin production. Variability was found in putative promoter consensus elements and coding region motifs, including motifs involved in developmental regulation (AbaA, BrlA), regulation of nitrogen source utilization (AreA), and pH regulation (PacC), and in coding region PEST domains. Some of these elements may affect expression of aflJ, a gene divergently transcribed from aflR, that also is required for aflatoxin accumulation. Comparisons of phylogenetic trees obtained with either aligned aflR intergenic region sequence or coding region sequence and the observed divergence in regulatory features among the taxa provide evidence that regulatory signals for aflatoxin production evolved to respond to a variety of environmental stimuli under differential selective pressures. Phylogenetic analyses also suggest that isolates currently assigned to the A. flavus morphotype SBG represent a distinct species and that A. Nomius is a diverse paraphyletic assemblage likely to contain several species.
Themis J Michailides - One of the best experts on this subject based on the ideXlab platform.
-
description of a distinctive aflatoxin producing strain of aspergillus Nomius that produces submerged sclerotia
Mycopathologia, 2009Co-Authors: M A Doster, Peter J Cotty, Themis J MichailidesAbstract:A new distinctive strain of Aspergillus Nomius that produces the potent mycotoxins, aflatoxins, is described from pistachio, pecan, and fig orchards in California. Similar to the typical strain of A. Nomius (as represented by the ex-type), the O strain produced both B and G aflatoxins but not cyclopiazonic acid, had similar conidial ornamentation, and grew poorly at 42°C. Furthermore, previous published DNA sequence supports that the new strain is very closely related to the ex-type of A. Nomius. However, the O strain differs from the ex-type in several morphological characters. The ex-type was initially described as producing “indeterminate sclerotia” that appear as large (up to 3 mm long) elongated sclerotia on surfaces of media. The O strain produces only small spherical sclerotia (mean diameter <0.3 mm) submerged in the medium. In addition, the O strain has predominantly uniseriate conidial heads, whereas the typical strain of A. Nomius has predominantly biseriate heads. The O strain colony color on both Czapek solution agar and Czapek yeast extract agar was more yellowish than the ex-type of A. Nomius and other common aflatoxin-producing fungi. Isolates of the O strain reported here from several orchards represent the first report of A. Nomius in California.
-
Description of a Distinctive Aflatoxin-Producing Strain of Aspergillus Nomius that Produces Submerged Sclerotia
Mycopathologia, 2009Co-Authors: M A Doster, Peter J Cotty, Themis J MichailidesAbstract:A new distinctive strain of Aspergillus Nomius that produces the potent mycotoxins, aflatoxins, is described from pistachio, pecan, and fig orchards in California. Similar to the typical strain of A. Nomius (as represented by the ex-type), the O strain produced both B and G aflatoxins but not cyclopiazonic acid, had similar conidial ornamentation, and grew poorly at 42°C. Furthermore, previous published DNA sequence supports that the new strain is very closely related to the ex-type of A. Nomius . However, the O strain differs from the ex-type in several morphological characters. The ex-type was initially described as producing “indeterminate sclerotia” that appear as large (up to 3 mm long) elongated sclerotia on surfaces of media. The O strain produces only small spherical sclerotia (mean diameter
-
a morphologically distinct strain of aspergillus Nomius
Mycologia, 1998Co-Authors: Toby P Feibelman, Peter J Cotty, M A Doster, Themis J MichailidesAbstract:DNA polymorphisms were used to infer relationships of a morphologically distinct new strain of aflatoxin-producing Aspergillus to other members of Aspergillus sect. Flavi. The new strain produced both Band G aflatoxins, and differed both morpho logically and physiologically from other aflatoxin pro ducers. Three isolates of the new fungus were com pared with representatives of three known aflatoxin producing species, Regions of the Taka-amylase A, 13 tubulin, calmodulin, and nitrate reductase genes were amplified using PCR and digested with restric tion enzymes. Restriction fragment length polymor phism analysis of all four gene regions indicated that the new Aspergillus isolates are closely related to A. Nomius, but are diverged from other' aflatoxin-pro ducing species.
S F Moody - One of the best experts on this subject based on the ideXlab platform.
-
restriction enzyme analysis of mitochondrial dna of the aspergillus flavus group a flavus a parasiticus and a Nomius
Applied and Environmental Microbiology, 1990Co-Authors: S F Moody, Brett M TylerAbstract:Mitochondrial DNA restriction fragment length polymorphisms were identified that clearly distinguish Aspergillus flavus, A. parasiticus, and A. Nomius. Mitochondrial DNAs of A. flavus and A. parasiticus were found to be circular, and their size was estimated size to be 32 kilobases. A restriction map was constructed for the mitochondrial genome of an A. parasiticus isolate by using four restriction endonucleases. Four genes tested were found to have the same order as in the mitochondrial genome of A. nidulans. The mitochondrial genome of A. Nomius was estimated to be 33 kilobases.
-
use of nuclear dna restriction fragment length polymorphisms to analyze the diversity of the aspergillus flavus group a flavus a parasiticus and a Nomius
Applied and Environmental Microbiology, 1990Co-Authors: S F Moody, Brett M TylerAbstract:Abstract Recombinant DNA clones carrying high-copy or low-copy sequences from Aspergillus nidulans and Neurospora crassa were used to identify restriction fragment length polymorphisms (RFLPs) diagnostic for members of the A. flavus group: A. flavus, A. parasiticus, and A. Nomius. These fungi were resolved into three distinct categories when they were grouped according to RFLP patterns. Subgroups within these categories were also evident. This limited RFLP analysis of nuclear DNA of members of the A. flavus group did not identify any RFLPs that differentiate these isolates on the basis of toxin production, but limited correlation with geographic location was observed.
Benedito Correa - One of the best experts on this subject based on the ideXlab platform.
-
Effect of temperature on growth, gene expression, and aflatoxin production by Aspergillus Nomius isolated from Brazil nuts
Mycotoxin Research, 2020Co-Authors: Nathália B. S. Yunes, Rodrigo C. Oliveira, Tatiana A. Reis, Arianne C. Baquião, Liliana O. Rocha, Benedito CorreaAbstract:Aspergillus Nomius is a potent producer of aflatoxins B and G and is one of the most common species of fungi found in Brazil nuts. Temperature is considered a major abiotic factor that influences fungal colonization and aflatoxin production in nuts during pre- and post-harvest. Therefore, assessment of the response of aflatoxigenic species to different temperatures is important to add information about the understanding of aflatoxin production by Aspergillus Nomius and may help in the development of new strategies to prevent aflatoxin contamination. The aim of this study was to evaluate the effect of temperature (25, 30, and 35 °C) on the radial growth, aflatoxin production (B and G), and aflatoxin gene expression of seven A. Nomius strains isolated from Brazil nuts. The optimal temperature for growth was 30 °C and was also the best condition for the expression of the aflR , aflD , and aflQ genes. However, maximum production of aflatoxins B and G occurred at 25 °C. Interestingly, high expression of the structural gene aflQ was observed in the maximum aflatoxin production condition (25 °C). The present study demonstrates that temperature may influence aflatoxin production by A. Nomius . The combination of molecular and physiological data aids the understanding of the aflatoxigenic species response to different temperatures and can assist in predicting the driving environmental factors that influence aflatoxin contamination of Brazil nuts.
-
Characterization of Aspergillus section Flavi isolated from organic Brazil nuts using a polyphasic approach.
Food Microbiology, 2014Co-Authors: Tatiana Alves Reis, Arianne Costa Baquião, Danielle Diniz Atayde, F. Grabarz, Benedito CorreaAbstract:Brazil nut (Bertholletia excelsa), an important non-timber forest product from Amazonia, is commercialized in worldwide markets. The main importers of this nut are North America and European countries, where the demand for organic products has grown to meet consumers concerned about food safety. Thus, the precise identification of toxigenic fungi is important because the Brazil nut is susceptible to colonization by these microorganisms. The present study aimed to characterize by polyphasic approach strains of Aspergillus section Flavi from organic Brazil nuts. The results showed Aspergillus flavus as the main species found (74.4%), followed by Aspergillus Nomius (12.7%). The potential mycotoxigenic revealed that 80.0% of A. flavus were toxin producers, 14.3% of which produced only aflatoxin B (AFB), 22.85% of which produced only cyclopiazonic acid (CPA), and 42.85% produced both them. All strains of A. Nomius were AFB and AFG producers and did not produce CPA. There is no consensus about what Aspergillus species predominates on Brazil nuts. Apparently, the origin, processing, transport and storage conditions of this commodity influence the species that are found. The understanding about population of fungi is essential for the development of viable strategies to control aflatoxins in organic Brazil nuts.
-
Polyphasic approach to the identification of Aspergillus section Flavi isolated from Brazil nuts.
Food chemistry, 2013Co-Authors: Arianne Costa Baquião, Maitê Martins Melo De Oliveira, Tatiana Alves Reis, Patricia Zorzete, Danielle Diniz Atayde, Benedito CorreaAbstract:The aim of this study was to use a polyphasic approach to identify Aspergillus section Flavi isolated from Brazil nuts collected in the Amazon forest: investigation of macro- and microscopic morphology, production of extrolites, heat-resistance fungi, and sequencing of DNA regions. The following Aspergillus section Flavi species were identified: Aspergillus flavus (75.5%), Aspergillus Nomius (22.3%), and Aspergillus parasiticus (2.2%). All A. Nomius and A. parasiticus isolates produced aflatoxins B and G, but not cyclopiazonic acid (CPA). A. flavus isolates were more diversified and a high frequency of mycotoxigenic strains was observed. The polyphasic approach permitted the reliable identification of section Flavi species. The rate of mycotoxigenic strains was high (92.7%) and mainly included A. flavus strains producing elevated levels of aflatoxins and CPA. These results highlight the possibility of co-occurrence of both toxins, increasing their potential toxic effect in this commodity.
