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A total of 69 samples of hay and straw collected during the winter period of 1984/85 were surveyed for their contamination by Aspergillus versicolor. The percentage of A. versicolor-positive samples was 14.5%. Nineteen A. versicolor strains mainly isolated from roughage were tested for the production of sterigmatocystin. All of the isolates examined were capable of producing different levels of sterigmatocystin on a cracked corn substrate. The majority of these strains were highly toxigenic; 53% of the isolates produced more than 500 mg/kg of sterigmatocystin. These findings suggest that corn is a very suitable substrate for sterigmatocystin production and that particularly in the surface layers of feed stocks and corn silos such toxigenic strains of A. versicolor can produce considerable growth and possibly sterigmatocystin, too. 相似文献
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AIMS: To report on aflatoxin B(1) and B(2) production from a species of Emericella. METHODS AND RESULTS: Aflatoxins and sterigmatocystin were determined by high-pressure liquid chromatography (HPLC) with diode array detection and confirmed by HPLC with mass spectrometry detection. Among 30 known species of Emericella only one species produced aflatoxin. Strains originating from the same geographical source material had different patterns of aflatoxin and sterigmatocystin production on different media, indicating that epigenetic factors may be involved in the regulation of aflatoxin production. However, two cultures from the same original genet were very similar. CONCLUSIONS: Emericella astellata can produce small amounts of sterigmatocystin and aflatoxin B(1) and B(2). SIGNIFICANCE AND IMPACT OF THE STUDY: Emericella has been used extensively in genetic studies and therefore the isolates producing aflatoxin can be used to elucidate the genetic, evolutionary and maybe ecological role of aflatoxins using molecular genetic methods. 相似文献
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Hodges RL Kelkar HS Xuei X Skatrud PL Keller NP Adams TH Kaiser RE Vinci VA McGilvray D 《Journal of industrial microbiology & biotechnology》2000,25(6):333-341
Echinocandin B (ECB), a lipopolypeptide used as a starting material for chemical manufacture of the anti-Candida agent LY303366,
is produced by fermentation using a strain of Aspergillus nidulans. In addition to ECB, the wild-type strain also produces a significant level of sterigmatocystin (ST), a potent carcinogen
structurally related to the aflatoxins. Characterization of a mutant designated A42355-OC-1 (OC-1), which is blocked in ST
biosynthesis, was the result of a chromosomal translocation. The chromosomal regions containing the breakpoints of the translocation
were isolated and DNA sequencing and PCR analysis of the chromosomal breakpoints demonstrated the translocation occurred within
the stcW gene of the ST biosynthetic pathway, resulting in disruption of the open reading frame for this gene. Biochemical feeding
studies indicate the involvement of this gene product in the conversion of averufin to 1-hydroxy versicolorone. This work
demonstrates an effective synergy between classical strain improvement methods and molecular genetics. Journal of Industrial Microbiology & Biotechnology (2000) 25, 333–341.
Received 27 April 2000/ Accepted in revised form 25 November 2000 相似文献
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Aflatoxins (AFs) are toxic and carcinogenic secondary metabolites produced by isolates of Aspergillus section Flavi as well as a number of Aspergillus isolates that are classified outside of section Flavi. Characterization of the AF and sterigmatocystin (ST) gene clusters and analysis of factors governing regulation of their
biosynthesis has resulted in these two mycotoxins being the most extensively studied of fungal secondary metabolites. This
wealth of information has allowed the determination of the molecular basis for non-production of AF in natural isolates of
A. flavus and domesticated strains of A. oryzae. This review provides an overview of the molecular analysis of the AF and ST gene clusters as well as new information on
an AF gene cluster identified in the non-section Flavi isolate, Aspergillus ochraceoroseus. Additionally, molecular phylogenetic analysis using AF biosynthetic gene sequences as well as ribosomal DNA internal transcribed
spacer (ITS) sequences between various section Flavi and non-section Flavi species has enabled determination of the probable evolutionary history of the AF and ST gene clusters. A model for the evolution
of the AF and ST gene clusters as well as possible biological roles for AF are discussed. 相似文献
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黄曲霉毒素氧化酶/壳聚糖-单壁碳纳米管/聚邻苯二胺修饰电极对杂色曲霉素的检测 总被引:1,自引:0,他引:1
将黄曲霉毒素氧化酶(AFO)固定在壳聚糖(CS)-单壁碳纳米管(SWCNTs)杂交膜中,组装在聚邻苯二胺(POPD)修饰的金电极(Au)表面,制备了对杂色曲霉素(ST)敏感的生物传感器(AFO/CS-SWCNTs/POPD/Au)。运用原子力显微镜(AFM)、傅立叶变换红外光谱(FT-IR)和交流阻抗技术(EIS)对电极组装过程进行了表征。循环伏安法研究表明,AFO在修饰电极上发生了准可逆的氧化还原反应,是表面控制过程,其式量电位为-0.436V(vs.Ag/AgCl),说明包埋在CS-SWCNTs中的AFO和电极之间发生了直接电子传递。AFO修饰电极对ST具有明显的电催化作用,其表观米氏常数appKM为7.13μmol/L,催化电流与ST浓度在10~310ng/mL范围内呈线性关系,相关系数为0.997,检出限为3ng/mL(S/N=3),响应时间小于10s。组装的生物传感器具有较好的稳定性与重现性,连续检测20ng/mL的ST标准溶液11次,电流值RSD为3.9%;放置一个月后,其电流响应值仍为初始值的85.6%。该方法具有较高的选择性和灵敏度,应用于实际样品检测时,其回收率在87.6%~105.5%之间... 相似文献
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Dothistromin is a mycotoxin that is remarkably similar in structure to versicolorin B, a precursor of both aflatoxin and sterigmatocystin.
Dothistromin-producing fungi also produce related compounds, including some aflatoxin precursors as well as alternative forms
of dothistromin. Dothistromin is synthesized by pathogenic species of Dothistroma in the red bands of pine needles associated with needle blight, but is also made in culture where it is strongly secreted
into the surrounding medium. Orthologs of aflatoxin and sterigmatocystin biosynthetic genes have been found that are required
for the biosynthesis of dothistromin, along with others that are speculated to be involved in the same pathway on the basis
of their sequence similarity to aflatoxin genes. An epoxide hydrolase gene that has no homolog in the aflatoxin or sterigmatocystin
gene clusters is also clustered with the dothistromin genes, and all these genes appear to be located on a minichromosome
in Dothistroma septosporum. The dothistromin genes are expressed at an early stage of growth, suggesting a role in the first stages of plant invasion
by the fungus. Future studies are expected to reveal more about the role of dothistromin in needle blight and about the genomic
organization and expression of dothistromin genes: these studies will provide for interesting comparisons with these aspects
of aflatoxin and sterigmatocystin biosynthesis. 相似文献
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Microbial secondary metabolite production is frequently associated with developmental processes such as sporulation, but there are few cases where this correlation is understood. Recent work with the filamentous fungus Aspergillus nidulans has provided new insights into the mechanisms coordinating production of the toxic secondary metabolite sterigmatocystin with asexual sporulation. These processes have been shown to be linked through a common need to inactivate a heterotrimeric G protein dependent signaling pathway that, when active, serves to stimulate growth while blocking both sporulation and sterigmatocystin biosynthesis. 相似文献
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Two wild-type laboratory populations of Drosophila melanogaster, Florida-9 (sensitive to aflatoxin (AF) B1-induced toxicity) and Lausanne-S (resistant to AFB1-induced toxicity) were tested to determine relative degress of sensitivity to growth from the egg stage on media containing 0.2, 0.6, 2.0, and 4.0 ppm AFB1, AFG1, AFB2, or sterigmatocystin (ST). Data indicate that strain Florida-9 is quite sensitive to AFG1 toxicity at both the egg-pupa and egg-adult stages of development while Lausanne-S is quite resistant to such toxic effects. For Lausanne-S, AFB1 > AFG1 in relative toxicity, while for Florida-9, AFG1 > AFB1. The latter is noteworthy since vertebrate studies consistently show that AFB1 is a significantly stronger carcinogen and mutagen than AFG1. Possible explanations are discussed. Neither strain tested displayed toxic responses to the presence of AFB2 or ST in the culture media; however, the 4.0-ppm Lausanne-S treatment displayed a significantly lower adult mortality rate than the control, indicating that Lausanne-S flies may benefit from the presence of ST in the culture medium. 相似文献
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