US Department of Agriculture, Agricultural Research Service, Western Regional Research Center, 800 Buchanan Street, Albany, CA, 94710, USA.
Department of Plant Sciences, University of California, Davis, One Shields Avenue, Davis, CA, 95616, USA.
Mycotoxin Res. 2018 May;34(2):151-157. doi: 10.1007/s12550-018-0309-2. Epub 2018 Feb 20.
Aflatoxins are toxic and carcinogenic secondary metabolites produced primarily by the filamentous fungi Aspergillus flavus and Aspergillus parasiticus and cause toxin contamination in food chain worldwide. Aspergillus oryzae and Aspergillus sojae are highly valued as koji molds in the traditional preparation of fermented foods, such as miso, sake, and shoyu. Koji mold species are generally perceived of as being nontoxigenic and are generally recognized as safe (GRAS). Fungal isolates were collected from a California orchard and a few were initially identified to be A. sojae using β-tubulin gene sequences blasted against NCBI data base. These new isolates all produced aflatoxins B, B, G, and G and were named as Pistachio Winter Experiment (PWE) strains. Thus, it is very important to further characterize these strains for food safety purposes. The full length of aflR gene of these new isolates was sequenced. Comparison of aflR DNA sequences of PWE, A. parasiticus and A. sojae, showed that the aflatoxigenic PWE strains had the six base insertion (CTCATG) similar to domesticated A. sojae, but a pre-termination codon TGA at nucleotide positions 1153-1155 was absent due to a nucleotide codon change from T to C. Colony morphology and scanning microscopic imaging of spore surfaces showed similarity of PWE strains to both A. parasiticus and A. sojae. Concordance analysis of multi locus DNA sequences indicated that PWE strains were closely linked between A. parasiticus and A. sojae. The finding documented the first report that such unique strains have been found in North America and in the world.
黄曲霉毒素是由丝状真菌黄曲霉和寄生曲霉主要产生的有毒和致癌的次生代谢物，导致全球食物链中的毒素污染。米曲霉和大豆曲霉在传统发酵食品（如味噌、清酒和酱油）的曲霉菌制备中被高度重视为曲霉菌。曲霉菌种通常被认为是非产毒的，并且通常被认为是安全的（GRAS）。从加利福尼亚果园中采集了真菌分离物，并用β-微管蛋白基因序列对 NCBI 数据库进行了轰击，初步鉴定了一些分离物为大豆曲霉。这些新的分离物都产生了黄曲霉毒素 B、B、G 和 G，并被命名为开心果冬季实验（PWE）菌株。因此，为了食品安全目的，进一步表征这些菌株非常重要。这些新分离物的 aflR 基因全长进行了测序。对 PWE、寄生曲霉和大豆曲霉的 aflR DNA 序列进行比较，结果表明，产黄曲霉毒素的 PWE 菌株具有类似于驯化的大豆曲霉的六碱基插入（CTCATG），但由于核苷酸密码子从 T 变为 C，在核苷酸位置 1153-1155 处不存在终止密码子 TGA。PWE 菌株的菌落形态和孢子表面扫描显微镜成像显示与寄生曲霉和大豆曲霉相似。多位点 DNA 序列的一致性分析表明，PWE 菌株在寄生曲霉和大豆曲霉之间紧密相关。这一发现记录了第一个在北美和世界范围内发现此类独特菌株的报告。
