Microbiology and Fermentation Technology, CSIR-Central Food Technological Research Institute, Mysuru, Karnataka, 570 020, India.
Academy of Scientific and Innovative Research (AcSIR), CSIR-Central Food Technological Research Institute Campus, Mysuru, Karnataka, 570 020, India.
Arch Microbiol. 2020 Jul;202(5):1143-1155. doi: 10.1007/s00203-020-01822-1. Epub 2020 Feb 15.
Aflatoxins are the most common mycotoxin contaminant reported in food and feed. Aflatoxin B, the most toxic among different aflatoxins, is known to cause hepatocellular carcinoma in animals. Aspergillus flavus and A. parasiticus are the main producers of aflatoxins and are widely distributed in tropical countries. Even though several robust strategies have been in use to control aflatoxin contamination, the control at the pre-harvest level is primitive and incompetent. Therefore, the aim of the study was to isolate and identify the non-aflatoxigenic A. flavus and to delineate the molecular mechanism for the loss of aflatoxin production by the non-aflatoxigenic isolates. Eighteen non-aflatoxigenic strains were isolated from various biological sources using cultural and analytical methods. Among the 18 isolates, 8 isolates produced sclerotia and 17 isolates had type I deletion in norB-cypA region. The isolates were confirmed as A. flavus using gene-specific PCR and sequencing of the ITS region. Later, aflatoxin gene-specific PCR revealed that the defect in one or more genes has led to non-aflatoxigenic phenotype. The strain R9 had maximum defect, and genes avnA and verB had the highest frequency of defect among the non-aflatoxigenic strains. Further, qRT-PCR confirmed that the non-aflatoxigenic strains had high frequency of defect or downregulation in the late pathway genes compared to early pathway genes. Thus, these non-aflatoxigenic strains can be the potential candidates for an effective and proficient strategy for the control of pre-harvest aflatoxin contamination.
黄曲霉毒素是食品和饲料中最常见的真菌毒素污染物。不同黄曲霉毒素中毒性最强的黄曲霉毒素 B1 已知可导致动物肝细胞癌。黄曲霉和寄生曲霉是黄曲霉毒素的主要生产者，广泛分布于热带国家。尽管已经有几种强大的策略用于控制黄曲霉毒素污染，但在收获前的控制仍然原始且低效。因此，本研究的目的是分离和鉴定非产毒黄曲霉，并阐明非产毒菌株丧失黄曲霉毒素产生能力的分子机制。使用培养和分析方法，从各种生物来源中分离出 18 株非产毒菌株。在 18 个分离株中，有 8 个分离株产生菌核，有 17 个分离株在 norB-cypA 区域发生 I 型缺失。通过基因特异性 PCR 和 ITS 区域测序，确认这些分离株为黄曲霉。随后，黄曲霉毒素基因特异性 PCR 显示，一个或多个基因的缺陷导致了非产毒表型。菌株 R9 的缺陷最大，在非产毒菌株中，avnA 和 verB 基因的缺陷频率最高。进一步的 qRT-PCR 证实，与早期途径基因相比，非产毒菌株的晚期途径基因缺陷或下调频率更高。因此，这些非产毒菌株可能是一种有效且高效的收获前控制黄曲霉毒素污染策略的潜在候选菌株。
