基于全基因组数据华根霉产真菌毒素分析

The safety analysis on mycotoxins of Rhizopus chinensis based on whole genomic sequences

摘要:

【目的】在对中国传统优势浓香型白酒产业中重要功能微生物华根霉菌株CCTCCM201021全基因组测序的基础上, 以生物信息学的方法和手段主要针对真菌毒素的合成代谢途径及关键基因进行分析, 考察微生物在食品工业应用中的安全性。【方法】应用Illumina平台Solexa测序技术对华根霉进行基因组测序, 运用SOAPdenovo组装软件进行拼接, 并进行一系列生物信息分析, 考察根霉素、小孢根霉素及典型丝状真菌毒素代谢的主要途径及相关基因, 包括PKS、NRPS与PKS-NRPS混合代谢途径; 萜类化合物代谢和其他代谢途径等, 判断华根霉是否具有产真菌毒素的潜在危害性。【结果】测序结果表明华根霉全基因组大小为45.70 Mb左右, GC含量为36.99%。通过基因预测软件分析得到基因17 676个, 共注释基因13 243个。通过进化树与同源基因比较分析, 与目前基因组测序完成的仅有的3株接合菌基因组相比, 序列相似性普遍偏低, 与华根霉存在较为显著的差异, 但同源基因的相似性在60%左右。代谢分析表明, 华根霉中仅存在较少聚酮合成、萜类化合物合成途径代谢基因, 存在大量异源物质降解途径基因。【结论】华根霉基本不具备产目前已知的真菌毒素的关键基因或合成能力, 可以认为其发酵产品是相对安全的。在酿造过程中, 不仅可作为糖化菌, 在混菌发酵时, 对部分具有抑菌能力的抗生物质具有降解功能, 是发酵工业中应用的相对安全的重要生产菌。

Abstract:

[Objective] Based on the bioinformations of the whole genomic sequences, we assessed biosynthetic pathway of mycotoxins and antibiotics in Rhizopus chinensis CCTCCM201021, an important fungus isolated from Daqu, a leaven used in the production of traditional Chinese liquor. [Methods] The sequencing was done using Solexa sequencing technology. The genome was assembled by using SOAP de novo software. Key synthetic pathways and genes of rhizoxin and rhizonin, as well as mycotoxins metabolism were analyzed, including PKS, NRPS and PKS-NRPS hybrid metabolic pathways, terpenoid metabolism and other metabolic pathways. [Results] The genome of R. chinensis has a total size of 45.70 Mb and a GC content of 36.99%. Compared with the genomes of the Zygomycetes, the sequence similarity is low, whereas the similarity of the homologous gene is about 60%. The genome differences between Rhizopus and the fungi belonging to the Zygomycete class were significant. By the analysis of typical mycotoxins synthesis pathways and genes based on the genome data, a few polyketide biosynthetic pathway metabolism and terpenoid metabolism genes were found in R. chinensis, but there were great quantity genes of xenobiotics biodegradation pathways. [Conclusion] R. chinensis cannot produce mycotoxins, and its products are generally considered as safe.