呕吐毒素降解菌A4的分离及降解特性研究

Isolation and degradation characteristics of deoxynivalenol degrading strain A4

为了给呕吐毒素(DON)污染的谷物和饲料脱毒提供菌株资源,本研究从赤霉病污染区域的小麦田采集土壤样品,通过富集培养,分离筛选到一株DON降解菌,通过形态、16S rDNA、gyrB基因序列对降解菌进行菌种鉴定,液相色谱串联质谱和核磁共振鉴定降解产物,明确其降解途径和解毒机制,通过菌株生长特性、降解特性和基因组间差异分析比较DON降解菌A4、A8和A16之间的差异。结果表明:分离筛选获得DON降解菌A4,该菌能在10 h内降解9.7μg·mL^(-1)DON,降解率高达97%。经鉴定,A4为德沃斯氏菌(Devosia sp.)。A4通过降解DON为3-keto-DON进行脱毒。A4的最适生长温度为35℃,最适NaCl浓度为2%,其耐热性和耐盐性优于菌株A8和A16。A4的最适降解温度为35℃、最适降解pH为8.0,其降解速率高于菌株A8和A16。通过平均核苷酸相似度(ANI)分析,A4与A8和A16之间的ANI分别为81.54%和77.87%,均低于95%,因此属于不同种的菌株。研究表明,筛选得到的新型DON脱毒菌株A4具有良好的抗逆性,为DON的污染控制提供了新的降解菌资源。

The purpose of this study was to isolate deoxynivalenol(DON)degrading strain and to evaluate its degradation characteristics and mechanism,so as to provide strain resources for the detoxification of DON-contaminated grains and feeds.Soil samples were collected from wheat fields contaminated with gibberella,and DON degrading bacteria were isolated through enrichment culture;they were identified by morphology and 16S rDNA,gyrB gene sequence.Liquid Chromatography-Tandem Mass Spectrometry and nuclear magnetic resonance were used to identify degradation products,determine degradation pathways,and understand the detoxification mechanisms.The differences between degrading bacteria A4 and DON degrading bacteria A8 and A16 were compared by analyzing strain growth and degradation characteristics,and intergenomic differences.The degradation rate for the DON degrading bacteria,A4,was reported to be 9.7μg·mL-1which increased by more than 97%within 10 h.A4 was identified as Devosia sp.,that produces 3-keto-DON in the process of degrading DON,thus reducing toxicity.A4 had an optimal growth temperature of 35°C and an optimal NaCl concentration of 2%.Its heat resistance and salt tolerance were found to be better than those of strains A8 and A16.To degrade DON,A4 requires an optimum pH and temperature of 8.0 and 35℃,respectively.In terms of degradation characteristics,A4 had highter rate than A8 and A16.Comparison between the average nucleotide similarity(ANI)analyses of the three strains showed that the ANI between A4,and A8 and A16 were81.54%and 77.87%,respectively.The ANI was lower by 95%,indicating that A4 was genetically different from the other two strains,implying it belongs to a different strain.This study has thus screened a novel DON detoxification strain,with good stress resistance,and provides new degrading bacteria resources for DON pollution control.