啤酒污染菌酒花抗性基因型的多样性分析

Evaluation of Genotypic Diversity in Hop Resistance of Beer Spoilage Bacteria

摘要:

为了评价采用酒花抗性基因horA和horC作为分子标记，快速检测和鉴定具有腐败能力的啤酒污染菌的准确性，对来自5家工厂的53株啤酒污染菌基因型和表型进行比较分析，包括M13-PCR指纹、horA/horC的PCR扩增、菌株的酒花抗性和啤酒腐败能力。M13-PCR指纹的聚类分析表明不属于同一菌种的指纹相似性一般小于70%，同菌种不同菌株之间的指纹也存在较大差异，因此53株菌株之间存在一定的个体差异。表型的比较分析表明，酒花抗性或腐败性较强的菌株，horA/horC检测结果一般为阳性，针对这一类菌株其检测准确性较高。然而，部分弱酒花抗性或无腐败能力的菌株，horA/horC检测结果也为阳性，其中无腐败能力的菌株的假阳性检出率达到了78.6%；部分弱腐败能力菌株的horA/horC检测为阴性，即假阴性率为28%。2株具有较强酒花抗性的菌株的horA/horC检测为阴性，表明可能存在新的酒花抗性机制。令人感兴趣的是，通过菌株间的比较分析表明horA/horC在L. plantarum中具有较高的保守性。以上研究结果表明，horA/horC作为单一的分子标记，难以准确地检测和鉴定所有啤酒污染菌的酒花抗性和腐败性。

Abstract:

To evaluate the accuracy of genetic markers of horA and horC genesto rapidly detect the spoilage ability of beer spoilage bacteria，the genotypes and phenotypes of 53 spoilage bacteria strains which were isolated from 5 Chinese breweries were compared in this study. The physiological features studied included M13-PCR fingerprint，horA and horC genes，beer spoilage ability and hop resistance ability. The clustering analysisof M13-PCR fingerprint indicated that the similaritycoefficient was less than 70% between different species and the similarity between strains in the same specie also varied greatly. Hence，the genotypes of 53 strains were different from each other. Phenotype analysis showed that almost all strains with strong spoilage ability or hop resistance ability contained horA or horC genes，which confirmedthe good accuracy of these genetic markers. However，some non-spoilage or weak hop-resistant strains also contained horA or horC genes，leading to a highfalse positive rate of 78.6%. A few weak spoilage strains did not contain horA or horC genes，which led to a false negative rate of 28%. Two strong hop-resistant strains did not contain horA or horC genes and they were supposed to have other mechanism of hop resistance. It is interesting that horA and horC geneswere found to be conserved in L. plantarum species. These results indicated that horA or horC genesare not suitable to be used as genetic markers for rapidly detectionof the spoilage ability and hop resistance of all beerspoilage bacteria.