Auxotrophy for uridine increases the sensitivity of Aspergillus niger to weak-acid preservatives.
Auxotrophy for uridine increases the sensitivity of Aspergillus niger to weak-acid preservatives.
复制标题
尿苷营养缺陷增加了黑曲霉对弱酸防腐剂的敏感性。
作者：
P. Melin;M. Stratford;A. Plumridge;D. Archer
弱酸性防腐剂，如山梨酸，被添加到食品中，以防止真菌腐败。弱酸性防腐剂的作用方式只有部分了解，在本文中，进一步深入了解弱酸抑制真菌生长的机制。尿苷需要菌株的尼日尔曲霉被证明是更敏感的弱酸（包括山梨酸，乙酸和苯甲酸）比野生型（WT）菌株。与此相反，其他非酸性，抗真菌物质的敏感性是相似的突变体和野生型菌株。通过互补A.具有完整pyrG基因的尼日尔，恢复了对弱酸性防腐剂的WT样抗性。用（14）C-标记的尿苷，山梨酸被证明完全抑制萌发的分生孢子在非竞争性方式的尿苷摄取。因此，pyrG（-）菌株的额外的弱酸敏感性是由弱酸抑制尿苷摄取引起的。其它几种营养缺陷型菌株的A.筛选尼日尔对乙酸、山梨酸和癸酸的敏感性。腺嘌呤或尿苷营养缺陷型菌株被发现具有增强的敏感性，但相比之下，氨基酸营养缺陷型显示出与WT相当的抗性。与WT菌株相比，酿酒酵母的尿苷营养缺陷型对弱酸并不更敏感。总之，本研究描述了一种以前未知的弱酸对丝状真菌A的作用机制。尼日尔，这可能从根本上影响我们对食品防腐腐败真菌的理解。
Weak-acid preservatives such as sorbic acid are added to foods to prevent fungal spoilage. The modes of action of weak-acid preservatives are only partially understood and, in this paper, further insight is presented into the mechanisms by which weak acids inhibit the growth of fungi. Uridine-requiring strains of Aspergillus niger were shown to be more sensitive to weak acids (including sorbic, acetic and benzoic acids) than wild-type (WT) strains. In contrast, sensitivity to other, non-acidic, antifungal substances was similar in mutant and WT strains. By complementing a pyrG(-) strain of A. niger with an intact pyrG gene, WT-like resistance to weak-acid preservatives was restored. Using (14)C-labelled uridine, sorbic acid was shown to completely inhibit uridine uptake in germinating conidia in a non-competitive manner. It is therefore proposed that the additional weak-acid sensitivity of the pyrG(-) strains was caused by weak-acid inhibition of uridine uptake. Several other auxotrophic strains of A. niger were screened for sensitivity to acetic, sorbic and decanoic acids. Strains auxotrophic for either adenine or uridine were found to have enhanced sensitivity but, in contrast, amino acid auxotrophs showed resistance comparable to that of the WT. Uridine auxotrophs of Saccharomyces cerevisiae were not more sensitive to weak acids compared to WT strains. In conclusion, this study describes a previously unknown mechanism of action of weak acids against the filamentous fungus A. niger, which may fundamentally affect our understanding of the preservation of food against spoilage fungi.