Document Detail

Auxotrophy for uridine increases the sensitivity of Aspergillus niger to weak-acid preservatives.
MedLine Citation:
PMID:  18375817     Owner:  NLM     Status:  MEDLINE    
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.
Petter Melin; Malcolm Stratford; Andrew Plumridge; David B Archer
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Microbiology (Reading, England)     Volume:  154     ISSN:  1350-0872     ISO Abbreviation:  Microbiology (Reading, Engl.)     Publication Date:  2008 Apr 
Date Detail:
Created Date:  2008-03-31     Completed Date:  2008-06-03     Revised Date:  2014-10-14    
Medline Journal Info:
Nlm Unique ID:  9430468     Medline TA:  Microbiology     Country:  England    
Other Details:
Languages:  eng     Pagination:  1251-7     Citation Subset:  IM    
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MeSH Terms
Antifungal Agents / pharmacology*
Aspergillus niger / drug effects*,  genetics,  growth & development,  metabolism*
Carbon Radioisotopes / metabolism
Carboxylic Acids / pharmacology*
Food Preservatives / pharmacology*
Genes, Fungal
Genetic Complementation Test
Microbial Sensitivity Tests
Saccharomyces cerevisiae / drug effects,  genetics
Sorbic Acid
Spores, Fungal / metabolism
Uridine / metabolism*
Grant Support
BB/D005388/1//Biotechnology and Biological Sciences Research Council; FQS69//Biotechnology and Biological Sciences Research Council
Reg. No./Substance:
0/Antifungal Agents; 0/Carbon Radioisotopes; 0/Carboxylic Acids; 0/Food Preservatives; WHI7HQ7H85/Uridine; X045WJ989B/Sorbic Acid

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