HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Melin, P. Articles by Archer, D. B. Search for Related Content PubMed PubMed Citation Articles by Melin, P. Articles by Archer, D. B. Agricola Articles by Melin, P. Articles by Archer, D. B.

Auxotrophy for uridine increases the sensitivity of Aspergillus niger to weak-acid preservatives

¹ School of Biology, University of Nottingham, University Park, Nottingham NG7 2RD, UK
² Department of Microbiology, Swedish University of Agricultural Sciences, PO Box 7025, SE-750 07 Uppsala, Sweden

Correspondence
Peter Melin
petter.melin{at}mikrob.slu.se

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 ¹⁴C-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.