TitleAmmonium toxicity and potassium limitation in yeast.
Publication TypeJournal Article
Year of Publication2006
AuthorsHess, DC, Lu, W, Rabinowitz, JD, Botstein, D
JournalPLoS Biol
Date Published2006 Oct
KeywordsAmino Acids, Ammonia, Antiporters, Cation Transport Proteins, Gene Expression Regulation, Fungal, Inactivation, Metabolic, Oligonucleotide Array Sequence Analysis, Potassium, Saccharomyces cerevisiae, Yeasts

DNA microarray analysis of gene expression in steady-state chemostat cultures limited for potassium revealed a surprising connection between potassium and ammonium: potassium limits growth only when ammonium is the nitrogen source. Under potassium limitation, ammonium appears to be toxic for Saccharomyces cerevisiae. This ammonium toxicity, which appears to occur by leakage of ammonium through potassium channels, is recapitulated under high-potassium conditions by over-expression of ammonium transporters. Although ammonium toxicity is well established in metazoans, it has never been reported for yeast. To characterize the response to ammonium toxicity, we examined the filtrates of these cultures for compounds whose excretion might serve to detoxify the ammonium (such as urea in mammals). Using liquid chromatography-tandem mass spectrometry to assay for a wide array of metabolites, we detected excreted amino acids. The amounts of amino acids excreted increased in relation to the severity of growth impairment by ammonium, suggesting that amino acid excretion is used by yeast for ammonium detoxification.

Alternate JournalPLoS Biol.