Potassium transport at the plasma membrane of the food spoilage yeast Zygosaccharomyces bailii.
Zygosaccharomyces bailii is a commercially important spoilage yeast capable of growth at low pH in the presence of weak organic acid preservatives, such as benzoic acid. A patch-clamp electrophysiological analysis of plasma membrane K+ transport revealed a high conductance pathway for low-affinity K+ uptake. In contrast to the equivalent K+ transporter in Saccharomyces cerevisiae, this system remained operative at low extracellular pH and may therefore facilitate K+ uptake in K(+)-rich and acidic beverages. Benzoate inhibited growth, increased intracellular K+ content, yet decreased the magnitude of the K+ uptake conductance; specifically, the hyperpolarization-activated inwardly-rectifying component was reduced. It is proposed that this adaptation helps maintain a hyperpolarized membrane voltage to effect continued ATPase-mediated H+ extrusion and so combat preservative-induced cytosolic acidosis. Again in contrast to S. cerevisiae, the K+ conductance was relatively insensitive to increased extracellular Ca2+. Paradoxically (and unlike S. cerevisiae) increasing extracellular Ca2+ inhibited growth, suggesting a simple expedient to limit spoilage by Z. bailii.
Demidchik
Vadim
V
Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.
Macpherson
Neil
N
Davies
Julia M
JM
D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D005516:Food Microbiology; D017136:Ion Transport; D018021:Lithium Chloride / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D013104:Spheroplasts / Q000502:physiology; D020068:Zygosaccharomyces / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*
D018021:Lithium Chloride; D011188:Potassium; D002118:Calcium