Demidchik Vadim, Macpherson Neil, Davies Julia M
Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.
Yeast. 2005 Jan 15;22(1):21-9. doi: 10.1002/yea.1194.
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.
拜耳接合酵母是一种具有重要商业价值的腐败酵母，能够在低pH值且存在苯甲酸等弱有机酸防腐剂的环境中生长。对质膜钾离子转运进行的膜片钳电生理分析揭示了一条用于低亲和力钾离子摄取的高电导途径。与酿酒酵母中的等效钾离子转运体不同，该系统在低细胞外pH值下仍可运行，因此可能有助于在富含钾离子的酸性饮料中摄取钾离子。苯甲酸盐抑制生长，增加细胞内钾离子含量，但降低钾离子摄取电导的幅度；具体而言，超极化激活的内向整流成分减少。有人提出，这种适应性有助于维持超极化的膜电压，以实现由ATP酶介导的持续氢离子外排，从而对抗防腐剂诱导的胞质酸中毒。同样与酿酒酵母不同的是，钾离子电导对细胞外钙离子增加相对不敏感。矛盾的是（与酿酒酵母不同），细胞外钙离子增加会抑制生长，这表明这是一种限制拜耳接合酵母腐败的简单方法。
