Thomé-Ortiz P E, Peña A, Ramírez J
Estación Puerto Morelos, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Cancún, Q. R., México.
Yeast. 1998 Nov;14(15):1355-71.
Debaryomyces hansenii showed an increased growth in the presence of either 1 M, KCl or 1 M NaCl and a low acidification of the medium, higher for the cells grown in the presence of NaCl. These cells accumulated high concentrations of the cations, and showed a very fast capacity to exchange either Na+ or K+ for the opposite cation. They showed a rapid uptake of 86Rb+ and 22Na+. 86Rb+ transport was saturable, with K(m) and Vmax values higher for cells grown in 1 M NaCl. 22Na+ uptake showed a diffusion component, also higher for the cells grown with NaCl. Changes depended on growth conditions, and not on further incubation, which changed the internal ion concentration. K+ stimulated proton pumping produced a rapid extrusion of protons, and also a decrease of the membrane potential. Cells grown in 1 M KCl showed a higher fermentation rate, but significantly lower respiratory capacity. ATP levels were higher in cells grown in the presence of NaCl; upon incubation with glucose, those grown in the presence of KCl reached values similar to the ones grown in the presence of NaCl. In both, the addition of KCl produced a transient decrease of the ATP levels. As to ion transport mechanisms, D. hansenii appears to have (a) an ATPase functioning as a proton pump, generating a membrane potential difference which drives K+ through a uniporter; (b) a K+/H+ exchange system; and (c) a rapid cation/cation exchange system. Most interesting is that cells grown in different ionic environments change their studied capacities, which are not dependent on the cation content, but on differences in their genetic expression during growth.
汉逊德巴利酵母在1M KCl或1M NaCl存在的情况下生长增加，培养基酸化程度较低，在NaCl存在下生长的细胞酸化程度更高。这些细胞积累了高浓度的阳离子，并表现出非常快速地将Na⁺或K⁺与相反阳离子进行交换的能力。它们表现出对⁸⁶Rb⁺和²²Na⁺的快速摄取。⁸⁶Rb⁺转运是可饱和的，在1M NaCl中生长的细胞其K(m)和Vmax值更高。²²Na⁺摄取显示出扩散成分，在NaCl中生长的细胞中该成分也更高。变化取决于生长条件，而不取决于进一步的孵育，进一步孵育会改变内部离子浓度。K⁺刺激质子泵产生质子的快速排出，同时膜电位也降低。在1M KCl中生长的细胞显示出更高的发酵速率，但呼吸能力明显较低。在NaCl存在下生长的细胞中ATP水平更高；与葡萄糖孵育后，在KCl存在下生长的细胞达到与在NaCl存在下生长的细胞相似的值。在这两种情况下，添加KCl都会使ATP水平暂时降低。至于离子转运机制，汉逊德巴利酵母似乎具有：(a) 一种作为质子泵起作用的ATP酶，产生膜电位差，通过单向转运体驱动K⁺；(b) 一种K⁺/H⁺交换系统；以及(c) 一种快速的阳离子/阳离子交换系统。最有趣的是，在不同离子环境中生长的细胞会改变其研究的能力，这些能力不取决于阳离子含量，而是取决于生长过程中基因表达的差异。
