Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, SI-1000 Ljubljana, Slovenia.
Fungal Biol. 2011 Oct;115(10):950-8. doi: 10.1016/j.funbio.2011.04.006. Epub 2011 May 7.
Our aim was to investigate the response of selected yeasts and yeast-like fungi from extreme environments to various temperatures at the level of their plasma membranes, in order to elucidate the connections between their plasma-membrane fluidity (measured by electron paramagnetic resonance spectroscopy - EPR), growth temperature range, stress tolerance, and ecological distribution. Although all studied fungi can be considered mesophilic according to their growth temperature profiles, their plasma-membrane fluidity indicated otherwise. Arctic yeast Rhodosporidium diobovatum could be classified as psychrotolerant due to its higher average membrane fluidity. Extremely halotolerant black yeast-like fungus Hortaea werneckii isolated from solar salterns, on the other hand, is not adapted to low temperature, which is reflected in the higher average rigidity of its plasma membrane and as a consequence its inability to grow at temperatures lower than 10°C. The plasma membrane of Aureobasidium sp. isolated so far exclusively from an Arctic glacier with its intermediate fluidity and high fluidity variation at different temperatures may indicate the specialization of this yeast-like fungus to the specific glacial environment. Similar behaviour of plasma membrane was detected in the reference yeast, non-extremophilic Saccharomyces cerevisiae. Its membranes of intermediate fluidity and with high fluidity fluctuation at different temperatures may reflect the specialization of this yeast to mesophilic environments and prevent its colonization of extreme environments. Halotolerant Aureobasidium pullulans from salterns, and Arctic Cryptococcus liquefaciens and Rhodotorula mucilaginosa with moderately fluctuating plasma membranes of intermediate fluidity are representatives of globally distributed generalistic and stress-tolerant species that can thrive in a variety of environments. Keeping the membranes stable and flexible is one of the necessities for the microorganisms to survive changes in extreme habitats. Our data suggest that plasma-membrane fluidity can be used as an indicator of fitness for survival in the extreme environments. In addition to the average fluidity of plasma membrane, the fluctuation of fluidity is an important determinant of stress tolerance: high absolute fluidity fluctuation is tied to decreased survival. The fluidity and its variation therefore reflect survival strategy and fitness in extreme environments and are good indicators of the adaptability of microorganisms.
我们的目的是研究来自极端环境的选定酵母和酵母样真菌对各种温度的反应，在其质膜水平上，以阐明它们的质膜流动性（通过电子顺磁共振波谱法 - EPR 测量）、生长温度范围、应激耐受性和生态分布之间的联系。尽管根据其生长温度曲线，所有研究的真菌都可以被认为是嗜温的，但它们的质膜流动性表明并非如此。极地酵母 Rhodosporidium diobovatum 由于其较高的平均膜流动性，可以被归类为耐冷菌。另一方面，从太阳盐场分离出来的极端耐盐黑酵母样真菌 Hortaea werneckii 并不适应低温，这反映在其质膜的平均刚性较高，因此无法在低于 10°C 的温度下生长。迄今为止仅从北极冰川中分离出来的 Aureobasidium sp. 的质膜具有中等流动性和不同温度下高流动性变化，这可能表明该酵母样真菌对特定冰川环境的专业化。在参考酵母非极端嗜热的酿酒酵母中也检测到了类似的质膜行为。其具有中等流动性和不同温度下高流动性波动的膜可能反映了该酵母对中温环境的专业化，并防止其在极端环境中定殖。来自盐场的耐盐 Aureobasidium pullulans 以及极地 Cryptococcus liquefaciens 和 Rhodotorula mucilaginosa，它们的质膜具有中等流动性和中等波动，是全球分布的普遍存在和应激耐受物种的代表，它们可以在多种环境中茁壮成长。保持膜的稳定和灵活是微生物在极端生境中生存变化的必要条件之一。我们的数据表明，质膜流动性可以作为在极端环境中生存适应性的指标。除了质膜的平均流动性外，流动性的波动也是应激耐受性的重要决定因素：高绝对流动性波动与存活率降低有关。因此，流动性及其变化反映了在极端环境中的生存策略和适应性，是微生物适应性的良好指标。
