Vimercati L, Hamsher S, Schubert Z, Schmidt S K
Department of Ecology and Evolutionary Biology, University of Colorado, Campus Box 334, Boulder, CO, 80309, USA.
Extremophiles. 2016 Sep;20(5):579-88. doi: 10.1007/s00792-016-0844-8. Epub 2016 Jun 17.
Soils above 6000 m.a.s.l. are among the most extreme environments on Earth, especially on high, dry volcanoes where soil temperatures cycle between -10 and 30 °C on a typical summer day. Previous studies have shown that such sites are dominated by yeast in the cryophilic Cryptococcus group, but it is unclear if they can actually grow (or are just surviving) under extreme freeze-thaw conditions. We carried out a series of experiments to determine if Cryptococcus could grow during freeze-thaw cycles similar to those measured under field conditions. We found that Cryptococcus phylotypes increased in relative abundance in soils subjected to 48 days of freeze-thaw cycles, becoming the dominant organisms in the soil. In addition, pure cultures of Cryptococcus isolated from these same soils were able to grow in liquid cultures subjected to daily freeze-thaw cycles, despite the fact that the culture medium froze solid every night. Furthermore, we showed that this organism is metabolically versatile and phylogenetically almost identical to strains from Antarctic Dry Valley soils. Taken together these results indicate that this organism has unique metabolic and temperature adaptations that make it able to thrive in one of the harshest and climatically volatile places on Earth.
海拔6000米以上的土壤是地球上最极端的环境之一，尤其是在高海拔、干燥的火山上，在典型的夏日里，土壤温度在-10至30摄氏度之间循环。先前的研究表明，此类地点以嗜冷隐球菌属的酵母为主，但尚不清楚它们在极端冻融条件下是否真的能够生长（或只是存活）。我们进行了一系列实验，以确定隐球菌在类似于野外条件下测得的冻融循环过程中是否能够生长。我们发现，经历48天冻融循环的土壤中，隐球菌的系统发育型相对丰度增加，成为土壤中的优势生物。此外，从这些相同土壤中分离出的隐球菌纯培养物能够在每天经历冻融循环的液体培养物中生长，尽管培养基每晚都会完全冻结。此外，我们表明这种生物具有多种代谢能力，并且在系统发育上几乎与南极干谷土壤中的菌株相同。综合这些结果表明，这种生物具有独特的代谢和温度适应性，使其能够在地球上最恶劣、气候最不稳定的地方之一茁壮成长。
