1 Department of Natural Resource Sciences, McGill University, Montreal, Canada.
2 Bigelow Laboratory for Ocean Sciences, East Boothbay Harbor, Maine.
Astrobiology. 2019 Jun;19(6):757-770. doi: 10.1089/ast.2018.1884. Epub 2019 Apr 8.
Water tracks in the Antarctic Dry Valleys are dark linear features of increased soil moisture that flow downslope over the spring and summer, providing a source of moisture in a cold-arid desert. They are typically sourced from melting snow, ground ice, and deliquescence (Levy , 2011 ). This research presents the first in-depth study of the activity potential and diversity of microbial communities of Antarctic water tracks. We investigated whether these water track soils are more habitable to microbial communities by ascertaining the differences in diversity, total and culturable cell counts, and microbial respiratory activity in water track soils compared with the adjacent dry soils in Pearse Valley. Total cell counts ranged from 1.47 × 10 to 4.17 × 10 cells/g dry weight soil. Water track soils had higher total and culturable biomass, in addition to higher microbial activity at 5° and -5°C, compared with adjacent dry soils. Microbial respiration was positively correlated with soil moisture content, but total cell counts and plate counts were not. Surprisingly, microbial community composition did not differ between wet and dry soil communities, and was not related to soil moisture content. The microbial community composition instead appeared to differ spatially based on location and depth. Overall, the data suggest that cold water tracks are more habitable than the surrounding cold-arid soils. Our results suggest that recurring slope lineae, which are dark linear features that grow downslope on Mars over the spring and summer, where liquid water might be a recurring phenomenon, could be sites of astrobiological potential.
南极干旱谷中的水道是土壤湿度增加的暗线特征，它们在春季和夏季沿坡下流，为寒冷干旱的沙漠提供了水分来源。它们通常来源于融雪、地冰和潮解（Levy，2011）。本研究首次深入研究了南极水道中微生物群落的活动潜力和多样性。我们通过确定与 Pearse 谷中相邻干燥土壤相比，水道土壤中微生物多样性、总细胞计数和可培养细胞计数以及微生物呼吸活性的差异，来研究这些水道土壤是否对微生物群落更具可居住性。总细胞计数范围为 1.47×10 到 4.17×10 个细胞/g 干重土壤。与相邻干燥土壤相比，水道土壤具有更高的总生物量和可培养生物量，以及在 5°C 和-5°C 时更高的微生物活性。微生物呼吸与土壤水分含量呈正相关，但总细胞计数和平板计数则不然。令人惊讶的是，湿土和干土的微生物群落组成没有差异，也与土壤水分含量无关。微生物群落组成似乎是根据位置和深度而在空间上存在差异。总的来说，数据表明寒冷的水道比周围寒冷干旱的土壤更适合居住。我们的研究结果表明，在火星上，随着春季和夏季的推移，反复出现的坡面线纹，即向下坡生长的暗线特征，液态水可能是一种反复出现的现象，这些特征可能是天体生物学潜力的所在地。
