College of Resources and Environment, University of Chinese Academy of Science, Beijing 100049, China.
State Key of Laboratory of Atmospheric Boundary Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.
Sci Rep. 2017 Jan 3;7:39673. doi: 10.1038/srep39673.
It has been known for several decades that some bioaerosols, such as ice-nucleation-active (INA) bacteria, especially Pseudomonas syringae strains, may play a critical potential role in the formation of clouds and precipitation. We investigated bacterial and fungal ice nuclei (IN) in rainwater samples collected from the Hulunber temperate grasslands in North China. The median freezing temperatures (T) for three years' worth of unprocessed rain samples were greater than -10 °C based on immersion freezing testing. The heat and filtration treatments inactivated 7-54% and 2-89%, respectively, of the IN activity at temperatures warmer than -10 °C. We also determined the composition of the microbial community. The majority of observed Pseudomonas strains were distantly related to the verified ice-nucleating Pseudomonas strains, as revealed by phylogenetic analysis. Here, we show that there are submicron INA particles <220 nm in rainwater that are not identifiable as the known species of high-INA bacteria and fungi and there may be a new potential type of efficient submicroscale or nanoscale ice nucleator in the regional rainwater samplers. Our results suggest the need for a reinterpretation of the source of high-INA material in the formation of precipitation and contribute to the search for new methods of weather modification.
几十年来，人们已经知道一些生物气溶胶，如冰核活性（INA）细菌，特别是丁香假单胞菌菌株，可能在云的形成和降水方面发挥关键的潜在作用。我们调查了从中国北方呼伦贝尔温带草原采集的雨水样本中的细菌和真菌冰核（IN）。根据浸没式冷冻测试，三年的未处理雨水样本的中位冻结温度（T）大于-10°C。在温度高于-10°C 的情况下，热和过滤处理分别使 IN 活性失活了 7-54%和 2-89%。我们还确定了微生物群落的组成。通过系统发育分析，观察到的大多数假单胞菌菌株与已验证的冰核假单胞菌菌株亲缘关系较远。在这里，我们表明，雨水中存在小于 220nm 的亚微米 INA 颗粒，无法识别为高 INA 细菌和真菌的已知种，并且在区域雨水采样器中可能存在新的潜在高效亚微米或纳米尺度的冰核。我们的结果表明需要重新解释降水形成中高 INA 物质的来源，并有助于寻找新的天气修正方法。
