School of Biology, Georgia Institute of Technology, Atlanta, GA 30332, USA.
Proc Natl Acad Sci U S A. 2013 Feb 12;110(7):2575-80. doi: 10.1073/pnas.1212089110. Epub 2013 Jan 28.
The composition and prevalence of microorganisms in the middle-to-upper troposphere (8-15 km altitude) and their role in aerosol-cloud-precipitation interactions represent important, unresolved questions for biological and atmospheric science. In particular, airborne microorganisms above the oceans remain essentially uncharacterized, as most work to date is restricted to samples taken near the Earth's surface. Here we report on the microbiome of low- and high-altitude air masses sampled onboard the National Aeronautics and Space Administration DC-8 platform during the 2010 Genesis and Rapid Intensification Processes campaign in the Caribbean Sea. The samples were collected in cloudy and cloud-free air masses before, during, and after two major tropical hurricanes, Earl and Karl. Quantitative PCR and microscopy revealed that viable bacterial cells represented on average around 20% of the total particles in the 0.25- to 1-μm diameter range and were at least an order of magnitude more abundant than fungal cells, suggesting that bacteria represent an important and underestimated fraction of micrometer-sized atmospheric aerosols. The samples from the two hurricanes were characterized by significantly different bacterial communities, revealing that hurricanes aerosolize a large amount of new cells. Nonetheless, 17 bacterial taxa, including taxa that are known to use C1-C4 carbon compounds present in the atmosphere, were found in all samples, indicating that these organisms possess traits that allow survival in the troposphere. The findings presented here suggest that the microbiome is a dynamic and underappreciated aspect of the upper troposphere with potentially important impacts on the hydrological cycle, clouds, and climate.
中层到高层大气（8-15 公里海拔）中微生物的组成和流行情况及其在气溶胶-云-降水相互作用中的作用，是生物学和大气科学中重要但尚未解决的问题。特别是，海洋上空的空气传播微生物基本上还没有被描述，因为迄今为止的大多数工作都仅限于在地球表面附近采集的样本。在这里，我们报告了在 2010 年加勒比海 Genesis 和 Rapid Intensification Processes 期间，美国国家航空航天局（NASA）DC-8 平台在低海拔和高海拔气团中采集的微生物组样本。这些样本是在两次主要热带飓风 Earl 和 Karl 之前、期间和之后，从云中和无云的气团中采集的。定量 PCR 和显微镜显示，在 0.25-1μm 直径范围内的总颗粒中，存活的细菌细胞平均约占 20%，并且比真菌细胞至少丰富一个数量级，这表明细菌是微米级大气气溶胶中一个重要且被低估的部分。来自两次飓风的样本具有明显不同的细菌群落，表明飓风使大量新细胞气溶胶化。尽管如此，在所有样本中都发现了 17 个细菌分类群，包括已知使用大气中存在的 C1-C4 碳化合物的分类群，这表明这些生物体具有在对流层中生存的特征。这里提出的发现表明，微生物组是高层大气中一个动态且被低估的方面，对水循环、云和气侯可能具有重要影响。
