Research on long distance movement of bacteria by Asian dust

“亚洲沙尘”是大量源自中国和蒙古干旱地区的土壤颗粒，如塔克拉玛干沙漠、戈壁沙漠和黄土高原，这些颗粒被盛行的西风输送到东亚（中国、韩国和日本）。在日本，估计每年有100多万吨尘埃颗粒落在地面上（日本国家环境研究所报告）。我们认为这些土壤颗粒可能是微生物的载体。为了阐明这些尘埃事件中微生物的动态，通过非培养方法检测附着在尘埃颗粒上的细菌细胞。(1)通过扫描电子显微镜（SEM）图像分析测量粒度分布。在北京和大坂采集的灰尘样品直径分别小于10μm和5μm，它们被认为是微生物的载体。(2)通过配备有能量分散X射线分析仪（SEM-EDX）的SEM检查颗粒特性。在北京和大坂收集的灰尘样品中含有许多具有独特土壤特征的小颗粒。(3)利用核糖体RNA靶向技术和扫描电子显微镜（SEM-ISH）技术，在颗粒上观察细菌细胞。(4)通过SEM-ISH分析，直接观察到了北京亚洲沙尘颗粒物上的细菌细胞。这表明细菌可以与“亚洲尘埃”一起“旅行”。(5)通过真实的时间PCR测定随亚洲灰尘移动的微生物的量。春季亚洲沙尘颗粒物上细菌细胞的数量为10^<13>^ cells<16>/month/km^2。(6)研制了一种新型粉尘采样器，并利用小型飞机采集了日本海拔1000 ~ 2000 m的粉尘颗粒，避免了地面土壤颗粒的污染。

"Asian Dust" is the transportation of a large amount of soil particles originated from arid regions in China and Mongolia such as Taklamakan desert, Gobi desert and Loess plateau, and these particles are transported to East Asia (China, Korea and Japan) by the prevailing westerly winds. In Japan, more than one million tons of dust particles are estimated to fall on ground per year (reported by the National Institute for Environmental Studies, Japan). We supposed that these soil particles could be carriers of microbes. In order to clarify the dynamics of microbes moving with these dust events, bacterial cells attached to dust particles were detected by culture-independent approaches.(1) Particle size distribution was measured by scanning electron microsrepic (SEM) image analysis. Dust samples collected in Beijing and Osaka were below 10μm and 5μm in diameter, respectively, and they are thought to be carriers of microbes.(2) Particle characteristics were examined by SEM equipped with an energy-dispersive X-ray analyzer (SEM-EDX). The dust samples collected in Beijing and Osaka contained many small particles with distinctive soil characteristics.(3) New technique to visualize the bacterial cells on particles by ribosomal RNA-targeted approach and scanning electron microscopy (SEM-ISH) was developed.(4) By SEM-ISH analysis, bacterial cells attached on Asian Dust particles collected in Beijing were directly visualized. This indicated that bacteria can "travel" with "Asian Dust".(5) Amount of microbes moving with Asian dust was determined by real time PCR. The voltune of bacterial cells on Asian dust particles to Beijing estimated as 10^<13>～^<16> cells/month/km^2 in spring season.(6) Newly fabricated dust sampler was developed and the dust particles at the altitude of 1000 to 2000m in Japan were collected by a small airplane to avoid contamination of soil particles from ground.