Research on long distance movement of bacteria by Asian dust

“亚洲沙尘”是由塔克拉玛干沙漠、戈壁沙漠和黄土高原等中国和蒙古的干旱地区产生的大量土壤颗粒被盛行的西风输送到东亚（中国、韩国和日本）而形成的。在日本，据估计每年有超过一百万吨的尘埃颗粒落在地面上（日本国立环境研究所报告）。我们猜想这些土壤颗粒可能是微生物的载体。为了阐明微生物在这些尘埃事件中移动的动力学，通过不依赖培养的方法检测附着在尘埃颗粒上的细菌细胞。(1)采用扫描电镜（SEM）图像分析方法测定颗粒粒径分布。在北京和大阪采集的灰尘直径分别小于10μm和5μm，被认为是微生物的载体。(2)采用能量色散x射线分析仪（SEM- edx）对颗粒进行扫描电镜表征。在北京和大阪采集的尘埃样本含有许多具有独特土壤特征的小颗粒。(3)建立了利用核糖体rna靶向法和扫描电镜（SEM-ISH）观察细菌颗粒上细胞的新技术。(4)通过SEM-ISH分析，直接观察了北京地区亚洲尘埃颗粒上附着的细菌细胞。这表明细菌可以随着“亚洲尘埃”“旅行”。(5) real - time PCR法测定随亚洲粉尘移动的微生物数量。据估计，春季到北京的亚洲尘埃颗粒上的细菌细胞量为10^<13>~^<16>细胞/月/km^2。(6)研制新制粉尘采样器，利用小型飞机采集日本1000 ~ 2000m高度的粉尘颗粒，避免地面土壤颗粒污染。

"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.