日偏食对乌鲁木齐空气可培养细菌群落的影响

利用自然沉降法采集2009年7月19日至24日日偏食前后乌鲁木齐空气微生物，以可培养法分析日偏食对其细菌群落组成的影响。结果如下：（1）细菌数量和种类均随日偏食临近而增多，当天达到峰值，随后减少。（2）所获81株细菌经测序及系统发育分析将其归为四个门，分别为放线菌门(Actinobacteria)、厚壁菌门(Firmicutes)、变形菌门(Proteobacteria)和拟杆菌门(Bacteroidetes)，其中放线菌门为优势类群，占细菌总数的54%。（3）不同采样时间细菌群落组成的聚类分析显示，日偏食发生前日（21日）和当日（22日）空气细菌组成较为相似聚为一类，其余日期的聚为一类。（4）典型相关分析(Canonical Correlation Analysis, CCA)发现，放线菌门中菌株与绝大多数大气环境因子呈正相关性；变形菌门和厚壁菌门与大多数大气环境因子呈正相关性；而拟杆菌门中的菌株只与温度、风速和太阳风速度呈正相关。结果表明，日偏食会增加乌鲁木齐空气可培养细菌的数量和种类。

Effect of partial solar eclipse on airborneculturable bacterial community in Urumqi

Partial solar eclipse is one kind of astronomical phenomenon. The studies of partial solar eclipse have been extensively explored, but most of them focused on geomagnetic field in low latitude, partial solar eclipse observation, Ne-spectrum assay during solar eclipse, sporadic-E, effects on ionosphere, and variation of atmosphere and so on. Biological effects induced by solar eclipse are mainly observed in some animals' behavior changes, like fish and birds, and physiological changes occurring at cotton and sea phytoplankton. While scientific understanding of partial solar eclipse is particularly weak for microbiology, and reports on this field were barely found out. Solar eclipse occurring on July 22nd 2009 lasted for six minutes and was recorded and expected as the longest one in China from 1814 AD to 2309 AD. The eclipse was formed an about 250 km width strip, and the most population was covered in Chinese territory. The partial solar eclipse observed in Xinjiang was about 68% of the total solar area. Parameters of meteorology and space weather measured by weather bureau of Xinjiang and center for space environment research and forecast (CSERF) showed that air pressure, humidity and UV index fell down to various extents, speed of solar wind rose and geomagnetic activity got stronger. In the paper, we used a culture-based method to investigate the effects of partial solar eclipse on airborne bacterial community composition; and tried to find the possible movement rule of airborne microorganisms. Air samples were collected from air of Urumqi from 19th to 24th July in 2009, before and after partial solar eclipse occurring, by gravity sampling method. Total DNA of all pure cultures were extracted and used as templates for 16S rDNA amplification by PCR with bacteria-specific rDNA primer sets. PCR products were sequenced, blasted and then constructed phylogenetic tree to define their taxonomic affiliations. Through pure culturing and phylogenetic analysis, 81 strains of bacteria were obtained from six days' cultivation and were divided into 4 phyla: Actinobacteria, Firmicutes, Proteobacteria and Bacteroidetes. Actinobacteria was the dominant group that accounted for 54% of total bacteria. Along with the advent of partial solar eclipse, both quantity and diversity of airborne microbes increased gradually, and reached the summit on the day, and then decreased in the following time. Clustering analysis, based on different sampling time and their corresponding bacterial community composition, showed that before the partial solar eclipse (July 21) and the day (July 22) were clustered together and separated from the following days' clusters, which formed a joint cluster. The correlation between air environmental factors and microbes were analyzed by Canonical Correlation Analysis (CCA), and the results indicated that the strains belonging to phyla Actinobacteria Proteobacteria and Firmicutes had the positive correlation with all or most of measured air environmental factors, but strains affiliated to phylum Bacteroidetes were positively related to only three factors (temperature, wind speed and solar wind speed). Those results suggested that the changes of air environmental factors caused by partial solar eclipse had positive effects on the quantity and type of cultivable airborne bacteria in Urumqi.