[Community Characteristics of Cultivable Bacteria in Fine Particles(PM_2.5) of Beijing and Baoding]

Fine particles(PM_2.5) collected by two middle volume air samplers in the suburbs of Baoding and the urban area of Beijing during Jan 10^th to 17^th, 2015, were used to compare the community characteristics of cultivable bacteria in the two sites. In this study, we observed the particle morphology of PM_2.5 using a field emission scanning electron microscope (FESEM), analyzed the air mass transportation source of the two sampling sites by the NOAA/ARL HYSPLIT-4 backward trajectory model, and measured the concentrations of the major water-soluble ions and heavy metal elements in the PM_2.5 samples using ion chromatography, continuous flow analyzer and ICP-MS. The results indicated that, the cultivable bacteria of PM_2.5 contained three phyla, which were Firmicutes, Actinobacteria and α-Proteobacteria. Nine genera and 17 species of cultivable airborne bacteria were isolated and identified. The most abundant phylum was Firmicutes. The Gram-positive bacteria accounted for more than 90%. The spore-forming Bacillus which was the dominant species contributed 68.15% and 75% to the total bacteria in urban Beijing and the suburbs of Baoding, respectively. The difference in the community structure of PM_2.5's cultivable bacteria in the two sampling areas may be affected by PM_2.5's physical and chemical properties and air mass transportation.