Study On The Community Composition And Distribution Characteristics Of Microorganisms In The Air Of Xiamen City

The sources, composition, migration and transformation of the microorganisms in TSP,PM₁₀and PM_2.5have drawn people’s extensive attention due to the frequently occurrence of fogand haze in recent years. More research focuses on the physicochemical characteristics of TSP,PM₁₀and PM_2.5, whereas the community composition and resources of microorganisms in TSP,PM₁₀and PM_2.5have been few investigated. Hence the community composition, sources anddistribution characteristics of the microorganisms in TSP, PM₁₀and PM_2.5in Xiamen are thefocus in this research.PM_2.5samples were collected in Xiamen in January2012, the community composition andpossible sources of both bacteria and eukaryotic microorganisms were analysed by T-RFLP,clone library and sequencing. The results reveal that higher diversities of bacterial and eukaryoticmicrobial communities in the PM_2.5samples obtained from Ruijing district, Xiamen. BLASTanalysis indicates that nearly half （42%） of the18S rRNA gene sequences of the eukaryoticmicroorganisms in PM_2.5showing a low similarity （<97%） with the known sequences.Taxonomic identification results implies that bacterial community in the PM_2.5samples is mainlyconstituted by Bacteroidetes, Actinobacteria, Firmicutes and Proteobacteria, while Stramenopiles,Alveolata, Metazoa, Viridiplantae and Fungiconstituted are the main part of eukaryotic microbialcommunity in the P M2.5.Sources analysis showes that bacteria in the PM_2.5samples are derived fromfreshwater（31.07%）, sediments（25.24%）, wastewater（21.36%）, animal（9.71%）, soil（5.83%） andseawater（0.97%）, while eukaryotic microorganisms in the PM_2.5samples are derived fromfreshwater（58.74%）, sediments（10.31%）, soil（10.31%）, plant（7.22%）, wastewater（6.19%） andseawater（5.15%）. Although Xiamen is a typical coastal city, freshwater, soils, sediments,wastewater and animal feces might be the main sources of microorganisms in the atmosphere ofXiamen instead of seawater.The communities’ composition of bacteria and eukaryotic microorganisms in the TSP, PM₁₀and PM_2.5samples collected in summer, autumn and winter in Xiamen were also analyzed byT-RFLP. The results show that more types of microorganisms exist in the TSP samples than inthe PM_2.5and PM₁₀samples. The most PM₁₀samples have more types of microorganisms than the PM_2.5samples. This demonstrates that the larger diameter of the particles, the more types ofmicroorganisms it involves. The abundant microorganisms in the PM_2.5and PM₁₀samples aresimilar but different from the abundant microorganisms in the TSP samples. The TSP samplescollected in the summer contain more types of microorganisms than the PM₁₀and the PM_2.5samples. Ultraviolet in sunlight can sterilize strongly, especially to the microorganisms in PM₁₀and PM_2.5. Smaller size the PM is, the longer time floating in the air and stronger sterilized byUV.By the diversity analysis, more bacterial and eukaryotic microbial communities areobserved in summer than in other seasons. Based on the analysis of microbial communitydiversity, the Simpson index is close to1. Although nutrients, water and other living necessitiesare limited, many bacteria live in the air. And there are no dominant microorganisms living in theair.The results of Mica analysis indicate that bacterial community consists of31phylua and67classes; they are mainly composed of Proteobacteria and Firmicutes with the content of39.46%and6.19%repectively. The five classes Proteobacteria phylum are Gammaproteobacteria,Alphaproteobacteria, Betaproteobacteria, Deltaproteobacteria and Epsilonproteobacteria with thecontribution of43.05%,26.60%,17.44%,10.15%,2.42%, respectively. And0.33%of bacteriaare unclassified, it reveals that some kinds of Proteobacteria maybe not indentified yet.