厦门冬季PM_(2.5)颗粒物中细菌和真核微型生物群落组成及其来源分析

Community composition and environmental sources of bacteria and eukaryotic microorganisms in fine air particulate (PM_(2.5)) of Xiamen in winter

近年来由于雾霾事件频发,有关细颗粒物PM2.5的来源、组成及迁移转化规律已经引起了人们的广泛关注,然而对于PM2.5颗粒物中微生物的组成和来源还知之甚少。本文应用T–RFLP、克隆文库和测序方法研究厦门2012年冬季PM2.5颗粒物中细菌和真核微型生物的群落组成,并分析其潜在的来源环境。研究结果表明:与克隆文库方法相比,T–RFLP分析所得的物种数量(TRF峰)相对较多,说明T–RFLP是快速、灵敏分析空气微生物群落特征的高效手段之一。T–RFLP和克隆文库结果表明,PM2.5颗粒物中细菌和真核微型生物群落多样性较高,其中2%的细菌16S rRNA基因和42%的真核微型生物18S rRNA基因序列与已知序列的相似度低于97%。分类分析表明,Bacteroidetes、Actinobacteria、Firmicutes和Proteobacteria是PM2.5颗粒物细菌的主要类群,其相对丰度分别为2.91%、10.68%、41.75%和44.66%;Stramenopiles、Alveolata、Metazoa、Fungi和Viridiplantae是PM2.5颗粒物真核微型生物的主要类群,其相对丰度分别为5%、7%、15%、20%和39%。然而,尚有14%的真核微型生物18S rRNA基因序列未能分类到已知门类,说明气溶胶真核微型生物方面的研究尚存在较大空白。与文献对比分析表明,厦门城区空气微生物的动态性较强,环境来源多变。环境来源分析表明,厦门虽然属于典型海滨城市,但其空气微生物的重要环境源可能为淡水,其次是土壤、水体沉积物、污水系统和动物粪便等。而季节性气团输送可能是厦门冬季气溶胶微生物多来源于淡水的原因之一。

Due to recent frequent occurrence of fog and haze, the sources, components, migration and transformation of fine air particulate （PM25） have received increasing attention. However, little is known about microbial community associated with PM2.5. Here, we analyzed community composition and environmental sources of bacteria and eukaryotic microorganisms in PM2.5 using T-RFLP and clone library sequencing. Our results indicated that species richness of PM2.5 microbial communities assessed based on T-RFLP （i.e. TRF） were higher than those of clone libraries, implying that T-RFLP provide a sensitive and rapid approach to monitor airborne microbial community. Moreover, both of T-RFLP and clone library sequencing revealed highly diverse PM2.5 bacterial and eukaryotic microbial communities. BLAST analysis indicated that 2% of bacterial 16S rRNA gene and nearly half （42%） of eukaryotic 18S rRNA gene sequences from PM2.5 are distantly related to known sequences （〈97% similarity）. The results of RDP Classifier analysis indicated that PM25 bacterial community was mainly composed ofBacteroidetes, Actinobacteria, Firmicutes and Proteobacteria, accounting for 2.91%, 10.68%, 41.75% and 44.66% respectively, while PM2.5 eukaryotic microbial community were numerically dominated by Strarnenopiles, Alveolata, Metazoa, Viridiplantae and Fungi, accounting for 5%, 7%, 15%, 15% and 20% respectively. However, 39% of eukaryotic 18S rRNA gene sequences could not be assigned into any known eukaryotic phyla, suggesting that further studies are needed to shed light on eukaryotic airborne community. Taken together with the findings of a previous winter study investigating airborne microbial community in Xiamen, these results indicated that the airborne microbial community in Xiamen displays high temporal variation, and also airborne microbes may originate from various environments. Although Xiamen is a typical coastal city in China, freshwater, soils, sediments, wastewater and animal feces might be important sources of microorganisms to the atmosphere of Xiamen. Seasonal air mass transport may be an important reason that freshwater are an important source of airborne microbes of Xiamen.