Microorganisms are ubiquitous in the atmosphere with hundreds of taxa being identified in air samples collected around the world. Despite their importance on human and ecosystem health, the majority of air microbiological studies have been limited to cultivation-based methods that may not capture all of the microbial diversity in the air. The present study used pyrosequencing analysis of 16S rDNA fragments, in order to examine the short-term variability of microbial assemblage composition in near-surface atmosphere of two coastal cities of Crete island, eastern Mediterranean Sea. A diverse range of 16S rRNA genes was identified at both cities consisting of 17,720 different operation taxonomic units, 23 bacterial and 3 archaeal phyla, 93 orders and 204 families. A core microbiome containing members of Proteobacteria, Actinobacteria and Firmicutes was evidenced at both study sites, regardless the origin of transported air masses. Nevertheless, the local biodiversity profiles presented extensive differences at lower taxonomic level (i.e., species). A total of 7699 sequences were closely related to 101 strains that are commonly found in many different habitats, including agricultural soil, water, air, marine water and sediment, as well as human microbiome. Several of these strains were closely related to pathogens or putative pathogens, which can trigger infections, such as bacteremia and endocarditis to humans and blackleg disease in plants. The identified large differences in local biodiversity together with the presence of many pathogenic relatives demonstrate the significance of spatial variability in atmospheric biogeography and the importance to include airborne microbes in air quality studies.

中文翻译：

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希腊克里特岛近地表大气微生物群落的高遗传多样性和变异性

微生物在大气中无处不在，在世界各地收集的空气样本中发现了数百种分类群。尽管它们对人类和生态系统健康很重要，但大多数空气微生物研究仅限于基于培养的方法，这些方法可能无法捕获空气中的所有微生物多样性。本研究使用 16S rDNA 片段的焦磷酸测序分析，以检查地中海东部克里特岛两个沿海城市近地表大气中微生物群落组成的短期变异性。在这两个城市都鉴定了多种 16S rRNA 基因，包括 17,720 个不同的操作分类单元、23 个细菌门和 3 个古细菌门、93 个目和 204 个科。包含变形杆菌成员的核心微生物组，无论运输气团的来源如何，两个研究地点都证实了放线菌和厚壁菌门。然而，当地生物多样性概况在较低的分类水平（即物种）上呈现出广泛的差异。共有 7699 个序列与 101 个菌株密切相关，这些菌株常见于许多不同的栖息地，包括农业土壤、水、空气、海水和沉积物，以及人类微生物组。其中一些菌株与病原体或推定的病原体密切相关，可引发感染，例如人类的菌血症和心内膜炎以及植物的黑腿病。