Airborne bacteria are widespread as a major proportion of bioaerosols, and their coexistence with dust particles enables both bacteria and dust particles to be more active in ice cloud formation and to be harmful to public health. However, the abundance and viability of particle-attached and free-floating bacteria in dusty air have not been quantitatively investigated. We researched this subject based on the fact that airborne bacterial cells are approximately 1 µm or smaller in aerodynamic diameter; therefore, particle-attached bacteria should occur in aerosol samples of particles larger than 1 µm, and free-floating bacteria should occur among particles smaller than 1 µm. Our observations at a coastal site in Japan in spring, when the westerlies frequently transported dust from the Asian continent, revealed that particle-attached bacteria in dust episodes, at the concentration of $\mathrm{3.2}\pm \mathrm{2.1}\times {\mathrm{10}}^{\mathrm{5}}$ cells m⁻³ on average, occupied 72±9 % of the total bacteria. In contrast, the fraction was 56±17 % during nondusty periods, and the concentration was $\mathrm{1.1}\pm \mathrm{0.7}\times {\mathrm{10}}^{\mathrm{5}}$ cells m⁻³. The viability, defined as the ratio of viable cells to total cells, of particle-attached bacteria was 69±19 % in dust episodes and 60±22 % during nondusty periods on average, both of which were considerably lower than the viabilities of free-floating bacteria (about 87 %) under either dusty or nondusty conditions. The presented cases suggest that dust particles carried substantial amounts of bacteria on their surfaces, more than half of which were viable, and spread these bacteria through the atmosphere. This implies that dust and bacteria have important roles as internally mixed assemblages in cloud formation and in linking geographically isolated microbial communities, as well as possibly having a synergistic impact on human health.

中文翻译：

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尘土飞扬的空气中附着颗粒和自由漂浮细菌的丰度和生存力

空气传播的细菌作为生物气溶胶的主要组成部分而广泛传播，它们与尘埃颗粒共存使细菌和尘埃颗粒在冰云形成中更具活性，并且对公众健康有害。但是，尚未对尘土飞扬的空气中附着有颗粒和漂浮的细菌的丰度和生存能力进行定量研究。我们研究了基于该事实，即空气中的细菌细胞是大约1这个问题 μ米或在空气动力学直径小; 因此，在大于1 µm的颗粒的气溶胶样品中应出现附着颗粒的细菌 ，而在小于1 µm的颗粒中应出现自由漂浮的细菌。 米 我们在春季的日本沿海地带观察发现，当时西风频繁地从亚洲大陆运来粉尘，结果表明，在粉尘事件中，附着颗粒的细菌的浓度为$\mathrm{3.2}\pm \mathrm{2.1}\times {\mathrm{10}}^{\mathrm{5}}$平均 细胞数m ^-3，占 细菌总数的72±9％。相反， 在非尘埃期，该分数为56±17％，浓度为$\mathrm{1.1}\pm \mathrm{0.7}\times {\mathrm{10}}^{\mathrm{5}}$ 单元格m ^-3。附着在颗粒上的细菌的生存能力（定义为活细胞与总细胞的比率） 在粉尘事件中 平均为69±19％，在非尘埃时期平均为60±22％，两者均远低于游离细菌的生存力。在多尘或不多尘的条件下漂浮的细菌（约87％）。提出的案例表明，尘埃颗粒在其表面上携带大量细菌，其中一半以上是可生存的，并通过大气传播这些细菌。这意味着灰尘和细菌作为内部混合组合物在云形成过程中以及在连接地理上隔离的微生物群落方面具有重要作用，并且可能对人类健康产生协同作用。