Abundance and viability of particle-attached and free-floating bacteria in dusty and nondust air [post]

Wei Hu, Kotaro Murata, Chunlan Fan, Shu Huang, Hiromi Matsusaki, Pingqing Fu, Daizhou Zhang
2020 unpublished
<p><strong>Abstract.</strong> Widespread bacteria are a major proportion of bioaerosols and their coexistence with dust enables both types of aerosols more active in ice cloud formation and 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
more » ... μm or smaller; 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 blew dust there from the Asian continent, revealed that particle-attached bacteria in dust episodes, at the concentration of 3.2 ± 2.1 × 10<sup>5</sup> cells m<sup>−3</sup>, occupied 72 ± 9 % in the total bacteria. In contrast, the fraction was 56 ± 17 % during nondust periods and the concentration was 1.1 ± 0.7 × 10<sup>5</sup> cells m<sup>−3</sup>. 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 nondust periods, both of which were considerably lower than the viabilities of free-floating bacteria (about 87 %) under either dusty or nondust conditions. The present cases suggest that dust particles carried substantial bacteria on their surfaces, more than half of which were viable, and spread these bacteria in the atmosphere. This implies that dust and bacteria have nonnegligible roles as internally mixed assemblages in various atmospheric processes and in linking geographically isolated microbial communities, as well as have synergistic effect on human health.</p>
doi:10.5194/bg-2020-94 fatcat:744pppglarazfm4n73o422ttwe