Concentration of Bacterial Aerosols Associated with Particles: Observations at a Southwestern Coastal Site of Japan in the Spring of 2013–2014

Abstract:

Airborne bacteria are the major group of bioaerosols in the air and are considered to have important climate effects by acting as ice nuclei. To investigate the dependence of bacteria on particles in the air, we enumerated bacterial cells in size-segregated airborne particle samples that were collected at a rural seaside site on the southwestern coast of Japan during dust and non-dust periods in the spring of 2013–2014. Proportion of particle-attached bacteria was 75–84% of total airborne bacterial concentration during dust periods and 27–76% during non-dust periods, both of which were equal to approximately 12% of >1 µm aerosol particle concentrations. The concentration of particle-attached bacteria was 3.2 times higher during dust periods, compared with that during non-dust periods. The viability, which is referring to the ratio of viable cells to total cells, of particle-attached bacteria was 33–82% during dust periods and 45–98% during non-dust periods. The predominance of particle-associated viable/non-viable bacteria during dust periods demonstrates a potential of bacteria to cooperate with dust in influencing the climate, ecosystems, and health where they arrive.