Airborne bacteria could affect human health and climate. In this study, the bacterial community structures were investigated by analyzing air samples collected from a suburban location in Toyama, central Japan. Sixty samples were collected almost weekly between March 2009 and February 2010. A cultivation-independent approach, PCR plus denaturing gradient gel electrophoresis (DGGE), was used to analyze changes in the structure of the airborne bacterial communities. The DGGE profiles showed significant differences between sampling days, reflecting quite different bacterial profiles. Sequencing of DGGE bands revealed that the bacterial community was dominated by c-Proteobacteria, Firmicutes, aProteobacteria, Bacteroidetes, and Actinobacteria. The most frequently observed genus was Pseudomonas, followed by Bacillus. The airborne bacterial assemblage in winter differed from that in the other seasons. The differences could be attributed a number of factors, such as temperature, relative humidity, wind direction, and snowfall. In spring, the largest number of bands was classified as plant chloroplasts, such as Japanese cedar (Cryptomeria japonica) and Pinus spp., which are the major pollen allergen sources in Japan. The airborne bacterial abundance estimated by real-time TaqMan PCR ranged from 1.1 9 10 3 to 1.3 9 10 5 cells m -3 .

Asian dust particles transported from Asian desert areas are trapped in spring snow on the western plateau of Mt. Tateyama, Japan. We investigated bacterial communities in snow layers containing Asian dust, and other underlying snow layers, on Mt. Tateyama during and. Several genera of bacteria were present among isolates obtained from Asian dust-containing snow layers, including the presumed dust-associated bacterial genus In particular, we detected isolates with identical S rDNA sequences (AB) over consecutive years, and these isolates were most closely related to PCR-denaturing gradient gel electrophoresis (DGGE) analysis showed that bacterial community profiles in the Asian dust-containing snow layers were similar over the years. The bacterial communities di ered between the Asian dust-containing layers and other layers. Total bacterial cell counts ranged from. to. cells ml , with higher values in the Asian dust-containing layers than in the other layers. A backward trajectory analysis showed that the possible source of Asian dust was similar each year. The bacterial community composition of the Asian dust-containing layers presumably reflected the long-distance transportation of microorganisms from dust source regions.