Abstract
Relocation of bacteria over long distances is a key issue in global bacterial inoculation. Certain of mobile bacteria then can adapt to their new location and affect the established ecosystem. Aeolian dust particles are thought to be carriers of microbes but definitive research is lacking. The contribution of aeolian dust to global migration of bacterial cells and their genes was therefore examined by culture-independent approaches. Asian dust particles were collected over the Japan Sea (10 km from coasts) at an altitude of 900 m to avoid contamination of soil particles lifted from ground, on 12 November 2010 (midst of the event, visibility: less than 10 km), 13 Nov. 2010, 16 Nov. 2010 (end of the event, visibility: 25 km) and 2 May 2011 (midst of the event, visibility: less than 10 km), with a sampler set in a small airplane. Microbial cells on dust particles were directly visualized by bio-imaging with laser scanning microscopy equipped with a microspectrophotometer, based on their specific fluorescence. 16S rRNA gene was directly extracted and it was then confirmed by quantitative PCR that bacterial abundance on collected dust particles drastically declined from 105 cells/m3 to less than 1/100 as the dust event subsided. Taxonomically diverse bacteria were found by sequencing of 16S rRNA genes of clones obtained from each collected Asian dust sample, such as Actinobacteria, Bacilli and Sphingobacteria. Some of these bacteria retained growth potential despite the long-range transportation. These results demonstrate that bacteria attach to aeolian dust particles and migrate globally during dust events thus may contribute to the diversity of the bacterial gene pool.
