Phylogenetic analysis of bacterial species compositions in sand dunes and dust aerosol in an Asian dust source area, the Taklimakan Desert

Abstract

Airborne microorganisms (bioaerosol) from the China desert region, which are released into the atmosphere, disperse by the Asian dust event and affect ecosystems, human life, and atmospheric processes in downwind areas. However, the dynamics of airborne bacteria over the China desert regions have rarely been investigated. In this study, we analyzed bacterial communities in aerosols of the Asian dust source region (Taklimakan Desert) and compared them with the bacterial communities in sand dunes, in order to evaluate the differences between the mixtures from the sand and from the atmosphere. Air samples were collected at 10 m above the ground level from Dunhuang city, during a dust event. The cell densities of airborne bacteria during a dust event were ten times more than that in non-dust periods. The 16S rDNA clone libraries from four air samples mainly belonged to two phyla, Firmicutes and Proteobacteria. During a dust event, the proportion of Proteobacteria clones decreased, whereas that of Firmicutes clones increased. Sand samples were collected from the sand dunes in four sampling sites of the Taklimakan Desert. The bacterial communities in sand samples comprised members of Firmicutes and Actinobacteria. The clones of Firmicutes in both air and sand samples included Bacillus species, constituting more than 10% of total clones. Airborne bacterial communities are likely carried by the dust events from sand dunes. Propionibacterium species from the class Actinobacteria that were dominant in sand samples were not detected in the air samples, suggesting that atmospheric stressors eliminate some bacterial species. Presumably, airborne bacterial communities in the Asian dust source region are composed of local environmental bacteria, and their dynamics depend on the occurrence of a dust event.3 Keywords: Asian dust, bacteria, Bacillus, sand dune 4 IntroductionSoil particles that are derived from the Chinese desert area are frequently transported over the East China Sea or the Yellow Sea to Japan during the spring season (Iwasaka et al. 1983). These Asian dust clouds, which are common atmospheric phenomena in Japan, are referred to as "Kosa," which literally means "yellow sands" in Japanese (Iwasaka et al. 1983). Desert winds aerosolize several billion tons of soilderived dust each year, including concentrated seasonal pulses from the Asian desert areas (Uematsu et al. 1983;Duce et al. 1980; Kim et al. 2010), causing damage to human health (Ichinose et al. 2005). Furthermore, these transoceanic and transcontinental dust events inject a large pulse of microorganisms and pollen (bioaerosol) into the atmosphere (Iwasaka et al. 2008; Kakikawa et al. 2008). The dispersal of bioaerosol by the Asian dust event could have a role in transporting pathogens or expanding the biogeographical range of some organisms by facilitating long-distance dispersal events (Kellogg and Griffin 2006; Kobayashi et al. 2015;Chung and Kim 2008). Results from in vivo assays in mice have also suggested that the Asian dust events transport...

Aeolian Dispersal of Bacteria Associated With Desert Dust and Anthropogenic Particles Over Continental and Oceanic Surfaces

“…Previous research has also reported marine bacterial transported by Asian dust (Maki et al, ) and African dust (Polymenakou et al, ) events. Members of Actinobacteria , which are frequently dominated in desert bacterial communities (An et al, ; Puspitasari et al, ) and in anthropogenic pollutants (Cao et al, ), tended to increase during dust events with anthropogenic pollutants in the both sites. The dust events came on the way of northern continental China (close to Siberia mountain areas) which avoided passing through industrial zones, would carry phyllospheric bacteria, such as Proteobacteria, and increase their abundances in atmosphere instead of Actinobacteria .…”

“…These bacteria were typically dominant populations associated with mineral dust particles and frequently detected from Asian‐dust aerosol samples collected at high altitudes above Asian desert (Dunhuang: Maki et al, ) and downwind areas (Korea: Cha et al, ; Jeon et al, , Japan: Maki, Hara, et al, ; Yamaguchi et al, ). The Bacilli lineage of phylum Firmicutes are generally found in terrestrial environments in the Gobi and Taklimakan Deserts (Puspitasari et al, ) and their ability to form endospores can help maintain viabilities against atmospheric stressors (Nicholson et al, ). Members of the Cytophagaceae lineage are often attach onto the organic aggregates (Newton et al, ), suggesting that the biofilm formation on organic aggregates can protect bacterial cells in atmosphere.…”

Variations in airborne bacterial communities at high altitudes over the Noto Peninsula (Japan) in response to Asian dust events

“…Furthermore, Actinobacteria sequences appeared in the samples collected from air masses that were transported throughout the Korean Peninsula on 19 March 2013, 28 April 2013, and 20 March 2015. Actinobacteria members are frequently dominant in terrestrial environments but seldom survive in the atmosphere for a long time, because they cannot form spores (Puspitasari et al, 2015). However, the family Micrococcaceae in Actinobacteria was primarily detected from anthropogenic particles collected in Beijing, China (Cao et al, 2014).…”

Impact of microbial air quality in preschools on paediatric respiratory health

“…Besides, human activities like walking and running disturb the settled dust particles making them re-circulate in the atmosphere [12]. Previous studies have identified that Pseudomonas, Bacillus and Acinetobacter species are associated with dust particles [33]. In addition, the presence of an attached washroom could be another reason.…”