Asian dust (Kosa) events transport airborne microorganisms that significantly impact biological ecosystems, human health, and ice-cloud formation in downwind areas.However, the composition and population dynamics of airborne bacteria have rarely been investigated in downwind areas during Kosa events. In this study, air samplings were sequentially performed at the top of a 10-m high building within the Kosa event arrival area (Kanazawa city, Japan) from May 1 to May 7, 2011, during a Kosa event.The particle concentrations of bacterial cells and mineral particles was ten-fold higher during the Kosa event than on non-Kosa event days. A 16S ribosomal DNA clone library prepared from the air samples primarily contained sequences from three phyla:Cyanobacteria, Firmicutes, and Alphaproteobacteria. The clones from Cyanobacteria were mainly from a marine type of Synechococcus species that was dominant during the first phase of the Kosa event and was continuously detected throughout the Kosa event.The clones from Alphaproteobacteria were mainly detected at the initial and final periods of the Kosa event, and phylogenetic analysis showed that their sequences clustered with those from a marine bacterial clade (the SAR clade) and Sphingomonas spp. During the middle of the Kosa event, the Firmicutes species Bacillus subtilis and Bacillus pumilus were predominant; these species are known to be predominat in the atmosphere above the Chinese desert, which is the source of the dust during Kosa events. The clones obtained after the Kosa event had finished were mainly from Bacillus megaterium, which is thought to originate from local terrestrial areas. Our results suggest that airborne bacterial communities at the ground level in areas affected 2 by Kosa events change their species compositions during a Kosa event toward those containing terrestrial and pelagic bacteria transported from the Sea of Japan and the continental area of China by the Kosa event.

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...

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Penelitian ini bertujuan untuk mengetahui pengaruh penggaraman dengan konsentrasi yang berbeda terhadap karakteristik kimia dan pertumbuhan bakteri pada ikan sepat rawa (Trichogaster trichopterus). Perlakuan yang diberikan adalah tanpa penambahan garam (A) sebagai kontrol, garam 5% (B), garam 10% (C) dan garam 15% (D). Analisis kadar air menggunakan metode pengeringan, analisis kadar protein menggunakan metode Kjeldahl, analisis asam amino menggunakan high performance liquid chromatography (HPLC) dan analisis pertumbuhan mikroba menggunakan metode angka lempeng total (ALT). Perlakuan terbaik adalah perlakuan D penambahan garam dengan konsentrasi 15% menghasilkan kadar air ikan sepat rawa sebesar 61,35%, kadar protein 31,61%, dan ALT 5,87 log10 CFU/mL. Profil asam amino esensial yang tertinggi pada perlakuan B yaitu lisina sebesar 2,20% dan asam amino non esensial yang tertinggi pada perlakuan B yaitu asam glutamat 4,34%.

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