Airborne microorganisms, especially those at high altitude, are exposed to hostile conditions, including ultraviolet (UV) radiation, desiccation, and low temperatures. This study was conducted to compare the composition and abundance of airborne microorganisms at a high-altitude site, Mt. Jodo [2,839 m above mean sea level (AMSL)] and a suburban site (23 m AMSL) in Toyama, Japan. To our knowledge, this is the first study to investigate microbial communities in air samples collected simultaneously at two sites in relatively close proximity, from low and high altitude. Air samples were collected over a period of 3 years during 2009–2011. We then examined the bacterial and eukaryotic communities and estimated the abundance of bacteria and fungi with real-time TaqMan PCR. The airborne bacterial and eukaryotic communities differed between high-altitude and suburban sites on each sampling day. Backward trajectory analysis of air masses that arrived at high-altitude and suburban sites on each sampling day displayed almost the same paths. The bacterial communities were dominated by Actinobacteria, Firmicutes, and Proteobacteria, while the eukaryotic communities included Ascomycota, Basidiomycota, and Streptophyta. We also predicted some application of such microbial communities. The airborne bacterial and fungal abundance at the high-altitude site was about two times lower than that at the suburban site. These results showed that each airborne microbial communities have locality even if they are collected close location.

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 .

The aim of this study was to assess the microbial diversity associated with Lake Nyos, a lake with an unusual chemistry in Cameroon. Water samples were collected during the dry season on March 2013. Bacterial and archaeal communities were profiled using Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) approach of the 16S rRNA gene. The results indicate a stratification of both communities along the water column. Altogether, the physico-chemical data and microbial sequences suggest a close correspondence of the potential microbial functions to the physico-chemical pattern of the lake. We also obtained evidence of a rich microbial diversity likely to include several novel microorganisms of environmental importance in the large unexplored microbial reservoir of Lake Nyos.

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