Comparison of airborne bacteria and fungi in different types of buildings in a temperate climate zone city, Kunming, China

The characteristics of airborne bacteria and fungi in different types of buildings are still unclear. This article applied the culturing and next-generation sequencing methods to characterize the airborne bacteria and fungi in five types of buildings during winter in Kunming, China. Results showed that the mean concentrations of fungi in different buildings were similar (approx. 387 +/- 388 CFU/m(3)). The highest culturable bacterial concentration was found in residences, while the lowest was in the library. Lowering relative humidity, PM2.5 concentration and occupant density can reduce the bacterial concentrations. The major bacterial size in residences and in a hospital was 1.1-2.1 mu m, while in other buildings was 2.1-3.3 mu m. The PM2.5 concentration and occupant activities are key factors that could affect the microorganism size distributions. The community structures of the bacteria in the library and fungi in the hospital showed distinctive differences from the results in other buildings. The community structure of outdoor microorganisms showed great differences between soil and air samples. This study is helpful to give practical implications for assessing microbial characteristics in different types of buildings and provide valuable data for the formulation of indoor bioaerosol standards in China.