Profile and Characteristics of Culturable Airborne Bacteria in Hangzhou, Southeast of China

Increased concentrations of airborne bacteria are known to be associated with decreased public health. As such, we evaluated the culturable concentration and distribution characteristics of airborne bacteria at four sampling sites in Hangzhou, southeast China. Results showed that the concentration of culturable bacteria in the air at selected sampling sites ranged from < 12 colony forming units (CFU) m(-3) to 3259 CFU m(-3) with a mean and a median of 292 and 201 CFU m-3, respectively. We identified a total of 789 airborne bacterial isolates from multiple sampling sites and between different seasons, which distributed across 55 genera and 184 species of bacteria. Micrococcus (16.48%), Bacillus (13.94%), Staphylococcus (11.28%), Kocuria (11.28%), and Pseudomonas (4.94%) accounted for 58% of the total species and the dominant bacterial species were Micrococcus luteus (9.51%), Kocuria roseus (6.84%), Bacillus megaterium (4.56%), Micrococcus roseus (3.42%), and Staphylococcus cohnii (2.53%). Significant variation between sampling sites was observed with significantly higher bacterial concentrations detected at Yan'an Road Business Street (YRBS), followed by Tianmushan and Jiaogong Cross Road (TJCR) and Zhejiang Gongshang University Jiaogong Campus (ZJGSUJC), while the lowest concentrations were found at Breeze-ruffled Lotus at Quyuan Garden (BLQG) (p < 0.05). Moreover, seasonal variation of bacterial concentrations was observed across the different sampling sites: the highest bacterial concentrations in both YRBS and ZJGSUJC were found in autumn, followed by spring, and the lowest was found in winter (p < 0.05). No significant differences in seasonal patterns were found in BLQG (p > 0.05). Taken together these results provide a baseline for airborne culturable bacteria in southeast China, and will enable evaluation of the risks to human health from exposure to the atmosphere in the region.