Figure 3

Hierarchical clustering of the bacterial community based on distance measurement using Bray–Curtis dissimilarity index and clustering algorithm using Ward distance. Air samples from suburban (> 1.1 µm, red, n = 18) grouped separately from those from suburban (< 1.1 µm, green, n = 9) and urban (> 1.1 µm, blue, n = 18, and < 1.1 µm, purple, n = 9) in most cases. The bacterial communities detected in the suburban (< 1.1 µm) and urban (> 1.1 µm, < 1.1 µm) groups could not be readily distinguished.