Height-Resolved\nAnalysis of Indoor Airborne Microbiome:\nComparison with Floor Dust-Borne Microbiome and the Significance of\nShoe Sole Dust

Exposure to the indoor airborne microbiome\nis closely related to\nthe air that individuals breathe. However, the floor dust-borne microbiome\nis commonly used as a proxy for indoor airborne microbiome, and the\nspatial distribution of indoor airborne microbiome is less well understood.\nThis study aimed to characterize indoor airborne microorganisms at\nvarying heights and compare them with those in floor dust. An assembly\nof three horizontally and three vertically positioned Petri dishes\ncoated with mineral oil was applied for passive air sampling continuously\nat three heights without interruption. The airborne microbiomes at\nthe three different heights showed slight stratification and differed\nsignificantly from those found in the floor dust. Based on the apportionment\nresults from the fast expectation–maximization algorithm (FEAST),\nshoe sole dust contributed approximately 4% to indoor airborne bacteria\nand 14% to airborne fungi, a contribution that is comparable to that\nfrom the floor dust-borne microbiome. The results indicated that floor\ndust may not be a reliable proxy for indoor airborne microbiome. Moreover,\nthe study highlights the need for height-resolved studies of indoor\nairborne microbiomes among humans in different activity modes and\nlife states. Additionally, shoe sole-dust-associated microorganisms\ncould potentially be a source to “re-wild” the indoor\nmicrobiota.