Variability of airborne microbiome at different urban sites across seasons: a case study in Rome

Introduction: Biogenic fraction of airborne PM10 dominated by bacteria and fungi,has been recognized as serious environmental and human health issues in cities.Methods: In the present study, we combined a high-throughput ampliconsequencing of the bacterial 16S rRNA gene and the fungal internal transcribedspacer (ITS) region, with elemental analysis of airborne particulate matter (PM10) toinvestigate the community compositions and structures of PM10-associatedbacteria and fungi across four different seasons in three urban sites of Romewith differential pollution rate.Results: In this study, a clear seasonal shift of bacterial and fungal communitystructure driven by PM10 mass concentrations and environmental factors, such astemperature and precipitations, has been identified. In addition, the seasonalimpact of local sources and long-range transported air masses on thecommunity structures of the microbes has been also postulated. Our datarevealed that the lack of precipitation and the subsequent resuspension of dustproduced by vehicular traffic might contribute to the maximum abundance ofsoil-associated microbes in winter and summer. However, the increase of PM10concentrations favoured also by climatic conditions, domestic heating and dustadvection event from African desert further shaped the community structure ofwinter. Across three seasons, the pollutant removal-hydrogen oxidation bacteriaand the opportunist-human pathogenic fungi progressively increased withpollution levels, in the sequence from green to residential and/or polluted areaclose to the traffic roads, with highest fraction during winter.Discussion: Hence, our results highlight a close interrelationship betweenpollution, climatic factors and abundance of certain bacterial and fungalpredicted functional groups also with potential implications for human health.