Diversity and Source of Airborne Microbial Communities at Differential Polluted Sites of Rome

Biogenic fraction of airborne PM10 which includes bacteria, viruses, fungi and pollens, hasbeen proposed as one of the potential causes of the PM10 toxicity. The present study aimed to providea comprehensive understanding of the microbial community variations associated to PM10, andtheir main local sources in the surrounding environment in three urban sites of Rome, characterizedby differential pollution rate: green area, residential area and polluted area close to the traffic roads.We combined high-throughput amplicon sequencing of the bacterial 16S rRNA gene and the fungalinternal transcribed spacer (ITS) region, with detailed chemical analysis of particulate matter sampledfrom air, paved road surfaces and leaf surfaces of Quercus ilex. Our results demonstrated thatbacterial and fungal airborne communities were characterized by the highest alpha-diversity andgrouped separately from epiphytic and road dust communities. The reconstruction of source-sinkrelationships revealed that the resuspension/deposition of road dust from traffic might contributeto the maximum magnitude of microbial exchanges. The relative abundance of extremotolerant microbeswas found to be enhanced in epiphytic communities and was associated to a progressivelyincrease of pollution levels as well as opportunistic human pathogenicity in fungal communities.