High levels of primary biogenic organic aerosols are driven by only a few plant-associated microbial taxa

Primary biogenic organic aerosols (PBOAs) represent a major fraction of coarse organic matter (OM) in air. Despite their implication in many atmospheric processes and human health problems, we surprisingly know little about PBOA characteristics (i.e., composition, dominant sources, and contribution to airborne particles). In addition, specific primary sugar compounds (SCs) are generally used as markers of PBOAs associated with bacteria and fungi, but our knowledge of microbial communities associated with atmospheric particulate matter (PM) remains incomplete. This work aimed at providing a comprehensive understanding of the microbial fingerprints associated with SCs in PM10 (particles smaller than 10 µm) and their main sources in the surrounding environment (soils and vegetation). An intensive study was conducted on PM10 collected at a rural background site located in an agricultural area in France. We combined high-throughput sequencing of bacteria and fungi with detailed physicochemical characterizations of PM10, soil, and plant samples and monitored meteorological and agricultural activities throughout the sampling period. Results show that in summer SCs in PM10 are a major contributor of OM in air, representing 0.8 % to 13.5 % of OM mass. SC concentrations are clearly determined by the abundance of only a few specific airborne fungal and bacterial taxa. The temporal fluctuations in the abundance of only four predominant fungal genera, namely Cladosporium, Alternaria, Sporobolomyces, and Dioszegia, reflect the temporal dynamics in SC concentrations. Among bacterial taxa, the abundance of only Massilia, Pseudomonas, Frigoribacterium, and Sphingomonas is positively correlated with SC species. These microbes are significantly enhanced in leaf over soil samples. Interestingly, the overall community structure of bacteria and fungi are similar within PM10 and leaf samples and significantly distinct between PM10 and soil samples, indicating that surrounding vegetation is the major source of SC-associated microbial taxa in PM10 in this rural area of France.