Exploring the Spatial Variability of Airborne Bacterial and Fungal Communities across Five Central Mediterranean Areas

In this study we investigated the distribution of airborne bacterial and fungal communities in five different areas of the Central Mediterranean (Salento Peninsula and Lamezia Terme in South Italy, Albania, Malta, and Zakynthos in Greece). Advanced DNA-based approaches and compositional data analysis (CoDa) were used to explore microbial community compositions and their spatial variability associated with the different types of sampling site (urban, rural, and coastal). Our results revealed distinct patterns of the airborne microbial community mainly shaped by geographic and environmental features. Among the identified airborne bacterial genera, we found Sphingomonas in all the selected sites, while Brevundimonas, Geodermatophilus, and Rubrobacter were prevalent in coastal and rural locations. Among the airborne fungal genera, Cladosporium and Alternaria were abundant in rural and coastal areas. The clustering of detected samples by geographic characteristics and monitoring site type was further highlighted by the Aitchison distance-based dendrograms and principal component analysis biplots by utilizing singular value decomposition. In fact, using this statistical approach we proved that some specific microbial genera were associated with different environmental characteristics related to the selected sampling areas. Therefore, this study points out the complex relationship between spatial variability and microbial distributions, underlining that environmental and geographic variations can significantly contribute to microbial community composition.