Airborne Bacterial and Eukaryotic Communities in Temuco, Chile, a City Dominated by Residential Wood Combustion.

Airborne particulate matter (PM) affects human health, especially in heavily polluted regions. This study focused on Temuco, a city dominated by residential wood combustion in southern Chile. For the first time, we characterized airborne eukaryotic microbial communities in this area, alongside a parallel analysis of bacterial communities, and explored their associations with water-soluble inorganic ions (WSIIs) and meteorological variables. Bacterial and eukaryotic communities were profiled using 16S and 18S rRNA gene sequencing, respectively. The results showed that the mean concentrations of PM2.5 and PM10 were 75.0 and 87.7 μg/m3, respectively, with PM2.5 exceeding the Chilean national air quality standards (PM2.5: 50 μg/m3; PM10: 130 μg/m3), highlighting the persistent fine particulate matter pollution in the region. Among the WSIIs, NO3- (5.6 μg/m3), SO42- (2.6 μg/m3), and K+ (2.6 μg/m3) were the most abundant, indicating important contributions from secondary aerosol formation and residential biomass burning. At the genus level, Clostridium (6.2%), Hymenobacter (4.3%), and Sphingomonas (4.3%) dominated the bacterial communities, whereas Coriolopsis (41.0%) and Hyphodontia (26.9%) were the predominant eukaryotic taxa. Community composition differed between seasons and particle-size fractions, with seasonal variation appearing to be more pronounced. Correlation analysis and redundancy analysis (RDA) further showed relatively high loadings of SO42- (loading = 0.7146) and temperature (Temp, loading = 0.7101) in the bacterial RDA, and of Cl- (loading = -0.9054) and SO42- (loading = -0.7176) in the eukaryotic RDA. Overall, these findings provide important insights into the ecology of atmospheric microorganisms and their potential environmental associations in a city dominated by residential wood combustion.