Abstract

Temuco city is one of the most air-polluted cities in South America; therefore, a daily air quality monitoring (AQM) program has been established. Using the AQM samples, we determined and compared the bacterial communities associated with the PM2.5 and PM10 fractions in different seasons and their correlations with the meteorological parameters. In addition, at different air quality levels (‘Good–Moderate’ [G–M] and ‘Alert–Preemergency’ [A–P]), we determined and compared the bacterial communities in the PM2.5 fraction, which is highly relevant to public health. A greater bacterial diversity was detected in the PM2.5 samples than in the PM10 samples, but no statistical differences (p < 0.05) were detected between the PM fractions or seasons. The PM fractions were dominated by Pseudomonadota (53–90%) and Bacteroidota (seven to 30%). In the colder seasons (fall and winter), PM2.5 bacterial diversity was negatively correlated with precipitation. A negative correlation between bacterial diversity in the PM2.5 and PM concentrations was also found in fall. For air quality levels, co-occurrence networks presented significantly greater positive relationships and connectivity in A–P than in G–M. Interestingly, Polaribacter in PM2.5 was an indicator taxon for winter and a hub taxon for G–M; however, Alteromonas was an indicator and hub taxon in the A–P samples. Sea-related taxa were relevant to the bacterial community in the Temuco and AQM samples, with associated functional groups such as heterotrophs involved in carbon and sulfur cycling. Complementing sampling methods and major spatiotemporal studies are still needed to elucidate the variation patterns of airborne bacterial communities. © The Author(s), under exclusive licence to Springer Nature B.V. 2025.