The atmosphere may be Earth’s largest microbial ecosystem. Connected to all of Earth’s surface ecosystems, it plays an important role in microbial dispersal. Despite this grand scale, surprisingly little is understood about the atmosphere itself as a microbial habitat, partly due to the substantial technical challenges posed by acutely low-biomass air samples. A key question remains unresolved: does the atmosphere simply transport microbes, or does it harbor adapted, resident and active microbial communities that overcome the physiological stressors and selection pressures the atmosphere poses to life? We hypothesise that the atmosphere hosts a genuine microbial ecosystem whose activities may influence global atmospheric processes.
In this pilot study, we have developed an ultra-clean approach to extract DNA from atmospheric microbes, which maximises retrieved biomass and minimises contaminating DNA. To explore patterns of biodiversity and genetic mechanisms for persistence and survival in different atmospheric habitats, air samples were collected from desert (n = 6), temperate forest (n = 6) and urban outdoor (n = 14) and indoor (n = 6) environments with two varieties of dry filter-based air sampler. DNA quantification by fluorometry and qPCR confirmed genuine microbial biomass with minimal contamination, with preliminary DNA sequencing revealing the environmentally resilient Geodermatophilaceae spp., Sphingomonadaceae spp. and Hymenobacteraceae spp. as major atmospheric community members.
Ongoing work focuses on the metabolic potential of atmospheric microbes above rainforest, alpine and polar environments. We are additionally investigating the contribution of resilient atmospheric microbes to the formation of new ecosystems via colonisation of the unique habitats offered by meteorites and glacier forelands. Understanding the atmospheric microbiome has far reaching implications across astrobiology, geobiology and microbial ecology, with further applications in pathogen transmission and planetary health.