Tutorial 3:

Investigating microbial aerosols in the outdoor atmosphere

Pierre Amato, Centre National de la Recherche Scientifique (CNRS); Institut de Chimie de Clermont-ferrand, Aubière, France

Abstract: The atmosphere carries diverse and highly variable numbers of biological aerosol particles (i.e. bioaerosols) including microbial cells and their products and propagules. These are transported from sources to sinks with a residence time aloft of up to a few days, during which they can travel long distances and reach high altitudes. In the meantime, harsh atmospheric conditions impair cell’s activity, survival and integrity. Still, microbial cells have unique properties and some of them are capable of maintaining viability and metabolic activity in the atmosphere, notably in clouds, where their interactions with physical and chemical processes have possible impacts on hydrological and biogeochemical cycles. This tutorial will summarize the main peculiarities of microorganisms among aerosol particles, and provide an overview of some of the most promising methods for characterizing their biodiversity, viability, metabolic activity and functioning, and evaluate their environmental impacts. Major analytical challenges and requirements associated with the low microbial biomass and the high diversity and variability in the atmosphere will be discussed, along with difficulties and pitfalls that may arise when attempting to provide global estimates of their impacts.

Short bio: Dr Pierre Amato is researcher at CNRS, France, investigating microorganisms in the outdoor atmosphere (clouds, aerosol, and precipitation) for ~20 years, with a particular focus on clouds at puy de Dôme Mountain site. He leads his group towards multiple aspects of atmospheric microbiology: microbial diversity, survival, maintenance and metabolic functioning, interactions between cells and their atmospheric environment, chemical and microphysical implications, etc. He develops and applies observations, experimental strategies and numeric approaches to address the questions related with the persistence of life in such extreme conditions, and decipher the role of the atmosphere as a microbiome.