Cloud water plays an important role as a habitat for bacteria to live in and as a medium for microbial processes. Live bacteria are capable of biologically transforming organic compounds (e.g., organic acids, aromatics) via microbial processes in cloud water to impact secondary organic aerosol (SOA) formation. One necessary condition is that the bacteria have to be metabolically active to be able to biologically transform organic compounds in cloud water. However, clouds are considered to be harsh environments for live bacteria because they are exposed to a variety of atmospheric conditions and species (e.g., solar radiation, oxidants) that are considered to be stressful to bacterial cells. We investigated the impacts of direct photolysis on two bacteria species that are among the most represented in cultivable community in atmospheric clouds. Photolysis experiments were performed using artificial solar radiation and sporing and non-sporing bacteria species affiliated to <i>Pseudomonas</i> and <i>Bacillus</i> in microcosms designed to mimic cloud chemical composition. We found that photolysis strongly affected the survival and energetic metabolism of the studied bacteria strains. In addition, various organic compounds (e.g., constituents of cell membrane) were emitted by the bacteria strains during different stages of photolysis. These organic compounds can potentially contribute to aqueous SOA formation. Overall, these results highlight different mechanisms by which live bacteria can affect SOA formation in atmospheric cloud water.

Effects of photolysis on bacteria under simulated cloud-like conditions

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.