Contribution of Microbial Activity to Carbon Chemistry in Clouds
Mickael Vaïtilingom,1,3 Pierre Amato,1,2 Martine Sancelme,1 Paolo Laj,3†
Maud Leriche,4,5 and Anne-Marie Delort1,2*
UMR 6504, CNRS-UBP, Department of Chemistry, 24 Avenue des
Landais, F-63177 Aubie`re, France.
The biodegradation of the most abundant atmospheric organic C1 to C4 compounds (formate, acetate,
lactate, succinate) by five selected representative microbial strains (three Pseudomonas strains, one Sphingomonas
strain, and one yeast strain) isolated from cloud water at the puy de Doˆme has been studied.
Experiments were first conducted under model conditions and consisted of a pure strain incubated in the
presence of a single organic compound. Kinetics showed the ability of the isolates to degrade atmospheric
compounds at temperatures representative of low-altitude clouds (5°C and 17°C). Then, to provide data that
can be extrapolated to real situations, microcosm experiments were developed. A solution that chemically
mimicked the composition of cloud water was used as an incubation medium for microbial strains. Under these
conditions, we determined that microbial activity would significantly contribute to the degradation of formate,
acetate, and succinate in cloud water at 5°C and 17°C, with lifetimes of 0.4 to 69.1 days. Compared with the
reactivity involving free radicals, our results suggest that biological activity drives the oxidation of carbonaceous
compounds during the night (90 to 99%), while its contribution accounts for 2 to 37% of the reactivity
during the day, competing with photochemistry.
strain,microbial strains,Pseudomonas, nitrate, chloride, sodium,biodegradation.
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