A fate for organic acids, formaldehyde and methanol in cloud water: their biotransformation by micro-organisms P. Amato1,2,*, F. Demeer1, A. Melaouhi1, S. Fontanella1, A.-S. Martin-Biesse1, M. Sancelme1, P. Laj2, and A.-M. Delort1 1Laboratoire de Synthèse et Etudes de Systèmes à Intérêt Biologique, UMR 6504 CNRS-Université Blaise Pascal, Aubière, France 2Laboratoire de Météorologie Physique, UMR 6016, CNRS-Université Blaise Pascal Aubière, France *now at: Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, USA
Abstract. The interactions between microbial and chemical contents of cloud water were
investigated. First, we observe that the bulk cloud water solution provides
a substantial environment where bacteria can develop significantly. Then, a
total number of 60 microbial strains originating from seven distinct samples
of cloud water and affiliated to various taxonomic groups were examined for
their ability to degrade some of the main atmospheric carboxylic compounds:
formate, acetate, lactate, succinate, as well as formaldehyde and methanol.
Biodegradation tests show that all these compounds can be transformed when
used as single carbonaceous substrates, with activities depending on both
the strain and the compound. The highest capacities of biodegradation are
observed towards formaldehyde, formate and acetate, which are also the more
concentrated compounds typically measured in cloud water. Hence, analyses by
1H NMR permitted to establish for instance that compounds like pyruvate
or fumarate can be produced and released in the media in relation to the
transformation of lactate or succinate. In addition, utilization of 13C
labelled formaldehyde showed that it can be transformed through many
metabolic pathways, similar to those induced by photochemistry and leading
to the production of formate and/or methanol. These results suggest that
microorganisms of cloud water can have various behaviours towards the
chemical compounds present in the atmosphere: they can represent either a
sink or source for organic carbon, and may have to be considered as actors
of cloud chemistry.
Citation: Amato, P., Demeer, F., Melaouhi, A., Fontanella, S., Martin-Biesse, A.-S., Sancelme, M., Laj, P., and Delort, A.-M.: A fate for organic acids, formaldehyde and methanol in cloud water: their biotransformation by micro-organisms, Atmos. Chem. Phys., 7, 4159-4169, doi:10.5194/acp-7-4159-2007, 2007.