Effect of endogenous microbiota on the molecular composition of cloud water: a study by Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS)

Abstract

A cloud water sample collected at the puy de Dôme observatory (PUY) has been incubated under dark conditions, with its endogenous microbiota at two different temperatures (5 and 15 °C), and the change in the molecular organic composition of this sample was analyzed by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Microorganisms were metabolically active and strongly modified the dissolved organic matter since they were able to form and consume many compounds. Using Venn diagrams, four fractions of compounds were identified: (1) compounds consumed by microbial activity; (2) compounds not transformed during incubation; (3) compounds resulting from dark chemistry (i.e., hydrolysis and Fenton reactions) and, finally, (4) compounds resulting from microbial metabolic activity. At 15 °C, microorganisms were able to consume 58% of the compounds initially present and produce 266 new compounds. For this cloud sample, the impact of dark chemistry was negligible. Decreasing the temperature to 5 °C led to the more efficient degradation of organic compounds (1716 compounds vs. 1094 at 15 °C) but with the less important production of new ones (173). These transformations were analyzed using a division into classes based on the O/C and H/C ratios: lipid-like compounds, aliphatic/peptide-like compounds, carboxylic-rich alicyclic molecule (CRAM)-like structures, carbohydrate-like compounds, unsaturated hydrocarbons, aromatic structures and highly oxygenated compounds (HOCs). Lipid-like, aliphatic/peptide-like and CRAMs-like compounds were the most impacted since they were consumed to maintain the microbial metabolism. On the contrary, the relative percentages of CRAMs and carbohydrates increased after incubation.

The global impact of bacterial processes on carbon mass

“…Additionally, the rapidly changing conditions in clouds, like condensationevaporation and freeze-thaw cycles, can cause strong physiological shocks and physical damage to cells, which can eventually be lethal. The viability of airborne microorganisms is thus very variable in space and time depending on environmental conditions (Fahlgren et al, 2010;Hu et al, 2017;Lighthart and Shaffer, 1995;Monteil et al, 2014), but yet the fact that a fraction of bacterial cells are viable was shown in many experiments of microbiological cultures from ambient aerosol samples (Amato et al, 2007b;Bovallius et al, 1978;Lighthart, 1997;Newman, 1948). This was specified and quantified more recently by direct observations and measurements of biological activity imprints (Amato et al, 2007aSattler et al, 2001;Wirgot et al, 2017).…”

Biodegradation of phenol and catechol in cloud water: Comparison to chemical oxidation in the atmospheric multiphase system

“…In general, the importance of aqueous phase processes increases with increasing solubility (Henry's law constants). Our recent cloud FT-ICR-MS analyses of cloud water samples have shown that about 50% of ~2100 identified compounds were utilized by cloud microorganisms (Bianco et al, 2019). Thus, microbial processes in cloud water may represent efficient sinks for numerous organics and might 375 even result in products different from those of chemical reactions (Husárová et al, 2011).…”

Cézeaux-Aulnat-Opme-Puy De Dôme: a multi-site for the long term survey of the tropospheric composition and climate change

“…CC BY 4.0 License. (Bianco et al, 2019b;Vaïtilingom et al, 2011Vaïtilingom et al, , 2013. They are also able to degrade pollutants such as phenols (Lallement et al, 2018b).…”