Potential for phenol biodegradation in cloud waters

Abstract

Abstract. Phenol is toxic and can be found in many environments, in particular in the atmosphere due to its high volatility. It can be emitted directly from manufacturing processes or natural sources, and it can also result from benzene oxidation. Although phenol biodegradation by microorganisms has been studied in many environments, the cloud medium has not been investigated yet as the discovery of active microorganisms in cloud is rather recent. The main objective of this work was to evaluate the potential degradation of phenol by cloud microorganisms. Phenol concentrations were measured by GC-MS on two cloud samples collected at the PUY station (summit of Puy de Dôme, 1465 m a.s.l., France): they ranged from 0.15 to 0.21 µg L−1. The strategy for investigating its potential biodegradation involved a metatranscriptomic analysis and metabolic screening of bacterial strains from cloud water collected at the PUY station for phenol degradation capabilities (from the 145 tested strains, 33 were isolated for this work). Among prokaryotic messenger RNA-enriched metatranscriptomes obtained from three cloud water samples, which were different from those used for phenol quantification, we detected transcripts of genes coding for enzymes involved in phenol degradation (phenol monooxygenases and phenol hydroxylases) and its main degradation product, catechol (catechol 1,2-dioxygenases). These enzymes were likely from Gammaproteobacteria, a dominant class in clouds, more specifically the genera Acinetobacter and Pseudomonas. Bacterial isolates from cloud water samples (Pseudomonas spp., Rhodococcus spp., and strains from the Moraxellaceae family) were screened for their ability to degrade phenol: 93 % of the 145 strains tested were positive. These findings highlight the possibility of phenol degradation by microorganisms in clouds. Metatranscriptomic analysis suggested that phenol could be biodegraded in clouds, while 93 % of 145 bacterial strains isolated from clouds were able to degrade phenol.

The global impact of bacterial processes on carbon mass

“…Comparison of previous global estimates of cloud coverage of 60 % (Pruppacher and Jaenicke, 1995) and the volume fraction of liquid clouds within the atmosphere of 15 % (Lelieveld and Crutzen, 1990) generally supports this relationship. The resulting F cloud values are summarized in Table 2 together with the cloud coverage data (F clc ) and the percentage area fraction of each ecosystem of the Earth's surface, taken from Burrows et al (2009b) and originally obtained from Olson (1992).…”

“…These substrates include organics (e.g., carboxylic acids, sugars); other elements (e.g., nitrogen, phosphorous, potassium, metals) are also needed and exist in bioavailable forms in cloud water. The biotransformation of formate, acetate, succinate, lactate, oxalate, formaldehyde (Ariya et al, 2002;Vaïtilingom et al, 2010), phenol (Lallement et al, 2018), and methane (Šantl-Temkiv et al, 2013) by bacteria and fungi was studied in aqueous solutions mimicking the typical chemical composition of cloud water, and it was suggested that under specific conditions microbial processes might be competitive to chemical radical processes as sinks for these compounds (Delort et al, 2010;Vaïtilingom et al, 2011Vaïtilingom et al, , 2013. The efficiency of such metabolic processes strongly depends on the bacteria types, substrates, and their availability within the cloud droplets.…”

Microbial composition in seasonal time series of free tropospheric air and precipitation reveals community separation

“…Clouds likely offer a more hospitable environment due to water availability and nutrients (Delort et al 2017;Deguillaume et al 2008;Bianco et al 2016). Bacteria might be able to multiply (Sattler et al 2001) and degrade substances (Lallement et al 2018) in cloud doplets.…”

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

“…(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). Moreover, they interact with reactive oxygen species, thus playing another role in cloud chemistry: they destroy oxidants that can potentially damage cells, reducing the concentration of precursors (H 2 O 2 in particular) of reactive oxygen species (Vaïtilingom et al, 2013;Wirgot et al, 2017).…”