Bacteria as Cloud Condensation Nuclei (CCN) in the Atmosphere

Abstract

Bacteria activation and cloud condensation nuclei (CCN) formation have been studied in the atmosphere using the classical theory of heterogeneous nucleation. Simulations were performed for the binary system of sulfuric acid/water using laboratory-determined contact angles. Realistic model simulations were performed at different atmospheric heights for a set of 140 different bacteria. Model simulations showed that bacteria activation is a potentially favorable process in the atmosphere which may be enhanced at lower temperatures. CCN formation from bacteria nuclei is dependent on ambient atmospheric conditions (temperature, relative humidity), bacteria size, and sulfuric acid concentration. Furthermore, a critical parameter for the determination of bacteria activation is the value of the intermolecular potential between the bacteria’s surface and the critical cluster formed at their surface. In the classical nucleation theory, this is parameterized with the contact angle between substrate and critical cluster. Therefore, the dataset of laboratory values for the contact angle of water on different bacteria substrates needs to be enriched for realistic simulations of bacteria activation in the atmosphere.

Stochastic microbial dispersal drives local extinction and global diversity

“…All these traits likely represent environmental dispersal filters, a role supported by the suggested non-neutrality of dispersal [ 40 , 68 – 70 ], affecting the travel distance and survival rates, or the biogeographic connectivity. On top, we note that, despite comparably harsh conditions, the atmosphere has been proposed as a habitat where microorganisms can be metabolically active and grow [ 71 – 74 ] as well as contribute to physical [ 75 – 77 ] and chemical [ 78 , 79 ] transformations, potentially modifying cloud formation processes [ 76 , 77 , 80 ] and thereby affecting the hydrological cycle [ 81 ] and Earth’s global energy budget. These are all mechanisms susceptible to affect system-specific parameters such as the typical dispersal distance or the growth rate in a species-dependent manner.…”

Potential for Phototrophy in Venus' Clouds

“…Apart from instrumental issues, we posit that these high values represent partial sampling of the aerosols, which hint at larger solution-phase reservoirs of water, per se, that may harbor solutes, as noted, that could lower the partial pressures of water and/or sulfuric acid. We speculate, therefore, that microbial survival in an aerosolized and water-restricted environment could include bio/chemical strategies to reduce vapor pressure and loss of solution-phase water, similar to microbial strategies associated with freezing point and temperature depression (Scotter et al, 2006;Möhlmann, 2012), inhibition of ice formation (Krembs and Deming, 2008;Raymond et al, 2008), and cloud condensation (Lazaridis, 2019).…”