Extreme smells: Volatile Organic Compounds from Greenlandic bacteria as biomarkers

Microbial Volatile Organic Compounds (mVOCs) are small organic molecules produced by microorganisms that readily evaporate at low temperatures. They have a number of functions, ranging from being waste products to modulating stress response and enhancing intra- and/or interspecies communication[1]. Furthermore, VOCs undergo complex chemical reactions in the atmosphere by reacting with hydroxyl radicals and nitrogen oxides, as well as forming secondary aerosols[2]. The production of mVOCs is influenced, among others, by changes in the environment. These molecules have the potential to be used as biomarkers in extreme environments to monitor the presence of life. They may also contribute to global element cycles in extreme environments, such as the sulfur cycle[3]. Lastly, they are also potential ways for extant life to influence the atmosphere of other planetary bodies.

This study aims to broaden our understanding of mVOCs in the High Arctic deserts of Northern Greenland, a terrestrial analogue of Mars-like planets characterized by low temperatures and low water availability. Three novel bacterial strains were isolated from Peary Land, northern Greenland: Oceanobacillus sp. and Nesterenkonia aurantiaca CMS1.6 from dry crust soil, and Arthrobacter sp. from permafrost. The three strains were grown at 0, 5 and 10% w/v NaCl. In the late exponential phase, the headspace was sampled and the volatiles were up-concentrated using Tenax tubes. Gas Chromatography – Mass Spectroscopy (GC-MS) was then used to analyse mVOCs in the samples. In a separate experiment, Proton Transfer Reaction Mass Spectroscopy (PTR-MS) was used to monitor the mVOC production of these strains over 72 hours, from the latent phase to the stationary phase.

Principal Component Analysis (PCA) of the mVOC profile revealed that each strain has a characteristic pattern, although the statistical effect of salt concentration is less clear. In particular, N. aurantiaca CMS1.6 produced large amounts of 2- and 3-methylbutanol under all conditions, which was not observed in the other strains. The real-time measurements also reveal different emission patterns for different compounds throughout the growth of the strains. These results highlight the potential of specific mVOCs as biomarkers in extreme environments, with potential applications in taxonomy, ecology, biotechnology and astrobiology.

 

[1] L. Weisskopf, S. Schulz, and P. Garbeva, “Microbial volatile organic compounds in intra-kingdom and inter-kingdom interactions,” Nat. Rev. Microbiol., vol. 19, no. 6, pp. 391–404, 2021, doi: 10.1038/s41579-020-00508-1.

[2] R. Atkinson, “Atmospheric chemistry of VOCs and NOx,” Atmos. Environ., vol. 34, no. 12, pp. 2063–2101, 2000, doi: https://doi.org/10.1016/S1352-2310(99)00460-4.

[3] D. J. Baumler, K.-F. Hung, K. C. Jeong, and C. W. Kaspar, “Production of methanethiol and volatile sulfur compounds by the archaeon ‘Ferroplasma acidarmanus,’” Extremophiles, vol. 11, no. 6, pp. 841–851, Nov. 2007, doi: 10.1007/s00792-007-0108-8.