Growth of Bacillus pumilus and Halomonas halodurans in sulfates: prospects for life on Europa

Abstract

The growth of Bacillus pumilus and Halomonas halodurans under different concentrations of NaCl, MgCl 2 , Na 2 SO 4 and MgSO 4 was investigated. The objective was to demonstrate whether these cultures have the ability to grow, not only in media enriched with sodium chloride, but also with other salts of astrobiological interest. The importance of this monitoring was to evaluate the fitness of these strains to the hypothetical salt content and composition of extraterrestrial sites, such as the ocean of Europa, one of the satellites of Jupiter.The mechanism of fitness used by these bacteria was investigated by characterizing the compatible solutes accumulated by each strain. Bacillus pumilus was cultivated at 0.23 M and 0.33 M NaCl (a w of 0.995 and 0.990, respectively) while Halomonas halodurans was cultivated at 0.44 M and 0.89 M NaCl (a w of 0.985 and 0.965, respectively). B. pumilus seems to accumulate principally betaine while H. halodurans accumulates betaine and glutamate, depending on the salt content of its environment. These results are discussed in the context of the salinity and salt composition of Europa's ocean and under their implications for the habitability of this Jovian satellite.Keywords: Water activity, Europa's habitability, icy satellites, halophiles, compatible solutes. Resumen

Salinity Tolerance and Osmoadaptation Strategies in Four Genera of Anammox Bacteria: Brocadia, Jettenia, Kuenenia, and Scalindua

“…Scalindua sp.” culture grown at 2.5% salinity (B), respectively. Signals corresponding to the chemical shifts of trehalose (60.58, 69.54–73.24, and 97.51 ppm), glutamate (27.03, 33.52, 54.72, 177.19, and 181.42 ppm), and glycine betaine (63.17 and 174.71 ppm) , were identified in the cell-free extract of “ Ca . Scalindua sp.” (B), whereas only trehalose signals were identified in “ Ca .…”

“…The 13 C NMR spectrum of “ Ca . Scalindua sp.” showed signals corresponding to trehalose, glutamate, and glycine betaine, , whereas only a trehalose signal was identified in “ Ca . B. sinica” (Figure ).…”

Experimental and Simulation Efforts in the Astrobiological Exploration of Exooceans

“…To investigate the potential of habitability in a sub-surface ocean, laboratory based simulation experiments are required. Work has predominantly focused on the compositional effect of the ocean on microbial growth (e.g., Stevens et al 2018;Avendaño et al 2015;Fox-Powell et al 2016). Although the environmental parameters within the sub-surface oceans of Europa (e.g., Kargel et al 2000;Zolotov and Kargel 2009) and Enceladus (e.g., Glein and Shock 2010;Zolotov 2007;Postberg et al 2009bPostberg et al , 2011bIess et al 2014; have been modelled, little is known if microorganisms could grow under such conditions.…”