Figure 1
From: Is there a common water-activity limit for the three domains of life?
Growth in relation to water activity and/or lower water-activity values at which growth was observed for halophilic Bacteria and Archaea cultured in high-magnesium saline substrates (except for data for H. saccharovorum and Salinicola strain LC26 that were obtained in high-NaCl media (see Table 1 and Supplementary Table S1), and for S. ruber and S. longa on NaCl-supplemented media indicated by black lines in (e) and (f) respectively). (a) Halophilic Archaea Halorubrum saccharovorum (strain NCIMB 2081T; shown in brown), Halobacterium sp. NRC-1 and Halococcus morrhuae (strain NCIMB 787T; both represented in yellow), Haloquadratum walsbyi (strain DSM 16790; black), Halococcus salifodinae (strain DSM 13046; purple), Halobacterium noricense (strain DSM 15987T; hashed) and Natrinema pallidum (strain NCIMB 777T; green), and Bacteria Salinicola strain LC26 and Pontibacillus strain AS2 (both represented in grey) cultured in media supplemented with various concentrations of NaCl and MgCl2 and/or glycerol and ethylene glycol to give a range of water-activity values and incubated at 20 °C for Pontibacillus strain AS2 and Salinicola strain LC26 or 37 °C for all other species (see Table 1 and Supplementary Table S1). (b) Haloarchaeal strains GN-2 and GN-5 shown in orange and black, respectively, cultured in bittern brines supplemented with peptone at 37 °C for 6 days (calculated and replotted against water activity using data from Javor, 1984). (c) A mixed halophile community (identified using DAPI; red line) and Bacteria within this community (quantified using molecular probes; black line) by inoculating a synthetic seawater medium with supplemented NaCl using crystalliser brine and incubating at 37 °C (calculated and replotted against water activity using data from Antón et al., 2000). (d) The archaeon Halobacterium strain 004.1 in a synthetic seawater medium supplemented with NaCl, MgCl2, Na2SO4 and KCl at 37 °C (see Materials and methods and Supplementary Table S2). (e) The bacterium Salinibacter ruber strain DSM 13855T in complex media supplemented with addition of water from the Dead Sea (0.812 to 0.777 aw) and without (0.840 aw) at 35 °C (yellow line) or complex media supplemented with NaCl and incubated at 37 °C (black line; calculated and replotted against water activity using data from Sher et al., 2004 and Peña et al., 2010; see also Materials and methods and Supplementary Table S6). (f) The bacterium Salisaeta longa strain DSM 21114T in complex media supplemented with addition of water from the Dead Sea (0.926 to 0.792 aw) at 35 °C (yellow line) or complex media supplemented with NaCl (black line; Materials and methods and Supplementary Table S7). For all media, water-activity values were determined as described in the Materials and methods and at the same temperature as incubation was carried out for each set of media. Curves were extrapolated via regression analyses (dotted lines; for details see Supplementary Table S1) in order to determine the theoretical water-activity minima for growth. Pink dashed lines indicate the previously accepted water-activity limit for extremely halophilic Bacteria and Archaea (see Brown, 1990; Grant, 2004; Kminek et al., 2010).
