PMC

Intracellular compatible solutes and radial growth rates of xerophile isolate JW07JP13 on MYPiA media supplemented with (A) a chaotropic (fructose at 2.6 M) or (B) a kosmotropic solute (sucrose at 2.2 M) over a range of incubation temperatures (+30 to +1.7 °C). Compatible solute concentrations are mean values calculated from extractions and analyses of three independent triplicate treatments, and the bars indicate SEM.

Growth profiles for two model psychrophiles. (A) M. frigida and (B) Psychrobacter urativorans on media supplemented with sucrose (continuous line), glucose (dashed line), and glycerol (dotted line) at either +1.7 °C (blue) or −5 °C (gray). Plots were constructed using Microsoft Office Excel 2007 based on growth-rate data shown in Table S2. Growth-rate units were derived by calculating the inverse of log (time taken for cultures to attain maximum colony density in weeks) (Table S2). Relative to the optimum activity of P. urativorans (B), growth rates were reduced by ≥85% under solute stress. By contrast, M. frigida (A) was able to retain high levels of activity even as solute concentrations increased.

Percentage survival of xerophile conidia for (A and B) isolate JH06GBM, (C and D) isolate JH06JPD, and (E and F) Xeromyces bisporus FRR 2347 that had been produced on MYPiA nutrient media and were harvested in liquid media, both of which had been supplemented with a chaotropic (A, C, and E; 4.5 M glycerol, 1.0 M MgCl₂, and 3.0 M fructose) or kosmotropic solute [B, D, and F; 2.9 M (NH₄)₂SO₄ and 2.2 M sucrose] and then exposed to low-temperature (−20 °C, light blue; −80 °C, dark blue), high-temperature (+55 °C, orange; +65 °C, red), or high-pressure treatments (300 MPa, gray; 750 MPa, black). One hundred conidia from each replicate spore suspension (i.e., 300 in total) were examined to determine percentage survival; plotted values are the means of these independent triplicates, and bars show SEM.

Growth of ecophysiologically diverse microbes on kosmotrope- and chaotrope-supplemented malt-extract, yeast-extract phosphate agar (MYPiA) nutrient media over a range of incubation temperatures. Radial growth rates of four xerophilic fungi [Eurotium herbariorum FRR 2418 (A–D), isolate JH06IN47 (E–H), E. herbariorum FRR 5354 (I–L), and isolate JW07JP13 (M–P)] on media with no added solute (control medium at 0.997 a_w shown in black), and media supplemented with kosmotropic (glucose at 3.8 M and 0.851 a_w shown in blue–black; sucrose at 2.2 M and 0.880 a_w shown in sky blue) or chaotropic solute(s) (fructose at 2.6 M and 0.929 a_w shown in red) at 30 °C (A, E, I, and M), 10 °C (B, F, J, and N), 5 °C (C, G, K, and O), and 1.7 °C (D, H, L, and P). Colony density of the psychrophile M. frigida DSM 70883 after incubation for 17 days (white), 24 days (hashed), 45 days (gray), and 59 days (black) at +1.7 °C and −5 °C on MYPiA supplemented with (Q) the kosmotropic solute sucrose (0.73 M and 0.982 a_w), and the chaotropic solutes (R) methanol (1.56 M and a_w not determined; SI Materials and Methods), (S) MgCl₂ (1.0 M and 0.934 a_w), and (T) glycerol (1.1 M and 0.978 a_w). Mean growth rates, calculated from three independent triplicate treatments, were plotted, and bars indicate SEM (A–P).