Effect of Growth Temperature and Culture Medium on the Cryotolerance of Permafrost Exiguobacterium Sibiricum 255-15 by Proteome-Wide Mass Mapping

Abstract

Exiguobacterium sibiricum 255-15 has shown significantly improved cryotolerance after liquid broth growth at 4 o C and agar surface growth at both 4 o C and 25 o C compared with liquid broth growth at 25 o C. The ability to survive freeze-thaw stress is expected to depend on the physiological state and protein composition of cells prior to freezing. Using 2-D liquid separation and an ESI-TOF MS-based mass mapping technique, we examined the differences in the proteomic profiles of the permafrost bacterium E. sibiricum 255-15 grown at two temperatures (4 o C and 25 o C) and two media (liquid broth and agar surface) before freeze-thawing treatments. In this study, a total of 330 proteins were identified. The cells cultured under the growth conditions associated with the improved cryotolerance have revealed a general downregulation of enzymes involved in major metabolic processes (glycolysis, anaerobic respiration, ATP synthesis, fermentation, electron transport, and sugar metabolism) as well as in the metabolism of lipids, amino acids, nucleotides and nucleic acids. In addition, eight proteins (2'-5' RNA ligase, hypoxanthine phosphoribosyl transferase, FeS assembly ATPase SufC, thioredoxin reductase and four hypothetical proteins) were observed to be up-regulated. This suggests these eight proteins might have a potential role to induce the improved cryotolerance.