Abstract
Exiguobacterium sibiricum 255-15 has shown significantly improved cryotolerance after liquid broth growth at
4oC and agar surface growth at both 4oC and 25oC compared with liquid broth growth at 25oC. 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 (4oC and 25oC) 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.