Changes in the Protein Composition of the Exiguobacterium sibiricum Membrane with Decreasing Temperature: A Proteomic Analysis

Objective: The psychrotrophic Gram-positive bacterium Exiguobacterium sibiricum, isolated from Siberian permafrost deposits, grows over a wide temperature range and remains viable after prolonged cryopreservation. To study its adaptation to environmental conditions, we investigated changes in the membrane proteome of the cells grown in a poor medium at 10°C. Methods: Proteins of the membrane fraction isolated from E. sibiricum were analyzed using the label-free quantitative liquid chromatography- tandem mass spectrometry. Results and Discussion: Comparison of the samples from the cells cultured at 10°C and at room temperature revealed significant differences in the content of many proteins involved in important physiological processes, including DNA and RNA binding proteins, membrane transporters, proteins providing protection against osmotic and oxidative stress, and others. Conclusions: The results of this study contribute to understanding of the mechanisms of the processes occurring in the cell membranes of psychrotrophic bacteria at low temperatures, and complement the existing views on the adaptation strategies of microorganisms living in permafrost deposits. The data obtained can also be used to search for potential biocatalysts with activity at low temperatures.