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Project Progress

Global protein profiling and comparative proteomic analysis of two bacterial strains that were isolated from Siberian permafrost, Psychrobacter 273-4 and Exiguobacterium 255-15, have been performed using two-dimensional HPLC and mass spectrometry. The results with Psychrobacter 273-4 indicate that more than 50 proteins were differentially regulated in response to a temperature shift from 22°C to 4°C. Of the cold-induced proteins, 14 had roles in translation indicating a need for major modifications of the translational apparatus at low temperature. In addition, there were increases in the levels of certain chaperons including HSP60 and HSP10 and a putative cold shock protein related to Escherichia coli CspA. Changes in the levels of more than 50 proteins were also observed to occur in response to high salinity (5% NaCl), most of which were in common with those affected by low temperature. Significantly, the transcript levels for many of the differentially expressed proteins did not change in response to low temperature or salinity indicating that these genes are regulated by posttranscriptional control mechanisms. Similar experiments with Exiguobacterium 255-15 have resulted in the detection of some 800 proteins, of which, about 60 were differentially expressed (by a factor of at least 5-fold) in response to a temperature downshift from 25°C to 4°C. Efforts are now in progress to determine the identities of these proteins. The long term goal is to determine whether the differentially expressed proteins of Psychrobacter 273-4 and Exiguobacterium 255-15 have critical roles in adaptation to low temperature and low water activity, conditions that are fundamental to the Siberian permafrost environment.