Notice: This is an archived and unmaintained page. For current information, please browse

2005 Annual Science Report

Michigan State University Reporting  |  JUL 2004 – JUN 2005

Transcriptomes of Permafrost Bacteria

4 Institutions
3 Teams
0 Publications
0 Field Sites
Field Sites

Project Progress

Bacteria in the Siberian permafrost environment must contend with low temperatures (-10°C) and low water activity (aw=0.85-0.9). To gain knowledge of microbial adaptation to low temperature and low water activity, the genome of a Siberian permafrost isolate, Psychrobacter arcticus 273-4, was sequenced and gene expression monitored using microarrays consisting of 70-mer oligonucleotides representing the large majority of predicted genes for this bacterium. Only a few genes known to be low temperature and salt responsive in certain mesophiles and psychrotrophs were differentially expressed in P. arcticus, although many were constitutively expressed. Experiments reveal that shifting P. arcticus from 22°C to 4°C resulted a 2-fold increase in transcripts for certain transport-associated and metabolic genes. Genes for increased synthesis and uptake of compatible solutes were up-regulated in the presence of high salinity (5% NaCl) which may help balance the cell’s internal osmolarity. Several genes with unknown functions were also up-regulated in response to low temperature and high salinity, which may indicate their importance in stress survival. Growth in 5% NaCl-amended 1/2 TSB lead to induction of capsule synthesis genes. A capsule was visible around cells grown at both 22°C and 4°C that could allow P. arcticus to adhere to soil particles within the permafrost. In addition, total respiratory activity increased in the presence of high salt (5% NaCl), perhaps due to increased expression of genes encoding a Na+-dependent dehydrogenase and a decarboxylase, suggesting that P. arcticus has adapted for energy generation in the low temperature and low water activity of the permafrost environment.

    Michael Thomashow Michael Thomashow
    Project Investigator
    James Tiedje

    Corien Bakermans

    Peter Bergholz
    Doctoral Student

    Monica Ponder
    Doctoral Student

    Objective 5.1
    Environment-dependent, molecular evolution in microorganisms

    Objective 5.3
    Biochemical adaptation to extreme environments

    Objective 7.2
    Biosignatures to be sought in nearby planetary systems