Molecular Cloning of cspA Homologous Gene in Psyclophilic and Moderately Barophilic Bacterium, Shewanella sp. Strain DSS12
Shinsuke FUJII*, Kaoru NAKASONE, and Koki HORIKOSHI
The DEEPSTAR group, Japan Marine Science & Technology Center, 2-15 Natsushima-cho, Yokosuka 237, JAPAN
Stress response in living organisms is an essential defense mechanism for cells to survive under ever-changing environmental conditions such as ionic strength, pHs, metal ions, temperatures, nutrients and so on. In contrast to heat shock response, cellular response to temperature down-shift has not been well understood, in spite of the fact that in nature, the exposure of living organisms to lower temperature is constantly happening, probably more frequently than the exposure to higher temperatures.
A family of cold shock proteins (CSPs) sharing highly conserved sequences (>45% identity) have been recognized in a variety of Gram-positive and Gram- negative bacteria. In Bacillus subtilis, B. cereus and Escherichia coli, three, six and seven CSPs, respectively, have been found, suggesting an important function for this protein family.
In a variety of bacteria, CSPs have been shown to be strongly induced in response to cold shock, so they have been proposed to function in the process of adaptation to low temperature. Indeed, among the E. coli cold shock proteins, CspA, has been shown to function as an RNA chaperone.
Shewanella Sp. strain DSS12 is a psyclophilic and moderately barophilic bacterium which was isolated from the mud of the Ryukyu Trench (5110m depth) collected by the SHINKAI 6500 System. This bacterium displays optimal growth at a temperature of 8℃ and at a pressure of 30 MPa, and exhibits almost the same growth under pressure of 0.1 MPa or 50 MPa. A pressure-regulated operon in this bacterium has been isolated and characterized by Kato et al (1).
We have been isolated some positive clones from DNA library of strain DSS 12 by plaque hybridization with E. coli cspA as a probe. One of them was subcloned and sequenced. We also compared strain DSS 12 with E. coli on the basis of the upstream and downstream regions of the cspA. This is the first report that cspA homologous gene is isolated in barophilic bacteria as well as psyclophilic bacteria.
1. Kato, C., Ikegami, A., Smorawinska, M., Usami, R., and Horikoshi, K. (1997) J. Mar. Biotecnol., 5, 210-218.
