Differentially expressed genes under simulated deep-sea conditions in the psychrotolerant yeast Cryptococcus sp. NIOCC#PY13.

Microorganisms exhibit varying degrees of tolerance to extreme conditions of pressure and temperature. In the present study, the psychrotolerant deep-sea yeast, Cryptococcus sp. NIOCC#PY13, was exposed to elevated hydrostatic pressure and low temperature to explore the differentially expressed genes responsible for its survival at such extreme conditions. The suppression subtractive hybridization technique was employed for identification of expressed upregulated genes at extreme conditions of pressure and temperature. The effect of elevated pressure was found to be different than that of combined pressure and temperature exposures. Altogether, 17 and 20 upregulated genes were identified at 50 MPa and 50 MPa/5 °C, respectively. These differentially expressed genes were similar to the NCBI database ESTs (expressed sequence tags), coding for proteins such as arachidonic acid metabolism, amino acid transport and unsaturation of membrane fatty acids, which have been previously demonstrated to assist in the survival of microorganisms under stress conditions. Interestingly, about 50 % of the upregulated genes matched with hypothetical proteins at a percentage similarity of ≤96, suggesting their probability of being novel. Detailed studies of the above genes/proteins from deep-sea microorganisms are suggested for future investigations, which may shed more light on the existence and adaptation mechanisms adopted by these for their survival under such extreme conditions.