Identification of regulatory sequences and expression analysis of OmpR gene under different stress conditions in the antarctic bacterium Psychrobacter sp. G.

An OmpR gene, named OmpR503, was cloned from the Antarctic psychrotrophic bacterium Psychrobacter sp. G according to its genomic draft. The deduced amino acid sequences of OmpR503 were highly conserved with other known protein members of OmpR family. qRT-PCR analysis showed that the expression of OmpR503 gene was significantly enhanced by high salinity (90, 120). The expression of OmpR503 gene was also significantly increased at low temperature (0, 10 °C), whereas depressed at high temperature (30 °C). When the strain was subjected to combined stress (0 °C with a salinity of 90), the expression of OmpR503 gene was increased significantly, which was up to 3.0-fold. In Antarctica, freezing tolerance of psychrotrophic bacteria is often accompanied by tolerance to osmotic stress caused by a lack of free water, thus the cold inducibility of OmpR503 gene might help the strain adapt to the harsh environment more efficiently.