Microarray transcriptional profiling of Arctic Mesorhizobium strain N33 at low temperature provides insights into cold adaption strategies

Arctic Mesorhizobium strain N33 was isolated from nodules of the Oxytropis arctobia in Canada’s eastern Arctic. This symbiotic bacterium can grow from 0 to 30°C, is one of the best known cold-adapted rhizobia, and can fix nitrogen at ~10°C. Here, the key molecular mechanisms of cold adaptation were investigated by determining changes in transcript profiles when cells were treated under eight different temperature conditions, including both sustained and transient cold treatments compared with cells grown at room temperature. The analysis used Arctic strain N33 (growth at room temperature) RNA as control (reference) samples for comparison to the experimental samples collected under constant growth at 4°C and 10°C, and five different cold treatment conditions at 2, 4, 8, 60, and 240 min (three biological replicates for each treatment). Dual-dye hybridizations were performed including three biological replicates and two technical replicates (dye flip, Cy5/Cy3) for each treatment for a total of 42 array hybridizations and 84 labelling reactions