["Arctic Mesorhizobium strain N33 was isolated from nodules of the legume Oxytropis arctobia in Canada's eastern Arctic. This symbiotic bacterium can grow at temperatures ranging from 0 to 30\xa0°C, fix nitrogen at 10\xa0°C, and is one of the best known cold-adapted rhizobia. Despite the economic potential of this bacterium for northern regions, the key molecular mechanisms of its cold adaptation remain poorly understood.", 'Using a microarray printed with 5760 Arctic Mesorhizobium genomic clones, we performed a partial transcriptome analysis of strain N33 grown under eight different temperature conditions, including both sustained and transient cold treatments, compared with cells grown at room temperature. Cells treated under constant (4 and 10\xa0°C) low temperatures expressed a prominent number of induced genes distinct from cells treated to short-term cold-exposure (<60\xa0min), but exhibited an intermediate expression profile when exposed to a prolonged cold exposure (240\xa0min). The most prominent up-regulated genes encode proteins involved in metabolite transport, transcription regulation, protein turnover, oxidoreductase activity, cryoprotection (mannitol, polyamines), fatty acid metabolism, and membrane fluidity. The main categories of genes affected in N33 during cold treatment are sugar transport and protein translocation, lipid biosynthesis, and NADH oxidoreductase (quinone) activity. Some genes were significantly down-regulated and classified in secretion, energy production and conversion, amino acid transport, cell motility, cell envelope and outer membrane biogenesis functions. This might suggest growth cessation or reduction, which is an important strategy to adjust cellular function and save energy under cold stress conditions.'] Does microarray transcriptional profiling of Arctic Mesorhizobium strain N33 at low temperature provide insights into cold adaption strategies?