BSi20429. Some of the recent studies of cold-adapted expression vectors that are able to direct the expression of thermo-labile and psychrophilic proteins

in psychrophilic bacteria are summarized in Table 3. Papa et al. (2007) constructed a cold-inducible expression system LDK378 by cloning into the vector pUCLT/Rtem (Tutino et al., 2002) a regulatory region from P. haloplanktis TAC125 that regulates a functional two-component system involved in the expression of a C4-dicarboxylate transporter, which is induced by l-malate (Papa et al., 2009). The inducible expression vector (pUCRP) contains a σ54-dependent promoter that is activated by the transcription factor, MalR, in response Sorafenib to the presence of l-malate. It has provided a valuable system for the production of ‘difficult’ proteins and biopharmaceuticals such as antibodies (Papa et al., 2007; Giuliani et al., 2011). These developments illustrate the great value of Antarctic plasmids as cold-adapted expression vectors and the huge potential of Antarctic bacteria, such as Pseudoaltermonas

strains, in the development of stable expression systems for high-level production of recombinant proteins. We recommend Rippa et al. (2012) and Parrilli et al. (2008) for a full description of effective inducible expression systems in cold-adapted 3-mercaptopyruvate sulfurtransferase bacteria and evaluation of optimal production of homologous or heterologous proteins. Hyper-thermophilic indole-3-glycerol-phosphate synthase mesophilic β-lactamase psychrophilic disulfide oxidoreductase Psychrophilic β-galactosidase mesophilic yeast α-glucosidase It has been shown that the expression of only a few genes from cold-adapted

microorganisms in mesophilic hosts allows them to grow at much lower temperatures, and they even become heat-sensitive. For example, the heterologous expression of chaperonin-encoding cpn60 and cpn10 genes from the psychrophilic bacterium Oleispira antarctica enables E. coli to grow at 5 °C (Ferrer et al., 2003). Substitution of psychrophilic gene orthologs of ligA (NAD-dependent DNA ligase) into the mammalian pathogenic strains Francisella tularensis, Salmonella enterica and Mycobacterium smegmatis, resulted in temperature-sensitive phenotypes (Duplantis et al., 2010). On the basis of these reports, Lorenzo (2010) argues that cold adaptation is just a survival trait that can be acquired by HGT of only a few genes among various bacterial species and thus changes their niche specificity leaving the rest of the genetic and physiological chassis untouched. Antarctica possesses a flourishing bacterial population actively modulated by many evolutionary forces.