pSW2, a Novel Low-Temperature-Inducible Gene Expression Vector Based on a Filamentous Phage of the Deep-Sea Bacterium Shewanella piezotolerans WP3

A low-temperature-inducible protein expression vector (pSW2) based on a filamentous phage (SW1) of the deep-sea bacterium Shewanella piezotolerans WP3 (WP3) was constructed. This vector replicated stably in Escherichia coli and Shewanella species, and its copy number increased at low temperatures. The pSW2 vector can be utilized as a complementation plasmid in WP3, and it also can be used for the production of complex cytochromes with multiple heme groups, which has the application potential for metal ion recovery or bioremediation. Promoters of low-temperature-inducible genes in WP3 were fused into the vector to construct a series of vectors for enhancing protein expression at low-temperature. The maximum GFP intensity was obtained when the promoter for the hfq gene was used. The WP3-pSW2 system can efficiently produce a patatin-like protein (PLP) from a metagenomic library that tends to form inclusion bodies in E. coli. The protein yield of PLP in the soluble fraction was 8.3 mg/liter and 4.7 mg/liter of culture at 4°C and 20°C, respectively. Moreover, the pSW2 vector can be broadly utilized in other Shewanella species, such as S. oneidensis MR-1 and S. psychrophila WP2.