Construction of a shuttle expression vector with a promoter functioning in both halophilic Archaea and Bacteria.

A shuttle expression vector, designated as pAJ, was constructed based on the Haloferax volcanii-Escherichia coli shuttle vector pSY1. This new construct contains the amyH promoter from Haloarcula hispanica and was able to confer the promoter activity in both Hfx. volcanii and E. coli. pAJ successfully expressed proteins in Hfx. volcanii or E. coli, rendering it feasible to express target proteins in corresponding domains. In addition, pAJ contains a multiple cloning site with 11 restriction sites and a 6×His tag sequence, and the vector size was decreased to 8903 bp. To the best of our knowledge, pAJ is the first reported shuttle expression vector that can express proteins in both Bacteria and Archaea. Importantly, pAJ can even express the haloarchaeal heat shock protein DnaK in both domains. In conclusion, this novel vector only provides researchers with a new means to manipulate genes or express proteins in Haloarchaea but also serves as a convenient tool for the comparative study of the function of some highly conserved genes in Haloarchaea and in Bacteria.