To construct efficient transformation and expression system and further improve desulfurizing activity of cells through expression of Vitreoscilla hemoglobin (VHb) in haloalkaliphilic Thialkalivibrio versutus SOB306. We transferred plasmids pKT230 and pBBR-sm(r) into T. versutus SOB306 via a conjugation method. We identified four promoters from among several predicted promoters by scoring for streptomycin resistance, and finally selected tac and p3 based on the efficiency of expression of red fluorescent protein (RFP). Expression of RFP when regulated by tac was more than three times that of p3 in SOB306. Further, we expressed VHb under the control of tac promoter in SOB306. Expression of VHb was verified using CO-difference spectra. The results showed that VHb expression can boost sulfur metabolism, as evidenced by an increase of about 11.7 +/- 1.8% in the average rate of thiosulfate removal in the presence of VHb. A conjugation transfer and an expression system for Thialkalivibrio, has been developed for the first time and used for expression of VHb to improve desulfurizing activity.