The bacterium Rhodococcus sp. IGTS8 contains the dsz operon encoding enzymes for the 4S pathway, which enables it to use dibenzothiophene (DBT... Show moreThe bacterium Rhodococcus sp. IGTS8 contains the dsz operon encoding enzymes for the 4S pathway, which enables it to use dibenzothiophene (DBT), an organic sulfur containing molecule found in petroleum, as the sole source of sulfur for its metabolism. The gene vgb from Vitreoscilla encoding hemoglobin (VHb) has been widely studied and is used for improving the usefulness of a large number of heterologous hosts, like prokaryotes, lower eukaryotes and even higher plants. We produced the engineered strain IGTS8[pRESX-vgb] in which vgb was introduced into Rhodococcus sp. IGTS8. We measured the growth and the ability of desulfurization of DBT for this transformed strain (compared to the untransformed host) under both high and low aeration conditions. From CO-difference spectra, we found that VHb was successfully expressed in this transformant and the expression level was similar to that in certain other heterologous hosts. The transformant had much greater growth than untransformed IGTS8, cultured under both high and low aeration in CDM with DBT as the only sulfur source (the transformed strain outgrew the untransformed strain by about 380 % under high aeration and 68 % under low aeration). Unfortunately, we found that the color of the product from reaction of the Gibbs reagent with the final metabolite of DBT produced by the transformant was not blue. This did not allow us to directly compare the desulfurization abilities of the transformant and the untransformed strain. We did another experiment to prove that IGTS8[pRESX-vgb] still used DBT as its sole source of sulfur by culturing this transformant in CDM without DBT. IGTS8[pRESX-vgb] cannot grow in CDM without DBT. One possible explanation for this result is that the final product of the 4S pathway in the transformant may be converted to a form other ix than 2-HBP. In any case, the much better growth of the transformant compared to that of the untransformed strain provides indirect evidence that VHb does enhance biodesulfurization. M.S. in Biology, May 2014 Show less
