A plasmid pSDK-1 containing the Escherichia coli phosphofructokinase-1 gene (pfkA) was constructed, and transferred into Acidithiobacillus thiooxidans Tt-7 by conjugation. The pfkA gene from E. coli could be expressed in this obligately autotrophic bacterium but the enzyme activity (18 U g(-1)) was lower than that in E. coli ( K12: 86 U g(-1); DF1010 carrying plasmid pSDK-1: 97 U g(-1)). In the presence of glucose, the Tt-7 transconjugant consumed glucose leading to a better growth yield.