1. A recombinant bacterial strain selected from the group consisting of Zymomonas and Zymobacter comprising a heterologous nucleic acid molecule encoding a polypeptide having xylose isomerase activity wherein the polypeptide is a Group I xylose isomerase and is included in the class of enzymes identified by EC 5.3.1.5, and wherein the strain utilizes xylose as a carbon source.