Abstract

A new gene organization related to carbohydrate metabolism of Citrobacter species has been identified on about 4.1 kb chromosomal DNA fragment. Sequence analysis revealed four open reading frames (ORFs), and gene orders were determined to be PTS system mannitol-specific transporter subunit EIICBA (MtlA), L-sorbose-1-phosphate reductase (SorE), class II fructose-1,6-biphosphatase (GlpX), and mannitol repressor (MtlR). The deduced amino acid sequences of these ORFs showed more than 80% identities to MtlA,SorE, GlpX, and MtlR of Escherichia coli, Shigella, and Salmonella enterica, respectively. The sorE gene was heterologously expressed in E. coli. The recombinant SorE clearly showed the L-sorbose-1-phosphate reductase activity.

Key words: Citrobactor sp., gene organization, carbohydrate catabolism, L-sorbose 1-phosphate reductase, gene expression.