Organization of the Escherichia coli K-12 gene cluster responsible for production of the extracellular polysaccharide colanic acid

The sequence of K-12 chromosome in Escherichia coli, which includes a 19-gene cluster responsible for the production of colanic acid, has been determined. The cluster includes genes for GDP-L-fucose synthesis and for the enzyme, GDP-D-mannose 4,6-dehydratase involved in this pathway. The first three genes encode a phosphatase, an outer and an inner membrane lipoprotein, and have homologs in other extracellular polysaccharide gene clusters. These help in the transport of polysaccharide from the cell.