Production of K5 polysaccharides of different molecular weight by Escherichia coli

An investigation was made of the molecular weight of the Escherichia coil antigenic K5 polysaccharide. Two components with molecular weights of 16,000 and 1,500 were observed. The ratio of these two components depended on a lyase produced by the same E. coli. This lyase acts by a beta-elimination mechanism to depolymerize the K5. At the end of the fermentation the thermally treated (to inactivate the lyase) and untreated twenty-four-hour-old cultures each contained two K5 components of different M(w), in different ratios. The two components were monitored over a fermentation time-course. C-13-NMR spectrometry was employed to verify the lyase mechanism of action.