Characterization and solution properties of a new exopolysaccharide excreted by the bacterium Alteromonas sp. strain 1644.

This paper concerns the study of a new bacterial exopolysaccharide. The ionic properties of the polymer are considered in relation to the first structural results. This polysaccharide is a carboxylic polyelectrolyte with a charge parameter of 1.33, and exhibits usual polyelectrolyte properties with monovalent and Mg2+ ions. In contrast, its affinity for the divalent ions Ca2+, Sr2+ and Ba2+ is greater than predicted from electrostatic theory. In solution, the polysaccharide undergoes a local conformational transition related to the number of divalent ions bound per carboxylic group. This interaction is mainly an intramolecular process. The dimensions of the polymeric chain were also considered using light-scattering and viscometric measurements. The intrinsic persistence length Lp is equal to 80 +/- 5 A and allows this polymer to be classified as a semi-rigid chain.