A bacterium yielding a polysaccharide with unusual properties

A yellow-pigmented bacterium, isolated in Czapek-Dox medium, yielded copious quantities of extracellular polysaccharide. Liquid cultures became bright yellow and increasingly viscous after incubation for 4–6 d. Characterization tests indicate that it is a starch-negative (amylase-negative), gelatinase-positive strain of Pseudomonas paucimobilis , closely resembling an organism previously described as Pseudomonas elodea. The polysaccharide contained L-rhamnose and D-glucose in a molar ratio of 0.66 : 1.0, together with 16% D-glucuronic acid and 10.4% acetate. Solutions of the polysaccharide were highly viscous: certain ions tended to cause gelation of aqueous solutions. After deacetylation with mild alkali the polymer at a concentration of 0.8% yielded a strong gel.