Influence of nutrient media on the characteristics of the exopolysaccharide produced by three mucoid Pseudomonas aeruginosa strains.

Mucoid strains of Pseudomonas aeruginosa of the 'gelatinous' (strain PM1) and 'mucoid' (strains PM3 and PM11) types (Wahba and Darrell, 1965), from cystic fibrosis patients were grown on different nutrient media, in liquid and on solid matrix, and their ability to synthesize uronic acid-containing exopolysaccharide of varying molecular sizes was assessed. Strain PM1 produced the exopolysaccharide in all liquid media tested. However, the exopolysaccharide was always polydispersed when citrate was present but monodispersed and of high molecular weight (HMW) in its absence. Strain PM1 also formed non-mucoid colonies on some solid media and on those media no exopolysaccharide was produced. On media, on which the organism was always mucoid monodispersed, HMW exopolysaccharide was recovered. Strains PM3 and PM1 produced monodispersed, HMW exopolysaccharide in liquid MacConkey's and V-8 media, but polydispersed or no exopolysaccharide in ll other liquid media tested. On MacConkey's agar these strains were mucoid initially but appeared non-mucoid as the cultures aged. This colonial change was accompanied by a quantitative and qualitative change in the exopolysaccharide. In media on which these strains produced only non-mucoid colonies little or no exopolysaccharide was recovered. Crude enzyme preparations from all three strains indicate that enzyme(s) capable of depolymerizing the indigenous exopolysaccharide exist in each organism.