Isolation of rough mutants of Klebsiella aerogenes and their synthesis of polysaccharides.

Two mutants which lacked both capsular and lipopolysaccharide O-antigen polysaccharides were isolated from Klebsiella aerogenes serotype 2 by phage selection; these were designated rough mutants. The polysaccharide fractions solubilized by partial acid hydrolysis of the lipopolysaccharide from both the wild type and mutants were chromatographed on Sephadex G-50. Analysis of the fractions obtained confirmed that the rough mutants lacked the galactan portion of the molecule, which is analogous to the Salmonella O-antigen polysaccharide. Membranes prepared from wild-type K. aerogenes, from a non-mucoid strain (lacking capsule only), and from one of the rough mutants were used in incubation mixtures to compare the biosynthesis of polysaccharides by these organisms. The incorporation of sugar nucleotides into both lipid intermediates and polymer was followed. Results show that the transferases were apparently present in all membranes, while the polymerases were absent in both the non-mucoid and rough mutants.