Depolymerases for Bacterial Exopolysaccharides obtained from Phage-Infected Bacteria

Abstract

SUMMARY: Several bacteriophages have been isolated which, in association with the host bacteria, produce enzymes that depolymerize the exopolysaccharide of Escherichia coli K12 and other slime polysaccharides of the same chemical type. Chemical analyses show the similarity of the polysaccharides produced by E. coli K12, by other E. coli strains and by Aerobacter cloacae NCTC 5920: all contain 28-33% fucose, 16-19% glucose, 25-28% galactose, 14-22% glucuronic acid. The action of the depolymerizing enzymes greatly decreases the viscosity of the polysaccharide solutions but does not liberate any fragments of low molecular weight. Partial purification of the enzymes was achieved by ammonium sulphate precipitation and chromatography on DEAE-cellulose. The enzymes are active against exopolysaccharides produced by bacteria in which the phages are unable to multiply. Evidence is presented to show that the structural genes for enzyme production are located on the phage genome rather than on the bacterial genome. One of the enzyme systems was unusual in that it was only produced following phage infection and lysis of mucoid host strains. Its production was induced by the polysaccharide substrate.