Use of Lectins to Characterize the Receptor Sites for Bacteriophage PL-1 of Lactobacillus casei

Abstract

SUMMARY: The polysaccharide (PS) located outside the peptidoglycan layer in Lactobacillus casei ATCC 27092 was found to inhibit the adsorption of PL-1 phage to cell wall preparations without inactivating free phage. Electron microscopic examination of adsorption mixtures showed that the phage were adsorbed to fragments of PS material in a tail-first orientation. Phage did not adsorb to isolated peptidoglycan. The PS was composed of l-rhamnose, d-glucose, d-glucosamine and d-galactosamine, with the hexosamines possibly in N-acetylated form. Prior treatment of L. casei with Streptomyces haemagglutinin, an anti-human blood group B agglutinin that binds specifically to l-rhamnose, resulted in a concentration-dependent inhibition of phage adsorption. Phage adsorption was inhibited partially by lectins specific for d-glucose and N-acetyl-d-glucosamine, but not by lectins specific for N-acetyl-d-glucosamine or N-acetyl-d-galactosamine. The inhibition of phage adsorption occurred immediately upon the addition of the effective lectins, and was reversed by the addition of the respective lectin inhibitors, α-phenyl galactoside or α-methyl glucoside. The results indicate that l-rhamnosyl residues are the main determinants of the PL-1 phage receptor sites, while d-glucosyl residues may be involved more indirectly.