Bacteriophage‐associated glycan hydrolases specific for Escherichia coli capsular serotype K12

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Abstract
Four bacteriophages were identified, which carry glycan hydrolases specific for the Escherichia coli K12 capsular polysaccharide. All these glycanases catalyze the hydrolysis of the α‐l‐rhamnosyl‐1,5‐β‐3‐deoxy‐d‐manno‐2‐octulosonic acid linkage as demonstrated with a special thiobarbituric acid assay procedure, which discriminates between the C5 substituted and unsubstituted 3‐deoxy‐d‐manno‐2‐octulosonic acid (dOclA). This assay, together with gel filtration, 1H‐NMR and 13C‐NMR spectroscopy showed that depolymerization led to the dimer of the K12 repeating unit, (,5‐β‐dOcl1Ap‐2,3‐α‐lRhap‐1,2‐αlRhap1,)2, as the primary degradation product. The phages (φ12‐W, φ12‐S, φ82‐W1, φ82‐W2) were tested for their ability to infect Escherichia coli strains Su65‐42 (O4:K12:H−) and CDC63‐57 [O139:K82(12):H1]. φ12‐W and φ12‐S, respectively, infected strain Su65‐42 only, φ82‐W2 CDC63‐57 only, and φ82‐W1 both bacterial strains. These distinct host specificities cannot be explained by differences in the action of the glycanases, which depolymerisze the capsules of both strains.

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