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Escherichia coli capsule bacteriophages. VII. Bacteriophage 29-host capsular polysaccharide interactions
Abstract:
Different interactions between particles of Escherichia coli capsule bacteriophage 29 and its receptor, the E. coli serotype 29 capsular polysaccharide have been studied. The inactivation of phage 29 (8 x 10(3) PFU/ml) by isolated host capsular glycan was found to be physiologically insignificant (50% inactivation dose equals 100 mug after 1 h at 37 C). No adsorption (less than 2 x 10(4) PFU/mug) of the viruses to K29 polysaccharide-coated erythroyctes (at 0 or 37 C) was observed either. The phage particles were, however, found to catalyze the hydrolysis of beta-D-glucosido-(1leads to 3)-D-glucuronic acid bonds (arrow) in the receptor polymer, leading, ultimately, to the formation of a mixture of K29 hexasaccharide (one repeating unit), dodecasaccharide, and octadecasaccharide: (see article). Testing derivatives of K29 polysaccharide, as well as 82 heterologous bacterial (mainly Enteriobactericeae) capsular glycans, the viral glycanase was found to be highly specific; in accordance with the host range of phage 29, only one enzymatic cross-reaction (with the Klebsiella K31 polysaccharide) was observed. These and previous results, as well as the electron optical findings of M. E. Bayer and H. Thurow (submitted for publication), are discussed in terms of a unifying mechanism of phage 29-host capsule interaction. We propose that the viruses penetrate the capsules by means of their spike-associated glycanase activity, which leads them along capsular polysaccharide strands to membrane-cell wall adhesions where ejection of the viral genomes occurs.
Insights
Bacteriophage 29 uses its glycanase activity to break down Escherichia coli capsular polysaccharides, facilitating viral entry and genome ejection. This enzyme shows high specificity for its host receptor.
Area of Science:
- Microbiology
- Virology
- Biochemistry
Background:
- Bacteriophage 29 interacts with Escherichia coli serotype 29 capsular polysaccharide.
- Understanding phage-host interactions is crucial for phage therapy and molecular biology.
Purpose of the Study:
- To investigate the interaction mechanisms between bacteriophage 29 and its E. coli K29 receptor.
- To elucidate the role of phage enzymes in host cell entry.
Main Methods:
- Studied phage inactivation by isolated host capsular glycan.
- Assessed virus adsorption to polysaccharide-coated erythrocytes.
- Analyzed phage-catalyzed hydrolysis of specific glycosidic bonds in the receptor polymer.
- Tested specificity using various polysaccharide derivatives and heterologous glycans.
Main Results:
- Phage 29 inactivation by isolated K29 glycan was physiologically insignificant.
- No significant adsorption of phage 29 to K29 polysaccharide-coated erythrocytes was observed.
- Phage 29 particles catalyzed hydrolysis of beta-D-glucosido-(1->3)-D-glucuronic acid bonds in the K29 polysaccharide.
- The viral glycanase demonstrated high specificity, with one cross-reaction observed with Klebsiella K31 polysaccharide.
Conclusions:
- Phage 29 possesses spike-associated glycanase activity that hydrolyzes host capsule components.
- This enzymatic activity is proposed to mediate phage penetration through the capsule.
- The mechanism facilitates movement along polysaccharide strands to cell-wall adhesions for genome ejection.