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Escherichia coli capsule bacteriophages. IV. Free capsule depolymerase 29.

W Bessler, F Fehmel, E Freund-Mölbert

Journal of Virology

|April 1, 1975

Summary

The purified depolymerase from Escherichia coli bacteriophage 29 is identical to free phage 29 spikes. This enzyme degrades host capsule polysaccharides, aiding in phage infection and plaque formation.

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Area of Science:

Microbiology
Molecular Biology
Biochemistry

Background:

Bacteriophages are viruses that infect bacteria.
Escherichia coli capsule bacteriophage no. 29 produces a depolymerase enzyme.
This enzyme causes haloes around phage plaques, indicating host cell lysis.

Purpose of the Study:

To purify and characterize the depolymerase enzyme.
To determine if the depolymerase is identical to phage 29 spikes.
To understand the role of depolymerase in bacteriophage infection.

Main Methods:

Purification of depolymerase to homogeneity.
Analysis of molecular weight by sedimentation equilibrium.
Determination of polypeptide chain sizes using SDS-PAA gel electrophoresis.

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Enzymatic activity assays on host capsular polysaccharide.

Electron optical imaging for structural comparison.

Main Results:

Purified depolymerase and phage 29 spikes share identical molecular weight, polypeptide composition, sedimentation coefficient, isoelectric point, and amino acid composition.
Both depolymerase and phage spikes hydrolyze host capsular polysaccharide into oligosaccharide fragments.
Phage 29 infection produces significantly more free depolymerase than incorporated spikes.

Conclusions:

The free depolymerase is composed of phage 29 spikes.
Phage spikes function as depolymerases, essential for degrading the bacterial capsule.
This mechanism facilitates phage entry and replication within the host bacterium.