Related Experiment Videos
Endo-N-acetylneuraminidase associated with bacteriophage particles
Abstract:
A bacteriophage (phi 1.2) has been isolated for Escherichia coli K235 (O1:K1:H-). phi 1.2 is specific for the host capsular polysaccharide (colominic acid). The phage forms plaques with acapsular halos and thus carries a glycanase activity for colominic acid, a homopolymer of alpha (2 leads to 8)-linked N-acetylneuraminic acid (NeuNAc) residues. Upon incubation with purified phi 1.2 particles, a solution of K1 polysaccharide loses viscosity and consumes increasing amounts of periodate. Also, by gel filtration, the production of colominic oligosaccharides (down to a size of two to three NeuNAc residues) can be demonstrated. No NeuNAc monomers, however, are formed. The capsules of E. coli strains with the K92 antigen, which consists of NeuNAc residues linked by alternating alpha (2 leads to 8) and alpha (2 leads to 9) bonds, are also depolymerized by the phi 1.2 enzyme. Under the electron microscope, phage phi 1.2 is seen to belong to Bradley's morphology group C (D. E. Bradley, Bacteriol. Rev. 31:230-314, 1967); it has an isometric head, carrying a baseplate with six spikes. By analogy to other virus particles with host capsule depolymerase activity, it is probable that the phi 1.2 endo-N-acetylneuraminidase activity is associated with these spikes.
Insights
A novel bacteriophage, phi 1.2, specifically targets and degrades Escherichia coli K1 capsular polysaccharide (colominic acid). This phage exhibits glycanase activity, breaking down the N-acetylneuraminic acid polymer, and may have enzyme activity located on its spikes.
Area of Science:
- Microbiology
- Virology
- Biochemistry
Background:
- Escherichia coli K1 strains possess a capsular polysaccharide composed of N-acetylneuraminic acid (NeuNAc).
- Bacteriophages are viruses that infect bacteria and can exhibit specific host interactions.
- Understanding phage-host interactions is crucial for microbial research and potential therapeutic applications.
Purpose of the Study:
- To isolate and characterize a bacteriophage targeting Escherichia coli K1.
- To investigate the enzymatic activity of the isolated bacteriophage on capsular polysaccharides.
- To determine the morphology and potential enzyme localization of the bacteriophage.
Main Methods:
- Isolation and characterization of bacteriophage phi 1.2 from Escherichia coli K235.
- Assay of phage activity on purified K1 polysaccharide, measuring viscosity loss and periodate consumption.
- Analysis of polysaccharide degradation products using gel filtration.
- Electron microscopy for phage morphology determination.
Main Results:
- Bacteriophage phi 1.2 was isolated and shown to be specific for Escherichia coli K1 capsular polysaccharide (colominic acid).
- Phi 1.2 exhibits glycanase activity, depolymerizing colominic acid into oligosaccharides without forming monomers.
- The phage also depolymerizes the K92 antigen, which contains NeuNAc residues.
- Electron microscopy revealed phi 1.2 belongs to morphology group C, with spikes on its baseplate.
Conclusions:
- Bacteriophage phi 1.2 possesses endo-N-acetylneuraminidase activity specific for colominic acid and related structures.
- The glycanase activity is likely associated with the spikes on the phage's baseplate.
- This phage represents a valuable tool for studying bacterial capsule structure and function.