Enzymatic action of coliphage omega8 and its possible role in infection

Area of Science:

• Microbiology
• Virology
• Biochemistry

Background:

• Coliphage omega8 infects Escherichia coli O8 by recognizing its O-specific mannan receptor.
• The E. coli O8 mannan receptor is characterized by specific alpha-mannosyl-1,3-linkages within its trisaccharide structure.

Purpose of the Study:

• To investigate the enzymatic activity of coliphage omega8 responsible for degrading its receptor.
• To elucidate the role of the phage-associated enzyme in the initial stages of coliphage infection.

Main Methods:

• Characterization of coliphage omega8's endo-alpha-1,3-mannosidase activity.
• Enzyme kinetic studies (Km, Vmax) using purified lipopolysaccharide and phage particles.
• Assessment of receptor degradation on whole E. coli O8 bacteria using radiolabeling.

Main Results:

• Coliphage omega8 produces an endo-alpha-1,3-mannosidase that cleaves the alpha-1,3-mannosyl linkages of the E. coli O8 mannan receptor.
• The enzyme efficiently hydrolyzes linkages in lipopolysaccharide, mannan, and oligosaccharides, with decreasing efficiency.
• Kinetic analysis revealed a high affinity (Km = 5 x 10(-8) M) for supermicellar lipopolysaccharide substrate.

Conclusions:

• The endo-alpha-1,3-mannosidase is integral to coliphage omega8 particles and plays a key role in receptor destruction.
• Enzymatic degradation of the mannan receptor is likely a critical step in the early stages of coliphage omega8 infection.
• The enzyme's irreversible binding to E. coli O8 supports its proposed function in initiating the infection process.