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🦠microbiology review

Core Oligosaccharide

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

The core oligosaccharide is a critical component of the lipopolysaccharide (LPS) molecule found in the outer membrane of Gram-negative bacteria. It serves as a link between the lipid A and the O-antigen, providing structural integrity and playing a key role in the identification and classification of microorganisms.

5 Must Know Facts For Your Next Test

  1. The core oligosaccharide is composed of a conserved inner core region and a more variable outer core region.
  2. The inner core region typically contains unusual sugars, such as 3-deoxy-D-manno-octulosonic acid (Kdo) and heptoses, which are important for the structural integrity of the LPS molecule.
  3. The outer core region is more variable and can contain common monosaccharides, such as glucose, galactose, and N-acetylglucosamine, which contribute to the serological specificity of the LPS.
  4. The core oligosaccharide plays a crucial role in the attachment and anchoring of the O-antigen to the lipid A component, ensuring the structural integrity of the LPS molecule.
  5. Variations in the core oligosaccharide structure can be used to differentiate between different bacterial species and strains, making it a valuable tool in the biochemical identification of microorganisms.

Review Questions

  • Explain the function of the core oligosaccharide within the lipopolysaccharide (LPS) molecule and its significance in the identification of Gram-negative bacteria.
    • The core oligosaccharide serves as a critical link between the lipid A and the O-antigen components of the LPS molecule in Gram-negative bacteria. It provides structural integrity to the LPS and plays a key role in the attachment and anchoring of the O-antigen. Variations in the core oligosaccharide structure can be used to differentiate between different bacterial species and strains, making it a valuable tool in the biochemical identification and classification of Gram-negative microorganisms.
  • Describe the composition and structural features of the core oligosaccharide that contribute to its role in the LPS molecule and the identification of Gram-negative bacteria.
    • The core oligosaccharide is composed of a conserved inner core region and a more variable outer core region. The inner core typically contains unusual sugars, such as 3-deoxy-D-manno-octulosonic acid (Kdo) and heptoses, which are important for the structural integrity of the LPS molecule. The outer core region is more variable and can contain common monosaccharides, such as glucose, galactose, and N-acetylglucosamine, which contribute to the serological specificity of the LPS. These structural features of the core oligosaccharide allow for the identification and differentiation of Gram-negative bacterial species and strains based on their unique LPS composition.
  • Analyze the role of the core oligosaccharide in the overall structure and function of the lipopolysaccharide (LPS) molecule, and explain how this relates to the use of LPS in the biochemical identification of Gram-negative bacteria.
    • The core oligosaccharide plays a crucial role in the structural integrity and function of the lipopolysaccharide (LPS) molecule in Gram-negative bacteria. As the link between the lipid A and the O-antigen components, the core oligosaccharide ensures the proper anchoring and attachment of the O-antigen to the LPS. This structural feature is essential for the overall stability and endotoxic properties of the LPS molecule. Furthermore, variations in the core oligosaccharide composition, particularly in the outer core region, contribute to the serological specificity of the LPS. These unique structural differences can be leveraged in the biochemical identification and classification of Gram-negative bacterial species and strains, making the core oligosaccharide a valuable tool in microbial identification and characterization.