Related Experiment Video
Updated: Aug 7, 2026
05:52
Separating Bacteria by Capsule Amount Using a Discontinuous Density Gradient
Published on: January 7, 2019
Characterization of Pasteurella multocida type B capsule biosynthesis proteins
Thomas R Smallman1, Chantelle M Cairns2, Frank St Michael2
1Infection Program, Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Victoria, Australia.
Infection and Immunity
|August 6, 2026
Summary
Researchers identified key proteins (BcbC, BcbE, BcbG, BcbH) essential for Pasteurella multocida type B capsule biosynthesis. These findings advance understanding of this animal pathogen
Area of Science:
- Bacteriology
- Molecular Biology
- Animal Health
Background:
- Pasteurella multocida causes severe animal diseases like hemorrhagic septicemia.
- Type B capsule is crucial for hemorrhagic septicemia, composed of N-acetyl glucosamine (GlcNAc) and N-acetyl mannosaminuronic acid (ManNAcA) with fructose and glycine side chains.
Purpose of the Study:
- To investigate the proteins involved in type B capsule biosynthesis in P. multocida strain M1404.
- To elucidate the roles of specific genes (bcbC, bcbE, bcbG, bcbH) in capsule production and structure.
Main Methods:
- Capsule absorbance assays, Alcian blue stains, and Western blots were used to assess capsule production and export.
- In-source collision-induced dissociation mass spectrometry determined capsule structure.
- Gene inactivation and heterologous expression were employed to study gene function.
Main Results:
- BcbC was identified as the likely capsule synthase.
- BcbE and BcbG are involved in fructose side chain addition, and BcbH is the probable glycine transferase.
- Inactivation of bcbE, bcbG, or bcbH significantly reduced capsule production. Heterologous expression of bcbABCDI produced the type B main chain in a capsule mutant.
Conclusions:
- The identified bcb genes are necessary and sufficient for the synthesis of the type B P. multocida capsule main chain.
- Understanding these genes provides insights into Pasteurella multocida pathogenesis and potential targets for control.
More Related Videos
Related Concept Videos
01:19Formation of Lipopolysaccharides
Lipopolysaccharides (LPS) are crucial components of the outer membrane of Gram-negative bacteria, serving both structural and functional roles. It contributes to membrane stability and protects bacteria from host immune responses. LPS is composed of three major regions—lipid A, a core oligosaccharide, and an O antigen. The biosynthesis and assembly of LPS involve a highly coordinated set of enzymatic reactions and transport mechanisms. Additionally, LPS is recognized as an endotoxin, triggering...
01:28Peptidoglycan Synthesis
Structure of PeptidoglycanPeptidoglycan is a vital structural component of the bacterial cell wall, providing mechanical strength and shape to the cell. It consists of repeating units of two sugars—N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)—linked by β-1,4 glycosidic bonds. These sugar chains are cross-linked by short peptide chains, forming a mesh-like polymer that surrounds the bacterial plasma membrane.Cytoplasmic Phase – Precursor SynthesisPeptidoglycan biosynthesis begins in...
01:23Inhibitors of Gram-positive Cell Wall Synthesis
Bacterial cell walls are typically rigid structures composed mainly of peptidoglycan, a mesh-like polymer that provides mechanical strength and maintains cell shape. The synthesis of peptidoglycan is a crucial process in bacterial growth and serves as a primary target for many antibiotics.Mechanism of Action of Beta-Lactam AntibioticsBeta-lactam antibiotics, such as penicillin, inhibit peptidoglycan synthesis in actively growing cells. These antibiotics share a characteristic four-membered...
01:28Regulation of Bacterial Virulence
Pathogenic bacteria employ a range of regulatory mechanisms to modulate the expression of virulence genes in response to environmental and host-derived signals. These mechanisms ensure that virulence factors are expressed only under favorable conditions, thereby optimizing infection and survival strategies.Mechanisms of Virulence RegulationKey regulatory strategies include:Two-Component Systems: These consist of a membrane-bound sensor kinase and a cytoplasmic response regulator. Environmental...
01:30Production of Pharmaceuticals
Industrial insulin production uses genetically engineered E. coli expressing a proinsulin gene controlled by a tryptophan promoter and containing a methionine linker for later cleavage. The cells also carry ampicillin resistance for selective growth. Seed cultures are stored at −80 °C and production begins by thawing a small amount to inoculate starter cultures, which are progressively scaled to a 50,000-L bioreactor. In the bioreactor, E. coli grow in nutrient-rich media under sterile, tightly...
01:18Outer Layers of the Cell Envelope
The outermost layers of prokaryotic cells play a critical role in their survival, virulence, and interaction with the environment. These layers, often composed of polysaccharides, polypeptides, or proteins, form protective and adhesive structures that vary in organization and function.Capsules and Slime LayersCapsules are highly organized, tightly bound layers that firmly attach to the bacterial cell wall. Capsules are usually made of polysaccharides, though some are made of polypeptides. These...