Brucella abortus choloylglycine hydrolase affects cell envelope composition and host cell internalization

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Molecular Biology

Background:

• Choloylglycine hydrolase (CGH) is a bacterial enzyme hydrolyzing conjugated bile acids.
• Brucella species cause brucellosis and utilize CGH for bile salt resistance and oral infection.
• Previous studies suggested CGH has roles beyond bile salt hydrolysis in Brucella virulence.

Purpose of the Study:

• To elucidate the multifaceted role of CGH in Brucella abortus virulence.
• To investigate the impact of CGH on host cell interaction and bacterial physiology.

Main Methods:

• Generation and characterization of a cgh-deletion mutant (Δcgh) in Brucella abortus.
• Infection assays with phagocytic and epithelial cells.
• Analysis of bacterial cell envelope protein composition using 2D electrophoresis and Western blotting.

Main Results:

• The Δcgh mutant exhibited defects in host cell internalization.
• The mutant showed increased resistance to polymyxin B, indicating altered cell envelope properties.
• Altered expression of outer membrane proteins Omp2b and the Omp25/31 family was observed in the Δcgh mutant.

Conclusions:

• Brucella CGH plays a dual role in virulence: bile salt deconjugation and modulation of cell envelope composition.
• CGH influences Brucella's ability to internalize host cells.
• These findings reveal novel functions of CGH in bacterial pathogenesis beyond bile salt metabolism.