The Glaesserella parasuis phosphoglucomutase is partially required for lipooligosaccharide synthesis

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Pathogenesis

Background:

• Lipooligosaccharides (LOSs) are key virulence factors in Glaesserella parasuis, a significant swine respiratory pathogen.
• Previous studies highlighted the importance of the galactose catabolism pathway for G. parasuis polysaccharide synthesis and serum resistance.

Purpose of the Study:

• To investigate the function of the HAPS_0849 gene in the lipooligosaccharide (LOS) synthesis pathway of Glaesserella parasuis.
• To characterize the biochemical activity of the HAPS_0849 protein and its role in G. parasuis virulence phenotypes.

Main Methods:

• Gene disruption of HAPS_0849 in G. parasuis SC096 and analysis of resulting LOS structure.
• Overexpression, purification, and biochemical assays of the HAPS_0849 protein to determine its enzymatic activity.
• Heterologous expression of an Escherichia coli pgm gene in the HAPS_0849 mutant to assess functional complementation.
• Evaluation of autoagglutination and biofilm formation in the HAPS_0849 mutant strain.

Main Results:

• The HAPS_0849 mutant exhibited a truncated LOS molecule and increased sensitivity to porcine serum.
• Biochemical assays confirmed that HAPS_0849 possesses phosphoglucomutase (PGM) activity, essential for LOS biosynthesis.
• Complementation with an E. coli pgm gene restored the wild-type LOS glycoform, validating HAPS_0849's PGM function.
• HAPS_0849 disruption led to increased autoagglutination and biofilm formation, particularly in the absence of glucose.

Conclusions:

• HAPS_0849 plays a significant role in G. parasuis LOS synthesis, likely functioning upstream of GalU in glucose 1-phosphate generation.
• The gene is partially required for LOS synthesis and contributes to bacterial virulence by influencing serum resistance and surface-associated behaviors.