Poster Presentation Lorne Infection and Immunity 2023

Helicobacter pylori extracellular vesicles contain urease and catalase which promote bacterial survival (#121)

Nina Colon 1 , Liam Gubbels 1 , Richard L Ferrero 1 2 3
  1. Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, VIC, Australia
  2. Biomedicine Discovery Institute, Department of Microbiology, Monash University , Clayton, Victoria, Australia
  3. Department of Molecular and Translational Science, Monash University, Clayton, Victoria, Australia

Extracellular vesicles (EVs) are released during bacterial growth and contain various cargo involved in pathogenesis. Proteomic studies showed that the gastric pathogen Helicobacter pylori produces EVs containing urease (UreA, UreB) and catalase (KatA), known to be essential for its survival and colonisation in the stomach. Nevertheless, little is known regarding the functional properties of these enzymes in EVs. We hypothesised that functionally active urease and catalase within H. pylori EVs may promote bacterial survival. To address this hypothesis, we first characterised the urease and catalase activities of H. pylori wild-type (WT) EVs and corresponding sonicated preparations of the whole bacteria. Western blotting confirmed the presence of UreA, UreB, and KatA subunits within sonicates and EVs. Bacterial sonicates and EVs had: urease activities of 0.618 ± 0.084 and 0.45 ± 0.099 µmol/min/mg protein, respectively (p=0.270); and catalase activities of 770.64 ± 10.51 and 729.36 ± 13.76 µmol/min/mg protein, respectively (p=0.076). These results indicate that EV-associated urease and catalase activities are comparable to those of the whole bacteria. Following this finding, we aimed to determine the impact of the EV-associated enzymes on bacterial survival under environmental stresses. H. pylori ureA and ureB mutant bacteria were challenged for one hour at pH 3.5 with and without EVs isolated from an H. pylori WT strain. Bacteria treated with WT EVs (100 µg/mL) showed 2.7- and 2.5-fold increases in survival of ureA and ureB mutants, respectively, compared to non-treated bacteria. Similarly, the survival of katA mutant bacteria in 10 mM H2O2 after 1 hour was restored to that of the WT in the presence of WT EVs (40 µg/mL). Together, these data highlight that H. pylori EVs contain functionally active enzymes which may contribute to bacterial survival in vivo.