First report on the physicochemical and proteomic characterization of Proteus mirabilis outer membrane vesicles under urine-mimicking growth conditions: comparative analysis with Escherichia coli

The OMVs ranged in size from 85 to 260 nm, with the largest vesicles observed in artificial urine. Proteomic analysis allowed the identification of 282 proteins in OMVs from <i>E. coli</i> and 353 proteins from P. mirabilis when cultured LB medium, while 215 were identified from <i>E. coli</i> and 103 from <i>P. mirabilis</i> when cultured in artificial urine. The majority of these proteins originated from the bacterial envelope, while others were linked to motility and adhesion. Notably, the protein composition of OMVs varied depending on the growth medium, and proteins associated with zinc and iron uptake being more prominent in artificial urine, suggesting their importance in the urinary environment. Crucially, this is the first report to characterize <i>P. mirabilis</i> OMVs under different culture conditions, offering novel insights into the role of OMVs in UTI pathogenesis. These findings provide a deeper understanding of the molecular mechanisms by which OMVs contribute to bacterial virulence, establishing the foundation for potential therapeutic interventions targeting OMV-mediated processes in UTIs.