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Histochemical and biochemical urease localization in the periplasm and outer membrane of two Proteus mirabilis
Abstract:
Proteus mirabilis, a gram-negative bacillus, is often implicated in the formation of infectious kidney stones. As ureolytic activity of this organism is thought to play a major role in its pathogenesis, we adapted our recently described urease localization technique to visualize urease activity in vivo. Urease activity was ultrastructurally localized in two clinically isolated P. mirabilis strains by precipitating the enzymatic reaction product (ammonia) with sodium tetraphenylboron. Subsequent silver staining of the cells revealed urease activity to be predominantly associated with the periplasm and outer membranes of each strain. Biochemical measurements of urease activity in P. mirabilis cell fractions correlated well with histochemical observations in that the majority of urease activity was associated with the periplasm. Membrane-bound urease activity of these strains was associated mainly with the peptidoglycan in the detergent-insoluble (outer membrane) fraction.
Insights
Proteus mirabilis, a bacterium linked to kidney stones, has urease activity primarily in its periplasm and outer membranes. This localization is key to understanding its role in infection pathogenesis.
Area of Science:
- Microbiology
- Urology
- Biochemistry
Background:
- Proteus mirabilis is a gram-negative bacillus frequently associated with infectious kidney stone formation.
- The ureolytic activity of P. mirabilis is a significant factor in its pathogenesis.
- Understanding the precise localization of urease is crucial for developing targeted interventions.
Purpose of the Study:
- To ultrastructurally localize urease activity in vivo within clinical isolates of Proteus mirabilis.
- To correlate histochemical findings with biochemical measurements of urease activity.
- To elucidate the role of urease localization in the pathogenesis of P. mirabilis infections.
Main Methods:
- Adapted a urease localization technique using sodium tetraphenylboron to precipitate ammonia, the enzymatic product.
- Employed silver staining for ultrastructural visualization of urease activity.
- Performed biochemical measurements of urease activity in isolated P. mirabilis cell fractions.
Main Results:
- Urease activity was predominantly localized to the periplasm and outer membranes of P. mirabilis strains.
- Histochemical observations were consistent with biochemical measurements, showing most urease activity in the periplasm.
- Membrane-bound urease activity was primarily associated with the peptidoglycan in the outer membrane fraction.
Conclusions:
- The periplasm and outer membranes are the primary sites of urease activity in Proteus mirabilis.
- These findings provide critical insights into the mechanism by which P. mirabilis contributes to kidney stone formation.
- The study validates the adapted urease localization technique for in vivo studies.