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Identification of iron-regulated outer membrane proteins in uropathogenic Proteus mirabilis and its relationship with
C D Piccini1, F M Barbé, C L Legnani-Fajardo
1División Microbiología, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay. piccini@iibce.edu.uy
Abstract:
The effect of iron deprivation on the expression of outer membrane proteins and the ability to use heme as an iron source by uropathogenic Proteus mirabilis, Pr 6515, was studied. Examination of iron-restricted bacteria showed three outer membrane proteins ranging from 66 to 75 kDa to be affected by iron restriction, as well as a newly expressed 64-kDa protein. These proteins were induced within 15 minutes of iron-deprivation. The strain grew in the presence of ferric citrate, hemin and hemoglobin as iron sources, but could not use transferrin, lactoferrin or siderophores from exogenous sources. The 64- and 66-kDa proteins showed hemin-binding activity by affinity chromatography, and both reacted in Western blots with sera from mice transurethrally infected with the same strain. We suggest that P. mirabilis expresses iron-regulated outer membrane proteins that could be involved in heme uptake and may have a role in pathogenesis.
Insights
Uropathogenic Proteus mirabilis alters outer membrane proteins under iron deprivation, enabling heme utilization. These iron-regulated proteins may play a role in bacterial pathogenesis.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Iron Metabolism
Background:
- Iron is essential for bacterial growth and virulence.
- Uropathogenic bacteria, such as Proteus mirabilis, must acquire iron from the host to establish infection.
- Outer membrane proteins play crucial roles in nutrient uptake and host-pathogen interactions.
Purpose of the Study:
- To investigate the impact of iron deprivation on outer membrane protein expression in uropathogenic Proteus mirabilis.
- To determine the ability of P. mirabilis to utilize heme and other iron sources under iron-restricted conditions.
- To explore the potential role of iron-regulated outer membrane proteins in heme uptake and pathogenesis.
Main Methods:
- Proteus mirabilis strain Pr 6515 was cultured under iron-restricted conditions.
- Outer membrane proteins were analyzed using SDS-PAGE and Western blotting.
- Heme-binding activity of specific proteins was assessed via affinity chromatography.
- Bacterial growth was tested with various iron sources (ferric citrate, hemin, hemoglobin, transferrin, lactoferrin).
Main Results:
- Iron deprivation induced three outer membrane proteins (66–75 kDa) and a new 64-kDa protein in P. mirabilis within 15 minutes.
- The strain could utilize ferric citrate, hemin, and hemoglobin but not transferrin, lactoferrin, or exogenous siderophores.
- The 64-kDa and 66-kDa proteins demonstrated hemin-binding activity and reacted with anti-sera from infected mice.
Conclusions:
- Proteus mirabilis upregulates specific outer membrane proteins in response to iron scarcity.
- These iron-regulated proteins are involved in heme iron acquisition.
- The identified proteins are potential virulence factors contributing to P. mirabilis pathogenesis in the urinary tract.