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Iron uptake and iron-repressible polypeptides in Yersinia pestis
T S Lucier1, J D Fetherston, R R Brubaker
1Department of Microbiology, Michigan State University, East Lansing 48824-1101, USA.
Abstract:
Pigmented (Pgm+) cells of Yersinia pestis are virulent, are sensitive to pesticin, adsorb exogenous hemin at 26 degrees C (Hms+), produce iron-repressible outer membrane proteins, and grow at 37 degrees C in iron-deficient media. These traits are lost upon spontaneous deletion of a chromosomal 102-kb pgm locus (Pgm-). Here we demonstrate that an Hms+ but pesticin-resistant (Pst(r)) mutant acquired a 5-bp deletion in the pesticin receptor gene (psn) encoding IrpB to IrpD. Growth and assimilation of iron by Pgm- and Hms+ Pst(r) mutants were markedly inhibited by ferrous chelators at 37 degrees C; inhibition by ferric and ferrous chelators was less effective at 26 degrees C. Iron-deficient growth at 26 degrees C induced iron-regulated outer membrane proteins of 34, 28.5, and 22.5 kDa and periplasmic polypeptides of 33.5 and 30 kDa. These findings provide a basis for understanding the psn-driven system of iron uptake, indicate the existence of at least one additional 26 degrees C-dependent iron assimilation system, and define over 30 iron-repressible proteins in Y. pestis.
Insights
Yersinia pestis iron uptake involves a pesticin receptor gene (psn) and multiple temperature-dependent systems. Understanding these mechanisms is crucial for Y. pestis virulence and iron assimilation.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Iron Metabolism
Background:
- Pigmented (Pgm+) Yersinia pestis cells are virulent, pesticin-sensitive, and adsorb hemin (Hms+).
- Loss of the 102-kb pgm locus (Pgm-) results in the loss of these virulent traits.
- Iron acquisition is critical for Y. pestis survival and virulence.
Purpose of the Study:
- To investigate the genetic basis of iron uptake in Yersinia pestis.
- To characterize the role of the pesticin receptor gene (psn) in iron assimilation.
- To identify additional iron assimilation systems in Y. pestis.
Main Methods:
- Genetic analysis of pesticin-resistant (Pst(r)) mutants.
- Growth assays in iron-deficient media at different temperatures (26°C and 37°C).
- Analysis of iron-repressible outer membrane proteins and periplasmic polypeptides via SDS-PAGE.
Main Results:
- A 5-bp deletion in the psn gene (encoding IrpB to IrpD) was identified in Hms+ Pst(r) mutants.
- Iron assimilation by Pgm- and Hms+ Pst(r) mutants was inhibited by ferrous chelators at 37°C, less so at 26°C.
- Iron-deficient growth at 26°C induced specific iron-regulated outer membrane and periplasmic proteins.
Conclusions:
- The psn gene is involved in a Y. pestis iron uptake system.
- At least one additional 26°C-dependent iron assimilation system exists in Y. pestis.
- Over 30 iron-repressible proteins in Y. pestis have been identified, contributing to virulence.