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Outer membrane peptides ofYersinia pestis mediating siderophore-independent assimilation of iron
Authors:Daniel J. Sikkema  Robert R. Brubaker
Affiliation:(1) Department of Microbiology and Public Health, Michigan State University, 48824 East Lansing, MI, USA
Abstract:Summary It is established that wild-type cells ofYersinia pestis absorb exogenous hemin or Congo red and thus grow as pigmented colonies at 26° C on media containing these chromatophores (Pgm+). Pgm+ isolates are known to possess a siderophore-independent mechanism of iron-transport (required for growth in iron-deficient medium) which is absent in avirulent Pgm mutants. Production of the bacteriocin pesticin and linked invasins (Pst+) is an additional defined virulence factor of yersiniae; mutation of Pgm+,Pst organisms to pesticin-resistance (Pstr) results in concomitant conversion to Pgm. In this study, autoradiograms of two-dimensional gels of [35S]methionine-labeled outer membranes from Pgm mutants were compared to those of the Pgm+,Pst+ or Pgm+,Pst parent. An apparently single predominant peptide present in these preparations (> 10% of total membrane protein) existed as a family of iron-modifiable 17.9-kDa molecules focusing down to isoelectric points of about 4.6 and up to 5.89. Expression of eight detectable Pst+-specific peptides was not significantly influenced by exogenous iron. Pgm+ yersiniae constitutively produced pigmentation-specific peptide F and five iron-repressible peptides termed IrpA to IrpE. Typical spontaneous mutation to Pgm resulted in loss of peptide F and IrpB-E. A rare Pgm+,Pstr mutant, selected on Congo red agar containing pesticin, also lost IrpB-E but retained peptide F. This isolate, like Pgm mutants, failed to grow in iron-deficient medium. Regardless of phenotype, all yersiniae utilized hemin, hemopexin, myoglobin, hemoglobin, and ferritin, but not transferrin or lactoferrin, as sole sources of iron.This is journal article no. 13025 of the Michigan Agricultural Experiment Station.
Keywords:Iron storage  Iron-repressible peptides   Yersinia pestis
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