Yersinia pestis TonB: role in iron, heme, and hemoprotein utilization

Abstract

In Yersinia pestis, the siderophore-dependent yersiniabactin (Ybt) iron transport system and heme transport system (Hmu) have putative TonB-dependent outer membrane receptors. Here we demonstrate that hemin uptake and iron utilization from Ybt are TonB dependent. However, the Yfe iron and manganese transport system does not require TonB.

FIG. 1.

Growth of Y. pestis strains KIM6+ (Ybt⁺ TonB⁺), KIM6-2045.1 (Psn⁻ TonB⁺), and KIM2073+ (Ybt⁺ TonB⁻) at 37°C in deferrated PMH with (+Fe) and without (−Fe) FeCl₃ supplementation to 10 μM was performed as previously described (8, 19).

FIG. 2.

Uptake of ⁵⁵FeCl₃ by Y. pestis strains KIM6+ (Ybt⁺ TonB⁺), KIM6-2073+ (Ybt⁺ TonB⁻), and KIM6-2045.1 (Psn⁻ TonB⁺) was monitored as described previously (1, 6). Where indicated (closed symbols), cells were metabolically poisoned by addition of 100 μM carbonyl cyanide m-chlorophenylhydrazone 10 min prior to addition of isotope. These data are from a single experiment but are representative of three independent assays.

FIG. 3.

Growth of Y. pestis KIM6 (Ybt⁻ Yfe⁺ TonB⁺ HasB⁺), KIM6-2031.1 (Ybt⁻ Yfe⁻ TonB⁺ HasB⁺), KIM6-2073 (Ybt⁻ Yfe⁺ TonB⁻ HasB⁺), and KIM6-2073.1 (Ybt⁻ Yfe⁻ TonB⁻ HasB⁺) at 30°C across PMH plates containing a gradient of the iron chelator conalbumin (0 to 5 μM) (1). Bars represent incremental growth against the concentration gradient over a 72-h period. Growth distances were recorded in millimeters from 0 (no growth) to 90 (confluent growth). The data shown are from a single growth assay but are representative of three independent experiments.

FIG. 4.

Uptake of ⁵⁵FeCl₃ by Y. pestis KIM6 (Ybt⁻ Yfe⁺ TonB⁺ HasB⁺), KIM6-2031.1 (Ybt⁻ Yfe⁻ TonB⁺ HasB⁺), KIM6-2073 (Ybt⁻ Yfe⁺ TonB⁻ HasB⁺), and KIM6-2073.1 (Ybt⁻ Yfe⁻ TonB⁻ HasB⁺) at 37°C. Where indicated (closed symbols), cells were metabolically poisoned by addition of 100 μM carbonyl cyanide m-chlorophenylhydrazone 10 min prior to addition of isotope. These data are from a single experiment but are representative of three independent assays.