The causative agent of plague — one of the most devastating infectious diseases in human history and a modern bioterrorism concern (Tier 1 Select Agent). Y. pestis depends on nickel for glyoxalase I-mediated metabolic detoxification and produces the archetypal dual-function metallophore yersiniabactin, which chelates both iron and nickel.
Nickel-Dependent Virulence
Ni-Glyoxalase I (GloI)
- Y. pestis possesses a confirmed Ni-dependent glyoxalase that detoxifies methylglyoxal, the reactive and mutagenic byproduct of glycolysis [1].
- During explosive growth in the host bloodstream (bacteremia can reach >10^8 CFU/mL in septicemic plague), high glycolytic flux generates toxic methylglyoxal concentrations.
- Without Ni-GloI, the pathogen's own metabolism becomes self-poisoning — nickel availability is thus essential for sustained bacteremic growth.
- Human GloI uses zinc, not nickel. This metal selectivity difference creates a potential target for selective inhibitors that would not affect host GloI.
Iron and Multi-Metal Acquisition
Yersiniabactin (Ybt)
- Y. pestis produces yersiniabactin, the founding member of this siderophore/metallophore family [2].
- Ybt binds Fe3+ with high affinity for classical iron acquisition during infection.
- Also chelates extracellular nickel and copper — a true multi-metal metallophore [1].
- The Ybt biosynthesis locus resides on the High Pathogenicity Island (HPI), which has been horizontally transferred to klebsiella pneumoniae, UPEC escherichia coli, and other Enterobacteriaceae — spreading multi-metal acquisition capability across pathogen families.
- Cu-Ybt complexes may help Y. pestis resist copper toxicity encountered in macrophage phagosomes.
Other Iron Systems
- Yersiniabactin is the primary siderophore; Y. pestis also acquires heme via the Hmu system.
- Iron acquisition is tightly regulated by Fur (ferric uptake regulator).
Pathogenesis and Metal Context
- Flea transmission: Y. pestis forms a biofilm in the flea proventriculus, blocking blood feeding and forcing the flea to regurgitate bacteria during subsequent bites. Iron availability in the flea blood meal likely supports biofilm formation.
- Bubonic plague: bacteria multiply in regional lymph nodes (buboes). Metal acquisition from lysed host cells provides iron and other metals.
- Septicemic plague: massive bloodstream infection. The Ni-GloI dependency is most critical during this phase due to the high metabolic rate.
- Pneumonic plague: person-to-person airborne transmission. The most lethal form (near 100% mortality if untreated).
Clinical Significance
- Plague: untreated bubonic plague has 60-90% mortality; septicemic and pneumonic forms approach 100%.
- Approximately 1,000-2,000 cases reported annually to WHO, with foci in Africa, Asia, and the Americas.
- Bioterrorism: classified as a CDC Category A bioterrorism agent. Aerosolized Y. pestis could cause pneumonic plague outbreaks.
- Treatment requires rapid administration of aminoglycosides (streptomycin, gentamicin) or doxycycline.
- Multidrug-resistant strains have been documented in Madagascar.
Connections
- glyoxalase — Ni-GloI for methylglyoxal detoxification during bacteremia
- siderophores metallophores — yersiniabactin as the archetypal dual Fe/Ni/Cu metallophore
- nickel — cofactor for GloI; also acquired via yersiniabactin
- iron — primary siderophore target; essential for growth in host
- copper — Ybt-Cu complexes resist macrophage copper toxicity
- metal dependent virulence — GloI and yersiniabactin as complementary metal-virulence systems
- klebsiella pneumoniae — acquired yersiniabactin HPI via horizontal transfer
- escherichia coli — UPEC strains carry yersiniabactin for Fe/Ni/Cu acquisition
- nutritional immunity — host iron/nickel restriction as defense against plague