Dysregulation of transition metal ion homeostasis is the molecular basis for cadmium toxicity in Streptococcus pneumoniae.

Nat Commun. 2015 Mar 3;6:6418. doi: 10.1038/ncomms7418.

Dysregulation of transition metal ion homeostasis is the molecular basis for cadmium toxicity in Streptococcus pneumoniae.

Begg SL1, Eijkelkamp BA1, Luo Z2, Couñago RM2, Morey JR1, Maher MJ3, Ong CL4, McEwan AG4, Kobe B2, O'Mara ML5, Paton JC1, McDevitt CA1.

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Abstract

Cadmium is a transition metal ion that is highly toxic in biological systems. Although relatively rare in the Earth's crust, anthropogenic release of cadmium since industrialization has increased biogeochemical cycling and the abundance of the ion in the biosphere. Despite this, the molecular basis of its toxicity remains unclear. Here we combine metal-accumulation assays, high-resolution structural data and biochemical analyses to show that cadmium toxicity, in Streptococcus pneumoniae, occurs via perturbation of first row transition metal ion homeostasis. We show that cadmium uptake reduces the millimolar cellular accumulation of manganese and zinc, and thereby increases sensitivity to oxidative stress. Despite this, high cellular concentrations of cadmium (~17 mM) are tolerated, with negligible impact on growth or sensitivity to oxidative stress, when manganese and glutathione are abundant. Collectively, this work provides insight into the molecular basis of cadmium toxicity in prokaryotes, and the connection between cadmium accumulation and oxidative stress.

PMID: 25731976 [PubMed - in process]