Linking the transcriptome to physiology: response of the proteome of Cupriavidus metallidurans to changing metal availability.

Cupriavidus metallidurans CH34 is a metal-resistant bacterium. Its metal homeostasis is based on a flow equilibrium of metal ion uptake and efflux reactions, which adapts to changing metal concentrations within an hour. At high metal concentrations, upregulation of the genes for metal efflux systems occurs within minutes.

Antisense transcription is associated with expression of metal resistance determinants in Cupriavidus metallidurans CH34.

Cupriavidus metallidurans is able to thrive in metal-rich environments but also survives metal starvation. Expression of metal resistance determinants in C. metallidurans was investigated on a global scale.

The efflux system CdfX exports zinc that cannot be transported by ZntA in .

is able to survive exposure to high concentrations of transition metals, but is also able to grow under metal starvation conditions. A prerequisite of cellular zinc homeostasis is a flow equilibrium combining zinc uptake and efflux processes. The mutant strain ∆e4 of the parental plasmid-free strain AE104 with a deletion of all four chromosomally encoded genes of previously known efflux systems ZntA, CadA, DmeF, and FieF was still able to efflux zinc in a pulse-chase experiment, indicating the existence of a fifth efflux system.

The metal-binding GTPases CobW2 and CobW3 are at the crossroads of zinc and cobalt homeostasis in .

The metal-resistant beta-proteobacterium is also able to survive conditions of metal starvation. We show that zinc-starved cells can substitute some of the required zinc with cobalt but not with nickel ions. The zinc importer ZupT was necessary for this process but was not essential for either zinc or cobalt import.

A flow equilibrium of zinc in cells of .

Unlabelled: The hypothesis was tested that a kinetical flow equilibrium of uptake and efflux reactions is responsible for balancing the cellular zinc content. The experiments were done with the metal-resistant bacterium . In pulse-chase experiments, the cells were loaded with radioactive Zn and chased with the 100-fold concentration of non-radioactive zinc chloride.