Abstract
Central to the ability of Cupriavidus metallidurans to maintain its metal homoeostasis is the metal transportome, composed of uptake and efflux systems. Seven secondary metal import systems, ZupT, PitA, CorA1, CorA2, CorA3, ZntB, and HoxN, interact and are at the core of the metal uptake transportome. The 7-fold deletion mutant Δ7 (ΔzupT ΔpitA ΔcorA1ΔcorA2ΔcorA3ΔzntB ΔhoxN) of parent strain AE104 is still able to maintain its cellular metal content, although at the cost of reduced fitness (M. Herzberg, L. Bauer, A. Kirsten, and D. H. Nies, Metallomics, in press, http://dx.doi.org/10.1039/C5MT00295H). Strain Δ7 does not express genes for backup importers, and so Δ7 should use metal uptake systems also produced in the AE104 parent cells. These systems should be activated in Δ7 by posttranscriptional regulatory processes. The decreased fitness of Δ7 correlated with a zinc-dependent downregulation of the overall metabolic backbone of the cells even at nontoxic external zinc concentrations. Responsible for this decreased fitness of Δ7 was a negative interference of the activity of two P-type ATPases, MgtA and MgtB, which, on the other hand, kept Δ7 at a fitness level higher than that of the Δ9 (Δ7 ΔmgtA::kan ΔmgtB) mutant strain. This revealed a complicated interplay of the metal uptake transportome of C.metallidurans, which is composed of the seven secondary uptake systems, MgtA, MgtB, and yet-unknown components, with cytoplasmic transition metal pools and posttranscriptional regulatory processes. IMPORTANCE Bacteria, including pathogenic strains, need to make use of the metal composition and speciation of their environment to fulfill the requirement of the cytoplasmic metal content and composition. This task is performed by the bacterial metal transportome, composed of uptake and efflux systems. Seven interacting secondary metal uptake systems are at the core of the metal transportome in C.metallidurans. This publication verifies that posttranscriptional events are responsible for activation of even more, yet-unknown, metal import systems in the 7-fold deletion mutant Δ7. Two P-type ATPases were identified as new members of the metal uptake transportome. This publication demonstrates the complexity of the metal transportome and the regulatory processes involved.
Highlights
IMPORTANCE Bacteria, including pathogenic strains, need to make use of the metal composition and speciation of their environment to fulfill the requirement of the cytoplasmic metal content and composition
The ΔzupT mutant strain suffers from various defects, indicating that ZupT is required for zinc uptake at low environmental concentrations and for efficient zinc allocation to client proteins [2, 10,11,12]
The number of zinc atoms per cell is lower in the ΔzupT mutant cells than in the parent strain AE104, namely, about 20,000 atoms per cell compared to 70,000 atoms in cells cultivated in mineral salts medium without added metals [2, 10]
Summary
IMPORTANCE Bacteria, including pathogenic strains, need to make use of the metal composition and speciation of their environment to fulfill the requirement of the cytoplasmic metal content and composition. It can be expected that subsequent deletion of one metal importer after the other should lead to a lethal phenotype or to cells in need of high external metal concentrations This point was not reached with the Δ7 mutant (ΔzupT ⌬pitA ⌬corA1 ⌬corA2 ⌬corA3 ⌬zntB ⌬hoxN); while deletion of transporter genes up to the preceding Δ6 mutant (ΔzupT ⌬pitA ⌬corA1 ⌬corA2 ⌬corA3 ⌬zntB) kept metal homoeostasis and cellular fitness of the Δ6 mutant at the level of the ΔzupT single mutant, additional deletion of hoxN in Δ6, leading to Δ7, decreased both features to another level [7]. Loss of importers in each mutant strain always could be compensated for by the respective remaining transporters This high plasticity of the metal uptake transportome allows the mutants up to Δ6 to remain at the fitness level of the ΔzupT single mutant strain, but in Δ7, this plasticity is diminished [7]. This paper starts with a transcriptome and morphology analysis of Δ7 to investigate the reason for the decreased fitness of this strain, which seems to result from a negative interference between the action of two metaltransporting P-type ATPases
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
