Characterization Of The Delta 7 Mutant Of Cupriavidus Metallidurans With Deletions Of Seven Secondary Metal Uptake Systems

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 Delta 7 (Delta zupT Delta pitA Delta corA1 Delta corA2 Delta corA3 Delta zntB Delta hoxN) 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 Delta 7 does not express genes for backup importers, and so Delta 7 should use metal uptake systems also produced in the AE104 parent cells. These systems should be activated in Delta 7 by posttranscriptional regulatory processes. The decreased fitness of Delta 7 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 Delta 7 was a negative interference of the activity of two P-type ATPases, MgtA and MgtB, which, on the other hand, kept Delta 7 at a fitness level higher than that of the Delta 9 (Delta 7 Delta mgtA:: kan Delta mgtB) 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 Delta 7. 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.