Abstract
Metallothioneins (MTs) are low molecular weight, Cys-rich proteins that sequester both essential and non-essential metal ions. Despite being highly conserved in the Pseudomonas genus of Gram-negative bacteria, knowledge of their physiological function in this species is scarce. Using the strain P. fluorescens Q2-87 as a model organism, we investigated the role of a conserved MT in zinc homeostasis, cadmium detoxification as well as its implications in stress response. We show that MT expression is only induced in the stationary phase and provides a fitness benefit for long-term starvation survival, while it is not required for metal resistance and acquisition, oxidative or nitrosative stress response, biofilm formation or motility.
Highlights
ZnII is considered to be an essential metal ion playing a role as a catalytic or structural cofactor of many key enzymes involved in DNA replication, protein synthesis, and other crucial enzymatic reactions in all organisms
Bioinformatic analysis of newly sequenced bacterial genomes has revealed that metallothionein from Pseudomonas fluorescens Q2-87 (MT) are conserved in 90% of the Pseudomonas species (Winsor et al, 2016), including pathogenic (e.g., P. aeruginosa and P. entomophila) and non-pathogenic strains (e.g., P. fluorescens and P. putida), which implies their possible involvement in physiological processes necessary for survival in host and non-host environments (Figure 1)
We focused on the involvement of this Pseudomonas metallothionein (PsdMT) in maintaining zinc homeostasis, including zinc limitation and excess, and its potential role in cadmium detoxification and stress response
Summary
ZnII is considered to be an essential metal ion playing a role as a catalytic or structural cofactor of many key enzymes involved in DNA replication, protein synthesis, and other crucial enzymatic reactions in all organisms. Bioinformatic analysis of newly sequenced bacterial genomes has revealed that MTs are conserved in 90% of the Pseudomonas species (Winsor et al, 2016), including pathogenic (e.g., P. aeruginosa and P. entomophila) and non-pathogenic strains (e.g., P. fluorescens and P. putida), which implies their possible involvement in physiological processes necessary for survival in host and non-host environments (Figure 1). This emerging group of Pseudomonas MTs (PsdMTs) shows a conserved Cys distribution pattern with cyanobacterial MTs, suggesting similar metal preferences and biological functions. We focused on the involvement of this PsdMT in maintaining zinc homeostasis, including zinc limitation and excess, and its potential role in cadmium detoxification and stress response
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