A Review of Pseudomonas aeruginosa Metallophores: Pyoverdine, Pyochelin and Pseudopaline

SIMPLE SUMMARY: The human pathogen Pseudomonas aeruginosa (P. aeruginosa) causes several infections, both acute and chronic, mainly in hosts with compromised immunity and in patients suffering from cystic fibrosis. The pathogenesis of this bacterium is caused by several factors. Metallophores, which are molecules for sequestering metal ions, are among these factors. P. aeruginosa secretes three types of metallophores, two for iron chelation (siderophores) named pyoverdine and pyochelin and the third one (pseudopaline) which can chelate zinc, nickel and cobalt. This review sums up in one paper all the important characteristics of these three metallophores, including their biosynthesis process, secretion, uptake after metal chelating and genetic regulation. ABSTRACT: P. aeruginosa is a common Gram-negative bacterium found in nature that causes severe infections in humans. As a result of its natural resistance to antibiotics and the ability of biofilm formation, the infection with this pathogen can be therapeutic challenging. During infection, P. aeruginosa produces secondary metabolites such as metallophores that play an important role in their virulence. Metallophores are metal ions chelating molecules secreted by bacteria, thus allowing them to survive in the host under metal scarce conditions. Pyoverdine, pyochelin and pseudopaline are the three metallophores secreted by P. aeruginosa. Pyoverdines are the primary siderophores that acquire iron from the surrounding medium. These molecules scavenge and transport iron to the bacterium intracellular compartment. Pyochelin is another siderophore produced by this bacterium, but in lower quantities and its affinity for iron is less than that of pyoverdine. The third metallophore, pseudopaline, is an opine narrow spectrum ion chelator that enables P. aeruginosa to uptake zinc in particular but can transport nickel and cobalt as well. This review describes all the aspects related to these three metallophore, including their main features, biosynthesis process, secretion and uptake when loaded by metals, in addition to the genetic regulation responsible for their synthesis and secretion.