Quinolobactin, a New Siderophore of Pseudomonas fluorescens ATCC 17400, the Production of Which Is Repressed by the Cognate Pyoverdine

Abstract

Transposon mutant strain 3G6 of Pseudomonas fluorescens ATCC 17400 which was deficient in pyoverdine production, was found to produce another iron-chelating molecule; this molecule was identified as 8-hydroxy-4-methoxy-quinaldic acid (designated quinolobactin). The pyoverdine-deficient mutant produced a supplementary 75-kDa iron-repressed outer membrane protein (IROMP) in addition to the 85-kDa IROMP present in the wild type. The mutant was also characterized by substantially increased uptake of 59 Fe-quinolobactin. The 75-kDa IROMP was produced by the wild type after induction by quinolobactin-containing culture supernatants obtained from the pyoverdine-negative mutant or by purified quinolobactin. Conversely, adding purified wild-type pyoverdine to the growth medium resulted in suppression of the 75-kDa IROMP in the pyoverdinedeficient mutant; however, suppression was not observed when Pseudomonas aeruginosa PAO1 pyoverdine, a siderophore utilized by strain 3G6, was added to the culture. Therefore, we assume that the quinolobactin receptor is the 75-kDa IROMP and that the quinolobactin-mediated iron uptake system is repressed by the cognate pyoverdine.

Co-ordination of iron acquisition, iron porphyrin chelation and iron–protoporphyrin export via the cytochrome c biogenesis protein CcmC in Pseudomonas fluorescens

“…To investigate whether the absence of CcmC also affects other siderophore-mediated iron uptake systems, besides PVD, we decided to introduce the ccmC mutation into a mutant of P. fluorescens ATCC 17400 deficient for the non-ribosomal peptide synthetase PvsA, which is needed for the PVD chromophore synthesis (Mossialos et al, 2002). The pvsA mutant still produces high levels of another siderophore, QB (Mossialos et al, 2000). The ccmC gene in the pvsA mutant was disrupted by double recombination.…”

“…fluorescens ATCC 17400 produces both a PVD and another, non-fluorescent, siderophore, quinolobactin (QB) (Mossialos et al, 2000;Cornelis & Matthijs, 2002). PVDs are composed of a conserved dihydroxyquinoline chromophore, a variable peptide chain, comprising 6-12 amino acids, specific to a producing strain, and a side-chain, generally a dicarboxylic acid or an amide (Ravel & Cornelis, 2003).…”

Switching between apparently redundant iron-uptake mechanisms benefits bacteria in changeable environments

“…The problem becomes particularly intriguing in instances where a molecular system seems disused. This is apparently the case for siderophore-based iron acquisition systems, where so-called 'secondary' siderophores are usually expressed only weakly or not at all under iron limitation [4,6,7]. An evolutionary consequence of this disuse should be that selection eliminates superfluous systems [8].…”

The Two-Component Regulators GacS and GacA Positively Regulate a Nonfluorescent Siderophore through the Gac/Rsm Signaling Cascade in High-Siderophore-Yielding Pseudomonas sp. Strain HYS

“…Among the various siderophores of pseudomonads, the fluorescent high-affinity peptidic pyoverdines are usually produced as the primary siderophore and have been studied intensively (10)(11)(12). Diverse secondary siderophores, such as pyochelin (13), pseudomonine (14), quinolobactin (15), and thioquinolobactin (16), are less well understood because their production and functions are usually masked by pyoverdines. However, these secondary siderophores could play essential roles in the growth of pyoverdine-negative mutants under iron-limited conditions and sometimes could provide additional functions, such as pathogenicity, biocontrol, and transport of other metals (16)(17)(18).…”