New insights into the metal specificity of the Pseudomonas aeruginosa pyoverdine–iron uptake pathway

Abstract

Pyoverdine (PvdI) is the major siderophore secreted by Pseudomonas aeruginosa PAOI in order to get access to iron. After being loaded with iron in the extracellular medium, PvdI is transported across the bacterial outer membrane by the transporter, FpvAI. We used the spectral properties of PvdI to show that in addition to Fe(3+), this siderophore also chelates, but with lower efficiencies, all the 16 metals used in our screening. Afterwards, FpvAI at the cell surface binds Ag(+), Al(3+), Cd(2+), Co(2+), Cu(2+), Fe(3+), Ga(3+), Hg(2+), Mn(2+), Ni(2+) or Zn(2+) in complex with PvdI. We used Inductively Coupled Plasma-Atomic Emission Spectrometry to monitor metal uptake in P. aeruginosa: TonB-dependent uptake, in the presence of PvdI, was only efficient for Fe(3+). Cu(2+), Ga(3+), Mn(2+) and Ni(2+) were also transported into the cell but with lower uptake rates. The presence of Al(3+), Cu(2+), Ga(3+), Mn(2+), Ni(2+) and Zn(2+) in the extracellular medium induced PvdI production in P. aeruginosa. All these data allow a better understanding of the behaviour of the PvdI uptake pathway in the presence of metals other than iron: FpvAI at the cell surface has broad metal specificity at the binding stage and it is highly selective for Fe(3+) only during the uptake process.

The Pseudomonas aeruginosa Pyochelin-Iron Uptake Pathway and Its Metal Specificity

“…Similar data were obtained with the Pvd uptake pathway in P. aeruginosa: there was a large metal specificity for the binding stage for FpvA, but only Cu 2ϩ , Ga 3ϩ , Mn 2ϩ , and Ni 2ϩ were transported and with uptake rates between 7-and 42-fold lower than that of Fe 3ϩ (6). This may be a common property of all siderophore outer membrane transporters.…”

Pigments influence the tolerance of Pseudomonas aeruginosa PAO1 to photodynamically induced oxidative stress

“…3). In accordance with the published effects of metals on pyoverdine fluorescence (Braud et al, 2009), a hypochromic effect was observed when FeCl 3 (100 mM) was added to the samples, whereas the addition of CuSO 4 (100 mM) caused a hyperchromic effect (data not shown).…”

“…The UV-vis absorption spectra obtained were compared to spectra of pigments already reported in the literature. The spectrum for pyomelanin was reported by Kurian et al (2014), those for phenazine-1-carboxylic acid (PCA) and pyocyanin by Mavrodi et al (2013) and that for pyoverdine by Braud et al (2009).…”

“…The soluble fluorescent pigment produced by overnight LB cultures showed an absorbance peak at 400 nm (Fig. S2) compatible with pyoverdine (Braud et al, 2009). Upon excitation at 380 nm the supernatant of YE cultures showed a fluorescence at 470 nm, 70-fold higher than that of P. aeruginosa PAO1 cultures (Fig.…”

Survival Strategies of the Plant-Associated Bacterium Enterobacter sp. Strain EG16 under Cadmium Stress

“…For instance, the Pseudomonas aeruginosa strain KUCd1, which also showed high Cd resistance, was reported to increase siderophore production when exposed to Cd (20). Similarly, Braud et al (54) found that the presence of Al, Cu, Ga, Mn, Ni, and Zn in the extracellular medium induced pyoverdine production in Pseudomonas aeruginosa PAO1, while Naik and Dubey (55) observed Pb-enhanced siderophore production when Pb-resistant Pseudomonas aeruginosa strain 4EA was cultured in a medium containing as much as 0.5 mM lead nitrate. In contrast, reduced siderophore production upon exposure to Cd (10 to 100 M) was observed in Bacillus amyloliquefaciens NAR38.1 by Gaonkar and Bhosle (56), together with severe inhibition of bacterial growth.…”