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Nocardamine-dependent iron uptake in Pseudomonas aeruginosa : exclusive implication of the FoxA outer membrane transporter

ABSTRACT: Iron is a key nutrient for almost all living organisms and paradoxically poorly soluble and consequently poorly bioavailable. To get access to this metal, bacteria have developed many different strategies. One of the most common consists of the use of siderophores, small compounds chelating ferric iron with a very high affinity. Many bacteria are able to produce their own siderophores or use those produced by other microorganisms (exosiderophores) in a piracy strategy. Pseudomonas aeruginosa produces two siderophores, pyoverdine and pyochelin and is able to use a large panel of exosiderophores. We investigated the ability of P. aeruginosa to use nocardamine (NOCA) and ferrioxamine B (DFOB) as exosiderophores under iron-limited planktonic growth conditions. Proteomic and RT-qPCR approaches showed an induction of the transcription and expression of the outer membrane transporter FoxA in the presence of NOCA or DFO in the bacterial environment. Expression of the proteins of the heme or pyoverdine and pyochelin dependent iron uptake pathways were not affected in the presence of these two tris-hydroxamate siderophores. 55Fe uptake assays using foxA mutants demonstrated that ferri-NOCA was exclusively transported by FoxA, while ferri-DFO was transported by FoxA and at least one another unidentified transporter. The crystal structure of FoxA in complex with NOCA revealed very similar siderophore binding sites between NOCA and DFO. Iron uptake by hydroxamate exosiderophores in P. aeruginosa cells is discussed in the light of these results.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Pseudomonas Aeruginosa Pao1

SUBMITTER: Lauriane Kuhn

LAB HEAD: Isabelle Schalk

PROVIDER: PXD020868 | Pride | 2021-04-29

REPOSITORIES: Pride

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Project description:Membrane protein and phospholipid (PL) compositions change in response to environmental cues and during infections. Covalent modification (e.g., unsaturation and cyclopropanation) and remodeling the acyl chain length of PLs is an important bacterial adaptation mechanism. However, little is known about which bacterial pathways are regulated in response to the alteration of PL composition. Here, we show that P. aeruginosa PlaF, which modulates membrane PL composition, is important for biofilm biogenesis, and we performed whole-cell quantitative proteomics of P. aeruginosa wild-type and ∆plaF biofilms to identify pathways regulated by PlaF. The results revealed profound alterations in the abundance of 14 two-component systems (TCS), including the PprA-PprB, which controls the transition to biofilm. Activation of PprA-the PprB system observed by proteomics was confirmed by mRNA quantification. Furthermore, we have observed a unique phosphorylation pattern of transcriptional regulators, transporters and metabolic enzymes, and differential production of nine proteases in ∆plaF, indicating that PlaF-mediated virulence adaptation involves complex transcriptional and post-transcriptional regulation. Moreover, proteomics revealed that the pyoverdin-mediated iron uptake pathway proteins were depleted in ∆plaF, which agrees with decreased concentrations of extracellular pyoverdine and intracellular iron in ∆plaF and is likely responsible for its prolonged lag phase due to reduced iron uptake. Conversely, the accumulation of proteins from alternative iron-uptake systems in ∆plaF suggests that PlaF may function as a switch between different iron-acquisition pathways. The observation that ∆plaF accumulates PL-acyl chain modifying enzymes and PlsX, an initiator of de novo PL synthesis, reveals novel insights into the relationship between degradation, covalent modification and biosynthesis of PLs for membrane homeostasis. Although the precise mechanism by which PlaF simultaneously affects multiple pathways remains to be elucidated, we suggest that PlaF-catalyzed degradation of PLs is a signal which is amplified by proteins of TCS, phosphorylation and proteolytic degradation systems to elicit the global adaptive response in P. aeruginosa.

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Nocardamine-dependent iron uptake in Pseudomonas aeruginosa : exclusive implication of the FoxA outer membrane transporter

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