Evolution of Physico-Chemical and Microbiological Parameters During Large-Scale Coffee-Pulp Silage

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Iterative Tree Algorithm to Evaluate Terahertz Signal Contribution of Specific Optical Paths within Multi-Layered Materials

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Opportunistic use of catecholamine neurotransmitters as siderophores to access iron by Pseudomonas aeruginosa

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Uptake Mechanisms and Regulatory Responses to MECAM- and DOTAM-Based Artificial Siderophores and Their Antibiotic Conjugates in Pseudomonas aeruginosa

International audienceThe development of new antibiotics against Gram-negative bacteria has to deal with the low permeability of the outer membrane. This obstacle can be overcome by utilizing siderophore-dependent iron uptake pathways as entrance routes for antibiotic uptake. Iron-chelating siderophores are actively imported by bacteria, and their conjugation to antibiotics allows smuggling the latter into bacterial cells. Synthetic siderophore mimetics based on MECAM (1,3,5-N,N′,N″-tris-(2,3-dihydroxybenzoyl)-triaminomethylbenzene) and DOTAM (1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane) cores, both chelating iron via catechol groups, have been recently applied as versatile carriers of functional cargo. In the present study, we show that MECAM and the MECAM-ampicillin conjugate 3 transport iron into Pseudomonas aeruginosa cells via the catechol-type outer membrane transporters PfeA and PirA and DOTAM solely via PirA. Differential proteomics and quantitative real-time polymerase chain reaction (qRT-PCR) showed that MECAM import induced the expression of pfeA, whereas 3 led to an increase in the expression of pfeA and ampc, a gene conferring ampicillin resistance. The presence of DOTAM did not induce the expression of pirA but upregulated the expression of two zinc transporters (cntO and PA0781), pointing out that bacteria become zinc starved in the presence of this compound. Iron uptake experiments with radioactive 55Fe demonstrated that import of this nutrient by MECAM and DOTAM was as efficient as with the natural siderophore enterobactin. The study provides a functional validation for DOTAM- and MECAM-based artificial siderophore mimetics as vehicles for the delivery of cargo into Gram-negative bacteria

Phenotypic adaptation of Pseudomonas aeruginosa in the presence of siderophoreantibiotic conjugates during epithelial cell infection

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A Key Role for the Periplasmic PfeE Esterase in Iron Acquisition via the Siderophore Enterobactin in Pseudomonas aeruginosa

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Nocardamine-Dependent Iron Uptake in Pseudomonas aeruginosa: Exclusive Involvement of the FoxA Outer Membrane Transporter

Iron is a key nutrient for almost all living organisms. Paradoxically, it is poorly soluble and consequently poorly bioavailable. Bacteria have thus developed multiple strategies to access this metal. One of the most common consists of the use of siderophores, small compounds that chelate ferric iron with 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 also 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 induction of the transcription and expression of the outer membrane transporter FoxA in the presence of NOCA or DFOB in the bacterial environment. Expression of the proteins of the heme- or pyoverdine- and pyochelin-dependent iron uptake pathways was not affected by the presence of these two tris-hydroxamate siderophores. $^{55}$Fe uptake assays using foxA mutants showed ferri-NOCA to be exclusively transported by FoxA, whereas ferri-DFOB was transported by FoxA and at least one other unidentified transporter. The crystal structure of FoxA complexed with NOCA-Fe revealed very similar siderophore binding sites between NOCA-Fe and DFOB-Fe. We discuss iron uptake by hydroxamate exosiderophores in P. aeruginosa cells in light of these results

Phenotypic Adaption of Pseudomonas aeruginosa by Hacking Siderophores Produced by Other Microorganisms

International audienceBacteria secrete siderophores to access iron, a key nutrient poorly bioavailable and the source of strong competition between microorganisms in most biotopes. Many bacteria also use siderophores produced by other microorganisms (exosiderophores) in a piracy strategy. Pseudomonas aeruginosa, an opportunistic pathogen, produces two siderophores, pyoverdine and pyochelin, and is also able to use a panel of exosiderophores. We first investigated expression of the various iron-uptake pathways of P. aeruginosa in three different growth media using proteomic and RT-qPCR approaches and observed three different phenotypic patterns, indicating complex phenotypic plasticity in the expression of the various iron-uptake pathways. We then investigated the phenotypic plasticity of iron-uptake pathway expression in the presence of various exosiderophores (present individually or as a mixture) under planktonic growth conditions, as well as in an epithelial cell infection assay. In all growth conditions tested, catechol-type exosiderophores were clearly more efficient in inducing the expression of their corresponding transporters than the others, showing that bacteria opt for the use of catechol siderophores to access iron when they are present in the environment. In parallel, expression of the proteins of the pyochelin pathway was significantly repressed under most conditions tested, as well as that of proteins of the pyoverdine pathway, but to a lesser extent. There was no effect on the expression of the heme and ferrous uptake pathways. Overall, these data provide precise insights on how P. aeruginosa adjusts the expression of its various iron-uptake pathways (phenotypic plasticity and switching) to match varying levels of iron and competition