Project description:Iron is an essential nutrient for the opportunistic pathogen Pseudomonas aeruginosa, as for almost all living organisms. To access this element, the pathogen is able to express at least 15 different iron-uptake pathways, the vast majority involving small iron chelators called siderophores. Indeed, P. aeruginosa produces two siderophores, pyoverdine and pyochelin, but can also use many produced by other microorganisms. This implies that the bacterium expresses appropriate TonB-dependent transporters (TBDTs) at the outer membrane to import the ferric form of each of the siderophores used. These transporters are highly selective for a given ferri-siderophore complex or for siderophores with similar chemical structures. Here, we show that P. aeruginosa can also use rhizoferrin, staphyloferrin A, aerobactin, and schizokinen as siderophores to access iron. Growth assays in iron-restricted conditions and 55Fe uptake assays showed that the two alpha-carboxylate type siderophores rhizoferrin-Fe and staphyloferrin A-Fe are transported into P. aeruginosa cells by the TBDT ActA (PA3268). Among the mixed alpha-carboxylate/hydroxamate type siderophores, we found aerobactin-Fe to be transported by ChtA (as previously described) and schizokinen-Fe by ChtA and another unidentified TBDT.
Project description:Fe-IMAC columns for robust and reproducible phosphopeptide ernichment, comparison to TiO2 batch and Ti-IMAC tip enrichment, large scale phosphoproteomics coupling Fe-IMAC column pre-enrichment to subsequent hSAX separation
Project description:Iron is an essential nutrient for bacterial growth but poorly bioavailable. To scavenge ferric iron present in their environment, bacteria synthesize and secrete siderophores, small compounds with a high affinity for iron. Pyochelin (PCH) is one of the two siderophores produced by the opportunistic pathogen Pseudomonas aeruginosa. Once having captured a ferric iron, PCH-Fe is imported back into bacteria first by the outer membrane transporter FptA and afterwards by the inner membrane permease FptX. Here using molecular biology, 55Fe uptake assays and LC-MS/MS quantification of PCH in the different bacterial cell fractions, we show that (i) PCH (probably under its PCH-Fe form) is able to rich bacterial periplasm and cytoplasm when both FptA and FptX are expressed, and (ii) that PchHI (a heterodimeric ABC transporter) plays a role in the translocation of siderophore-free iron siderophore-free iron across the inner membrane into the cytoplasm. Consequently, probably the first fraction of PCH-Fe internalized by FptA may be transported further by FptX in the bacterial cytoplasm to activate the transcriptional regulator PchR, regulating the transcription of all genes of the PCH pathway. The further fractions of PCH-Fe transported by FptA may dissociate in the bacterial periplasm by an unknown mechanism, with the siderophore-free iron being transported into the cytoplasm by PchHI.
Project description:Siderophores are specialized molecules with different chemical structures, produced by bacteria and fungi to scavenge iron from the environment, a crucial nutrient for their growth and metabolism. These iron-chelating compounds enable bacteria to overcome iron limitation, a key factor in microbial survival and pathogenesis. Catecholate-type siderophores are primarily produced by bacteria, while hydroxamates are predominantly produced by fungi. The capacity of nine hydroxamate-type siderophores produced by fungi to serve as siderophores for iron acquisition by Pseudomonas aeruginosa, a human pathogen, has been investigated. Growth assays under iron limitation and 55Fe incorporation tests clearly highlighted that all nine siderophores promoted bacterial growth and facilitated iron transport. Additionally, the study aimed to identify the TonB-dependent transporters (TBDTs) responsible for iron import mediated by the tested siderophores. Mutant strains lacking genes encoding TBDTs were employed, revealing that iron is imported into P. aeruginosa cells solely by FpvB for the siderophores coprogen, triacetylfusarinine C, fusigen, ferrirhodin, and ferrirubin siderophores. Iron complexed by desferioxamine G is imported by two TBDTs, FpvB and FoxA. Ferricrocin-Fe and ferrichrycin-Fe complexes are imported by FpvB and FiuA. Lastly, rhodotorulic acid-Fe complexes are imported by FpvB, FiuA, and another unidentified TBDT. In conclusion, the data illustrate the effectiveness of hydroxamate-type siderophores in transporting iron into P. aeruginosa cells and provide insights into the intricate molecular mechanisms involved in iron acquisition, which have implications for understanding bacterial pathogenesis and developing potential therapeutic strategies.