ABSTRACT: This project tested if siderophores are publig goods in Pseudomonas, and involved resequencing a well used siderophore mutant made by non-specific mutagenesis techniques
Project description:Bacteria access iron, a key nutrient, by producing siderophores or using siderophores produced by other microorganisms. The pathogen Pseudomonas aeruginosa produces two siderophores but is also able to pirate enterobactin (ENT), the siderophore produced by Escherichia coli. ENT-Fe complexes are imported across the outer membranes of P. aeruginosa by the two-outer membrane transporters PfeA and PirA. Iron is released from ENT in the P. aeruginosa periplasm by hydrolysis of ENT by the esterase PfeE. We show here that pfeE gene deletion renders P. aeruginosa unable to grow in the presence of ENT because it is unable to access iron via this siderophore. Two-species co-culture under iron-restricted conditions show that P. aeruginosa strongly represses the growth of E. coli as long it is able to produce its own siderophores. Both strains are present in similar proportions in the culture as long as the siderophore-deficient P. aeruginosa strain is able to use ENT produced by E. coli to access iron. If pfeE is deleted, E. coli has the upper hand in the culture and P. aeruginosa growth is repressed. Overall, these data show that PfeE is the Achilles heel of P. aeruginosa in communities with bacteria producing ENT.
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:Pseudomonas aeruginosa is a common nosocomial pathogen which produces siderophores to solubilize and transport chelated Fe3+ to aid its survival in both the environment and the host. However, there is a lack of comprehensive understanding regarding the molecular mechanisms underlying siderophore synthesis, uptake, and regulation within various ecological niches. In this study, we demonstrated that the BfmRS two-component system, part of the core genome of P. aeruginosa, plays a crucial role in siderophore metabolism. We have identified BfmS as an osmosensing histidine kinase that responds to external osmolytes, then modulates the activation of the response regulator BfmR. Under high osmolality, BfmR could directly bind to the promoters of pvd, fpv, and femARI gene clusters, thereby enhancing their expression and promoting siderophore metabolism. The proteomic and phenotypic analyses confirmed that deletion of bfmRS results in reduced expression levels of siderophore-related proteins as well as siderophore production. Importantly, loss of bfmR or bfmS significantly impaired bacterial survival in both iron deficiency medium and mouse lung infection models. Furthermore, phylogenetic analysis revealed that BfmRS is highly conserved and widely distributed across Pseudomonas species, evidences also proved that the BfmR of P. putida KT2440 and P. sp. MRSN12121 activated siderophore genes in response to high osmolality. Overall, this study sheds light on the previously unexplored signal transduction pathway, BfmRS, which governs the siderophore regulation in Pseudomonas species through perceiving an osmotic upshift. Considering that siderophores serve as unique social mediators, our findings contribute to a better understanding of how siderophores facilitate bacterial interactions with their eukaryotic hosts and contribute to the establishment of stable communities.
Project description:Lipocalin 24p3 (24p3) is a neutrophil secondary granule protein. 24p3 is also a siderocalin, which binds several bacterial siderophores. It was therefore proposed that synthesis and secretion of 24p3 by stimulated macrophages or release of 24p3 upon neutrophil degranulation sequesters iron-laden siderophores to attenuate bacterial growth. Accordingly, 24p3-deficient mice are susceptible to bacterial pathogens whose siderophores would normally be chelated by 24p3. Specific granule deficiency (SGD) is a rare congenital disorder characterized by complete absence of proteins in secondary granules. Neutrophils from SGD patients, who are prone to bacterial infections, lack normal functions but the potential role of 24p3 in neutrophil dysfunction in SGD is not known. Here we show that neutrophils from 24p3-deficient mice are defective in many neutrophil functions. Specifically, neutrophils in 24p3-deficient mice do not extravasate to sites of infection and are defective for chemotaxis. A transcriptome analysis revealed that genes that control cytoskeletal reorganization are selectively suppressed in 24p3-deficient neutrophils. Additionally, small regulatory RNAs (miRNAs) that control upstream regulators of cytoskeletal proteins are also increased in 24p3-deficient neutrophils. Further, 24p3-deficient neutrophils failed to phagocytose bacteria, which may account for the enhanced sensitivity of 24p3-deficient mice to both intracellular (Listeria monocytogenes) and extracellular (Candida albicans, Staphylococcus aureus) pathogens. Interestingly, Listeria does not secrete siderophores and additionally, the siderophore secreted by Candida is not sequestered by 24p3. Therefore, the heightened sensitivity of 24p3-deficient mice to these pathogens is not due to sequestration of siderophores limiting iron availability, but is a consequence of impaired neutrophil function. Key words: Lipocalin, 24p3, neutrophils, cell motility, chemotaxis, MIRNA-362-3p To address the role of lipocalin 2 in regulating miRNA expression profiling in neutrophils derived from mouse bone marrow, we performed microarray analysis of miRNAs in wild type (N=2) and lcn2 knockout (N=2) neutrophils.
Project description:Bacterial metabolites are substrates of virulence factors of uropathogenic Escherichia coli (UPEC), but the mechanism underlying the role of functional metabolites in bacterial virulence from the perspective of small molecular metabolism is unclear. In the present study, we used a strategy of functional metabolomics integrated with bacterial genetics in attempt to decipher the mechanism of virulence formation in Escherichia coli (E. coli) from the viewpoint of small molecule metabolism. We identified the virulence-associated metabolome via analysis of the primary metabolome of the pathogenic UTI89 strain and the non-pathogenic MG1655 strain. Then, the iron-mediated virulence associated metabolome was identified by an iron fishing strategy. Also, the mechanism of siderophores in regulating pathogenicity in different environments was explored by investigating the effect of iron on siderophore biosynthesis. Finally, by knocking out genes related to siderophore biosynthesis, siderophore transport and iron utilization, siderophores dependent iron-regulating virulence associated metabolome, including 18 functional metabolites, was identified and verified to be involved in the regulation of bacterial virulence. Based on this we found that these functional metabolites regulated the virulence of E. coli by targeting multiple metabolic pathways in an iron-siderophores dependent manner. Moreover, a quantitative proteomics approach was implemented to further elucidate the mechanism of functional metabolites and functional proteins in modulating bacterial virulence. And our findings demonstrated that functional proteins regulated the virulence of E. coli by mediating iron binding, iron-siderophore transmembrane transport, and the biosynthesis and expression of functional metabolites. Interestingly, we found that functional metabolites enhance the virulence of E. coli by specifically modulating the key metabolic pathways involved in purine metabolism, proline metabolism, arginine metabolism and pyrimidine metabolism. Taken together, our study identified for the first time 18 functional metabolites regulating the of E. coli virulence, greatly enriching our understanding of the mechanism of functional metabolites that regulate the E. coli virulence by targeting primary metabolism, which will largely contribute to the development of new strategies to target virulence-based diagnosis and therapy of infections caused by different pathogens.
Project description:Bacterial metabolites are substrates of virulence factors of uropathogenic Escherichia coli (UPEC), but the mechanism underlying the role of functional metabolites in bacterial virulence from the perspective of small molecular metabolism is unclear. In the present study, we used a strategy of functional metabolomics integrated with bacterial genetics in attempt to decipher the mechanism of virulence formation in Escherichia coli (E. coli) from the viewpoint of small molecule metabolism. We identified the virulence-associated metabolome via analysis of the primary metabolome of the pathogenic UTI89 strain and the non-pathogenic MG1655 strain. Then, the iron-mediated virulence associated metabolome was identified by an iron fishing strategy. Also, the mechanism of siderophores in regulating pathogenicity in different environments was explored by investigating the effect of iron on siderophore biosynthesis. Finally, by knocking out genes related to siderophore biosynthesis, siderophore transport and iron utilization, siderophores dependent iron-regulating virulence associated metabolome, including 18 functional metabolites, was identified and verified to be involved in the regulation of bacterial virulence. Based on this we found that these functional metabolites regulated the virulence of E. coli by targeting multiple metabolic pathways in an iron-siderophores dependent manner. Moreover, a quantitative proteomics approach was implemented to further elucidate the mechanism of functional metabolites and functional proteins in modulating bacterial virulence. And our findings demonstrated that functional proteins regulated the virulence of E. coli by mediating iron binding, iron-siderophore transmembrane transport, and the biosynthesis and expression of functional metabolites. Interestingly, we found that functional metabolites enhance the virulence of E. coli by specifically modulating the key metabolic pathways involved in purine metabolism, proline metabolism, arginine metabolism and pyrimidine metabolism. Taken together, our study identified for the first time 18 functional metabolites regulating the of E. coli virulence, greatly enriching our understanding of the mechanism of functional metabolites that regulate the E. coli virulence by targeting primary metabolism, which will largely contribute to the development of new strategies to target virulence-based diagnosis and therapy of infections caused by different pathogens.
Project description:Bacterial metabolites are substrates of virulence factors of uropathogenic Escherichia coli (UPEC), but the mechanism underlying the role of functional metabolites in bacterial virulence from the perspective of small molecular metabolism is unclear. In the present study, we used a strategy of functional metabolomics integrated with bacterial genetics in attempt to decipher the mechanism of virulence formation in Escherichia coli (E. coli) from the viewpoint of small molecule metabolism. We identified the virulence-associated metabolome via analysis of the primary metabolome of the pathogenic UTI89 strain and the non-pathogenic MG1655 strain. Then, the iron-mediated virulence associated metabolome was identified by an iron fishing strategy. Also, the mechanism of siderophores in regulating pathogenicity in different environments was explored by investigating the effect of iron on siderophore biosynthesis. Finally, by knocking out genes related to siderophore biosynthesis, siderophore transport and iron utilization, siderophores dependent iron-regulating virulence associated metabolome, including 18 functional metabolites, was identified and verified to be involved in the regulation of bacterial virulence. Based on this we found that these functional metabolites regulated the virulence of E. coli by targeting multiple metabolic pathways in an iron-siderophores dependent manner. Moreover, a quantitative proteomics approach was implemented to further elucidate the mechanism of functional metabolites and functional proteins in modulating bacterial virulence. And our findings demonstrated that functional proteins regulated the virulence of E. coli by mediating iron binding, iron-siderophore transmembrane transport, and the biosynthesis and expression of functional metabolites. Interestingly, we found that functional metabolites enhance the virulence of E. coli by specifically modulating the key metabolic pathways involved in purine metabolism, proline metabolism, arginine metabolism and pyrimidine metabolism. Taken together, our study identified for the first time 18 functional metabolites regulating the of E. coli virulence, greatly enriching our understanding of the mechanism of functional metabolites that regulate the E. coli virulence by targeting primary metabolism, which will largely contribute to the development of new strategies to target virulence-based diagnosis and therapy of infections caused by different pathogens.
Project description:Bacterial metabolites are substrates of virulence factors of uropathogenic Escherichia coli (UPEC), but the mechanism underlying the role of functional metabolites in bacterial virulence from the perspective of small molecular metabolism is unclear. In the present study, we used a strategy of functional metabolomics integrated with bacterial genetics in attempt to decipher the mechanism of virulence formation in Escherichia coli (E. coli) from the viewpoint of small molecule metabolism. We identified the virulence-associated metabolome via analysis of the primary metabolome of the pathogenic UTI89 strain and the non-pathogenic MG1655 strain. Then, the iron-mediated virulence associated metabolome was identified by an iron fishing strategy. Also, the mechanism of siderophores in regulating pathogenicity in different environments was explored by investigating the effect of iron on siderophore biosynthesis. Finally, by knocking out genes related to siderophore biosynthesis, siderophore transport and iron utilization, siderophores dependent iron-regulating virulence associated metabolome, including 18 functional metabolites, was identified and verified to be involved in the regulation of bacterial virulence. Based on this we found that these functional metabolites regulated the virulence of E. coli by targeting multiple metabolic pathways in an iron-siderophores dependent manner. Moreover, a quantitative proteomics approach was implemented to further elucidate the mechanism of functional metabolites and functional proteins in modulating bacterial virulence. And our findings demonstrated that functional proteins regulated the virulence of E. coli by mediating iron binding, iron-siderophore transmembrane transport, and the biosynthesis and expression of functional metabolites. Interestingly, we found that functional metabolites enhance the virulence of E. coli by specifically modulating the key metabolic pathways involved in purine metabolism, proline metabolism, arginine metabolism and pyrimidine metabolism. Taken together, our study identified for the first time 18 functional metabolites regulating the of E. coli virulence, greatly enriching our understanding of the mechanism of functional metabolites that regulate the E. coli virulence by targeting primary metabolism, which will largely contribute to the development of new strategies to target virulence-based diagnosis and therapy of infections caused by different pathogens.
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:Lipocalin 24p3 (24p3) is a neutrophil secondary granule protein. 24p3 is also a siderocalin, which binds several bacterial siderophores. It was therefore proposed that synthesis and secretion of 24p3 by stimulated macrophages or release of 24p3 upon neutrophil degranulation sequesters iron-laden siderophores to attenuate bacterial growth. Accordingly, 24p3-deficient mice are susceptible to bacterial pathogens whose siderophores would normally be chelated by 24p3. Specific granule deficiency (SGD) is a rare congenital disorder characterized by complete absence of proteins in secondary granules. Neutrophils from SGD patients, who are prone to bacterial infections, lack normal functions but the potential role of 24p3 in neutrophil dysfunction in SGD is not known. Here we show that neutrophils from 24p3-deficient mice are defective in many neutrophil functions. Specifically, neutrophils in 24p3-deficient mice do not extravasate to sites of infection and are defective for chemotaxis. A transcriptome analysis revealed that genes that control cytoskeletal reorganization are selectively suppressed in 24p3-deficient neutrophils. Additionally, small regulatory RNAs (miRNAs) that control upstream regulators of cytoskeletal proteins are also increased in 24p3-deficient neutrophils. Further, 24p3-deficient neutrophils failed to phagocytose bacteria, which may account for the enhanced sensitivity of 24p3-deficient mice to both intracellular (Listeria monocytogenes) and extracellular (Candida albicans, Staphylococcus aureus) pathogens. Interestingly, Listeria does not secrete siderophores and additionally, the siderophore secreted by Candida is not sequestered by 24p3. Therefore, the heightened sensitivity of 24p3-deficient mice to these pathogens is not due to sequestration of siderophores limiting iron availability, but is a consequence of impaired neutrophil function. Key words: Lipocalin, 24p3, neutrophils, cell motility, chemotaxis, MIRNA-362-3p