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Bruna RE, Kendra CG, Pontes MH. An intracellular phosphorus-starvation signal activates the PhoB/PhoR two-component system in Salmonella enterica. mBio 2024:e0164224. [PMID: 39152718 DOI: 10.1128/mbio.01642-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2024] [Accepted: 07/01/2024] [Indexed: 08/19/2024] Open
Abstract
Bacteria acquire P primarily as inorganic orthophosphate (Pi, PO43-). Once internalized, Pi is rapidly assimilated into biomass during the synthesis of ATP. Because Pi is essential, but excessive ATP is toxic, the acquisition of environmental Pi is tightly regulated. In the bacterium Salmonella enterica (Salmonella), growth in Pi-limiting environments activates the membrane sensor histidine kinase PhoR, leading to the phosphorylation of its cognate transcriptional regulator PhoB and subsequent transcription of genes involved in adaptations to low Pi. Pi limitation promotes PhoR kinase activity by altering the conformation of a membrane signaling complex comprised of PhoR, the multicomponent Pi transporter system PstSACB and the regulatory protein PhoU. However, the identity of the Pi-starvation signal and how it controls PhoR activity remain unknown. Here, we identify conditions where the PhoB and PhoR signal transduction proteins can be maintained in an inactive state when Salmonella is grown in media lacking Pi. Our results demonstrate that PhoB/PhoR is activated by an intracellular P-insufficiency signal.IMPORTANCEIn enteric bacteria, the transcriptional response to phosphorus (P) starvation is controlled by a specialized signal transduction system comprised of a membrane-bound, multicomponent signal sensor, and a cytoplasmic transcriptional factor. Whereas this system has been primarily studied in the context of phosphate (Pi) starvation, it is currently unknown how this stress initiates signal transduction. In the current study, we establish that this signaling system is regulated by a cytoplasmic signal arising from insufficient P. We demonstrate that rather than responding to extracellular conditions, cells couple the activation of their P starvation response to the availability of cytoplasmic P. This regulatory logic may enable cells to prevent toxicity resulting from excessive Pi acquisition and hinder the onset of a P starvation response when their metabolic demands are being met through the consumption of P sources other than Pi.
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Affiliation(s)
- Roberto E Bruna
- Department of Pathology and Laboratory Medicine, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
- The One Health Microbiome Center, Huck Institute of the Life Sciences, Pennsylvania State University, Camp Hill, Pennsylvania, USA
| | - Christopher G Kendra
- Department of Pathology and Laboratory Medicine, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
- The One Health Microbiome Center, Huck Institute of the Life Sciences, Pennsylvania State University, Camp Hill, Pennsylvania, USA
| | - Mauricio H Pontes
- Department of Pathology and Laboratory Medicine, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
- The One Health Microbiome Center, Huck Institute of the Life Sciences, Pennsylvania State University, Camp Hill, Pennsylvania, USA
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Bruna RE, Kendra CG, Pontes MH. Phosphorus starvation response and PhoB-independent utilization of organic phosphate sources by Salmonella enterica. Microbiol Spectr 2023; 11:e0226023. [PMID: 37787565 PMCID: PMC10715179 DOI: 10.1128/spectrum.02260-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Accepted: 08/21/2023] [Indexed: 10/04/2023] Open
Abstract
IMPORTANCE Phosphorus (P) is the fifth most abundant element in living cells. This element is acquired mainly as inorganic phosphate (Pi, PO4 3-). In enteric bacteria, P starvation activates a two-component signal transduction system which is composed of the membrane sensor protein PhoR and its cognate transcription regulator PhoB. PhoB, in turn, promotes the transcription of genes that help maintain Pi homeostasis. Here, we characterize the P starvation response of the bacterium Salmonella enterica. We determine the PhoB-dependent and independent transcriptional changes promoted by P starvation and identify proteins enabling the utilization of a range of organic substrates as sole P sources. We show that transcription and activity of a subset of these proteins are independent of PhoB and Pi availability. These results establish that Salmonella enterica can maintain Pi homeostasis and repress PhoB/PhoR activation even when cells are grown in medium lacking Pi.
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Affiliation(s)
- Roberto E. Bruna
- Department of Pathology and Laboratory Medicine, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
- The One Health Microbiome Center, Huck Institute of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania, USA
| | - Christopher G. Kendra
- Department of Pathology and Laboratory Medicine, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
- The One Health Microbiome Center, Huck Institute of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania, USA
| | - Mauricio H. Pontes
- Department of Pathology and Laboratory Medicine, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
- The One Health Microbiome Center, Huck Institute of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania, USA
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Bruna RE, Kendra CG, Pontes MH. An intracellular phosphorus-starvation signal activates the PhoB/PhoR two-component system in Salmonella enterica. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.23.533958. [PMID: 36993483 PMCID: PMC10055408 DOI: 10.1101/2023.03.23.533958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
Bacteria acquire P primarily as inorganic orthophosphate (Pi, PO43-). Once internalized, Pi is rapidly assimilated into biomass during the synthesis of ATP. Because Pi is essential, but excessive ATP is toxic, the acquisition of environmental Pi is tightly regulated. In the bacterium Salmonella enterica (Salmonella), growth in Pi-limiting environments activates the membrane sensor histidine kinase PhoR, leading to the phosphorylation of its cognate transcriptional regulator PhoB and subsequent transcription of genes involved in adaptations to low Pi. Pi limitation is thought to promote PhoR kinase activity by altering the conformation of a membrane signaling complex comprised by PhoR, the multicomponent Pi transporter system PstSACB and the regulatory protein PhoU. However, the identity of the low Pi signal and how it controls PhoR activity remain unknown. Here we characterize the PhoB-dependent and independent transcriptional changes elicited by Salmonella in response to P starvation, and identify PhoB-independent genes that are required for the utilization of several organic-P sources. We use this knowledge to identify the cellular compartment where the PhoR signaling complex senses the Pi-limiting signal. We demonstrate that the PhoB and PhoR signal transduction proteins can be maintained in an inactive state even when Salmonella is grown in media lacking Pi. Our results establish that PhoR activity is controlled by an intracellular signal resulting from P insufficiency.
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Affiliation(s)
- Roberto E. Bruna
- Department of Pathology and Laboratory Medicine, Pennsylvania State College of Medicine, Hershey, PA 17033, United States of America
| | - Christopher G. Kendra
- Department of Pathology and Laboratory Medicine, Pennsylvania State College of Medicine, Hershey, PA 17033, United States of America
| | - Mauricio H. Pontes
- Department of Pathology and Laboratory Medicine, Pennsylvania State College of Medicine, Hershey, PA 17033, United States of America
- Department of Microbiology and Immunology, Pennsylvania State College of Medicine, Hershey, PA 17033, United States of America
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Park Y, Solhtalab M, Thongsomboon W, Aristilde L. Strategies of organic phosphorus recycling by soil bacteria: acquisition, metabolism, and regulation. ENVIRONMENTAL MICROBIOLOGY REPORTS 2022; 14:3-24. [PMID: 35001516 PMCID: PMC9306846 DOI: 10.1111/1758-2229.13040] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 12/07/2021] [Accepted: 12/14/2021] [Indexed: 05/12/2023]
Abstract
Critical to meeting cellular phosphorus (P) demand, soil bacteria deploy a number of strategies to overcome limitation in inorganic P (Pi ) in soils. As a significant contributor to P recycling, soil bacteria secrete extracellular enzymes to degrade organic P (Po ) in soils into the readily bioavailable Pi . In addition, several Po compounds can be transported directly via specific transporters and subsequently enter intracellular metabolic pathways. In this review, we highlight the strategies that soil bacteria employ to recycle Po from the soil environment. We discuss the diversity of extracellular phosphatases in soils, the selectivity of these enzymes towards various Po biomolecules and the influence of the soil environmental conditions on the enzyme's activities. Moreover, we outline the intracellular metabolic pathways for Po biosynthesis and transporter-assisted Po and Pi uptake at different Pi availabilities. We further highlight the regulatory mechanisms that govern the production of phosphatases, the expression of Po transporters and the key metabolic changes in P metabolism in response to environmental Pi availability. Due to the depletion of natural resources for Pi , we propose future studies needed to leverage bacteria-mediated P recycling from the large pools of Po in soils or organic wastes to benefit agricultural productivity.
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Affiliation(s)
- Yeonsoo Park
- Department of Civil and Environmental Engineering, McCormick School of Engineering and Applied ScienceNorthwestern UniversityEvanstonIL60208USA
- Department of Biological and Environmental EngineeringCornell University, Riley‐Robb HallIthacaNY14853USA
| | - Mina Solhtalab
- Department of Civil and Environmental Engineering, McCormick School of Engineering and Applied ScienceNorthwestern UniversityEvanstonIL60208USA
- Department of Biological and Environmental EngineeringCornell University, Riley‐Robb HallIthacaNY14853USA
| | - Wiriya Thongsomboon
- Department of Civil and Environmental Engineering, McCormick School of Engineering and Applied ScienceNorthwestern UniversityEvanstonIL60208USA
- Department of Chemistry, Faculty of ScienceMahasarakham UniversityMahasarakham44150Thailand
| | - Ludmilla Aristilde
- Department of Civil and Environmental Engineering, McCormick School of Engineering and Applied ScienceNorthwestern UniversityEvanstonIL60208USA
- Department of Biological and Environmental EngineeringCornell University, Riley‐Robb HallIthacaNY14853USA
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Albermann C, Weiner M, Tröndle J, Weuster-Botz D, Sprenger GA. Utilization of organophosphate:phosphate antiporter for isotope-labeling experiments in E. coli. FEMS Microbiol Lett 2014; 361:52-61. [PMID: 25273627 DOI: 10.1111/1574-6968.12612] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Revised: 09/04/2014] [Accepted: 09/25/2014] [Indexed: 12/01/2022] Open
Abstract
The transport of organophosphates across the cytoplasma membrane is mediated by organophosphate:phosphate antiporter proteins. In this work, we present the application of a recombinant phosphoenolpyruvate:phosphate antiporter for isotopic labeling experiments in E. coli strains. The antiporters UhpT, UhpT-D388C, and PgtP were investigated regarding transport activity and growth on phosphoenolpyruvate as sole carbon source. The expression of the protein variant UhpT-D388C in a shikimic acid producing E. coli strain was used to show the successful isotopic labeling of shikimic acid from extracellular phosphoenolpyruvate. The results demonstrate the possibility of a direct incorporation of exogenously applicated glycolysis intermediates into E. coli cells for 13C-labeling experiments.
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Affiliation(s)
| | - Michael Weiner
- Institute of Biochemical Engineering, Technische Universität München, Garching, Germany
| | - Julia Tröndle
- Institute of Biochemical Engineering, Technische Universität München, Garching, Germany
| | - Dirk Weuster-Botz
- Institute of Biochemical Engineering, Technische Universität München, Garching, Germany
| | - Georg A Sprenger
- Institute of Microbiology, Universität Stuttgart, Stuttgart, Germany
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Min T, Vedadi M, Watson DC, Wasney GA, Munger C, Cygler M, Matte A, Young NM. Specificity of Campylobacter jejuni adhesin PEB3 for phosphates and structural differences among its ligand complexes. Biochemistry 2009; 48:3057-67. [PMID: 19236052 DOI: 10.1021/bi802195d] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PEB3 is a glycoprotein adhesin from Campylobacter jejuni whose structure suggested a role in transport. We have investigated potential ligands for PEB3 and characterized their binding properties using biophysical methods in solution and by X-ray crystallography. A thermal aggregation assay of PEB3 with a library of physiological compounds identified three possible ligands [3-phosphoglycerate (3-PG), phosphoenolpyruvate (PEP), and aconitate], which stabilized wild-type PEB3 but did not stabilize either a PEB3 form containing two mutations at the ligand-binding site, T138A/S139A, or a second PEB3 mutant, K135E, at a site approximately 14 A away. Fluorescence titration experiments and cocrystal structures with various ligands were used to characterize the binding of 3-PG, PEP, and phosphate to PEB3. Further, a C. jejuni growth experiment in minimal medium supplemented with 3-PG showed that this molecule enhances the growth of wild-type C. jejuni, but not of the PEB3 mutants. Crystallographic analysis of PEB3 complexes revealed that the Ser171-Gln180 region in the presence of 3-PG or other phosphates is helical and similar to those of other transport proteins, but it is nonhelical when citrate is bound. The K135E mutation resulted in expression of a more highly glycosylated form of PEB3 in vivo, and its crystal structure showed the conformation of the first two residues of the glycan. On the basis of our findings, we suggest that PEB3 is a transport protein that may function in utilization of 3-PG or other phosphate-containing molecules from the host.
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Affiliation(s)
- Tongpil Min
- Department of Biochemistry, McGill University, Montreal, QC, H3G 1Y6 Canada
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Hall JA, Fann MC, Maloney PC. Altered substrate selectivity in a mutant of an intrahelical salt bridge in UhpT, the sugar phosphate carrier of Escherichia coli. J Biol Chem 1999; 274:6148-53. [PMID: 10037698 DOI: 10.1074/jbc.274.10.6148] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Site-directed and second site suppressor mutagenesis identify an intrahelical salt bridge in the eleventh transmembrane segment of UhpT, the sugar phosphate carrier of Escherichia coli. Glucose 6-phosphate (G6P) transport by UhpT is inactivated if cysteine replaces either Asp388 or Lys391 but not if both are replaced. This suggests that Asp388 and Lys391 are involved in an intrahelical salt bridge and that neither is required for normal UhpT function. This interpretation is strengthened by the finding that mutations at Lys391 (K391N, K391Q, and K391T) are recovered as revertants of the inactive D388C variant. Further work shows that although the D388C variant is null for G6P transport, movement of 32Pi by homologous Pi/Pi exchange is unaffected. This raises the possibility that this derivative may have latent function, a possibility confirmed by showing that D388C is a gain-of-function mutation in which phosphoenolpyruvate (PEP) is the preferred substrate. Added study of the Pi/Pi exchange shows that in wild type UhpT this partial reaction is readily blocked by G6P but not PEP. By contrast, in the D388C variant, Pi/Pi exchange is unaffected by G6P but is inhibited by both PEP and 3-phosphoglycerate. These latter substrates are used by PgtP, a related Pi-linked antiporter, which lacks the Asp388-Lys391 salt bridge but has instead an uncompensated arginine at position 391. For this reason, we conclude that in both UhpT and PgtP position 391 can serve as a determinant of substrate selectivity by acting as a receptor for the anionic carboxyl brought into the translocation pathway by PEP.
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Affiliation(s)
- J A Hall
- Department of Physiology, Johns Hopkins University Medical School, Baltimore, Maryland 21205, USA
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Veld GI, Driessen AJ, Konings WN. Bacterial solute transport proteins in their lipid environment. FEMS Microbiol Rev 1993; 12:293-314. [PMID: 8268004 DOI: 10.1111/j.1574-6976.1993.tb00024.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The cytoplasmic membrane of bacteria is a selective barrier that restricts entry and exit of solutes. Transport of solutes across this membrane is catalyzed by specific membrane proteins. Integral membrane proteins usually require specific lipids for optimal activity and are inhibited by other lipid species. Their activities are also sensitive to the lipid bilayer dynamics and physico-chemical state. Bacteria can adapt to changes in the environments (respective temperature, hydrostatic pressure, and pH) by altering the lipid composition of the membrane. Homeoviscous adaptation results in the maintenance of the liquid-crystalline phase through alterations in the degree of acyl chain saturation and branching, acyl chain length and the sterol content of the membrane. Homeophasic adaptation prevents the formation of non-bilayer phases, which would disrupt membrane organization and increase permeability. A balance is maintained between the lamellar phase, preferring lipids, and those that adopt a non-bilayer organization. As a result, the membrane proteins are optimally active under physiological conditions. The molecular basis of lipid-protein interactions is still obscure. Annular lipids stabilize integral membrane proteins. Stabilization occurs through electrostatic and possibly other interactions between the lipid headgroups and the charged amino acid residues close to the phospholipid-water interface, and hydrophobic interactions between the fatty acyl chains and the membrane-spanning segments. Reconstitution techniques allow manipulation of the lipid composition of the membrane in a way that is difficult to achieve in vivo. The physical characteristics of membrane lipids that affect protein-mediated transport functions have been studied in liposomal systems that separate an inner and outer compartment. The activity of most transport proteins is modulated by the bulk physical characteristics of the lipid bilayer, while specific lipid requirements appear rare.
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Affiliation(s)
- G I Veld
- Department of Microbiology, University of Groningen, The Netherlands
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