1
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Bing C, Mengjuan A, Xinyu M, Chixin Z, Xinyao T, Yan S, Zhi L. Efflux pump inhibitor chlorpromazine effectively increases the susceptibility of Escherichia coli to antimicrobial peptide Brevinin-2CE. Future Microbiol 2024; 19:771-782. [PMID: 38683168 PMCID: PMC11290751 DOI: 10.2217/fmb-2023-0272] [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: 12/02/2023] [Accepted: 02/21/2024] [Indexed: 05/01/2024] Open
Abstract
Aim: The response of E. coli ATCC8739 to Brevinin-2CE (B2CE) was evaluated as a strategy to prevent the development of antimicrobial peptide (AMP)-resistant bacteria. Methods: Gene expression levels were detected by transcriptome sequencing and RT-PCR. Target genes were knocked out using CRISPR-Cas9. MIC was measured to evaluate strain resistance. Results: Expression of acrZ and sugE were increased with B2CE stimulation. ATCC8739ΔacrZ and ATCC8739ΔsugE showed twofold and fourfold increased sensitivity, respectively. The survival rate of ATCC8739 was reduced in the presence of B2CE/chlorpromazine (CPZ). Combinations of other AMPs with CPZ also showed antibacterial effects. Conclusion: The results indicate that combinations of AMPs/efflux pump inhibitors (EPIs) may be a potential approach to combat resistant bacteria.
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Affiliation(s)
- Cao Bing
- College of Life Sciences, Shaanxi Normal University, Xi'an, 710119, PR China
| | - An Mengjuan
- College of Life Sciences, Shaanxi Normal University, Xi'an, 710119, PR China
| | - Ma Xinyu
- College of Life Sciences, Shaanxi Normal University, Xi'an, 710119, PR China
| | - Zhu Chixin
- College of Life Sciences, Shaanxi Normal University, Xi'an, 710119, PR China
| | - Tan Xinyao
- College of Life Sciences, Shaanxi Normal University, Xi'an, 710119, PR China
| | - Sun Yan
- College of Life Sciences, Shaanxi Normal University, Xi'an, 710119, PR China
| | - Li Zhi
- College of Life Sciences, Shaanxi Normal University, Xi'an, 710119, PR China
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2
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Hirakata Y, Mei R, Morinaga K, Katayama T, Tamaki H, Meng XY, Watari T, Yamaguchi T, Hatamoto M, Nobu MK. Identification and cultivation of anaerobic bacterial scavengers of dead cells. THE ISME JOURNAL 2023; 17:2279-2289. [PMID: 37872273 PMCID: PMC10689501 DOI: 10.1038/s41396-023-01538-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 10/06/2023] [Accepted: 10/09/2023] [Indexed: 10/25/2023]
Abstract
The cycle of life and death and Earth's carbon cycle(s) are intimately linked, yet how bacterial cells, one of the largest pools of biomass on Earth, are recycled back into the carbon cycle remains enigmatic. In particular, no bacteria capable of scavenging dead cells in oxygen-depleted environments have been reported thus far. In this study, we discover the first anaerobes that scavenge dead cells and the two isolated strains use distinct strategies. Based on live-cell imaging, transmission electron microscopy, and hydrolytic enzyme assays, one strain (designated CYCD) relied on cell-to-cell contact and cell invagination for degrading dead food bacteria where as the other strain (MGCD) degraded dead food bacteria via excretion of lytic extracellular enzymes. Both strains could degrade dead cells of differing taxonomy (bacteria and archaea) and differing extents of cell damage, including those without artificially inflicted physical damage. In addition, both depended on symbiotic metabolic interactions for maximizing cell degradation, representing the first cultured syntrophic Bacteroidota. We collectively revealed multiple symbiotic bacterial decomposition routes of dead prokaryotic cells, providing novel insight into the last step of the carbon cycle.
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Affiliation(s)
- Yuga Hirakata
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8566, Japan.
| | - Ran Mei
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8566, Japan
| | - Kana Morinaga
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8566, Japan
| | - Taiki Katayama
- Geomicrobiology Research Group, Research Institute for Geo-Resources and Environment, Geological Survey of Japan (GSJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8567, Japan
| | - Hideyuki Tamaki
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8566, Japan
| | - Xian-Ying Meng
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8566, Japan
| | - Takahiro Watari
- Department of Civil and Environmental Engineering, Nagaoka University of Technology, Nagaoka, 940-2188, Japan
| | - Takashi Yamaguchi
- Department of Civil and Environmental Engineering, Nagaoka University of Technology, Nagaoka, 940-2188, Japan
- Department of Science of Technology Innovation, Nagaoka University of Technology, Nagaoka, 940-2188, Japan
| | - Masashi Hatamoto
- Department of Civil and Environmental Engineering, Nagaoka University of Technology, Nagaoka, 940-2188, Japan
| | - Masaru K Nobu
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8566, Japan.
- Institute for Extra-Cutting-Edge Science and Technology Avant-Garde Research (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, 237-0061, Japan.
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3
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Will V, Gasser V, Kuhn L, Fritsch S, Heinrichs DE, Schalk IJ. Siderophore specificities of the Pseudomonas aeruginosa TonB-dependent transporters ChtA and ActA. FEBS Lett 2023; 597:2963-2974. [PMID: 37758521 DOI: 10.1002/1873-3468.14740] [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: 07/27/2023] [Revised: 09/12/2023] [Accepted: 09/13/2023] [Indexed: 09/29/2023]
Abstract
Iron is an essential nutrient for the survival and virulence of Pseudomonas aeruginosa. The pathogen expresses at least 15 different iron-uptake pathways, the majority involving small iron chelators called siderophores. P. aeruginosa produces two siderophores, 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. Here, we show that the two α-carboxylate-type siderophores rhizoferrin-Fe and staphyloferrin A-Fe are transported into P. aeruginosa cells by the TBDT ActA. Among the mixed α-carboxylate/hydroxamate-type siderophores, we found aerobactin-Fe to be transported by ChtA and schizokinen-Fe and arthrobactin-Fe by ChtA and another unidentified TBDT. Our findings enhance the understanding of the adaptability of P. aeruginosa and hold significant implications for developing novel strategies to combat antibiotic resistance.
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Affiliation(s)
- Virginie Will
- CNRS, University of Strasbourg, UMR7242, ESBS, Strasbourg, France
- University of Strasbourg, UMR7242, ESBS, Strasbourg, France
| | - Véronique Gasser
- CNRS, University of Strasbourg, UMR7242, ESBS, Strasbourg, France
- University of Strasbourg, UMR7242, ESBS, Strasbourg, France
| | - Lauriane Kuhn
- Plateforme Proteomique Strasbourg - Esplanade, Institut de Biologie Moléculaire et Cellulaire, CNRS FR1589, Strasbourg Cedex, France
| | - Sarah Fritsch
- CNRS, University of Strasbourg, UMR7242, ESBS, Strasbourg, France
- University of Strasbourg, UMR7242, ESBS, Strasbourg, France
| | - David E Heinrichs
- Department of Microbiology and Immunology, University of Western Ontario, London, Canada
| | - Isabelle J Schalk
- CNRS, University of Strasbourg, UMR7242, ESBS, Strasbourg, France
- University of Strasbourg, UMR7242, ESBS, Strasbourg, France
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4
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Hubert T, Madec M, Schalk IJ. Experimental and computational methods to highlight behavioural variations in TonB-dependent transporter expression in Pseudomonas aeruginosa versus siderophore concentration. Sci Rep 2023; 13:20015. [PMID: 37974013 PMCID: PMC10654771 DOI: 10.1038/s41598-023-46585-z] [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: 07/25/2023] [Accepted: 11/02/2023] [Indexed: 11/19/2023] Open
Abstract
Iron is a key nutrient for bacterial growth. The source can be either heme or siderophore-Fe complexes. Siderophores are small molecules synthesized by bacteria to scavenge iron from the bacterial environment. The pathogen Pseudomonas aeruginosa can express at least 15 different iron uptake pathways and all but one involve a TonB-dependent transporter (TBDT) for the uptake of iron across the outer membrane. Little is known about how bacteria modulate and adapt the expression of their different iron import pathways according to their environment. Here, we have developed fluorescent reporters between the promoter region of genes encoding a TBDT and the fluorescent reporter mCherry. With these constructs, we can follow the expression of TBDTs under different growth conditions. Mathematical modelling of the data obtained showed the transcription and expression of the gene encoding the TBDT PfeA to have a sigmoidal shape, whereas it was logarithmic for the TBDT gene foxA. Maximum transcription for pfeA was reached in the presence of 3 µM enterobactin, the siderophore recognized by PfeA, whereas the maximum was not reached for foxA with 100 µM nocardamine, the siderophore of FoxA.
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Affiliation(s)
- Thibaut Hubert
- CNRS, UMR7242, ESBS, University of Strasbourg, Bld Sébastien Brant, 67412, Illkirch, Strasbourg, France
- ICube Laboratory, CNRS, UMR 7357, University of Strasbourg, Bld Sébastien Brant, 67412, Illkirch, Strasbourg, France
| | - Morgan Madec
- ICube Laboratory, CNRS, UMR 7357, University of Strasbourg, Bld Sébastien Brant, 67412, Illkirch, Strasbourg, France.
| | - Isabelle J Schalk
- CNRS, UMR7242, ESBS, University of Strasbourg, Bld Sébastien Brant, 67412, Illkirch, Strasbourg, France.
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5
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Wimalasiri VW, Jurczak KA, Wieliniec MK, Nilaweera TD, Nakamoto RK, Cafiso DS. A disulfide chaperone knockout facilitates spin labeling and pulse EPR spectroscopy of outer membrane transporters. Protein Sci 2023; 32:e4704. [PMID: 37312651 PMCID: PMC10288552 DOI: 10.1002/pro.4704] [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: 02/17/2023] [Revised: 05/18/2023] [Accepted: 06/06/2023] [Indexed: 06/15/2023]
Abstract
Pulse EPR measurements provide information on distances and distance distributions in proteins but require the incorporation of pairs of spin labels that are usually attached to engineered cysteine residues. In previous work, we demonstrated that efficient in vivo labeling of the Escherichia coli outer membrane vitamin B12 transporter, BtuB, could only be achieved using strains defective in the periplasmic disulfide bond formation (Dsb) system. Here, we extend these in vivo measurements to FecA, the E. coli ferric citrate transporter. As seen for BtuB, pairs of cysteines cannot be labeled when the protein is present in a standard expression strain. However, incorporating plasmids that permit an arabinose induced expression of FecA into a strain defective in the thiol disulfide oxidoreductase, DsbA, enables efficient spin-labeling and pulse EPR of FecA in cells. A comparison of the measurements made on FecA in cells with measurements made in reconstituted phospholipid bilayers suggests that the cellular environment alters the behavior of the extracellular loops of FecA. In addition to these in situ EPR measurements, the use of a DsbA minus strain for the expression of BtuB improves the EPR signals and pulse EPR data obtained in vitro from BtuB that is labeled, purified, and reconstituted into phospholipid bilayers. The in vitro data also indicate the presence of intermolecular BtuB-BtuB interactions, which had not previously been observed in a reconstituted bilayer system. This result suggests that in vitro EPR measurements on other outer membrane proteins would benefit from protein expression in a DsbA minus strain.
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Affiliation(s)
- Viranga W. Wimalasiri
- Department of Chemistry and Center for Membrane BiologyUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - Kinga A. Jurczak
- Department of Chemistry and Center for Membrane BiologyUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - Monika K. Wieliniec
- Department of Chemistry and Center for Membrane BiologyUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - Thushani D. Nilaweera
- Department of Chemistry and Center for Membrane BiologyUniversity of VirginiaCharlottesvilleVirginiaUSA
- Present address:
Genetics and Biochemistry BranchNational Institute of Diabetes and Digestive and Kidney DiseasesBethesdaMarylandUSA
| | - Robert K. Nakamoto
- Department of Molecular Physiology and Biological PhysicsUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - David S. Cafiso
- Department of Chemistry and Center for Membrane BiologyUniversity of VirginiaCharlottesvilleVirginiaUSA
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6
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Peukert C, Gasser V, Orth T, Fritsch S, Normant V, Cunrath O, Schalk IJ, Brönstrup M. Trojan Horse Siderophore Conjugates Induce Pseudomonas aeruginosa Suicide and Qualify the TonB Protein as a Novel Antibiotic Target. J Med Chem 2023; 66:553-576. [PMID: 36548006 PMCID: PMC9841981 DOI: 10.1021/acs.jmedchem.2c01489] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Indexed: 12/24/2022]
Abstract
Rising infection rates with multidrug-resistant pathogens calls for antibiotics with novel modes of action. Herein, we identify the inner membrane protein TonB, a motor of active uptake in Gram-negative bacteria, as a novel target in antimicrobial therapy. The interaction of the TonB box of outer membrane transporters with TonB is crucial for the internalization of essential metabolites. We designed TonB box peptides and coupled them with synthetic siderophores in order to facilitate their uptake into bacteria in up to 32 synthetic steps. Three conjugates repressed the growth of Pseudomonas aeruginosa cells unable to produce their own siderophores, with minimal inhibitory concentrations between 0.1 and 0.5 μM. The transporters mediating uptake of these compounds were identified as PfeA and PirA. The study illustrates a variant of cellular suicide where a transporter imports its own inhibitor and demonstrates that artificial siderophores can import cargo with molecular weights up to 4 kDa.
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Affiliation(s)
- Carsten Peukert
- Department
of Chemical Biology, Helmholtz Centre for
Infection Research, Inhoffenstraße 7, 38124 Braunschweig, Germany
| | - Véronique Gasser
- CNRS, University
of Strasbourg, UMR7242, ESBS, Boulevard Sébastien Brant, F-67412 Illkirch, Strasbourg, France
| | - Till Orth
- Department
of Chemical Biology, Helmholtz Centre for
Infection Research, Inhoffenstraße 7, 38124 Braunschweig, Germany
| | - Sarah Fritsch
- CNRS, University
of Strasbourg, UMR7242, ESBS, Boulevard Sébastien Brant, F-67412 Illkirch, Strasbourg, France
| | - Vincent Normant
- CNRS, University
of Strasbourg, UMR7242, ESBS, Boulevard Sébastien Brant, F-67412 Illkirch, Strasbourg, France
| | - Olivier Cunrath
- CNRS, University
of Strasbourg, UMR7242, ESBS, Boulevard Sébastien Brant, F-67412 Illkirch, Strasbourg, France
| | - Isabelle J. Schalk
- CNRS, University
of Strasbourg, UMR7242, ESBS, Boulevard Sébastien Brant, F-67412 Illkirch, Strasbourg, France
| | - Mark Brönstrup
- Department
of Chemical Biology, Helmholtz Centre for
Infection Research, Inhoffenstraße 7, 38124 Braunschweig, Germany
- German
Center for Infection Research (DZIF), Site Hannover-Braunschweig, 38124 Braunschweig, Germany
- Center for
Biomolecular Drug Research (BMWZ), Schneiderberg 38, 30167 Hannover, Germany
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7
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Resistance Mechanism and Physiological Effects of Microcin Y in Salmonella enterica subsp. enterica Serovar Typhimurium. Microbiol Spectr 2022; 10:e0185922. [PMID: 36453909 PMCID: PMC9769762 DOI: 10.1128/spectrum.01859-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Salmonella bacteria pose a significant threat to animal husbandry and human health due to their virulence and multidrug resistance. The lasso peptide MccY is a recently discovered antimicrobial peptide that acts against various serotypes of Salmonella. In this study, we further explore the resistance mechanism and activity of MccY. Mutants of Ton system genes, including tonB, exbB, and exbD, in Salmonella enterica subsp. enterica serovar Typhimurium were constructed, and the MICs to MccY exhibited significant increases in these deletion mutants compared to the MIC of the parent strain. Subsequently, MccY resistance was quantitatively analyzed, and these mutants also showed greatly reduced rates of killing, even with a high concentration of MccY. In addition, a minimal medium with low iron environment enhanced the sensitivity of these mutants to MccY. Measurements of a series of physiological indicators, including iron utilization, biofilm formation, and motility, demonstrated that MccY may decrease the virulence of S. Typhimurium. Transcriptomic analysis showed that iron utilization, biofilm formation, flagellar assembly, and virulence-related genes were downregulated to varying degrees when S. Typhimurium was treated with MccY. In conclusion, deletion of Ton system genes resulted in resistance to MccY and the susceptibility of these mutants to MccY was increased and differed under a low-iron condition. This lasso peptide can alter multiple physiological properties of S. Typhimurium. Our study will contribute to improve the knowledge and understanding of the mechanism of MccY resistance in Salmonella strains. IMPORTANCE The resistance of Salmonella to traditional antibiotics remains a serious challenge. Novel anti-Salmonella drugs are urgently needed to address the looming crisis. The newly identified antimicrobial peptide MccY shows broad prospects for development and application because of its obvious antagonistic effect on various serotypes of Salmonella. However, our previous study showed that the peptide could confer resistance to Salmonella by disrupting the receptor gene fhuA. In this study, we further explored the potential resistance mechanism of MccY and demonstrated the importance of the Salmonella Ton complex for MccY transport. Disruption in Ton system genes resulted in S. Typhimurium resistance to this peptide, and MccY could alter multiple bacterial physiological properties. In summary, this study further explored the resistance mechanism and antibacterial effect of MccY in S. Typhimurium and provided a scientific basis for its development and application.
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8
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Bartelli NL, Passanisi VJ, Michalska K, Song K, Nhan DQ, Zhou H, Cuthbert BJ, Stols LM, Eschenfeldt WH, Wilson NG, Basra JS, Cortes R, Noorsher Z, Gabraiel Y, Poonen-Honig I, Seacord EC, Goulding CW, Low DA, Joachimiak A, Dahlquist FW, Hayes CS. Proteolytic processing induces a conformational switch required for antibacterial toxin delivery. Nat Commun 2022; 13:5078. [PMID: 36038560 PMCID: PMC9424206 DOI: 10.1038/s41467-022-32795-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 08/12/2022] [Indexed: 02/08/2023] Open
Abstract
Many Gram-negative bacteria use CdiA effector proteins to inhibit the growth of neighboring competitors. CdiA transfers its toxic CdiA-CT region into the periplasm of target cells, where it is released through proteolytic cleavage. The N-terminal cytoplasm-entry domain of the CdiA-CT then mediates translocation across the inner membrane to deliver the C-terminal toxin domain into the cytosol. Here, we show that proteolysis not only liberates the CdiA-CT for delivery, but is also required to activate the entry domain for membrane translocation. Translocation function depends on precise cleavage after a conserved VENN peptide sequence, and the processed ∆VENN entry domain exhibits distinct biophysical and thermodynamic properties. By contrast, imprecisely processed CdiA-CT fragments do not undergo this transition and fail to translocate to the cytoplasm. These findings suggest that CdiA-CT processing induces a critical structural switch that converts the entry domain into a membrane-translocation competent conformation.
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Affiliation(s)
- Nicholas L Bartelli
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Victor J Passanisi
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Karolina Michalska
- Midwest Center for Structural Genomics, Argonne National Laboratory, Lemont, IL, USA
- Center for Structural Genomics of Infectious Diseases, University of Chicago, Chicago, IL, USA
- Structural Biology Center, X-ray Science Division, Argonne National Laboratory, Lemont, IL, USA
| | - Kiho Song
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA, USA
| | - Dinh Q Nhan
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Hongjun Zhou
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Bonnie J Cuthbert
- Department of Molecular Biology & Biochemistry, University of California, Irvine, CA, USA
| | - Lucy M Stols
- Midwest Center for Structural Genomics, Argonne National Laboratory, Lemont, IL, USA
| | - William H Eschenfeldt
- Midwest Center for Structural Genomics, Argonne National Laboratory, Lemont, IL, USA
| | - Nicholas G Wilson
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Jesse S Basra
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Ricardo Cortes
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Zainab Noorsher
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Youssef Gabraiel
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Isaac Poonen-Honig
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Elizabeth C Seacord
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Celia W Goulding
- Department of Molecular Biology & Biochemistry, University of California, Irvine, CA, USA
- Pharmaceutical Sciences, University of California, Irvine, CA, USA
| | - David A Low
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA, USA
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Andrzej Joachimiak
- Midwest Center for Structural Genomics, Argonne National Laboratory, Lemont, IL, USA
- Center for Structural Genomics of Infectious Diseases, University of Chicago, Chicago, IL, USA
- Structural Biology Center, X-ray Science Division, Argonne National Laboratory, Lemont, IL, USA
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA
| | - Frederick W Dahlquist
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA, USA
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Christopher S Hayes
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA, USA.
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA.
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9
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Abstract
The Ton complex is a molecular motor at the inner membrane of Gram-negative bacteria that uses a proton gradient to apply forces on outer membrane (OM) proteins to permit active transport of nutrients into the periplasmic space. Recently, the structure of the ExbB–ExbD subcomplex was determined in several bacterial species, but the complete structure and stoichiometry of TonB have yet to be determined. The C-terminal end of TonB is known to cross the periplasm and interact with TonB-dependent outer membrane transport proteins with high affinity. Yet despite having significant knowledge of these transport proteins, it is not clear how the Ton motor opens a pathway across the outer membrane for nutrient import. Additionally, the mechanism by which energy is harnessed from the inner membrane subcomplex and transduced to the outer membrane via TonB is not well understood. In this review, we will discuss the gaps in the knowledge about the complete structure of the Ton motor complex and the relationship between ion flow used to generate mechanical work at the outer membrane and the nutrient transport process.
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10
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Braun V, Hartmann MD, Hantke K. Transcription regulation of iron carrier transport genes by ECF sigma factors through signaling from the cell surface into the cytoplasm. FEMS Microbiol Rev 2022; 46:6524835. [PMID: 35138377 PMCID: PMC9249621 DOI: 10.1093/femsre/fuac010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 01/26/2022] [Accepted: 02/07/2022] [Indexed: 12/02/2022] Open
Abstract
Bacteria are usually iron-deficient because the Fe3+ in their environment is insoluble or is incorporated into proteins. To overcome their natural iron limitation, bacteria have developed sophisticated iron transport and regulation systems. In gram-negative bacteria, these include iron carriers, such as citrate, siderophores, and heme, which when loaded with Fe3+ adsorb with high specificity and affinity to outer membrane proteins. Binding of the iron carriers to the cell surface elicits a signal that initiates transcription of iron carrier transport and synthesis genes, referred to as “cell surface signaling”. Transcriptional regulation is not coupled to transport. Outer membrane proteins with signaling functions contain an additional N-terminal domain that in the periplasm makes contact with an anti-sigma factor regulatory protein that extends from the outer membrane into the cytoplasm. Binding of the iron carriers to the outer membrane receptors elicits proteolysis of the anti-sigma factor by two different proteases, Prc in the periplasm, and RseP in the cytoplasmic membrane, inactivates the anti-sigma function or results in the generation of an N-terminal peptide of ∼50 residues with pro-sigma activity yielding an active extracytoplasmic function (ECF) sigma factor. Signal recognition and signal transmission into the cytoplasm is discussed herein.
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Affiliation(s)
- Volkmar Braun
- Max Planck Institute for Biology, Department of Protein Evolution, Max Planck Ring 5, 72076 Tübingen, Germany
| | - Marcus D Hartmann
- Max Planck Institute for Biology, Department of Protein Evolution, Max Planck Ring 5, 72076 Tübingen, Germany
| | - Klaus Hantke
- IMIT Institute, University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
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11
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Normant V, Kuhn L, Munier M, Hammann P, Mislin GLA, Schalk IJ. How the Presence of Hemin Affects the Expression of the Different Iron Uptake Pathways in Pseudomonas aeruginosa Cells. ACS Infect Dis 2022; 8:183-196. [PMID: 34878758 DOI: 10.1021/acsinfecdis.1c00525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Iron is an essential nutriment for almost all organisms, but this metal is poorly bioavailable. During infection, bacteria access iron from the host by importing either iron or heme. Pseudomonas aeruginosa, a gram-negative pathogen, secretes two siderophores, pyoverdine (PVD) and pyochelin (PCH), to access iron and is also able to use many siderophores produced by other microorganisms (called xenosiderophores). To access heme, P. aeruginosa uses three distinct uptake pathways, named Has, Phu, and Hxu. We previously showed that P. aeruginosa expresses the Has and Phu heme uptake systems and the PVD- and PCH-dependent iron uptake pathways in iron-restricted growth conditions, using proteomic and RT-qPCR approaches. Here, using the same approaches, we show that physiological concentrations of hemin in the bacterial growth medium result in the repression of the expression of the proteins of the PVD- and PCH-dependent iron uptake pathways, leading to less production of these two siderophores. This indicates that the pathogen adapts its phenotype to use hemin as an iron source rather than produce PVD and PCH to access iron. Moreover, the presence of both hemin and a xenosiderophore resulted in (i) the strong induction of the expression of the proteins of the added xenosiderophore uptake pathway, (ii) repression of the PVD- and PCH-dependent iron uptake pathways, and (iii) no effect on the expression levels of the Has, Phu, or Hxu systems, indicating that bacteria use both xenosiderophores and heme to access iron.
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Affiliation(s)
- Vincent Normant
- CNRS/Université de Strasbourg, UMR7242, ESBS, Bld Sébastien Brant, Illkirch, F-67412 Strasbourg, France
| | - Lauriane Kuhn
- Plateforme Proteomique Strasbourg - Esplanade, Institut de Biologie Moléculaire et Cellulaire, CNRS, FR1589, 15 rue Descartes, F-67084 Strasbourg Cedex, France
| | - Mathilde Munier
- CNRS/Université de Strasbourg, UMR7242, ESBS, Bld Sébastien Brant, Illkirch, F-67412 Strasbourg, France
| | - Philippe Hammann
- Plateforme Proteomique Strasbourg - Esplanade, Institut de Biologie Moléculaire et Cellulaire, CNRS, FR1589, 15 rue Descartes, F-67084 Strasbourg Cedex, France
| | - Gaëtan L. A. Mislin
- CNRS/Université de Strasbourg, UMR7242, ESBS, Bld Sébastien Brant, Illkirch, F-67412 Strasbourg, France
| | - Isabelle J. Schalk
- CNRS/Université de Strasbourg, UMR7242, ESBS, Bld Sébastien Brant, Illkirch, F-67412 Strasbourg, France
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12
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Rieu M, Krutyholowa R, Taylor NMI, Berry RM. A new class of biological ion-driven rotary molecular motors with 5:2 symmetry. Front Microbiol 2022; 13:948383. [PMID: 35992645 PMCID: PMC9389320 DOI: 10.3389/fmicb.2022.948383] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 07/04/2022] [Indexed: 11/15/2022] Open
Abstract
Several new structures of three types of protein complexes, obtained by cryo-electron microscopy (cryo-EM) and published between 2019 and 2021, identify a new family of natural molecular wheels, the "5:2 rotary motors." These span the cytoplasmic membranes of bacteria, and their rotation is driven by ion flow into the cell. They consist of a pentameric wheel encircling a dimeric axle within the cytoplasmic membrane of both Gram-positive and gram-negative bacteria. The axles extend into the periplasm, and the wheels extend into the cytoplasm. Rotation of these wheels has never been observed directly; it is inferred from the symmetry of the complexes and from the roles they play within the larger systems that they are known to power. In particular, the new structure of the stator complex of the Bacterial Flagellar Motor, MotA5B2, is consistent with a "wheels within wheels" model of the motor. Other 5:2 rotary motors are believed to share the core rotary function and mechanism, driven by ion-motive force at the cytoplasmic membrane. Their structures diverge in their periplasmic and cytoplasmic parts, reflecting the variety of roles that they perform. This review focuses on the structures of 5:2 rotary motors and their proposed mechanisms and functions. We also discuss molecular rotation in general and its relation to the rotational symmetry of molecular complexes.
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Affiliation(s)
- Martin Rieu
- Department of Physics, University of Oxford, Oxford, United Kingdom
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin Building University of Oxford, Oxford, United Kingdom
| | - Roscislaw Krutyholowa
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
| | - Nicholas M. I. Taylor
- Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Copenhagen, Denmark
- Nicholas M. I. Taylor,
| | - Richard M. Berry
- Department of Physics, University of Oxford, Oxford, United Kingdom
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin Building University of Oxford, Oxford, United Kingdom
- *Correspondence: Richard M. Berry,
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13
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Fujita M, Yano S, Shibata K, Kondo M, Hishiyama S, Kamimura N, Masai E. Functional roles of multiple Ton complex genes in a Sphingobium degrader of lignin-derived aromatic compounds. Sci Rep 2021; 11:22444. [PMID: 34789769 PMCID: PMC8599685 DOI: 10.1038/s41598-021-01756-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 10/27/2021] [Indexed: 01/04/2023] Open
Abstract
TonB-dependent transporters (TBDTs) mediate outer membrane transport of nutrients using the energy derived from proton motive force transmitted from the TonB–ExbB–ExbD complex localized in the inner membrane. Recently, we discovered ddvT encoding a TBDT responsible for the uptake of a 5,5-type lignin-derived dimer in Sphingobium sp. strain SYK-6. Furthermore, overexpression of ddvT in an SYK-6-derivative strain enhanced its uptake capacity, improving the rate of platform chemical production. Thus, understanding the uptake system of lignin-derived aromatics is fundamental for microbial conversion-based lignin valorization. Here we examined whether multiple tonB-, exbB-, and exbD-like genes in SYK-6 contribute to the outer membrane transport of lignin-derived aromatics. The disruption of tonB2–6 and exbB3 did not reduce the capacity of SYK-6 to convert or grow on lignin-derived aromatics. In contrast, the introduction of the tonB1–exbB1–exbD1–exbD2 operon genes into SYK-6, which could not be disrupted, promoted the conversion of β-O-4-, β-5-, β-1-, β-β-, and 5,5-type dimers and monomers, such as ferulate, vanillate, syringate, and protocatechuate. These results suggest that TonB-dependent uptake involving the tonB1 operon genes is responsible for the outer membrane transport of the above aromatics. Additionally, exbB2/tolQ and exbD3/tolR were suggested to constitute the Tol-Pal system that maintains the outer membrane integrity.
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Affiliation(s)
- Masaya Fujita
- Department of Bioengineering, Nagaoka University of Technology, Nagaoka, Niigata, 940-2188, Japan.,Structural Biology Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, Japan
| | - Shodai Yano
- Department of Bioengineering, Nagaoka University of Technology, Nagaoka, Niigata, 940-2188, Japan
| | - Koki Shibata
- Department of Bioengineering, Nagaoka University of Technology, Nagaoka, Niigata, 940-2188, Japan
| | - Mizuki Kondo
- Center for Integrated Technology Support, Nagaoka University of Technology, Nagaoka, Niigata, Japan
| | - Shojiro Hishiyama
- Forestry and Forest Products Research Institute, Tsukuba, Ibaraki, Japan
| | - Naofumi Kamimura
- Department of Bioengineering, Nagaoka University of Technology, Nagaoka, Niigata, 940-2188, Japan
| | - Eiji Masai
- Department of Bioengineering, Nagaoka University of Technology, Nagaoka, Niigata, 940-2188, Japan.
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14
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Abstract
Colicins are protein antibiotics deployed by Escherichia coli to eliminate competing strains. Colicins frequently exploit outer membrane (OM) nutrient transporters to penetrate the selectively permeable bacterial cell envelope. Here, by applying live-cell fluorescence imaging, we were able to monitor the entry of the pore-forming toxin colicin B (ColB) into E. coli and localize it within the periplasm. We further demonstrate that single-stranded DNA coupled to ColB can also be transported to the periplasm, emphasizing that the import routes of colicins can be exploited to carry large cargo molecules into bacteria. Moreover, we characterize the molecular mechanism of ColB association with its OM receptor FepA by applying a combination of photoactivated cross-linking, mass spectrometry, and structural modeling. We demonstrate that complex formation is coincident with large-scale conformational changes in the colicin. Thereafter, active transport of ColB through FepA involves the colicin taking the place of the N-terminal half of the plug domain that normally occludes this iron transporter. IMPORTANCE Decades of excessive use of readily available antibiotics has generated a global problem of antibiotic resistance and, hence, an urgent need for novel antibiotic solutions. Bacteriocins are protein-based antibiotics produced by bacteria to eliminate closely related competing bacterial strains. Bacteriocin toxins have evolved to bypass the complex cell envelope in order to kill bacterial cells. Here, we uncover the cellular penetration mechanism of a well-known but poorly understood bacteriocin called colicin B that is active against Escherichia coli. Moreover, we demonstrate that the colicin B-import pathway can be exploited to deliver conjugated DNA cargo into bacterial cells. Our work leads to a better understanding of the way bacteriocins, as potential alternative antibiotics, execute their mode of action as well as highlighting how they might even be exploited in the genomic manipulation of Gram-negative bacteria.
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15
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Hu H, Santiveri M, Wadhwa N, Berg HC, Erhardt M, Taylor NMI. Structural basis of torque generation in the bi-directional bacterial flagellar motor. Trends Biochem Sci 2021; 47:160-172. [PMID: 34294545 DOI: 10.1016/j.tibs.2021.06.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2021] [Revised: 06/16/2021] [Accepted: 06/18/2021] [Indexed: 12/11/2022]
Abstract
The flagellar stator unit is an oligomeric complex of two membrane proteins (MotA5B2) that powers bi-directional rotation of the bacterial flagellum. Harnessing the ion motive force across the cytoplasmic membrane, the stator unit operates as a miniature rotary motor itself to provide torque for rotation of the flagellum. Recent cryo-electron microscopic (cryo-EM) structures of the stator unit provided novel insights into its assembly, function, and subunit stoichiometry, revealing the ion flux pathway and the torque generation mechanism. Furthermore, in situ cryo-electron tomography (cryo-ET) studies revealed unprecedented details of the interactions between stator unit and rotor. In this review, we summarize recent advances in our understanding of the structure and function of the flagellar stator unit, torque generation, and directional switching of the motor.
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Affiliation(s)
- Haidai Hu
- Structural Biology of Molecular Machines Group, Protein Structure & Function Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Mònica Santiveri
- Structural Biology of Molecular Machines Group, Protein Structure & Function Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Navish Wadhwa
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA; Rowland Institute at Harvard, Harvard University, 100 Edwin H. Land Blvd, Cambridge, MA 02142, USA
| | - Howard C Berg
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA; Rowland Institute at Harvard, Harvard University, 100 Edwin H. Land Blvd, Cambridge, MA 02142, USA
| | - Marc Erhardt
- Institut für Biologie/Bakterienphysiologie, Humboldt-Universität zu Berlin, Philippstr. 13, 10115 Berlin, Germany
| | - Nicholas M I Taylor
- Structural Biology of Molecular Machines Group, Protein Structure & Function Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark.
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16
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Guérin J, Buchanan SK. Protein import and export across the bacterial outer membrane. Curr Opin Struct Biol 2021; 69:55-62. [PMID: 33901701 DOI: 10.1016/j.sbi.2021.03.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 03/09/2021] [Accepted: 03/21/2021] [Indexed: 01/06/2023]
Abstract
The bacterial outer membrane forms an impermeable barrier to the environment, but a wide variety of substances must cross it without compromising the membrane. Perhaps, the most fascinating transport phenomenon is the import and export of very large protein toxins using relatively small β-barrel proteins residing in the outer membrane. Progress has been made on three systems in recent years that shed light on this process. In this review, we summarize bacteriocin (toxin) import using TonB-dependent transporters and protein secretion by autotransporters and two partner secretion systems.
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Affiliation(s)
- Jérémy Guérin
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Susan K Buchanan
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA.
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Rhizobiales-Specific RirA Represses a Naturally "Synthetic" Foreign Siderophore Gene Cluster To Maintain Sinorhizobium-Legume Mutualism. mBio 2021; 13:e0290021. [PMID: 35130720 PMCID: PMC8822346 DOI: 10.1128/mbio.02900-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Iron homeostasis is strictly regulated in cellular organisms. The Rhizobiales order enriched with symbiotic and pathogenic bacteria has evolved a lineage-specific regulator, RirA, responding to iron fluctuations. However, the regulatory role of RirA in bacterium-host interactions remains largely unknown. Here, we report that RirA is essential for mutualistic interactions of Sinorhizobium fredii with its legume hosts by repressing a gene cluster directing biosynthesis and transport of petrobactin siderophore. Genes encoding an inner membrane ABC transporter (fat) and the biosynthetic machinery (asb) of petrobactin siderophore are sporadically distributed in Gram-positive and Gram-negative bacteria. An outer membrane siderophore receptor gene (fprA) was naturally assembled with asb and fat, forming a long polycistron in S. fredii. An indigenous regulation cascade harboring an inner membrane protease (RseP), a sigma factor (FecI), and its anti-sigma protein (FecR) were involved in direct activation of the fprA-asb-fat polycistron. Operons harboring fecI and fprA-asb-fat, and those encoding the indigenous TonB-ExbB-ExbD complex delivering energy to the outer membrane transport activity, were directly repressed by RirA under iron-replete conditions. The rirA deletion led to upregulation of these operons and iron overload in nodules, impaired intracellular persistence, and symbiotic nitrogen fixation of rhizobia. Mutualistic defects of the rirA mutant can be rescued by blocking activities of this naturally "synthetic" circuit for siderophore biosynthesis and transport. These findings not only are significant for understanding iron homeostasis of mutualistic interactions but also provide insights into assembly and integration of foreign machineries for biosynthesis and transport of siderophores, horizontal transfer of which is selected in microbiota. IMPORTANCE Iron is a public good explored by both eukaryotes and prokaryotes. The abundant ferric form is insoluble under neutral and basic pH conditions, and many bacteria secrete siderophores forming soluble ferric siderophore complexes, which can be then taken up by specific receptors and transporters. Siderophore biosynthesis and uptake machineries can be horizontally transferred among bacteria in nature. Despite increasing attention on the importance of siderophores in host-microbiota interactions, the regulatory integration process of transferred siderophore biosynthesis and transport genes is poorly understood in an evolutionary context. By focusing on the mutualistic rhizobium-legume symbiosis, here, we report how a naturally synthetic foreign siderophore gene cluster was integrated with the rhizobial indigenous regulation cascade, which is essential for maintaining mutualistic interactions.
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