1
|
Domínguez-Maqueda M, Espinosa-Ruíz C, Esteban MÁ, Alarcón FJ, Tapia-Paniagua ST, Balebona MC, Moriñigo MÁ. An ex vivo Approach in European Seabass Leucocytes Supports the in vitro Regulation by Postbiotics of Aip56 Gene Expression of Photobacterium damselae subsp. piscicida. Probiotics Antimicrob Proteins 2024:10.1007/s12602-024-10255-x. [PMID: 38652230 DOI: 10.1007/s12602-024-10255-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/05/2024] [Indexed: 04/25/2024]
Abstract
Shewanella putrefaciens Pdp11 (SpPdp11) is a probiotic strain assayed in aquaculture; however, its postbiotic potential is unknown. Postbiotics are bacterial metabolites, including extracellular products (ECPs) that improve host physiology and immunity. Their production and composition can be affected by different factors such as the growing conditions of the probiotics. Photobacterium damselae subsp. piscicida strain Lg 41/01 (Phdp) is one of the most important pathogens in marine aquaculture. The major virulent factor of this bacterium is the exotoxin aip56, responsible for inducing apoptosis of fish leucocytes. Viable SpPdp11 cells have been reported to increase resistance to challenges with Phdp. This work aimed to evaluate the effect of two ECPs, T2348-ECP and FM1548-ECP, obtained from SpPdp11 grown under different culture conditions that previously demonstrated to exert different degradative and non-cytotoxic activities, as well as the effect on pathogens biofilm formation. These SpPdp11-ECPs were then analyzed by their effect on the viability, phagocytosis, respiratory burst and apoptogenic activity against European sea bass leucocytes infected or not with Phdp supernatant. Both ECPs, T2348-ECP and FM1548-ECP, were not cytotoxic against leucocytes and significantly reduced their apoptosis. Phagocytosis and respiratory burst of leucocytes were significantly reduced by incubation with Phdp supernatant, and not influenced by incubation with T2348-ECP or FM1548-ECP. However, both activities were significantly increased after leucocyte incubation with combined T2348-ECP and FM1548-ECP with Phdp supernatant, compared to those incubated only with Phdp supernatant. Finally, both T2348-ECP and FM1548-ECP significantly reduced the relative in vitro expression of the Phdp aip56 encoding gene.
Collapse
Affiliation(s)
- Marta Domínguez-Maqueda
- Departamento de Microbiología, Facultad de Ciencias, Instituto Andaluz de Biotecnología y Desarrollo Azul (IBYDA), Universidad de Málaga, Ceimar-Universidad de Málaga, Málaga, Spain
| | - Cristóbal Espinosa-Ruíz
- Departamento de Biología Celular e Histología, Facultad de Biología, Universidad de Murcia, Murcia, Spain
| | - María Ángeles Esteban
- Departamento de Biología Celular e Histología, Facultad de Biología, Universidad de Murcia, Murcia, Spain
| | - Francisco Javier Alarcón
- Departamento de Biología y Geología, Universidad de Almería, Ceimar-Universidad de Almería, Almería, Spain
- Lifebioencapsulation SL, 0413-El Alquián, Almería, Spain
| | - Silvana T Tapia-Paniagua
- Departamento de Microbiología, Facultad de Ciencias, Instituto Andaluz de Biotecnología y Desarrollo Azul (IBYDA), Universidad de Málaga, Ceimar-Universidad de Málaga, Málaga, Spain.
| | - María Carmen Balebona
- Departamento de Microbiología, Facultad de Ciencias, Instituto Andaluz de Biotecnología y Desarrollo Azul (IBYDA), Universidad de Málaga, Ceimar-Universidad de Málaga, Málaga, Spain
| | - Miguel Ángel Moriñigo
- Departamento de Microbiología, Facultad de Ciencias, Instituto Andaluz de Biotecnología y Desarrollo Azul (IBYDA), Universidad de Málaga, Ceimar-Universidad de Málaga, Málaga, Spain
| |
Collapse
|
2
|
Elery ZK, Myers-Morales T, Phillips ED, Garcia EC. Relaxed specificity of BcpB transporters mediates interactions between Burkholderia cepacia complex contact-dependent growth inhibition systems. mSphere 2023; 8:e0030323. [PMID: 37498085 PMCID: PMC10449530 DOI: 10.1128/msphere.00303-23] [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: 06/07/2023] [Accepted: 06/11/2023] [Indexed: 07/28/2023] Open
Abstract
Belonging to the two-partner secretion family of proteins, contact-dependent growth inhibition (CDI) systems mediate interbacterial antagonism among closely related Gram-negative bacteria. The toxic portion of a large surface protein, BcpA/CdiA, is delivered to the cytoplasm of neighboring cells where it inhibits growth. Translocation of the antibacterial polypeptide out of the producing cell requires an associated outer membrane transporter, BcpB/CdiB. Some bacteria, including many Burkholderia species, encode multiple distinct CDI systems, but whether there is interaction between these systems is largely unknown. Using Burkholderia cepacia complex species as a model, here we show that related BcpB transporters exhibit considerable secretion flexibility and can secrete both cognate and non-cognate BcpA substrates. We also identified an additional unique Burkholderia dolosa CDI system capable of mediating interbacterial competition and demonstrated that its BcpB transporter has similar relaxed substrate specificity. Our results showed that two BcpB transporters (BcpB-2 and BcpB-3) were able to secrete all four of the B. dolosa BcpA toxins, while one transporter (BcpB-1) appeared unable to secrete even its cognate BcpA substrate under the tested conditions. This flexibility provided a competitive advantage, as strains lacking the full repertoire of BcpB proteins had decreased CDI activity. Similar results were obtained in Burkholderia multivorans, suggesting that secretion flexibility may be a conserved feature of Burkholderia CDI systems. Together these findings suggest that the interaction between distinct CDI systems enhances the efficiency of bacterial antagonism. IMPORTANCE The Burkholderia cepacia complex (Bcc) is a group of related opportunistic bacterial pathogens that occupy a diverse range of ecological niches and exacerbate disease in patients with underlying conditions. Contact-dependent growth inhibition (CDI) system proteins, produced by Gram-negative bacteria, contain antagonistic properties that allow for intoxication of closely related neighboring bacteria via a secreted protein, BcpA. Multiple unique CDI systems can be found in the same bacterial strain, and here we show that these distinct systems interact in several Bcc species. Our findings suggest that the interaction between CDI system proteins is important for interbacterial toxicity. Understanding the mechanism of interplay between CDI systems provides further insight into the complexity of bacterial antagonism. Moreover, since many bacterial species are predicted to encode multiple CDI systems, this study suggests that interactions between these distinct systems likely contribute to the overall competitive fitness of these species.
Collapse
Affiliation(s)
- Zaria K. Elery
- University of Kentucky College of Medicine, Lexington, Kentucky, USA
| | | | - Erica D. Phillips
- University of Kentucky College of Medicine, Lexington, Kentucky, USA
| | - Erin C. Garcia
- University of Kentucky College of Medicine, Lexington, Kentucky, USA
| |
Collapse
|
3
|
Li P, Zhang S, Wang J, Al-Shamiri MM, Han B, Chen Y, Han S, Han L. Uncovering the Secretion Systems of Acinetobacter baumannii: Structures and Functions in Pathogenicity and Antibiotic Resistance. Antibiotics (Basel) 2023; 12:antibiotics12020195. [PMID: 36830106 PMCID: PMC9952577 DOI: 10.3390/antibiotics12020195] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 01/06/2023] [Accepted: 01/16/2023] [Indexed: 01/19/2023] Open
Abstract
Infections led by Acinetobacter baumannii strains are of great concern in healthcare environments due to the strong ability of the bacteria to spread through different apparatuses and develop drug resistance. Severe diseases can be caused by A. baumannii in critically ill patients, but its biological process and mechanism are not well understood. Secretion systems have recently been demonstrated to be involved in the pathogenic process, and five types of secretion systems out of the currently known six from Gram-negative bacteria have been found in A. baumannii. They can promote the fitness and pathogenesis of the bacteria by releasing a variety of effectors. Additionally, antibiotic resistance is found to be related to some types of secretion systems. In this review, we describe the genetic and structural compositions of the five secretion systems that exist in Acinetobacter. In addition, the function and molecular mechanism of each secretion system are summarized to explain how they enable these critical pathogens to overcome eukaryotic hosts and prokaryotic competitors to cause diseases.
Collapse
Affiliation(s)
- Pu Li
- School of Public Health, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Sirui Zhang
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Jingdan Wang
- School of Public Health, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Mona Mohamed Al-Shamiri
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Bei Han
- School of Public Health, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Yanjiong Chen
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Shaoshan Han
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an 710061, China
| | - Lei Han
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
- Correspondence:
| |
Collapse
|
4
|
Crisan CV, Goldberg JB. Antibacterial contact-dependent proteins secreted by Gram-negative cystic fibrosis respiratory pathogens. Trends Microbiol 2022; 30:986-996. [PMID: 35487848 PMCID: PMC9474641 DOI: 10.1016/j.tim.2022.03.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 02/25/2022] [Accepted: 03/29/2022] [Indexed: 01/11/2023]
Abstract
Cystic fibrosis (CF) is a genetic disease that affects almost 100 000 people worldwide. CF patients suffer from chronic bacterial airway infections that are often polymicrobial and are the leading cause of mortality. Interactions between pathogens modulate expression of genes responsible for virulence and antibiotic resistance. One of the ways bacteria can interact is through contact-dependent systems, which secrete antibacterial proteins (effectors) that confer advantages to cells that harbor them. Here, we highlight recent work that describes effectors used by Gram-negative CF pathogens to eliminate competitor bacteria. Understanding the mechanisms of secreted effectors may lead to novel insights into the ecology of bacteria that colonize respiratory tracts and could also pave the way for the design of new therapeutics.
Collapse
Affiliation(s)
- Cristian V Crisan
- Department of Pediatrics, Division of Pulmonary, Asthma, Cystic Fibrosis, and Sleep, Emory University School of Medicine, Atlanta, GA, USA; Emory+Children's Center for Cystic Fibrosis and Airway Disease Research, Emory University School of Medicine, Atlanta, GA, USA
| | - Joanna B Goldberg
- Department of Pediatrics, Division of Pulmonary, Asthma, Cystic Fibrosis, and Sleep, Emory University School of Medicine, Atlanta, GA, USA; Emory+Children's Center for Cystic Fibrosis and Airway Disease Research, Emory University School of Medicine, Atlanta, GA, USA.
| |
Collapse
|
5
|
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.
Collapse
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.
| |
Collapse
|
6
|
Sicoli G, Konijnenberg A, Guérin J, Hessmann S, Del Nero E, Hernandez-Alba O, Lecher S, Rouaut G, Müggenburg L, Vezin H, Cianférani S, Sobott F, Schneider R, Jacob-Dubuisson F. Large-Scale Conformational Changes of FhaC Provide Insights Into the Two-Partner Secretion Mechanism. Front Mol Biosci 2022; 9:950871. [PMID: 35936790 PMCID: PMC9355242 DOI: 10.3389/fmolb.2022.950871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Accepted: 06/24/2022] [Indexed: 11/30/2022] Open
Abstract
The Two-Partner secretion pathway mediates protein transport across the outer membrane of Gram-negative bacteria. TpsB transporters belong to the Omp85 superfamily, whose members catalyze protein insertion into, or translocation across membranes without external energy sources. They are composed of a transmembrane β barrel preceded by two periplasmic POTRA domains that bind the incoming protein substrate. Here we used an integrative approach combining in vivo assays, mass spectrometry, nuclear magnetic resonance and electron paramagnetic resonance techniques suitable to detect minor states in heterogeneous populations, to explore transient conformers of the TpsB transporter FhaC. This revealed substantial, spontaneous conformational changes on a slow time scale, with parts of the POTRA2 domain approaching the lipid bilayer and the protein’s surface loops. Specifically, our data indicate that an amphipathic POTRA2 β hairpin can insert into the β barrel. We propose that these motions enlarge the channel and initiate substrate secretion. Our data propose a solution to the conundrum how TpsB transporters mediate protein secretion without the need for cofactors, by utilizing intrinsic protein dynamics.
Collapse
Affiliation(s)
- Giuseppe Sicoli
- Laboratoire Avancé de Spectroscopie pour les Interactions, la Réactivité et l’Environnement (LASIRE), UMR CNRS 8516, Université de Lille, Lille, France
| | | | - Jérémy Guérin
- CNRS, INSERM, Institut Pasteur de Lille, Université de Lille, U1019-UMR9017-CIIL-Center for Infection and Immunity of Lille, Lille, France
| | - Steve Hessmann
- Laboratoire de Spectrométrie de Masse BioOrganique, Université de Strasbourg, CNRS, Strasbourg, France
- Infrastructure Nationale de Protéomique ProFI – FR 2048, Strasbourg, France
| | - Elise Del Nero
- Laboratoire de Spectrométrie de Masse BioOrganique, Université de Strasbourg, CNRS, Strasbourg, France
- Infrastructure Nationale de Protéomique ProFI – FR 2048, Strasbourg, France
| | - Oscar Hernandez-Alba
- Laboratoire de Spectrométrie de Masse BioOrganique, Université de Strasbourg, CNRS, Strasbourg, France
- Infrastructure Nationale de Protéomique ProFI – FR 2048, Strasbourg, France
| | - Sophie Lecher
- CNRS, INSERM, Institut Pasteur de Lille, Université de Lille, U1019-UMR9017-CIIL-Center for Infection and Immunity of Lille, Lille, France
| | - Guillaume Rouaut
- CNRS EMR9002 Integrative Structural Biology, Lille, France
- INSERM, CHU Lille, U1167 - RID-AGE - Risk Factors and Molecular Determinants of Aging-Related Diseases, Institut Pasteur de Lille, Université de Lille, Lille, France
| | - Linn Müggenburg
- CNRS EMR9002 Integrative Structural Biology, Lille, France
- INSERM, CHU Lille, U1167 - RID-AGE - Risk Factors and Molecular Determinants of Aging-Related Diseases, Institut Pasteur de Lille, Université de Lille, Lille, France
| | - Hervé Vezin
- Laboratoire Avancé de Spectroscopie pour les Interactions, la Réactivité et l’Environnement (LASIRE), UMR CNRS 8516, Université de Lille, Lille, France
| | - Sarah Cianférani
- Laboratoire de Spectrométrie de Masse BioOrganique, Université de Strasbourg, CNRS, Strasbourg, France
- Infrastructure Nationale de Protéomique ProFI – FR 2048, Strasbourg, France
| | - Frank Sobott
- BAMS Research Group, University of Antwerp, Antwerp, Belgium
- Astbury Centre for Structural Molecular Biology and the School of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
| | - Robert Schneider
- CNRS EMR9002 Integrative Structural Biology, Lille, France
- INSERM, CHU Lille, U1167 - RID-AGE - Risk Factors and Molecular Determinants of Aging-Related Diseases, Institut Pasteur de Lille, Université de Lille, Lille, France
- *Correspondence: Robert Schneider, ; Françoise Jacob-Dubuisson,
| | - Françoise Jacob-Dubuisson
- CNRS, INSERM, Institut Pasteur de Lille, Université de Lille, U1019-UMR9017-CIIL-Center for Infection and Immunity of Lille, Lille, France
- *Correspondence: Robert Schneider, ; Françoise Jacob-Dubuisson,
| |
Collapse
|
7
|
Doyle MT, Bernstein HD. Function of the Omp85 Superfamily of Outer Membrane Protein Assembly Factors and Polypeptide Transporters. Annu Rev Microbiol 2022; 76:259-279. [PMID: 35650668 DOI: 10.1146/annurev-micro-033021-023719] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The Omp85 protein superfamily is found in the outer membrane (OM) of all gram-negative bacteria and eukaryotic organelles of bacterial origin. Members of the family catalyze both the membrane insertion of β-barrel proteins and the translocation of proteins across the OM. Although the mechanism(s) by which these proteins function is unclear, striking new insights have emerged from recent biochemical and structural studies. In this review we discuss the entire Omp85 superfamily but focus on the function of the best-studied member, BamA, which is an essential and highly conserved component of the bacterial barrel assembly machinery (BAM). Because BamA has multiple functions that overlap with those of other Omp85 proteins, it is likely the prototypical member of the Omp85 superfamily. Furthermore, BamA has become a protein of great interest because of the recent discovery of small-molecule inhibitors that potentially represent an important new class of antibiotics. Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Collapse
Affiliation(s)
- Matthew Thomas Doyle
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA; ,
| | - Harris D Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA; ,
| |
Collapse
|
8
|
Cuthbert BJ, Hayes CS, Goulding CW. Functional and Structural Diversity of Bacterial Contact-Dependent Growth Inhibition Effectors. Front Mol Biosci 2022; 9:866854. [PMID: 35558562 PMCID: PMC9086364 DOI: 10.3389/fmolb.2022.866854] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 03/07/2022] [Indexed: 12/25/2022] Open
Abstract
Bacteria live in complex communities and environments, competing for space and nutrients. Within their niche habitats, bacteria have developed various inter-bacterial mechanisms to compete and communicate. One such mechanism is contact-dependent growth inhibition (CDI). CDI is found in many Gram-negative bacteria, including several pathogens. These CDI+ bacteria encode a CdiB/CdiA two-partner secretion system that delivers inhibitory toxins into neighboring cells upon contact. Toxin translocation results in the growth inhibition of closely related strains and provides a competitive advantage to the CDI+ bacteria. CdiB, an outer-membrane protein, secretes CdiA onto the surface of the CDI+ bacteria. When CdiA interacts with specific target-cell receptors, CdiA delivers its C-terminal toxin region (CdiA-CT) into the target-cell. CdiA-CT toxin proteins display a diverse range of toxic functions, such as DNase, RNase, or pore-forming toxin activity. CDI+ bacteria also encode an immunity protein, CdiI, that specifically binds and neutralizes its cognate CdiA-CT, protecting the CDI+ bacteria from auto-inhibition. In Gram-negative bacteria, toxin/immunity (CdiA-CT/CdiI) pairs have highly variable sequences and functions, with over 130 predicted divergent toxin/immunity complex families. In this review, we will discuss biochemical and structural advances made in the characterization of CDI. This review will focus on the diverse array of CDI toxin/immunity complex structures together with their distinct toxin functions. Additionally, we will discuss the most recent studies on target-cell recognition and toxin entry, along with the discovery of a new member of the CDI loci. Finally, we will offer insights into how these diverse toxin/immunity complexes could be harnessed to fight human diseases.
Collapse
Affiliation(s)
- Bonnie J. Cuthbert
- Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, United States
| | - Christopher S. Hayes
- Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Celia W. Goulding
- Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, United States
- Pharmaceutical Sciences, University of California, Irvine, Irvine, CA, United States
| |
Collapse
|
9
|
Lipidation of Class IV CdiA Effector Proteins Promotes Target Cell Recognition during Contact-Dependent Growth Inhibition. mBio 2021; 12:e0253021. [PMID: 34634941 PMCID: PMC8510554 DOI: 10.1128/mbio.02530-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Contact-dependent growth inhibition (CDI) systems enable the direct transfer of protein toxins between competing Gram-negative bacteria. CDI+ strains produce cell surface CdiA effector proteins that bind specific receptors on neighboring bacteria to initiate toxin delivery. Three classes of CdiA effectors that recognize different outer membrane protein receptors have been characterized in Escherichia coli to date. Here, we describe a fourth effector class that uses the lipopolysaccharide (LPS) core as a receptor to identify target bacteria. Selection for CDI-resistant target cells yielded waaF and waaP “deep-rough” mutants, which are unable to synthesize the full LPS core. The CDI resistance phenotypes of other waa mutants suggest that phosphorylated inner-core heptose residues form a critical CdiA recognition epitope. Class IV cdi loci also encode putative lysyl acyltransferases (CdiC) that are homologous to enzymes that lipidate repeats-in-toxin (RTX) cytolysins. We found that catalytically active CdiC is required for full target cell killing activity, and we provide evidence that the acyltransferase appends 3-hydroxydecanoate to a specific Lys residue within the CdiA receptor-binding domain. We propose that the lipid moiety inserts into the hydrophobic leaflet of lipid A to anchor CdiA interactions with the core oligosaccharide. Thus, LPS-binding CDI systems appear to have co-opted an RTX toxin-activating acyltransferase to increase the affinity of CdiA effectors for the target cell outer membrane.
Collapse
|
10
|
Curley CL, Fedrigoni TP, Flaherty EM, Woodilla CJ, Hagan CL. Bacterial Contact-Dependent Inhibition Protein Binds near the Open Lateral Gate in BamA Prior to Toxin Translocation. Biochemistry 2021; 60:2956-2965. [PMID: 34541845 DOI: 10.1021/acs.biochem.1c00337] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Contact-dependent inhibition (CDI) is a mechanism of interbacterial competition in Gram-negative bacteria. The critical component of CDI systems is a large protein named CdiA; it forms a filament on the bacterial cell surface and contains a toxin domain at its C-terminal end. Upon binding to a receptor protein on the surface of a neighboring cell, CdiA delivers the toxin domain through the outer membrane of the neighboring bacterium. The mechanism of that delivery process is poorly understood. We have characterized how CdiA from E. coli EC93 binds to its receptor, BamA, to understand how this binding event might initiate the process of toxin delivery. BamA is an essential protein that assembles β-barrel proteins into the outer membranes of all Gram-negative bacteria; this assembly process depends on BamA's unique ability to open laterally in the lipid bilayer through a gate in its own membrane-embedded β-barrel. Through site-specific photo-cross-linking and mutational analysis, we demonstrate that the BamA-CdiA interaction depends on a small number of non-conserved amino acids on the extracellular surface of BamA, but the protein interface extends over a region near BamA's lateral gate. We further demonstrate that BamA's lateral gate can open without disrupting the interaction with CdiA. CdiA thus appears to initially engage BamA in a manner that could allow it to utilize BamA's lateral gate in subsequent steps in the toxin translocation process.
Collapse
Affiliation(s)
- Cameron L Curley
- Department of Chemistry, The College of the Holy Cross, Worcester, Massachusetts 01610, United States
| | - Thomas P Fedrigoni
- Department of Chemistry, The College of the Holy Cross, Worcester, Massachusetts 01610, United States
| | - Erin M Flaherty
- Department of Chemistry, The College of the Holy Cross, Worcester, Massachusetts 01610, United States
| | - Christopher J Woodilla
- Department of Chemistry, The College of the Holy Cross, Worcester, Massachusetts 01610, United States
| | - Christine L Hagan
- Department of Chemistry, The College of the Holy Cross, Worcester, Massachusetts 01610, United States
| |
Collapse
|
11
|
Gumbart JC, Ferreira JL, Hwang H, Hazel AJ, Cooper CJ, Parks JM, Smith JC, Zgurskaya HI, Beeby M. Lpp positions peptidoglycan at the AcrA-TolC interface in the AcrAB-TolC multidrug efflux pump. Biophys J 2021; 120:3973-3982. [PMID: 34411576 DOI: 10.1016/j.bpj.2021.08.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 07/02/2021] [Accepted: 08/11/2021] [Indexed: 01/07/2023] Open
Abstract
The multidrug efflux pumps of Gram-negative bacteria are a class of complexes that span the periplasm, coupling both the inner and outer membranes to expel toxic molecules. The best-characterized example of these tripartite pumps is the AcrAB-TolC complex of Escherichia coli. However, how the complex interacts with the peptidoglycan (PG) cell wall, which is anchored to the outer membrane (OM) by Braun's lipoprotein (Lpp), is still largely unknown. In this work, we present molecular dynamics simulations of a complete, atomistic model of the AcrAB-TolC complex with the inner membrane, OM, and PG layers all present. We find that the PG localizes to the junction of AcrA and TolC, in agreement with recent cryo-tomography data. Free-energy calculations reveal that the positioning of PG is determined by the length and conformation of multiple Lpp copies anchoring it to the OM. The distance between the PG and OM measured in cryo-electron microscopy images of wild-type E. coli also agrees with the simulation-derived spacing. Sequence analysis of AcrA suggests a conserved role for interactions with PG in the assembly and stabilization of efflux pumps, one that may extend to other trans-envelope complexes as well.
Collapse
Affiliation(s)
- James C Gumbart
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia.
| | - Josie L Ferreira
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Hyea Hwang
- School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia
| | - Anthony J Hazel
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia
| | - Connor J Cooper
- UT/ORNL Center for Molecular Biophysics, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - Jerry M Parks
- UT/ORNL Center for Molecular Biophysics, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - Jeremy C Smith
- UT/ORNL Center for Molecular Biophysics, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee
| | - Helen I Zgurskaya
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma
| | - Morgan Beeby
- Department of Life Sciences, Imperial College London, London, United Kingdom
| |
Collapse
|
12
|
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: 1] [Impact Index Per Article: 0.3] [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.
Collapse
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.
| |
Collapse
|