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Elliott K, Veley KM, Jensen G, Gilbert KB, Norton J, Kambic L, Yoder M, Weil A, Motomura-Wages S, Bart RS. CRISPR/Cas9-generated mutations in a sugar transporter gene reduce cassava susceptibility to bacterial blight. PLANT PHYSIOLOGY 2024; 195:2566-2578. [PMID: 38701041 PMCID: PMC11288762 DOI: 10.1093/plphys/kiae243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 04/02/2024] [Accepted: 04/02/2024] [Indexed: 05/05/2024]
Abstract
Bacteria from the genus Xanthomonas are prolific phytopathogens that elicit disease in over 400 plant species. Xanthomonads carry a repertoire of specialized proteins called transcription activator-like (TAL) effectors that promote disease and pathogen virulence by inducing the expression of host susceptibility (S) genes. Xanthomonas phaseoli pv. manihotis (Xpm) causes bacterial blight on the staple food crop cassava (Manihot esculenta Crantz). The Xpm effector TAL20 induces ectopic expression of the S gene Manihot esculenta Sugars Will Eventually be Exported Transporter 10a (MeSWEET10a), which encodes a sugar transporter that contributes to cassava bacterial blight (CBB) susceptibility. We used CRISPR/Cas9 to generate multiple cassava lines with edits to the MeSWEET10a TAL20 effector binding site and/or coding sequence. In several of the regenerated lines, MeSWEET10a expression was no longer induced by Xpm, and in these cases, we observed reduced CBB disease symptoms post Xpm infection. Because MeSWEET10a is expressed in cassava flowers, we further characterized the reproductive capability of the MeSWEET10a promoter and coding sequence mutants. Lines were crossed to themselves and to wild-type plants. The results indicated that expression of MeSWEET10a in female, but not male, flowers is critical to produce viable F1 seed. In the case of promoter mutations that left the coding sequence intact, viable F1 progeny were recovered. Taken together, these results demonstrate that blocking MeSWEET10a induction is a viable strategy for decreasing cassava susceptibility to CBB and that ideal lines will contain promoter mutations that block TAL effector binding while leaving endogenous expression of MeSWEET10a unaltered.
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Affiliation(s)
- Kiona Elliott
- Donald Danforth Plant Science Center, Saint Louis, MO 63132, USA
- Division of Biological and Biomedical Sciences, Washington University in Saint Louis, St. Louis, MO 63110, USA
| | - Kira M Veley
- Donald Danforth Plant Science Center, Saint Louis, MO 63132, USA
| | - Greg Jensen
- Donald Danforth Plant Science Center, Saint Louis, MO 63132, USA
| | | | - Joanna Norton
- College of Tropical Agriculture & Human Resources, University of Hawaii at Manoa, Hilo, HI 96720, USA
| | - Lukas Kambic
- College of Tropical Agriculture & Human Resources, University of Hawaii at Manoa, Hilo, HI 96720, USA
| | - Marisa Yoder
- Donald Danforth Plant Science Center, Saint Louis, MO 63132, USA
| | - Alex Weil
- Donald Danforth Plant Science Center, Saint Louis, MO 63132, USA
| | - Sharon Motomura-Wages
- College of Tropical Agriculture & Human Resources, University of Hawaii at Manoa, Hilo, HI 96720, USA
| | - Rebecca S Bart
- Donald Danforth Plant Science Center, Saint Louis, MO 63132, USA
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Armitage JP. Twists and turns: 40 years of investigating how and why bacteria swim. MICROBIOLOGY (READING, ENGLAND) 2024; 170:001432. [PMID: 38363121 PMCID: PMC10924463 DOI: 10.1099/mic.0.001432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Accepted: 01/23/2024] [Indexed: 02/17/2024]
Abstract
Fifty years of research has transformed our understanding of bacterial movement from one of description, based on a limited number of electron micrographs and some low-magnification studies of cells moving towards or away from chemical effectors, to probably the best understood behavioural system in biology. We have a molecular understanding of how bacteria sense and respond to changes in their environment and detailed structural insights into the workings of one of the most complex motor structures we know of. Thanks to advances in genomics we also understand how, through evolution, different species have tuned and adapted a core shared system to optimize behaviour in their specific environment. In this review, I will highlight some of the unexpected findings we made during my over 40-year career, how those findings changed some of our understanding of bacterial behaviour and biochemistry and some of the battles to have those observations accepted.
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3
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Li JB, Xiong LT, Lu YR, Zhang YQ, Xu XL, Wang HH, Deng X, Hu XH, Cui ZN. Novel pyrimidin-4-one derivatives as potential T3SS inhibitors against Xanthomonas campestris pv. campestris. PEST MANAGEMENT SCIENCE 2023; 79:3666-3675. [PMID: 37184259 DOI: 10.1002/ps.7545] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 05/10/2023] [Accepted: 05/11/2023] [Indexed: 05/16/2023]
Abstract
BACKGROUND Cruciferous black rot is caused by Xanthomonas campestris pv. campestris (Xcc) infection and is a widespread disease worldwide. Excessive and repeated use of bactericide is an important cause of the development of bacterial resistance. It is imperative to take new approaches to screening compounds that target virulence factors rather than kill bacterial pathogens. The type III secretion system (T3SS) invades a variety of cells by transporting virulence effector factors into the cytoplasm and is an attractive antitoxic target. Toward the search of new T3SS inhibitors, an alternative series of novel pyrimidin-4-one derivatives were designed and synthesized and assessed for their effect in blocking the virulence. RESULTS All of the target compounds were characterized by proton (1 H) nuclear magnetic resonance (NMR), carbon-13 (13 C) NMR, fluorine-19 (19 F) NMR and high-resolution mass spectrometry (HRMS). All compounds were evaluated using high-throughput screening systems against Xcc. The results of the biological activity test revealed that the compound SPF-9 could highly inhibit the activity of xopN gene promoter and the hypersensitivity (HR) of tobacco without affecting bacterial growth. Moreover, messenger RNA (mRNA) level measurements showed that compound SPF-9 inhibited the expression of some representative genes (hrp/hrc genes). Compound SPF-9 weakened the pathogenicity of Xcc to Raphanus sativus L. CONCLUSION Compound SPF-9 has good potential for further development as a novel T3SS inhibitor against Xcc. © 2023 Society of Chemical Industry.
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Affiliation(s)
- Jia-Bao Li
- National Key Laboratory of Green Pesticide, Integrative Microbiology Research Center, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, College of Plant Protection, South China Agricultural University, Guangzhou, China
| | - Lan-Tu Xiong
- National Key Laboratory of Green Pesticide, Integrative Microbiology Research Center, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, College of Plant Protection, South China Agricultural University, Guangzhou, China
| | - Yan-Rong Lu
- National Key Laboratory of Green Pesticide, Integrative Microbiology Research Center, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, College of Plant Protection, South China Agricultural University, Guangzhou, China
| | - Yu-Qing Zhang
- National Key Laboratory of Green Pesticide, Integrative Microbiology Research Center, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, College of Plant Protection, South China Agricultural University, Guangzhou, China
| | - Xiao-Li Xu
- Instrumental Analysis and Research Center, South China Agricultural University, Guangzhou, China
| | - Hai-Hong Wang
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China
| | - Xin Deng
- Department of Biomedical Sciences, City University of Hong Kong, Hong Kong, China
- Shenzhen Research Institute, City University of Hong Kong, Shenzhen, China
| | - Xu-Hong Hu
- Institute of Advanced Synthesis, School of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing, China
| | - Zi-Ning Cui
- National Key Laboratory of Green Pesticide, Integrative Microbiology Research Center, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, College of Plant Protection, South China Agricultural University, Guangzhou, China
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Blasey N, Rehrmann D, Riebisch AK, Mühlen S. Targeting bacterial pathogenesis by inhibiting virulence-associated Type III and Type IV secretion systems. Front Cell Infect Microbiol 2023; 12:1065561. [PMID: 36704108 PMCID: PMC9872159 DOI: 10.3389/fcimb.2022.1065561] [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: 10/09/2022] [Accepted: 12/19/2022] [Indexed: 01/12/2023] Open
Abstract
Infections caused by Gram-negative pathogens pose a major health burden. Both respiratory and gastrointestinal infections are commonly associated with these pathogens. With the increase in antimicrobial resistance (AMR) over the last decades, bacterial infections may soon become the threat they have been before the discovery of antibiotics. Many Gram-negative pathogens encode virulence-associated Type III and Type IV secretion systems, which they use to inject bacterial effector proteins across bacterial and host cell membranes into the host cell cytosol, where they subvert host cell functions in favor of bacterial replication and survival. These secretion systems are essential for the pathogens to cause disease, and secretion system mutants are commonly avirulent in infection models. Hence, these structures present attractive targets for anti-virulence therapies. Here, we review previously and recently identified inhibitors of virulence-associated bacterial secretions systems and discuss their potential as therapeutics.
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A Highly Unstable and Elusive Plasmid That Encodes the Type III Secretion System Is Necessary for Full Virulence in the Marine Fish Pathogen Photobacterium damselae subsp. piscicida. Int J Mol Sci 2022; 23:ijms23094729. [PMID: 35563122 PMCID: PMC9105992 DOI: 10.3390/ijms23094729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 04/21/2022] [Accepted: 04/22/2022] [Indexed: 01/27/2023] Open
Abstract
The marine bacterium Photobacterium damselae subsp. piscicida (Pdp) causes photobacteriosis in fish and important financial losses in aquaculture, but knowledge of its virulence factors is still scarce. We here demonstrate that an unstable plasmid (pPHDPT3) that encodes a type III secretion system (T3SS) is highly prevalent in Pdp strains from different geographical origins and fish host species. We found that pPHDPT3 undergoes curing upon in vitro cultivation, and this instability constitutes a generalized feature of pPHDPT3-like plasmids in Pdp strains. pPHDPT3 markers were detected in tissues of naturally-infected moribund fish and in the Pdp colonies grown directly from the fish tissues but were undetectable in a fraction of the colonies produced upon the first passage of the primeval colonies on agar plates. Notably, cured strains exhibited a marked reduction in virulence for fish, demonstrating that pPHDPT3 is a major virulence factor of Pdp. The attempts to stabilize pPHDPT3 by insertion of antibiotic resistance markers by allelic exchange caused an even greater reduction in virulence. We hypothesize that the existence of a high pressure to shed pPHDPT3 plasmid in vitro caused the selection of clones with off-target mutations and gene rearrangements during the process of genetic modification. Collectively, these results show that pPHDPT3 constitutes a novel, hitherto unreported virulence factor of Pdp that shows a high instability in vitro and warn that the picture of Pdp virulence genes has been historically underestimated, since the loss of the T3SS and other plasmid-borne genes may have occurred systematically in laboratories for decades.
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Rahmatelahi H, El-Matbouli M, Menanteau-Ledouble S. Delivering the pain: an overview of the type III secretion system with special consideration for aquatic pathogens. Vet Res 2021; 52:146. [PMID: 34924019 PMCID: PMC8684695 DOI: 10.1186/s13567-021-01015-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 11/08/2021] [Indexed: 11/10/2022] Open
Abstract
Gram-negative bacteria are known to subvert eukaryotic cell physiological mechanisms using a wide array of virulence factors, among which the type three-secretion system (T3SS) is often one of the most important. The T3SS constitutes a needle-like apparatus that the bacterium uses to inject a diverse set of effector proteins directly into the cytoplasm of the host cells where they can hamper the host cellular machinery for a variety of purposes. While the structure of the T3SS is somewhat conserved and well described, effector proteins are much more diverse and specific for each pathogen. The T3SS can remodel the cytoskeleton integrity to promote intracellular invasion, as well as silence specific eukaryotic cell signals, notably to hinder or elude the immune response and cause apoptosis. This is also the case in aquatic bacterial pathogens where the T3SS can often play a central role in the establishment of disease, although it remains understudied in several species of important fish pathogens, notably in Yersinia ruckeri. In the present review, we summarise what is known of the T3SS, with a special focus on aquatic pathogens and suggest some possible avenues for research including the potential to target the T3SS for the development of new anti-virulence drugs.
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Affiliation(s)
- Hadis Rahmatelahi
- Clinical Division of Fish Medicine, University of Veterinary Medicine, 1210, Vienna, Austria
| | - Mansour El-Matbouli
- Clinical Division of Fish Medicine, University of Veterinary Medicine, 1210, Vienna, Austria
| | - Simon Menanteau-Ledouble
- Clinical Division of Fish Medicine, University of Veterinary Medicine, 1210, Vienna, Austria.
- Department of Chemistry and Bioscience, Aalborg University, Fredrik Bajers Vej 7H, 9220, Aalborg Ø, Denmark.
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Pourhassan N Z, Smits SHJ, Ahn JH, Schmitt L. Biotechnological applications of type 1 secretion systems. Biotechnol Adv 2021; 53:107864. [PMID: 34767962 DOI: 10.1016/j.biotechadv.2021.107864] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 10/30/2021] [Accepted: 10/31/2021] [Indexed: 02/06/2023]
Abstract
Bacteria have evolved a diverse range of secretion systems to export different substrates across their cell envelope. Although secretion of proteins into the extracellular space could offer advantages for recombinant protein production, the low secretion titers of the secretion systems for some heterologous proteins remain a clear drawback of their utility at commercial scales. Therefore, a potential use of most of secretion systems as production platforms at large scales are still limited. To overcome this limitation, remarkable efforts have been made toward improving the secretion efficiency of different bacterial secretion systems in recent years. Here, we review the progress with respect to biotechnological applications of type I secretion system (T1SS) of Gram-negative bacteria. We will also focus on the applicability of T1SS for the secretion of heterologous proteins as well as vaccine development. Last but not least, we explore the employed engineering strategies that have enhanced the secretion efficiencies of T1SS. Attention is also paid to directed evolution approaches that may offer a more versatile approach to optimize secretion efficiency of T1SS.
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Affiliation(s)
- Zohreh Pourhassan N
- Institute of Biochemistry, Heinrich Heine University Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany
| | - Sander H J Smits
- Institute of Biochemistry, Heinrich Heine University Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany
| | - Jung Hoon Ahn
- Department of Chemistry and Biology, Korea Science Academy of Korea Advanced Institute of Science and Technology, Busan 47162, South Korea
| | - Lutz Schmitt
- Institute of Biochemistry, Heinrich Heine University Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany.
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8
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Hornef MW, Jantsch J. On microbial syringes: Advances in our understanding of type III secretion systems in bacterial pathogenesis: Comment on "An elegant nano-injection machinery for sabotaging the host: Role of Type III secretion system in virulence of different human and animal pathogenic bacteria" by Dipshika Chakravortty et al. Phys Life Rev 2021; 39:96-98. [PMID: 34364795 DOI: 10.1016/j.plrev.2021.07.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 07/21/2021] [Indexed: 10/20/2022]
Affiliation(s)
- Mathias W Hornef
- Institute of Medical Microbiology, RWTH University Hospital Aachen, RWTH Aachen University, Aachen, Germany.
| | - Jonathan Jantsch
- Institute of Clinical Microbiology and Hygiene, University Hospital of Regensburg and University of Regensburg, Regensburg, Germany.
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Hajra D, Nair AV, Chakravortty D. An elegant nano-injection machinery for sabotaging the host: Role of Type III secretion system in virulence of different human and animal pathogenic bacteria. Phys Life Rev 2021; 38:25-54. [PMID: 34090822 DOI: 10.1016/j.plrev.2021.05.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2021] [Accepted: 05/23/2021] [Indexed: 01/22/2023]
Abstract
Various Gram-negative bacteria possess a specialized membrane-bound protein secretion system known as the Type III secretion system (T3SS), which transports the bacterial effector proteins into the host cytosol thereby helping in bacterial pathogenesis. The T3SS has a special needle-like translocon that can sense the contact with the host cell membrane and translocate effectors. The export apparatus of T3SS recognizes these effector proteins bound to chaperones and translocates them into the host cell. Once in the host cell cytoplasm, these effector proteins result in modulation of the host system and promote bacterial localization and infection. Using molecular biology, bioinformatics, genetic techniques, electron microscopic studies, and mathematical modeling, the structure and function of the T3SS and the corresponding effector proteins in various bacteria have been studied. The strategies used by different human pathogenic bacteria to modulate the host system and thereby enhance their virulence mechanism using T3SS have also been well studied. Here we review the history, evolution, and general structure of the T3SS, highlighting the details of its comparison with the flagellar export machinery. Also, this article provides mechanistic details about the common role of T3SS in subversion and manipulation of host cellular processes. Additionally, this review describes specific T3SS apparatus and the role of their specific effectors in bacterial pathogenesis by considering several human and animal pathogenic bacteria.
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Affiliation(s)
- Dipasree Hajra
- Department of Microbiology & Cell Biology, Indian Institute of Science, India
| | - Abhilash Vijay Nair
- Department of Microbiology & Cell Biology, Indian Institute of Science, India
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Hook JC, Blagotinsek V, Pané-Farré J, Mrusek D, Altegoer F, Dornes A, Schwan M, Schier L, Thormann KM, Bange G. A Proline-Rich Element in the Type III Secretion Protein FlhB Contributes to Flagellar Biogenesis in the Beta- and Gamma-Proteobacteria. Front Microbiol 2020; 11:564161. [PMID: 33384667 PMCID: PMC7771051 DOI: 10.3389/fmicb.2020.564161] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 10/26/2020] [Indexed: 11/24/2022] Open
Abstract
Flagella are bacterial organelles of locomotion. Their biogenesis is highly coordinated in time and space and relies on a specialized flagellar type III secretion system (fT3SS) required for the assembly of the extracellular hook, rod, and filament parts of this complex motor device. The fT3SS protein FlhB switches secretion substrate specificity once the growing hook reaches its determined length. Here we present the crystal structure of the cytoplasmic domain of the transmembrane protein FlhB. The structure visualizes a so-far unseen proline-rich region (PRR) at the very C-terminus of the protein. Strains lacking the PRR show a decrease in flagellation as determined by hook- and filament staining, indicating a role of the PRR during assembly of the hook and filament structures. Phylogenetic analysis shows that the PRR is a primary feature of FlhB proteins of flagellated beta- and gamma-proteobacteria. Taken together, our study adds another layer of complexity and organismic diversity to the process of flagella biogenesis.
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Affiliation(s)
- John C Hook
- Department of Microbiology and Molecular Biology, Justus-Liebig-Universität, Giessen, Germany
| | - Vitan Blagotinsek
- SYNMIKRO Research Center, Department of Chemistry, Philipps-University Marburg, Marburg, Germany
| | - Jan Pané-Farré
- SYNMIKRO Research Center, Department of Chemistry, Philipps-University Marburg, Marburg, Germany
| | - Devid Mrusek
- SYNMIKRO Research Center, Department of Chemistry, Philipps-University Marburg, Marburg, Germany
| | - Florian Altegoer
- SYNMIKRO Research Center, Department of Chemistry, Philipps-University Marburg, Marburg, Germany
| | - Anita Dornes
- SYNMIKRO Research Center, Department of Chemistry, Philipps-University Marburg, Marburg, Germany
| | - Meike Schwan
- Department of Microbiology and Molecular Biology, Justus-Liebig-Universität, Giessen, Germany
| | - Lukas Schier
- SYNMIKRO Research Center, Department of Chemistry, Philipps-University Marburg, Marburg, Germany
| | - Kai M Thormann
- Department of Microbiology and Molecular Biology, Justus-Liebig-Universität, Giessen, Germany
| | - Gert Bange
- SYNMIKRO Research Center, Department of Chemistry, Philipps-University Marburg, Marburg, Germany
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Chemical Targeting and Manipulation of Type III Secretion in the Phytopathogen Xanthomonas campestris for Control of Disease. Appl Environ Microbiol 2020; 86:AEM.02349-19. [PMID: 31732574 PMCID: PMC6974632 DOI: 10.1128/aem.02349-19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 11/07/2019] [Indexed: 12/21/2022] Open
Abstract
The bacterium Xanthomonas campestris pv. campestris is known to cause black rot disease in many socioeconomically important vegetable crops worldwide. The management and control of black rot disease have been tackled with chemical and host resistance methods with variable success. This has motivated the development of alternative methods for preventing this disease. Here, we identify a set of novel small molecules capable of inhibiting X. campestris pv. campestris virulence, which may represent leading compounds for the further development of antivirulence agents that could be used in the control of black rot disease. Xanthomonas campestris pv. campestris is the causative agent of black rot disease in crucifer plants. This Gram-negative bacterium utilizes the type III secretion system (T3SS), encoded by the hrp gene cluster, to aid in its resistance to host defenses and the ability to cause disease. The T3SS injects a set of proteins known as effectors into host cells that come into contact with the bacterium. The T3SS is essential for the virulence and hypersensitive response (HR) of X. campestris pv. campestris, making it a potential target for disease control strategies. Using a unique and straightforward high-throughput screening method, we examined a large collection of diverse small molecules for their potential to modulate the T3SS without affecting the growth of X. campestris pv. campestris. Screening of 13,129 different compounds identified 10 small molecules that had a significant inhibitory influence on T3SS. Moreover, reverse transcription-quantitative PCR (qRT-PCR) assays demonstrated that all 10 compounds repress the expression of the hrp genes. Interestingly, the effect of these small molecules on hrp genes may be through the HpaS and ColS sensor kinase proteins that are key to the regulation of the T3SS in planta. Five of the compounds were also capable of inhibiting X. campestris pv. campestris virulence in a Chinese radish leaf-clipping assay. Furthermore, seven of the small molecules significantly weakened the HR in nonhost pepper plants challenged with X. campestris pv. campestris. Taken together, these small molecules may provide potential tool compounds for the further development of antivirulence agents that could be used in disease control of the plant pathogen X. campestris pv. campestris. IMPORTANCE The bacterium Xanthomonas campestris pv. campestris is known to cause black rot disease in many socioeconomically important vegetable crops worldwide. The management and control of black rot disease have been tackled with chemical and host resistance methods with variable success. This has motivated the development of alternative methods for preventing this disease. Here, we identify a set of novel small molecules capable of inhibiting X. campestris pv. campestris virulence, which may represent leading compounds for the further development of antivirulence agents that could be used in the control of black rot disease.
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Abstract
The independent naming of components of injectisome-type type III secretion systems in different bacterial species has resulted in considerable confusion, impeding accessibility of the literature and hindering communication between scientists of the same field. A unified nomenclature had been proposed by Hueck more than 20 years ago. It found little attention for many years, but usage was sparked again by recent reviews and an international type III secretion meeting in 2016. Here, we propose that the field consistently switches to an extended version of this nomenclature to be no longer lost in translation.
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13
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Dias GM, de Sousa Pires A, Grilo VS, Castro MR, de Figueiredo Vilela L, Neves BC. Comparative genomics of Paraburkholderia kururiensis and its potential in bioremediation, biofertilization, and biocontrol of plant pathogens. Microbiologyopen 2019; 8:e00801. [PMID: 30811107 PMCID: PMC6692535 DOI: 10.1002/mbo3.801] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 12/19/2018] [Accepted: 12/29/2018] [Indexed: 12/23/2022] Open
Abstract
Burkholderia harbors versatile Gram-negative species and is β-Proteobacteria. Recently, it was proposed to split the genus in two main branches: one of animal and plant pathogens and another, Paraburkholderia, harboring environmental and plant-beneficial species. Currently, Paraburkholderia comprises more than 70 species with ability to occupy very diverse environmental niches. Herein, we sequenced and analyzed the genome of Paraburkholderia kururiensis type strain KP23T , and compared to P. kururiensis M130, isolated in Brazil, and P. kururiensis susbp. thiooxydans, from Korea. This study focused on the gene content of the three genomes with special emphasis on their potential of plant-association, biocontrol, and bioremediation. The comparative analyses revealed several genes related to plant benefits, including biosynthesis of IAA, ACC deaminase, multiple efflux pumps, dioxygenases, and degradation of aromatic compounds. Importantly, a range of genes for protein secretion systems (type III, IV, V, and VI) were characterized, potentially involved in P. kururiensis well documented ability to establish endophytic association with plants. These findings shed light onto bacteria-plant interaction mechanisms at molecular level, adding novel information that supports their potential application in bioremediation, biofertilization, and biocontrol of plant pathogens. P. kururiensis emerges as a promising model to investigate adaptation mechanisms in different ecological niches.
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Affiliation(s)
- Graciela M. Dias
- Department of BiochemistryChemistry InstituteFederal University of Rio de JaneiroRio de JaneiroBrazil
| | - Araceli de Sousa Pires
- Department of BiochemistryChemistry InstituteFederal University of Rio de JaneiroRio de JaneiroBrazil
| | - Vinicius S. Grilo
- Department of BiochemistryChemistry InstituteFederal University of Rio de JaneiroRio de JaneiroBrazil
| | - Michele R. Castro
- Department of BiochemistryChemistry InstituteFederal University of Rio de JaneiroRio de JaneiroBrazil
- Department of BiologyFederal Institute of Rio de JaneiroRio de JaneiroBrazil
| | | | - Bianca C. Neves
- Department of BiochemistryChemistry InstituteFederal University of Rio de JaneiroRio de JaneiroBrazil
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14
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Feng C, Huang Y, He W, Cheng X, Liu H, Huang Y, Ma B, Zhang W, Liao C, Wu W, Shao Y, Xu D, Su Z, Lu W. Tanshinones: First-in-Class Inhibitors of the Biogenesis of the Type 3 Secretion System Needle of Pseudomonas aeruginosa for Antibiotic Therapy. ACS CENTRAL SCIENCE 2019; 5:1278-1288. [PMID: 31403076 PMCID: PMC6662154 DOI: 10.1021/acscentsci.9b00452] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Indexed: 05/17/2023]
Abstract
The type 3 secretion system (T3SS) found as cell-surface appendages of many pathogenic Gram-negative bacteria, although nonessential for bacterial survival, is an important therapeutic target for drug discovery and development aimed at inhibiting bacterial virulence without inducing antibiotic resistance. We designed a fluorescence-polarization-based assay for high-throughput screening as a mechanistically well-defined general strategy for antibiotic discovery targeting the T3SS and made a serendipitous discovery of a subset of tanshinones-natural herbal compounds in traditional Chinese medicine widely used for the treatment of cardiovascular and cerebrovascular diseases-as effective inhibitors of the biogenesis of the T3SS needle of multi-drug-resistant Pseudomonas aeruginosa. By inhibiting the T3SS needle assembly and, thus, cytotoxicity and pathogenicity, selected tanshinones reduced the secretion of bacterial virulence factors toxic to macrophages in vitro, and rescued experimental animals challenged with lethal doses of Pseudomonas aeruginosa in a murine model of acute pneumonia. As first-in-class inhibitors with a demonstrable safety profile in humans, tanshinones may be used directly to alleviate Pseudomonas-aeruginosa-associated pulmonary infections without inducing antibiotic resistance. Since the T3SS is highly conserved among Gram-negative bacteria, this antivirulence strategy may be applicable to the discovery and development of novel classes of antibiotics refractory to existing resistance mechanisms for the treatment of many bacterial infections.
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Affiliation(s)
- Chao Feng
- Center
for Translational Medicine, Frontier Institute of Science
and Technology, Shaanxi Institute of Pediatric Diseases, Affiliated Children’s
Hospital, and Key Laboratory of Biomedical Information Engineering of the Ministry
of Education, School of Life Science and Technology, Xi’an Jiaotong University, Xi’an 710054, China
| | - Yinong Huang
- Center
for Translational Medicine, Frontier Institute of Science
and Technology, Shaanxi Institute of Pediatric Diseases, Affiliated Children’s
Hospital, and Key Laboratory of Biomedical Information Engineering of the Ministry
of Education, School of Life Science and Technology, Xi’an Jiaotong University, Xi’an 710054, China
| | - Wangxiao He
- Center
for Translational Medicine, Frontier Institute of Science
and Technology, Shaanxi Institute of Pediatric Diseases, Affiliated Children’s
Hospital, and Key Laboratory of Biomedical Information Engineering of the Ministry
of Education, School of Life Science and Technology, Xi’an Jiaotong University, Xi’an 710054, China
| | - Xiyao Cheng
- Department
of Biological and Food Engineering, Hubei
University of Technology, Wuhan 430068, China
| | - Huili Liu
- State
Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese
Academy of Sciences, Wuhan 430071, China
| | - Yongqi Huang
- Department
of Biological and Food Engineering, Hubei
University of Technology, Wuhan 430068, China
| | - Bohan Ma
- Center
for Translational Medicine, Frontier Institute of Science
and Technology, Shaanxi Institute of Pediatric Diseases, Affiliated Children’s
Hospital, and Key Laboratory of Biomedical Information Engineering of the Ministry
of Education, School of Life Science and Technology, Xi’an Jiaotong University, Xi’an 710054, China
| | - Wei Zhang
- Center
for Translational Medicine, Frontier Institute of Science
and Technology, Shaanxi Institute of Pediatric Diseases, Affiliated Children’s
Hospital, and Key Laboratory of Biomedical Information Engineering of the Ministry
of Education, School of Life Science and Technology, Xi’an Jiaotong University, Xi’an 710054, China
| | - Chongbing Liao
- Center
for Translational Medicine, Frontier Institute of Science
and Technology, Shaanxi Institute of Pediatric Diseases, Affiliated Children’s
Hospital, and Key Laboratory of Biomedical Information Engineering of the Ministry
of Education, School of Life Science and Technology, Xi’an Jiaotong University, Xi’an 710054, China
| | - Weihui Wu
- State Key
Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular
Microbiology and Technology of the Ministry of Education, Department
of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Yongping Shao
- Center
for Translational Medicine, Frontier Institute of Science
and Technology, Shaanxi Institute of Pediatric Diseases, Affiliated Children’s
Hospital, and Key Laboratory of Biomedical Information Engineering of the Ministry
of Education, School of Life Science and Technology, Xi’an Jiaotong University, Xi’an 710054, China
| | - Dan Xu
- Center
for Translational Medicine, Frontier Institute of Science
and Technology, Shaanxi Institute of Pediatric Diseases, Affiliated Children’s
Hospital, and Key Laboratory of Biomedical Information Engineering of the Ministry
of Education, School of Life Science and Technology, Xi’an Jiaotong University, Xi’an 710054, China
| | - Zhengding Su
- Department
of Biological and Food Engineering, Hubei
University of Technology, Wuhan 430068, China
| | - Wuyuan Lu
- Institute
of Human Virology and Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland 21201, United States
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15
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Abstract
Antibiotic resistance is a major public health threat that has stimulated the scientific community to search for nontraditional therapeutic targets. Because virulence, but not the growth, of many Gram-negative bacterial pathogens depends on the multicomponent type three secretion system injectisome (T3SSi), the T3SSi has been an attractive target for identifying small molecules, peptides, and monoclonal antibodies that inhibit its function to render the pathogen avirulent. While many small-molecule lead compounds have been identified in whole-cell-based high-throughput screens (HTSs), only a few protein targets of these compounds are known; such knowledge is an important step to developing more potent and specific inhibitors. Evaluation of the efficacy of compounds in animal studies is ongoing. Some efforts involving the development of antibodies and vaccines that target the T3SSi are further along and include an antibody that is currently in phase II clinical trials. Continued research into these antivirulence therapies, used alone or in combination with traditional antibiotics, requires combined efforts from both pharmaceutical companies and academic labs.
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16
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The Structure of an Injectisome Export Gate Demonstrates Conservation of Architecture in the Core Export Gate between Flagellar and Virulence Type III Secretion Systems. mBio 2019; 10:mBio.00818-19. [PMID: 31239376 PMCID: PMC6593402 DOI: 10.1128/mbio.00818-19] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Export of proteins through type III secretion systems (T3SS) is critical for motility and virulence of many major bacterial pathogens. Proteins are exported through a genetically defined export gate complex consisting of three proteins. We have recently shown at 4.2 Å that the flagellar complex of these three putative membrane proteins (FliPQR in flagellar systems, SctRST in virulence systems) assembles into an extramembrane helical assembly that likely seeds correct assembly of the rod. Here we present the structure of an equivalent complex from the Shigella virulence system at 3.5 Å by cryo-electron microscopy. This higher-resolution structure yields a more precise description of the structure and confirms the prediction of structural conservation in this core complex. Analysis of particle heterogeneity also suggests how the SctS/FliQ subunits sequentially assemble in the complex.IMPORTANCE Although predicted on the basis of sequence conservation, the work presented here formally demonstrates that all classes of type III secretion systems, flagellar or virulence, share the same architecture at the level of the core structures. This absolute conservation of the unusual extramembrane structure of the core export gate complex now allows work to move to focusing on both mechanistic studies of type III but also on fundamental studies of how such a complex is assembled.
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17
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Abstract
Genetic coding in bacteria largely operates via the "one gene-one protein" paradigm. However, the peculiarities of the mRNA structure, the versatility of the genetic code, and the dynamic nature of translation sometimes allow organisms to deviate from the standard rules of protein encoding. Bacteria can use several unorthodox modes of translation to express more than one protein from a single mRNA cistron. One such alternative path is the use of additional translation initiation sites within the gene. Proteins whose translation is initiated at different start sites within the same reading frame will differ in their N termini but will have identical C-terminal segments. On the other hand, alternative initiation of translation in a register different from the frame dictated by the primary start codon will yield a protein whose sequence is entirely different from the one encoded in the main frame. The use of internal mRNA codons as translation start sites is controlled by the nucleotide sequence and the mRNA folding. The proteins of the alternative proteome generated via the "genes-within-genes" strategy may carry important functions. In this review, we summarize the currently known examples of bacterial genes encoding more than one protein due to the utilization of additional translation start sites and discuss the known or proposed functions of the alternative polypeptides in relation to the main protein product of the gene. We also discuss recent proteome- and genome-wide approaches that will allow the discovery of novel translation initiation sites in a systematic fashion.
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18
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Diepold A. Assembly and Post-assembly Turnover and Dynamics in the Type III Secretion System. Curr Top Microbiol Immunol 2019; 427:35-66. [PMID: 31218503 DOI: 10.1007/82_2019_164] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The type III secretion system (T3SS) is one of the largest transmembrane complexes in bacteria, comprising several intricately linked and embedded substructures. The assembly of this nanomachine is a hierarchical process which is regulated and controlled by internal and external cues at several critical points. Recently, it has become obvious that the assembly of the T3SS is not a unidirectional and deterministic process, but that parts of the T3SS constantly exchange or rearrange. This article aims to give an overview on the assembly and post-assembly dynamics of the T3SS, with a focus on emerging general concepts and adaptations of the general assembly pathway.
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Affiliation(s)
- Andreas Diepold
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Straße 10, 35043, Marburg, Germany.
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19
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Impacts of horizontal gene transfer on the compact genome of the clavulanic acid-producing Streptomyces strain F613-1. 3 Biotech 2018; 8:472. [PMID: 30456006 DOI: 10.1007/s13205-018-1498-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 11/01/2018] [Indexed: 12/27/2022] Open
Abstract
Mobile genetic elements involved in mediating horizontal transfer events contribute to bacterial evolution, and bacterial genomic plasticity and instability result in variation in functional genetic information in Streptomyces secondary metabolism. In a previous study, we reported the complete genome sequence of the industrial Streptomyces strain F613-1, which produces high yields of clavulanic acid. In this study, we used comparative genomics and bioinformatics to investigate the unique genomic features of this strain. Taken together, comparative genomics were used to systematically investigate secondary metabolism capabilities and indicated that frequent exchange of genetic materials between Streptomyces replicons may shape the remarkable diversities in their secondary metabolite repertoires. Moreover, a 136.9-kb giant region of plasticity (RGP) was found in the F613-1 chromosome, and the chromosome and plasmid pSCL4 are densely packed with an exceptionally large variety of potential secondary metabolic gene clusters, involving several determinants putatively accounting for antibiotic production. In addition, the differences in the architecture and size of plasmid pSCL4 between F613-1 and ATCC 27064 suggest that the pSCL4 plasmid could evolve from pSCL4-like and pSCL2-like extrachromosomal replicons. Furthermore, the genomic analyses revealed that strain F613-1 has developed specific genomic architectures and genetic patterns that are well suited to meet the requirements of industrial innovation processes.
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20
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Kovács N, Jankovics H, Vonderviszt F. Deletion analysis of the flagellum-specific secretion signal in Salmonella flagellin. FEBS Lett 2018; 592:3074-3081. [PMID: 30043975 DOI: 10.1002/1873-3468.13200] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 06/30/2018] [Accepted: 07/13/2018] [Indexed: 11/10/2022]
Abstract
The export signal recognized by the flagellum-specific export machinery is harbored within the highly conserved 26-47 segment of the disordered N-terminal part of Salmonella flagellin. In this work, we aimed to further localize the essential part of the export signal by deletion analysis and investigated how the length of the spacer segment preceding the signal affects export efficiency. Export signal variants were attached to a reporter protein, the CCP2 domain of human C1r protein, and export efficiency of the fusion constructs was studied. Our results suggest that almost any continuous oligopeptide of 8-10 residues within the 26-47 segment can efficiently direct flagellar export if preceded by a spacer segment of at least 15 amino acids without any specific sequential requirement.
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Affiliation(s)
- Noémi Kovács
- Bio-Nanosystems Laboratory, Research Institute of Biomolecular and Chemical Engineering, University of Pannonia, Veszprém, Hungary
| | - Hajnalka Jankovics
- Bio-Nanosystems Laboratory, Research Institute of Biomolecular and Chemical Engineering, University of Pannonia, Veszprém, Hungary
| | - Ferenc Vonderviszt
- Bio-Nanosystems Laboratory, Research Institute of Biomolecular and Chemical Engineering, University of Pannonia, Veszprém, Hungary
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21
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Kuhlen L, Abrusci P, Johnson S, Gault J, Deme J, Caesar J, Dietsche T, Mebrhatu MT, Ganief T, Macek B, Wagner S, Robinson CV, Lea SM. Structure of the core of the type III secretion system export apparatus. Nat Struct Mol Biol 2018; 25:583-590. [PMID: 29967543 PMCID: PMC6233869 DOI: 10.1038/s41594-018-0086-9] [Citation(s) in RCA: 117] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 06/01/2018] [Indexed: 12/04/2022]
Abstract
Export of proteins through type III secretion systems is critical for motility and virulence of many major bacterial pathogens. Three putative integral membrane proteins (FliP, FliQ, FliR) are suggested to form the core of an export gate in the inner membrane, but their structure, assembly and location within the final nanomachine remain unclear. Here, we present the cryoelectron microscopy structure of the Salmonella Typhimurium FliP-FliQ-FliR complex at 4.2 Å. None of the subunits adopt canonical integral membrane protein topologies, and common helix-turn-helix structural elements allow them to form a helical assembly with 5:4:1 stoichiometry. Fitting of the structure into reconstructions of intact secretion systems, combined with cross-linking, localize the export gate as a core component of the periplasmic portion of the machinery. This study thereby identifies the export gate as a key element of the secretion channel and implies that it primes the helical architecture of the components assembling downstream.
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Affiliation(s)
- Lucas Kuhlen
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Patrizia Abrusci
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
- Structural Genomics Consortium, University of Oxford, Oxford, UK
| | - Steven Johnson
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Joseph Gault
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Justin Deme
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
- Central Oxford Structural Microscopy and Imaging Centre, University of Oxford, Oxford, UK
| | - Joseph Caesar
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
- Central Oxford Structural Microscopy and Imaging Centre, University of Oxford, Oxford, UK
| | - Tobias Dietsche
- Section of Cellular and Molecular Microbiology, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Tübingen, Germany
| | - Mehari Tesfazgi Mebrhatu
- Section of Cellular and Molecular Microbiology, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Tübingen, Germany
| | - Tariq Ganief
- Proteome Center Tübingen, University of Tübingen, Tübingen, Germany
| | - Boris Macek
- Proteome Center Tübingen, University of Tübingen, Tübingen, Germany
| | - Samuel Wagner
- Section of Cellular and Molecular Microbiology, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Tübingen, Germany
- German Center for Infection Research, Partner-site Tübingen, Tübingen, Germany
| | | | - Susan M Lea
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK.
- Central Oxford Structural Microscopy and Imaging Centre, University of Oxford, Oxford, UK.
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22
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Yang L, Gan Y, Yang L, Jiang B, Tang J. Peptidoglycan hydrolysis mediated by the amidase AmiC and its LytM activator NlpD is critical for cell separation and virulence in the phytopathogen Xanthomonas campestris. MOLECULAR PLANT PATHOLOGY 2018; 19:1705-1718. [PMID: 29240286 PMCID: PMC6638016 DOI: 10.1111/mpp.12653] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Revised: 11/10/2017] [Accepted: 12/11/2017] [Indexed: 06/07/2023]
Abstract
The essential stages of bacterial cell separation are described as the synthesis and hydrolysis of septal peptidoglycan (PG). The amidase, AmiC, which cleaves the peptide side-chains linked to the glycan strands, contributes critically to this process and has been studied extensively in model strains of Escherichia coli. However, insights into the contribution of this protein to other processes in the bacterial cell have been limited. Xanthomonas campestris pv. campestris (Xcc) is a phytopathogen that causes black rot disease in many economically important plants. We investigated how AmiC and LytM family regulators, NlpD and EnvC, contribute to virulence and cell separation in this organism. Biochemical analyses of purified AmiC demonstrated that it could hydrolyse PG and its activity could be potentiated by the presence of the regulator NlpD. We also established that deletion of the genes encoding amiC1 or nlpD led to a reduction in virulence as well as effects on colony-forming units and cell morphology. Moreover, further genetic and biochemical evidence showed that AmiC1 and NlpD affect the secretion of type III effector XC3176 and hypersensitive response (HR) induction in planta. These findings indicate that, in addition to their well-studied role(s) in cell separation, AmiC and NlpD make an important contribution to the type III secretion (T3S) and virulence regulation in this important plant pathogen.
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Affiliation(s)
- Li‐Chao Yang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐bioresources, College of Life Science and TechnologyGuangxi UniversityNanningGuangxi 530004China
| | - Yong‐Liang Gan
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐bioresources, College of Life Science and TechnologyGuangxi UniversityNanningGuangxi 530004China
| | - Li‐Yan Yang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐bioresources, College of Life Science and TechnologyGuangxi UniversityNanningGuangxi 530004China
| | - Bo‐Le Jiang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐bioresources, College of Life Science and TechnologyGuangxi UniversityNanningGuangxi 530004China
| | - Ji‐Liang Tang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐bioresources, College of Life Science and TechnologyGuangxi UniversityNanningGuangxi 530004China
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23
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Li L, Li RF, Ming ZH, Lu GT, Tang JL. Identification of a novel type III secretion-associated outer membrane-bound protein from Xanthomonas campestris pv. campestris. Sci Rep 2017; 7:42724. [PMID: 28198457 PMCID: PMC5309889 DOI: 10.1038/srep42724] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 01/13/2017] [Indexed: 12/31/2022] Open
Abstract
Many bacterial pathogens employ the type III secretion system (T3SS) to translocate effector proteins into eukaryotic cells to overcome host defenses. To date, most of our knowledge about the T3SS molecular architecture comes from the studies on animal pathogens. In plant pathogens, nine Hrc proteins are believed to be structural components of the T3SS, of which HrcC and HrcJ form the outer and inner rings of the T3SS, respectively. Here, we demonstrated that a novel outer membrane-bound protein (HpaM) of Xanthomonas campestris pv. campestris is critical for the type III secretion and is structurally and functionally conserved in phytopathogenic Xanthomonas spp. We showed that the C-terminus of HpaM extends into the periplasm to interact physically with HrcJ and the middle part of HpaM interacts physically with HrcC. It is clear that the outer and inner rings compose the main basal body of the T3SS apparatus in animal pathogens. Therefore, we presume that HpaM may act as a T3SS structural component, or play a role in assisting assembling or affecting the stability of the T3SS apparatus. HpaM is a highly prevalent and specific protein in Xanthomonas spp., suggesting that the T3SS of Xanthomonas is distinctive in some aspects from other pathogens.
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Affiliation(s)
- Lei Li
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
| | - Rui-Fang Li
- Guangxi Key Laboratory of Biology for Crop Diseases and Insect Pests, Plant Protection Research Institute, Guangxi Academy of Agricultural Sciences, 174 Daxue Road, Nanning, Guangxi 530007, China
| | - Zhen-Hua Ming
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
| | - Guang-Tao Lu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
| | - Ji-Liang Tang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
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24
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Dietsche T, Tesfazgi Mebrhatu M, Brunner MJ, Abrusci P, Yan J, Franz-Wachtel M, Schärfe C, Zilkenat S, Grin I, Galán JE, Kohlbacher O, Lea S, Macek B, Marlovits TC, Robinson CV, Wagner S. Structural and Functional Characterization of the Bacterial Type III Secretion Export Apparatus. PLoS Pathog 2016; 12:e1006071. [PMID: 27977800 PMCID: PMC5158082 DOI: 10.1371/journal.ppat.1006071] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 11/17/2016] [Indexed: 02/04/2023] Open
Abstract
Bacterial type III protein secretion systems inject effector proteins into eukaryotic host cells in order to promote survival and colonization of Gram-negative pathogens and symbionts. Secretion across the bacterial cell envelope and injection into host cells is facilitated by a so-called injectisome. Its small hydrophobic export apparatus components SpaP and SpaR were shown to nucleate assembly of the needle complex and to form the central “cup” substructure of a Salmonella Typhimurium secretion system. However, the in vivo placement of these components in the needle complex and their function during the secretion process remained poorly defined. Here we present evidence that a SpaP pentamer forms a 15 Å wide pore and provide a detailed map of SpaP interactions with the export apparatus components SpaQ, SpaR, and SpaS. We further refine the current view of export apparatus assembly, consolidate transmembrane topology models for SpaP and SpaR, and present intimate interactions of the periplasmic domains of SpaP and SpaR with the inner rod protein PrgJ, indicating how export apparatus and needle filament are connected to create a continuous conduit for substrate translocation. Many Gram-negative bacteria use type III secretion systems to inject bacterial proteins into eukaryotic host cells in order to promote their own survival and colonization. These systems are large molecular machines with the ability to transport proteins across three cell membranes in one step. It is believed that the only gated barrier of these systems lies in the bacterial cytoplasmic membrane but it was unclear so far how this gate looks like and of which components it is composed. Here we present evidence based on in depth biochemical and genetic characterization that an assembly of five SpaP proteins forms this gate in the cytoplasmic membrane of the type III secretion system of Salmonella pathogenicity island 1. We further show that one subunit each of the proteins SpaQ, SpaR, and SpaS are closely associated to the SpaP gate and may function in the gating mechanism, and that the protein PrgJ is attached to this gate on the outside to connect it to the hollow needle filament projecting towards the host cell. Our findings elucidate a hitherto ill-defined aspect of type III secretion systems and may help to develop novel antiinfective therapies targeting these virulence-associated molecular devices.
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Affiliation(s)
- Tobias Dietsche
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Section of Cellular and Molecular Microbiology, Tübingen, Germany
| | - Mehari Tesfazgi Mebrhatu
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Section of Cellular and Molecular Microbiology, Tübingen, Germany
| | - Matthias J. Brunner
- Center for Structural Systems Biology (CSSB), University Medical Center Hamburg-Eppendorf (UKE) and German Electron Synchrotron Centre (DESY), Hamburg, Germany
- Institute of Molecular Biotechnology (IMBA), Vienna Biocenter (VBC), Vienna, Austria
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria
| | - Patrizia Abrusci
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
| | - Jun Yan
- Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | | | | | - Susann Zilkenat
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Section of Cellular and Molecular Microbiology, Tübingen, Germany
| | - Iwan Grin
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Section of Cellular and Molecular Microbiology, Tübingen, Germany
| | - Jorge E. Galán
- Yale University School of Medicine, Department of Microbial Pathogenesis, New Haven, Connecticut, United States of America
| | - Oliver Kohlbacher
- University of Tübingen, Center for BioinformaticsTübingen, Germany
- Max Planck Institute for Developmental Biology, Biomolecular Interactions, Tübingen, Germany
| | - Susan Lea
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
| | - Boris Macek
- University of Tübingen, Proteome Center Tübingen, Tübingen, Germany
| | - Thomas C. Marlovits
- Center for Structural Systems Biology (CSSB), University Medical Center Hamburg-Eppendorf (UKE) and German Electron Synchrotron Centre (DESY), Hamburg, Germany
- Institute of Molecular Biotechnology (IMBA), Vienna Biocenter (VBC), Vienna, Austria
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria
| | - Carol V. Robinson
- Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Samuel Wagner
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Section of Cellular and Molecular Microbiology, Tübingen, Germany
- German Center for Infection Research (DZIF), Partner-site Tübingen, Tübingen, Germany
- * E-mail:
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25
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Abstract
Type III secretion systems (T3SSs) afford Gram-negative bacteria an intimate means of altering the biology of their eukaryotic hosts--the direct delivery of effector proteins from the bacterial cytoplasm to that of the eukaryote. This incredible biophysical feat is accomplished by nanosyringe "injectisomes," which form a conduit across the three plasma membranes, peptidoglycan layer, and extracellular space that form a barrier to the direct delivery of proteins from bacterium to host. The focus of this chapter is T3SS function at the structural level; we will summarize the core findings that have shaped our understanding of the structure and function of these systems and highlight recent developments in the field. In turn, we describe the T3SS secretory apparatus, consider its engagement with secretion substrates, and discuss the posttranslational regulation of secretory function. Lastly, we close with a discussion of the future prospects for the interrogation of structure-function relationships in the T3SS.
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26
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Functional Characterization of EscK (Orf4), a Sorting Platform Component of the Enteropathogenic Escherichia coli Injectisome. J Bacteriol 2016; 199:JB.00538-16. [PMID: 27795324 DOI: 10.1128/jb.00538-16] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 10/03/2016] [Indexed: 02/07/2023] Open
Abstract
The type III secretion system (T3SS) is a supramolecular machine used by many bacterial pathogens to translocate effector proteins directly into the eukaryotic host cell cytoplasm. Enteropathogenic Escherichia coli (EPEC) is an important cause of infantile diarrheal disease in underdeveloped countries. EPEC virulence relies on a T3SS encoded within a chromosomal pathogenicity island known as the locus of enterocyte effacement (LEE). In this work, we pursued the functional characterization of the LEE-encoded protein EscK (previously known as Orf4). We provide evidence indicating that EscK is crucial for efficient T3S and belongs to the SctK (OrgA/YscK/MxiK) protein family, whose members have been implicated in the formation of a sorting platform for secretion of T3S substrates. Bacterial fractionation studies showed that EscK localizes to the inner membrane independently of the presence of any other T3SS component. Combining yeast two-hybrid screening and pulldown assays, we identified an interaction between EscK and the C-ring/sorting platform component EscQ. Site-directed mutagenesis of conserved residues revealed amino acids that are critical for EscK function and for its interaction with EscQ. In addition, we found that T3S substrate overproduction is capable of compensating for the absence of EscK. Overall, our data suggest that EscK is a structural component of the EPEC T3SS sorting platform, playing a central role in the recruitment of T3S substrates for boosting the efficiency of the protein translocation process. IMPORTANCE The type III secretion system (T3SS) is an essential virulence determinant for enteropathogenic Escherichia coli (EPEC) colonization of intestinal epithelial cells. Multiple EPEC effector proteins are injected via the T3SS into enterocyte cells, leading to diarrheal disease. The T3SS is encoded within a genomic pathogenicity island termed the locus of enterocyte effacement (LEE). Here we unravel the function of EscK, a previously uncharacterized LEE-encoded protein. We show that EscK is central for T3SS biogenesis and function. EscK forms a protein complex with EscQ, the main component of the cytoplasmic sorting platform, serving as a docking site for T3S substrates. Our results provide a comprehensive functional analysis of an understudied component of T3SSs.
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Abstract
Bacterial pathogens utilize a multitude of methods to invade mammalian hosts, damage tissue sites, and thwart the immune system from responding. One essential component of these strategies for many bacterial pathogens is the secretion of proteins across phospholipid membranes. Secreted proteins can play many roles in promoting bacterial virulence, from enhancing attachment to eukaryotic cells, to scavenging resources in an environmental niche, to directly intoxicating target cells and disrupting their functions. Many pathogens use dedicated protein secretion systems to secrete virulence factors from the cytosol of the bacteria into host cells or the host environment. In general, bacterial protein secretion apparatuses can be divided into classes, based on their structures, functions, and specificity. Some systems are conserved in all classes of bacteria and secrete a broad array of substrates, while others are only found in a small number of bacterial species and/or are specific to only one or a few proteins. In this chapter, we review the canonical features of several common bacterial protein secretion systems, as well as their roles in promoting the virulence of bacterial pathogens. Additionally, we address recent findings that indicate that the innate immune system of the host can detect and respond to the presence of protein secretion systems during mammalian infection.
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Elhenawy W, Bording-Jorgensen M, Valguarnera E, Haurat MF, Wine E, Feldman MF. LPS Remodeling Triggers Formation of Outer Membrane Vesicles in Salmonella. mBio 2016; 7:e00940-16. [PMID: 27406567 PMCID: PMC4958258 DOI: 10.1128/mbio.00940-16] [Citation(s) in RCA: 100] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 06/09/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Outer membrane vesicles (OMV) are proposed to mediate multiple functions during pathogenesis and symbiosis. However, the mechanisms responsible for OMV formation remain poorly understood. It has been shown in eukaryotic membranes that lipids with an inverted-cone shape favor the formation of positive membrane curvatures. Based on these studies, we formulated the hypothesis that lipid A deacylation might impose shape modifications that result in the curvature of the outer membrane (OM) and subsequent OMV formation. We tested the effect of lipid A remodeling on OMV biogenesis employing Salmonella enterica serovar Typhimurium as a model organism. Expression of the lipid A deacylase PagL resulted in increased vesiculation, without inducing an envelope stress response. Mass spectrometry analysis revealed profound differences in the patterns of lipid A in OM and OMV, with accumulation of deacylated lipid A forms exclusively in OMV. OMV biogenesis by intracellular bacteria upon macrophage infection was drastically reduced in a pagL mutant strain. We propose a novel mechanism for OMV biogenesis requiring lipid A deacylation in the context of a multifactorial process that involves the orchestrated remodeling of the outer membrane. IMPORTANCE The role of lipid remodeling in vesiculation is well documented in eukaryotes. Similarly, bacteria produce membrane-derived vesicles; however, the molecular mechanisms underlying their production are yet to be determined. In this work, we investigated the role of outer membrane remodeling in OMV biogenesis in S Typhimurium. We showed that the expression of the lipid A deacylase PagL results in overvesiculation with deacylated lipid A accumulation exclusively in OMV. An S Typhimurium ΔpagL strain showed a significant reduction in intracellular OMV secretion relative to the wild-type strain. Our results suggest a novel mechanism for OMV biogenesis that involves outer membrane remodeling through lipid A modification. Understanding how OMV are produced by bacteria is important to advance our understanding of the host-pathogen interactions.
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Affiliation(s)
- Wael Elhenawy
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | | | - Ezequiel Valguarnera
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, St. Louis, Missouri, USA
| | - M Florencia Haurat
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Eytan Wine
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | - Mario F Feldman
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, St. Louis, Missouri, USA
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Diepold A, Armitage JP. Type III secretion systems: the bacterial flagellum and the injectisome. Philos Trans R Soc Lond B Biol Sci 2016; 370:rstb.2015.0020. [PMID: 26370933 DOI: 10.1098/rstb.2015.0020] [Citation(s) in RCA: 139] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The flagellum and the injectisome are two of the most complex and fascinating bacterial nanomachines. At their core, they share a type III secretion system (T3SS), a transmembrane export complex that forms the extracellular appendages, the flagellar filament and the injectisome needle. Recent advances, combining structural biology, cryo-electron tomography, molecular genetics, in vivo imaging, bioinformatics and biophysics, have greatly increased our understanding of the T3SS, especially the structure of its transmembrane and cytosolic components, the transcriptional, post-transcriptional and functional regulation and the remarkable adaptivity of the system. This review aims to integrate these new findings into our current knowledge of the evolution, function, regulation and dynamics of the T3SS, and to highlight commonalities and differences between the two systems, as well as their potential applications.
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Affiliation(s)
- Andreas Diepold
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Judith P Armitage
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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Portaliou AG, Tsolis KC, Loos MS, Zorzini V, Economou A. Type III Secretion: Building and Operating a Remarkable Nanomachine. Trends Biochem Sci 2016; 41:175-189. [DOI: 10.1016/j.tibs.2015.09.005] [Citation(s) in RCA: 121] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Revised: 09/16/2015] [Accepted: 09/18/2015] [Indexed: 12/21/2022]
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McDowell MA, Marcoux J, McVicker G, Johnson S, Fong YH, Stevens R, Bowman LAH, Degiacomi MT, Yan J, Wise A, Friede ME, Benesch JLP, Deane JE, Tang CM, Robinson CV, Lea SM. Characterisation of Shigella Spa33 and Thermotoga FliM/N reveals a new model for C-ring assembly in T3SS. Mol Microbiol 2015; 99:749-66. [PMID: 26538516 PMCID: PMC4832279 DOI: 10.1111/mmi.13267] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/02/2015] [Indexed: 11/06/2022]
Abstract
Flagellar type III secretion systems (T3SS) contain an essential cytoplasmic‐ring (C‐ring) largely composed of two proteins FliM and FliN, whereas an analogous substructure for the closely related non‐flagellar (NF) T3SS has not been observed in situ. We show that the spa33 gene encoding the putative NF‐T3SS C‐ring component in Shigella flexneri is alternatively translated to produce both full‐length (Spa33‐FL) and a short variant (Spa33‐C), with both required for secretion. They associate in a 1:2 complex (Spa33‐FL/C2) that further oligomerises into elongated arrays in vitro. The structure of Spa33‐C2 and identification of an unexpected intramolecular pseudodimer in Spa33‐FL reveal a molecular model for their higher order assembly within NF‐T3SS. Spa33‐FL and Spa33‐C are identified as functional counterparts of a FliM–FliN fusion and free FliN respectively. Furthermore, we show that Thermotoga maritima
FliM and FliN form a 1:3 complex structurally equivalent to Spa33‐FL/C2, allowing us to propose a unified model for C‐ring assembly by NF‐T3SS and flagellar‐T3SS.
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Affiliation(s)
| | - Julien Marcoux
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Gareth McVicker
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Steven Johnson
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Yu Hang Fong
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Rebecca Stevens
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Lesley A H Bowman
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | | | - Jun Yan
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Adam Wise
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Miriam E Friede
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | | | - Janet E Deane
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Christoph M Tang
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | | | - Susan M Lea
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
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Murfin KE, Whooley AC, Klassen JL, Goodrich-Blair H. Comparison of Xenorhabdus bovienii bacterial strain genomes reveals diversity in symbiotic functions. BMC Genomics 2015; 16:889. [PMID: 26525894 PMCID: PMC4630870 DOI: 10.1186/s12864-015-2000-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 10/03/2015] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Xenorhabdus bacteria engage in a beneficial symbiosis with Steinernema nematodes, in part by providing activities that help kill and degrade insect hosts for nutrition. Xenorhabdus strains (members of a single species) can display wide variation in host-interaction phenotypes and genetic potential indicating that strains may differ in their encoded symbiosis factors, including secreted metabolites. METHODS To discern strain-level variation among symbiosis factors, and facilitate the identification of novel compounds, we performed a comparative analysis of the genomes of 10 Xenorhabdus bovienii bacterial strains. RESULTS The analyzed X. bovienii draft genomes are broadly similar in structure (e.g. size, GC content, number of coding sequences). Genome content analysis revealed that general classes of putative host-microbe interaction functions, such as secretion systems and toxin classes, were identified in all bacterial strains. In contrast, we observed diversity of individual genes within families (e.g. non-ribosomal peptide synthetase clusters and insecticidal toxin components), indicating the specific molecules secreted by each strain can vary. Additionally, phenotypic analysis indicates that regulation of activities (e.g. enzymes and motility) differs among strains. CONCLUSIONS The analyses presented here demonstrate that while general mechanisms by which X. bovienii bacterial strains interact with their invertebrate hosts are similar, the specific molecules mediating these interactions differ. Our data support that adaptation of individual bacterial strains to distinct hosts or niches has occurred. For example, diverse metabolic profiles among bacterial symbionts may have been selected by dissimilarities in nutritional requirements of their different nematode hosts. Similarly, factors involved in parasitism (e.g. immune suppression and microbial competition factors), likely differ based on evolution in response to naturally encountered organisms, such as insect hosts, competitors, predators or pathogens. This study provides insight into effectors of a symbiotic lifestyle, and also highlights that when mining Xenorhabdus species for novel natural products, including antibiotics and insecticidal toxins, analysis of multiple bacterial strains likely will increase the potential for the discovery of novel molecules.
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Affiliation(s)
- Kristen E Murfin
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, 53706, USA.
| | - Amy C Whooley
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, 53706, USA.
| | - Jonathan L Klassen
- Department of Molecular & Cell Biology, University of Connecticut, Storrs, CT, 06269, USA.
| | - Heidi Goodrich-Blair
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, 53706, USA.
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McShan AC, De Guzman RN. The bacterial type III secretion system as a target for developing new antibiotics. Chem Biol Drug Des 2015; 85:30-42. [PMID: 25521643 DOI: 10.1111/cbdd.12422] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 08/25/2014] [Accepted: 08/26/2014] [Indexed: 01/14/2023]
Abstract
Antibiotic resistance in pathogens requires new targets for developing novel antibacterials. The bacterial type III secretion system (T3SS) is an attractive target for developing antibacterials as it is essential in the pathogenesis of many Gram-negative bacteria. The T3SS consists of structural proteins, effectors, and chaperones. Over 20 different structural proteins assemble into a complex nanoinjector that punctures a hole on the eukaryotic cell membrane to allow the delivery of effectors directly into the host cell cytoplasm. Defects in the assembly and function of the T3SS render bacteria non-infective. Two major classes of small molecules, salicylidene acylhydrazides and thiazolidinones, have been shown to inhibit multiple genera of bacteria through the T3SS. Many additional chemically and structurally diverse classes of small molecule inhibitors of the T3SS have been identified as well. While specific targets within the T3SS of a few inhibitors have been suggested, the vast majority of specific protein targets within the T3SS remain to be identified or characterized. Other T3SS inhibitors include polymers, proteins, and polypeptides mimics. In addition, T3SS activity is regulated by its interaction with biologically relevant molecules, such as bile salts and sterols, which could serve as scaffolds for drug design.
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Affiliation(s)
- Andrew C McShan
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS, 66045, USA
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Ji H, Dong H. Key steps in type III secretion system (T3SS) towards translocon assembly with potential sensor at plant plasma membrane. MOLECULAR PLANT PATHOLOGY 2015; 16:762-73. [PMID: 25469869 PMCID: PMC6638502 DOI: 10.1111/mpp.12223] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Many plant- and animal-pathogenic Gram-negative bacteria employ the type III secretion system (T3SS) to translocate effector proteins from bacterial cells into the cytosol of eukaryotic host cells. The effector translocation occurs through an integral component of T3SS, the channel-like translocon, assembled by hydrophilic and hydrophobic proteinaceous translocators in a two-step process. In the first, hydrophilic translocators localize to the tip of a proteinaceous needle in animal pathogens, or a proteinaceous pilus in plant pathogens, and associate with hydrophobic translocators, which insert into host plasma membranes in the second step. However, the pilus needs to penetrate plant cell walls in advance. All hydrophilic translocators so far identified in plant pathogens are characteristic of harpins: T3SS accessory proteins containing a unitary hydrophilic domain or an additional enzymatic domain. Two-domain harpins carrying a pectate lyase domain potentially target plant cell walls and facilitate the penetration of the pectin-rich middle lamella by the bacterial pilus. One-domain harpins target plant plasma membranes and may play a crucial role in translocon assembly, which may also involve contrapuntal associations of hydrophobic translocators. In all cases, sensory components in the target plasma membrane are indispensable for the membrane recognition of translocators and the functionality of the translocon. The conjectural sensors point to membrane lipids and proteins, and a phosphatidic acid and an aquaporin are able to interact with selected harpin-type translocators. Interactions between translocators and their sensors at the target plasma membrane are assumed to be critical for translocon assembly.
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Affiliation(s)
- Hongtao Ji
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing, 210095, Jiangsu Province, China
| | - Hansong Dong
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing, 210095, Jiangsu Province, China
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De la Cruz MA, Pérez-Morales D, Palacios IJ, Fernández-Mora M, Calva E, Bustamante VH. The two-component system CpxR/A represses the expression of Salmonella virulence genes by affecting the stability of the transcriptional regulator HilD. Front Microbiol 2015; 6:807. [PMID: 26300871 PMCID: PMC4526804 DOI: 10.3389/fmicb.2015.00807] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 07/22/2015] [Indexed: 11/30/2022] Open
Abstract
Salmonella enterica can cause intestinal or systemic infections in humans and animals mainly by the presence of pathogenicity islands SPI-1 and SPI-2, containing 39 and 44 genes, respectively. The AraC-like regulator HilD positively controls the expression of the SPI-1 genes, as well as many other Salmonella virulence genes including those located in SPI-2. A previous report indicates that the two-component system CpxR/A regulates the SPI-1 genes: the absence of the sensor kinase CpxA, but not the absence of its cognate response regulator CpxR, reduces their expression. The presence and absence of cell envelope stress activates kinase and phosphatase activities of CpxA, respectively, which in turn controls the level of phosphorylated CpxR (CpxR-P). In this work, we further define the mechanism for the CpxR/A-mediated regulation of SPI-1 genes. The negative effect exerted by the absence of CpxA on the expression of SPI-1 genes was counteracted by the absence of CpxR or by the absence of the two enzymes, AckA and Pta, which render acetyl-phosphate that phosphorylates CpxR. Furthermore, overexpression of the lipoprotein NlpE, which activates CpxA kinase activity on CpxR, or overexpression of CpxR, repressed the expression of SPI-1 genes. Thus, our results provide several lines of evidence strongly supporting that the absence of CpxA leads to the phosphorylation of CpxR via the AckA/Pta enzymes, which represses both the SPI-1 and SPI-2 genes. Additionally, we show that in the absence of the Lon protease, which degrades HilD, the CpxR-P-mediated repression of the SPI-1 genes is mostly lost; moreover, we demonstrate that CpxR-P negatively affects the stability of HilD and thus decreases the expression of HilD-target genes, such as hilD itself and hilA, located in SPI-1. Our data further expand the insight on the different regulatory pathways for gene expression involving CpxR/A and on the complex regulatory network governing virulence in Salmonella.
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Affiliation(s)
- Miguel A De la Cruz
- Unidad de Investigación Médica en Enfermedades Infecciosas y Parasitarias, Centro Médico Nacional Siglo XX1-IMSS México DF, Mexico
| | - Deyanira Pérez-Morales
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México Cuernavaca, Morelos, Mexico
| | - Irene J Palacios
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México Cuernavaca, Morelos, Mexico
| | - Marcos Fernández-Mora
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México Cuernavaca, Morelos, Mexico
| | - Edmundo Calva
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México Cuernavaca, Morelos, Mexico
| | - Víctor H Bustamante
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México Cuernavaca, Morelos, Mexico
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Leighton TL, Buensuceso RNC, Howell PL, Burrows LL. Biogenesis of Pseudomonas aeruginosa type IV pili and regulation of their function. Environ Microbiol 2015; 17:4148-63. [PMID: 25808785 DOI: 10.1111/1462-2920.12849] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 03/13/2015] [Accepted: 03/14/2015] [Indexed: 12/27/2022]
Abstract
Type IV pili (T4P) are bacterial virulence factors involved in a wide variety of functions including deoxyribonucleic acid uptake, surface attachment, biofilm formation and twitching motility. While T4P are common surface appendages, the systems that assemble them and the regulation of their function differ between species. Pseudomonas aeruginosa, Neisseria spp. and Myxococcus xanthus are common model systems used to study T4P biology. This review focuses on recent advances in P. aeruginosa T4P structural biology, and the regulatory pathways controlling T4P biogenesis and function.
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Affiliation(s)
- Tiffany L Leighton
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada
| | - Ryan N C Buensuceso
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada
| | - P Lynne Howell
- Program in Molecular Structure & Function, The Hospital for Sick Children, Toronto, ON, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Lori L Burrows
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada
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Visualization of the type III secretion sorting platform of Shigella flexneri. Proc Natl Acad Sci U S A 2015; 112:1047-52. [PMID: 25583506 DOI: 10.1073/pnas.1411610112] [Citation(s) in RCA: 170] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Bacterial type III secretion machines are widely used to inject virulence proteins into eukaryotic host cells. These secretion machines are evolutionarily related to bacterial flagella and consist of a large cytoplasmic complex, a transmembrane basal body, and an extracellular needle. The cytoplasmic complex forms a sorting platform essential for effector selection and needle assembly, but it remains largely uncharacterized. Here we use high-throughput cryoelectron tomography (cryo-ET) to visualize intact machines in a virulent Shigella flexneri strain genetically modified to produce minicells capable of interaction with host cells. A high-resolution in situ structure of the intact machine determined by subtomogram averaging reveals the cytoplasmic sorting platform, which consists of a central hub and six spokes, with a pod-like structure at the terminus of each spoke. Molecular modeling of wild-type and mutant machines allowed us to propose a model of the sorting platform in which the hub consists mainly of a hexamer of the Spa47 ATPase, whereas the MxiN protein comprises the spokes and the Spa33 protein forms the pods. Multiple contacts among those components are essential to align the Spa47 ATPase with the central channel of the MxiA protein export gate to form a unique nanomachine. The molecular architecture of the Shigella type III secretion machine and its sorting platform provide the structural foundation for further dissecting the mechanisms underlying type III secretion and pathogenesis and also highlight the major structural distinctions from bacterial flagella.
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Cheung M, Shen DK, Makino F, Kato T, Roehrich AD, Martinez-Argudo I, Walker ML, Murillo I, Liu X, Pain M, Brown J, Frazer G, Mantell J, Mina P, Todd T, Sessions RB, Namba K, Blocker AJ. Three-dimensional electron microscopy reconstruction and cysteine-mediated crosslinking provide a model of the type III secretion system needle tip complex. Mol Microbiol 2014; 95:31-50. [PMID: 25353930 PMCID: PMC4539596 DOI: 10.1111/mmi.12843] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/26/2014] [Indexed: 01/14/2023]
Abstract
Type III secretion systems are found in many Gram-negative bacteria. They are activated by contact with eukaryotic cells and inject virulence proteins inside them. Host cell detection requires a protein complex located at the tip of the device's external injection needle. The Shigella tip complex (TC) is composed of IpaD, a hydrophilic protein, and IpaB, a hydrophobic protein, which later forms part of the injection pore in the host membrane. Here we used labelling and crosslinking methods to show that TCs from a ΔipaB strain contain five IpaD subunits while the TCs from wild-type can also contain one IpaB and four IpaD subunits. Electron microscopy followed by single particle and helical image analysis was used to reconstruct three-dimensional images of TCs at ∼ 20 Å resolution. Docking of an IpaD crystal structure, constrained by the crosslinks observed, reveals that TC organisation is different from that of all previously proposed models. Our findings suggest new mechanisms for TC assembly and function. The TC is the only site within these secretion systems targeted by disease-protecting antibodies. By suggesting how these act, our work will allow improvement of prophylactic and therapeutic strategies.
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Affiliation(s)
- Martin Cheung
- Schools of Cellular & Molecular Medicine and Biochemistry, University of Bristol, Bristol, BS8 1TD, UK
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Impact of detergent on biophysical properties and immune response of the IpaDB fusion protein, a candidate subunit vaccine against Shigella species. Infect Immun 2014; 83:292-9. [PMID: 25368115 DOI: 10.1128/iai.02457-14] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Shigella spp. are causative agents of bacillary dysentery, a human illness with high global morbidity levels, particularly among elderly and infant populations. Shigella infects via the fecal-oral route, and its virulence is dependent upon a type III secretion system (T3SS). Two components of the exposed needle tip complex of the Shigella T3SS, invasion plasmid antigen D (IpaD) and IpaB, have been identified as broadly protective antigens in the mouse lethal pneumonia model. A recombinant fusion protein (DB fusion) was created by joining the coding sequences of IpaD and IpaB. The DB fusion is coexpressed with IpaB's cognate chaperone, IpgC, for proper recombinant expression. The chaperone can then be removed by using the mild detergents octyl oligooxyethelene (OPOE) or N,N-dimethyldodecylamine N-oxide (LDAO). The DB fusion in OPOE or LDAO was used for biophysical characterization and subsequent construction of an empirical phase diagram (EPD). The EPD showed that the DB fusion in OPOE is most stable at neutral pH below 55 °C. In contrast, the DB fusion in LDAO exhibited remarkable thermal plasticity, since this detergent prevents the loss of secondary and tertiary structures after thermal unfolding at 90 °C, as well as preventing thermally induced aggregation. Moreover, the DB fusion in LDAO induced higher interleukin-17 secretion and provided a higher protective efficacy in a mouse challenge model than did the DB fusion in OPOE. These data indicate that LDAO might introduce plasticity to the protein, promoting thermal resilience and enhanced protective efficacy, which may be important in its use as a subunit vaccine.
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