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Popoff MR. Overview of Bacterial Protein Toxins from Pathogenic Bacteria: Mode of Action and Insights into Evolution. Toxins (Basel) 2024; 16:182. [PMID: 38668607 PMCID: PMC11054074 DOI: 10.3390/toxins16040182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Revised: 03/29/2024] [Accepted: 03/30/2024] [Indexed: 04/29/2024] Open
Abstract
Bacterial protein toxins are secreted by certain bacteria and are responsible for mild to severe diseases in humans and animals. They are among the most potent molecules known, which are active at very low concentrations. Bacterial protein toxins exhibit a wide diversity based on size, structure, and mode of action. Upon recognition of a cell surface receptor (protein, glycoprotein, and glycolipid), they are active either at the cell surface (signal transduction, membrane damage by pore formation, or hydrolysis of membrane compound(s)) or intracellularly. Various bacterial protein toxins have the ability to enter cells, most often using an endocytosis mechanism, and to deliver the effector domain into the cytosol, where it interacts with an intracellular target(s). According to the nature of the intracellular target(s) and type of modification, various cellular effects are induced (cell death, homeostasis modification, cytoskeleton alteration, blockade of exocytosis, etc.). The various modes of action of bacterial protein toxins are illustrated with representative examples. Insights in toxin evolution are discussed.
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Affiliation(s)
- Michel R Popoff
- Unité des Toxines Bactériennes, Institut Pasteur, Université Paris Cité, CNRS UMR 2001 INSERM U1306, F-75015 Paris, France
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2
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Prithvisagar KS, Gollapalli P, D’Souza C, Rai P, Karunasagar I, Karunasagar I, Ballamoole KK. Genome analysis of clinical genotype Vibrio vulnificus isolated from seafood in Mangaluru Coast, India provides insights into its pathogenicity. Vet Q 2023; 43:1-17. [PMID: 37478018 PMCID: PMC10438861 DOI: 10.1080/01652176.2023.2240389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 07/17/2023] [Accepted: 07/19/2023] [Indexed: 07/23/2023] Open
Abstract
Vibrio vulnificus an opportunistic human pathogen native to marine/estuarine environment, is one of the leading causes of death due to seafood consumption and exposure of wounds to seawater worldwide. The present study involves the whole genome sequence analysis of an environmental strain of V. vulnificus (clinical genotype) isolated from seafood along the Mangaluru coast of India. The sequenced genome data was subjected to in-silico analysis of phylogeny, virulence genes, antimicrobial resistance determinants, and secretary proteins using suitable bioinformatics tools. The sequenced isolate had an overall genome length of 4.8 Mb and GC content of 46% with 4400 coding DNA sequences. The sequenced strain belongs to a new sequence type (Multilocus sequence typing) and was also found to branch with a phylogenetic lineage that groups the most infectious strains of V. vulnificus. The seafood isolate had complete genes involved in conferring serum resistance yet showed limited serum resistance. The study identified several genes against the antibiotics that are commonly used in their treatment, highlighting the need for alternative treatments. Also, the secretory protein analysis revealed genes associated with major pathways like ABC transporters, two-component systems, quorum sensing, biofilm formation, cationic antimicrobial peptide (CAMP) resistance, and others that play a critical role in the pathogenesis of the V. vulnificus. To the best of our knowledge, this is the first report of a detailed analysis of the genomic information of a V. vulnificus isolated from the Indian subcontinent and provides evidence that raises public health concerns about the safety of seafood.
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Affiliation(s)
- Kattapuni Suresh Prithvisagar
- Department of Infectious Diseases and Microbial Genomics, Nitte University Centre for Science Education and Research, Nitte (Deemed to be University), Mangaluru, India
| | - Pavan Gollapalli
- Center for Bioinformatics and Biostatistics, Nitte (Deemed to be University), Mangaluru, India
| | - Caroline D’Souza
- Department of Infectious Diseases and Microbial Genomics, Nitte University Centre for Science Education and Research, Nitte (Deemed to be University), Mangaluru, India
| | - Praveen Rai
- Department of Infectious Diseases and Microbial Genomics, Nitte University Centre for Science Education and Research, Nitte (Deemed to be University), Mangaluru, India
| | - Iddya Karunasagar
- Department of Infectious Diseases and Microbial Genomics, Nitte University Centre for Science Education and Research, Nitte (Deemed to be University), Mangaluru, India
| | - Indrani Karunasagar
- Department of Infectious Diseases and Microbial Genomics, Nitte University Centre for Science Education and Research, Nitte (Deemed to be University), Mangaluru, India
| | - Krishna Kumar Ballamoole
- Department of Infectious Diseases and Microbial Genomics, Nitte University Centre for Science Education and Research, Nitte (Deemed to be University), Mangaluru, India
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3
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Hernández-Cabanyero C, Sanjuán E, Mercado L, Amaro C. Evidence that fish death after Vibrio vulnificus infection is due to an acute inflammatory response triggered by a toxin of the MARTX family. FISH & SHELLFISH IMMUNOLOGY 2023; 142:109131. [PMID: 37832748 DOI: 10.1016/j.fsi.2023.109131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 09/27/2023] [Accepted: 10/01/2023] [Indexed: 10/15/2023]
Abstract
Vibrio vulnificus is an emerging zoonotic pathogen associated with fish farms that is capable of causing a hemorrhagic septicemia known as warm-water vibriosis. According to a recent transcriptomic and functional study, the death of fish due to vibriosis is more related to the inflammatory response of the host than to the tissue lesions caused by the pathogen. In this work, we hypothesize that the RtxA1 toxin (a V. vulnificus toxin of the MARTX (Multifunctional Autoprocessing Repeats in Toxin) family) is the key virulence factor that would directly or indirectly trigger this fatal inflammatory response. Our hypothesis was based on previous studies that showed that rtxA1-deficient mutants maintained their ability to colonize and invade, but were unable to kill fish. To demonstrate this hypothesis, we infected eels (model of fish vibriosis) by immersion with a mutant deficient in RtxA1 production and analyzed their transcriptome in blood, red blood cells and white blood cells during early vibriosis (0, 3 and 12 h post-infection). The transcriptomic results were compared with those obtained in the previous study in which eels were infected with the V. vulnificus parental strain, and were functionally validated. Overall, our results confirm that fish death after V. vulnificus infection is due to an acute, early and atypical inflammatory response triggered by RtxA1 in which red blood cells seem to play a central role. These results could be relevant to other vibriosis as the toxins of this family are widespread in the Vibrio genus.
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Affiliation(s)
- Carla Hernández-Cabanyero
- Instituto Universitario de Biotecnología y Biomedicina (BIOTECMED), Universitat de València, Dr. Moliner, 50, 46100, Valencia, Spain
| | - Eva Sanjuán
- Instituto Universitario de Biotecnología y Biomedicina (BIOTECMED), Universitat de València, Dr. Moliner, 50, 46100, Valencia, Spain
| | - Luis Mercado
- Instituto de Biología. Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - Carmen Amaro
- Instituto Universitario de Biotecnología y Biomedicina (BIOTECMED), Universitat de València, Dr. Moliner, 50, 46100, Valencia, Spain.
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4
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Waidner LA, Potdukhe TV. Tools to Enumerate and Predict Distribution Patterns of Environmental Vibrio vulnificus and Vibrio parahaemolyticus. Microorganisms 2023; 11:2502. [PMID: 37894160 PMCID: PMC10609196 DOI: 10.3390/microorganisms11102502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 09/28/2023] [Accepted: 10/03/2023] [Indexed: 10/29/2023] Open
Abstract
Vibrio vulnificus (Vv) and Vibrio parahaemolyticus (Vp) are water- and foodborne bacteria that can cause several distinct human diseases, collectively called vibriosis. The success of oyster aquaculture is negatively impacted by high Vibrio abundances. Myriad environmental factors affect the distribution of pathogenic Vibrio, including temperature, salinity, eutrophication, extreme weather events, and plankton loads, including harmful algal blooms. In this paper, we synthesize the current understanding of ecological drivers of Vv and Vp and provide a summary of various tools used to enumerate Vv and Vp in a variety of environments and environmental samples. We also highlight the limitations and benefits of each of the measurement tools and propose example alternative tools for more specific enumeration of pathogenic Vv and Vp. Improvement of molecular methods can tighten better predictive models that are potentially important for mitigation in more controlled environments such as aquaculture.
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Affiliation(s)
- Lisa A. Waidner
- Hal Marcus College of Science and Engineering, University of West Florida, 11000 University Pkwy, Building 58, Room 108, Pensacola, FL 32514, USA
| | - Trupti V. Potdukhe
- GEMS Program, College of Medicine, University of Illinois Chicago, 1853 W. Polk St., Chicago, IL 60612, USA;
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5
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Characteristic Metabolic Changes in Skeletal Muscle Due to Vibrio vulnificus Infection in a Wound Infection Model. mSystems 2023; 8:e0068222. [PMID: 36939368 PMCID: PMC10153474 DOI: 10.1128/msystems.00682-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/21/2023] Open
Abstract
Vibrio vulnificus is a bacterium that inhabits warm seawater or brackish water environments and causes foodborne diseases and wound infections. In severe cases, V. vulnificus invades the skeletal muscle tissue, where bacterial proliferation leads to septicemia and necrotizing fasciitis with high mortality. Despite this characteristic, information on metabolic changes in tissue infected with V. vulnificus is not available. Here, we elucidated the metabolic changes in V. vulnificus-infected mouse skeletal muscle using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS). Metabolome analysis revealed changes in muscle catabolites and energy metabolites during V. vulnificus infection. In particular, succinic acid accumulated but fumaric acid decreased in the infected muscle. However, the virulence factor deletion mutant revealed that changes in metabolites and bacterial proliferation were abolished in skeletal muscle infected with a multifunctional-autoprocessing repeats-in-toxin (MARTX) mutant. On the other hand, mice that were immunosuppressed via cyclophosphamide (CPA) treatment exhibited a similar level of bacterial counts and metabolites between the wild type and MARTX mutant. Therefore, our data indicate that V. vulnificus induces metabolic changes in mouse skeletal muscle and proliferates by using the MARTX toxin to evade the host immune system. This study indicates a new correlation between V. vulnificus infections and metabolic changes that lead to severe reactions or damage to host skeletal muscle. IMPORTANCE V. vulnificus causes necrotizing skin and soft tissue infections (NSSTIs) in severe cases, with high mortality and sign of rapid deterioration. Despite the severity of the infection, the dysfunction of the host metabolism in skeletal muscle triggered by V. vulnificus is poorly understood. In this study, by using a mouse wound infection model, we revealed characteristic changes in muscle catabolism and energy metabolism in skeletal muscle associated with bacterial proliferation in the infected tissues. Understanding such metabolic changes in V. vulnificus-infected tissue may provide crucial information to identify the mechanism via which V. vulnificus induces severe infections. Moreover, our metabolite data may be useful for the recognition, identification, or detection of V. vulnificus infections in clinical studies.
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6
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Choi G, Choi SH. Complex regulatory networks of virulence factors in Vibrio vulnificus. Trends Microbiol 2022; 30:1205-1216. [PMID: 35753865 DOI: 10.1016/j.tim.2022.05.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 05/13/2022] [Accepted: 05/18/2022] [Indexed: 01/13/2023]
Abstract
The fulminating zoonotic pathogen Vibrio vulnificus is the causative agent of fatal septicemia in humans and fish, raising tremendous economic burdens in healthcare and the aquaculture industry. V. vulnificus exploits various virulence factors, including biofilm-related factors and exotoxins, for its persistence in nature and pathogenesis during infection. Substantial studies have found that the expression of virulence factors is coordinately regulated by numerous transcription factors that recognize the changing environments. Here, we summarize and discuss the recent discoveries of the physiological roles of virulence factors in V. vulnificus and their regulation by transcription factors in response to various environmental signals. This expanded understanding of molecular pathogenesis would provide novel clues to develop an effective antivirulence therapy against V. vulnificus infection.
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Affiliation(s)
- Garam Choi
- National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, Seoul National University, Seoul 08826, Republic of Korea; Center for Food and Bioconvergence, Seoul National University, Seoul 08826, Republic of Korea
| | - Sang Ho Choi
- National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, Seoul National University, Seoul 08826, Republic of Korea; Center for Food and Bioconvergence, Seoul National University, Seoul 08826, Republic of Korea.
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7
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Kling K, Trinh SA, Leyn SA, Rodionov DA, Rodionov ID, Herrera A, Cervantes K, Pankey G, Ashcraft D, Ozer EA, Godzik A, Satchell KJF. Genetic Divergence of Vibrio vulnificus Clinical Isolates with Mild to Severe Outcomes. mBio 2022; 13:e0150022. [PMID: 36169197 PMCID: PMC9600620 DOI: 10.1128/mbio.01500-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 09/01/2022] [Indexed: 11/20/2022] Open
Abstract
The marine bacterium Vibrio vulnificus infects humans via food or water contamination, leading to serious manifestations, including gastroenteritis, wound infections, and septic shock. Previous studies suggest phylogenetic Lineage 1 isolates with the vcgC allele of the vcg gene cause human infections, whereas Lineage 2 isolates with the vcgE allele are less pathogenic. Mouse studies suggest that some variants of the primary toxin could drive more serious infections. A collection of 109 V. vulnificus United States human clinical isolates from 2001 to 2019 with paired clinical outcome data were assembled. The isolates underwent whole-genome sequencing, multilocus-sequence phylogenetic analysis, and toxinotype analysis of the multifunctional autoprocessing repeats-in-toxin (MARTX) toxin. In contrast to prior reports, clinical isolates were equally distributed between lineages. We found no correlation between phylogenetic lineage or MARTX toxinotype and disease severity. Infections caused by isolates in Lineage 1 demonstrated a borderline statistically significant higher mortality. Lineage 1 isolates had a trend toward a higher proportion of M-type MARTX toxins compared with Lineage 2, although this was not statistically significant. IMPORTANCE Vibrio vulnificus is an aquatic pathogen that is capable of causing severe disease in humans. Previous studies have suggested that pathogenic isolates were restricted to certain phylogenetic lineages and possibly toxinotype. Our study demonstrated that phylogenetic lineage and multifunctional autoprocessing repeats-in-toxin (MARTX) toxinotype do not predict severity of infection. V. vulnificus strains capable of causing severe human disease are not concentrated in Lineage 1 but are genetically diverse. Thus, food surveillance based on lineage type or toxinotype may not be an appropriate intervention measure to control this rare but serious infection.
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Affiliation(s)
- Kendall Kling
- Division of Infectious Diseases, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Sonya A. Trinh
- Division of Infectious Diseases, Ochsner Medical Center, New Orleans, Louisiana, USA
| | - Semen A. Leyn
- Sanford Burnham Prebys Medical Discovery Institute, LaJolla, California, USA
| | - Dmitry A. Rodionov
- Sanford Burnham Prebys Medical Discovery Institute, LaJolla, California, USA
| | | | - Alfa Herrera
- Division of Infectious Diseases, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Kasey Cervantes
- Division of Infectious Diseases, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - George Pankey
- Infectious Disease Translational Research, Ochsner Clinic Foundation, New Orleans, Louisiana, USA
| | - Deborah Ashcraft
- Infectious Disease Translational Research, Ochsner Clinic Foundation, New Orleans, Louisiana, USA
| | - Egon A. Ozer
- Division of Infectious Diseases, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Adam Godzik
- Biosciences Division, University of California Riverside School of Medicine, Riverside, California, USA
| | - Karla J. F. Satchell
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
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8
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Vibrio vulnificus PlpA facilitates necrotic host cell death induced by the pore forming MARTX toxin. J Microbiol 2022; 60:224-233. [PMID: 35102528 DOI: 10.1007/s12275-022-1448-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 01/10/2022] [Accepted: 01/10/2022] [Indexed: 10/19/2022]
Abstract
Opportunistic pathogen Vibrio vulnificus causes severe systemic infection in humans with high mortality. Although multiple exotoxins have been characterized in V. vulnificus, their interactions and potential synergistic roles in pathogen-induced host cell death have not been investigated previously. By employing a series of multiple exotoxin deletion mutants, we investigated whether specific exotoxins of the pathogen functioned together to achieve severe and rapid necrotic cell death. Human epithelial cells treated with V. vulnificus with a plpA deletion background exhibited an unusually prolonged cell blebbing, suggesting the importance of PlpA, a phospholipase A2, in rapid necrotic cell death by this pathogen. Additional deletion of the rtxA gene encoding the multifunctional autoprocessing repeats-in-toxin (MARTX) toxin did not result in necrotic cell blebs. However, if the rtxA gene was engineered to produce an effector-free MARTX toxin, the cell blebbing was observed, indicating that the pore forming activity of the MARTX toxin is sufficient, but the MARTX toxin effector domains are not necessary, for the blebbing. When a recombinant PlpA was treated on the blebbed cells, the blebs were completely disrupted. Consistent with this, MARTX toxin-pendent rapid release of cytosolic lactate dehydrogenase was significantly delayed in the plpA deletion background. Mutations in other exotoxins such as elastase, cytolysin/hemolysin, and/or extracellular metalloprotease did not affect the bleb formation or disruption. Together, these findings indicate that the pore forming MARTX toxin and the phospholipase A2, PlpA, cooperate sequentially to achieve rapid necrotic cell death by inducing cell blebbing and disrupting the blebs, respectively.
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9
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Loss of the acetate switch in Vibrio vulnificus enhances predation defence against Tetrahymena pyriformis. Appl Environ Microbiol 2021; 88:e0166521. [PMID: 34731052 PMCID: PMC8788688 DOI: 10.1128/aem.01665-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vibrio vulnificus is an opportunistic human pathogen and autochthonous inhabitant of coastal marine environments, where the bacterium is under constant predation by heterotrophic protists or protozoans. As a result of this selection pressure, genetic variants with antipredation mechanisms are selected for and persist in the environment. Such natural variants may also be pathogenic to animal or human hosts, making it important to understand these defense mechanisms. To identify antipredator strategies, 13 V. vulnificus strains of different genotypes isolated from diverse environments were exposed to predation by the ciliated protozoan Tetrahymena pyriformis, and only strain ENV1 was resistant to predation. Further investigation of the cell-free supernatant showed that ENV1 acidifies the environment by the excretion of organic acids, which are toxic to T. pyriformis. As this predation resistance was dependent on the availability of iron, transcriptomes of V. vulnificus in iron-replete and iron-deplete conditions were compared. This analysis revealed that ENV1 ferments pyruvate and the resultant acetyl-CoA leads to acetate synthesis under aerobic conditions, a hallmark of overflow metabolism. The anaerobic respiration global regulator arcA was upregulated when iron was available. An ΔarcA deletion mutant of ENV1 accumulated less acetate and, importantly, was sensitive to grazing by T. pyriformis. Based on the transcriptome response and quantification of metabolites, we conclude that ENV1 has adapted to overflow metabolism and has lost a control switch that shifts metabolism from acetate excretion to acetate assimilation, enabling it to excrete acetate continuously. We show that overflow metabolism and the acetate switch contribute to prey-predator interactions. IMPORTANCE Bacteria in the environment, including Vibrio spp., interact with protozoan predators. To defend against predation, bacteria evolve antipredator mechanisms ranging from changing morphology, biofilm formation, and secretion of toxins or virulence factors. Some of these adaptations may result in strains that are pathogenic to humans. Therefore, it is important to study predator defense strategies of environmental bacteria. V. vulnificus thrives in coastal waters and infects humans. Very little is known about the defense mechanisms V. vulnificus expresses against predation. Here, we show that a V. vulnificus strain (ENV1) has rewired the central carbon metabolism, enabling the production of excess organic acid that is toxic to the protozoan predator T. pyriformis. This is a previously unknown mechanism of predation defense that protects against protozoan predators.
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Carmona-Salido H, Fouz B, Sanjuán E, Carda M, Delannoy CMJ, García-González N, González-Candelas F, Amaro C. The widespread presence of a family of fish virulence plasmids in Vibrio vulnificus stresses its relevance as a zoonotic pathogen linked to fish farms. Emerg Microbes Infect 2021; 10:2128-2140. [PMID: 34702148 PMCID: PMC8635547 DOI: 10.1080/22221751.2021.1999177] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Vibrio vulnificus is a pathogen of public health concern that causes either primary septicemia after ingestion of raw shellfish or secondary septicemia after wound exposure to seawater. In consequence, shellfish and seawater are considered its main reservoirs. However, there is one aspect of its biology that is systematically overlooked: its association with fish in its natural environment. This association led in 1975 to the emergence of a zoonotic clade within phylogenetic lineage 2 following successive outbreaks of vibriosis in farmed eels. Although this clade is now worldwide distributed, no new zoonotic clades were subsequently reported. In this work, we have performed phylogenetic, genomic and functional studies to show that other zoonotic clades are in fact present in 4 of the 5 lineages of the species. Further, we associate these clades, most of them previously but incompletely described, with the acquisition of a family of fish virulence plasmids containing genes essential for resistance to the immune system of certain teleosts of interest in aquaculture. Consequently, our results provide several pieces of evidence about the importance of this species as a zoonotic agent linked to fish farms, as well as on the relevance of these artificial environments acting as drivers that accelerate the evolution of the species.
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Affiliation(s)
- Héctor Carmona-Salido
- Departamento de Microbiología y Ecología, & Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED), Universitat de València. Burjassot, Valencia, Spain
| | - Belén Fouz
- Departamento de Microbiología y Ecología, & Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED), Universitat de València. Burjassot, Valencia, Spain
| | - Eva Sanjuán
- Departamento de Microbiología y Ecología, & Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED), Universitat de València. Burjassot, Valencia, Spain
| | - Miguel Carda
- Departamento de Microbiología y Ecología, & Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED), Universitat de València. Burjassot, Valencia, Spain
| | | | - Neris García-González
- Joint Research Unit Infection and Public Health FISABIO-University of Valencia, Institute for Integrative Systems Biology I2SysBio (UV-CSIC), Valencia, Spain
| | - Fernando González-Candelas
- Joint Research Unit Infection and Public Health FISABIO-University of Valencia, Institute for Integrative Systems Biology I2SysBio (UV-CSIC), Valencia, Spain.,CIBER in Epidemiology and Public Health, Madrid, Spain
| | - Carmen Amaro
- Departamento de Microbiología y Ecología, & Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED), Universitat de València. Burjassot, Valencia, Spain
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11
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Lasa A, Auguste M, Lema A, Oliveri C, Borello A, Taviani E, Bonello G, Doni L, Millard AD, Bruto M, Romalde JL, Yakimov M, Balbi T, Pruzzo C, Canesi L, Vezzulli L. A deep-sea bacterium related to coastal marine pathogens. Environ Microbiol 2021; 23:5349-5363. [PMID: 34097814 PMCID: PMC8519021 DOI: 10.1111/1462-2920.15629] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 05/26/2021] [Accepted: 06/06/2021] [Indexed: 11/29/2022]
Abstract
Evolution of virulence traits from adaptation to environmental niches other than the host is probably a common feature of marine microbial pathogens, whose knowledge might be crucial to understand their emergence and pathogenetic potential. Here, we report genome sequence analysis of a novel marine bacterial species, Vibrio bathopelagicus sp. nov., isolated from warm bathypelagic waters (3309 m depth) of the Mediterranean Sea. Interestingly, V. bathopelagicus sp. nov. is closely related to coastal Vibrio strains pathogenic to marine bivalves. V. bathopelagicus sp. nov. genome encodes genes involved in environmental adaptation to the deep-sea but also in virulence, such as the R5.7 element, MARTX toxin cluster, Type VI secretion system and zinc-metalloprotease, previously associated with Vibrio infections in farmed oysters. The results of functional in vitro assays on immunocytes (haemocytes) of the Mediterranean mussel Mytilus galloprovincialis and the Pacific oyster Crassostrea gigas, and of the early larval development assay in Mytilus support strong toxicity of V. bathopelagicus sp. nov. towards bivalves. V. bathopelagicus sp. nov., isolated from a remote Mediterranean bathypelagic site, is an example of a planktonic marine bacterium with genotypic and phenotypic traits associated with animal pathogenicity, which might have played an evolutionary role in the origin of coastal marine pathogens.
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Affiliation(s)
- Aide Lasa
- Department of Earth, Environmental and Life Sciences (DISTAV)University of GenoaGenoaCorso Europa 26, 16132Italy
- Department of Microbiology and ParasitologyCIBUS‐Facultade de Bioloxía & Institute CRETUS, Universidade de Santiago de CompostelaSantiago de Compostela15782Spain
| | - Manon Auguste
- Department of Earth, Environmental and Life Sciences (DISTAV)University of GenoaGenoaCorso Europa 26, 16132Italy
| | - Alberto Lema
- Department of Microbiology and ParasitologyCIBUS‐Facultade de Bioloxía & Institute CRETUS, Universidade de Santiago de CompostelaSantiago de Compostela15782Spain
| | - Caterina Oliveri
- Department of Earth, Environmental and Life Sciences (DISTAV)University of GenoaGenoaCorso Europa 26, 16132Italy
| | - Alessio Borello
- Department of Earth, Environmental and Life Sciences (DISTAV)University of GenoaGenoaCorso Europa 26, 16132Italy
| | - Elisa Taviani
- Department of Earth, Environmental and Life Sciences (DISTAV)University of GenoaGenoaCorso Europa 26, 16132Italy
| | - Guido Bonello
- Department of Earth, Environmental and Life Sciences (DISTAV)University of GenoaGenoaCorso Europa 26, 16132Italy
| | - Lapo Doni
- Department of Earth, Environmental and Life Sciences (DISTAV)University of GenoaGenoaCorso Europa 26, 16132Italy
| | - Andrew D. Millard
- Department of Genetics and Genome BiologyUniversity of LeicesterUniversity Road, LeicesterUK
| | - Maxime Bruto
- Sorbonne Universités, UPMC Paris 06, CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff CS 90074Roscoff CedexF‐29688France
| | - Jesus L. Romalde
- Department of Microbiology and ParasitologyCIBUS‐Facultade de Bioloxía & Institute CRETUS, Universidade de Santiago de CompostelaSantiago de Compostela15782Spain
| | - Michail Yakimov
- Institute of Biological Resources and Marine Biotechnology, National Research Council (IRBIM‐CNR)Messina98122Italy
| | - Teresa Balbi
- Department of Earth, Environmental and Life Sciences (DISTAV)University of GenoaGenoaCorso Europa 26, 16132Italy
| | - Carla Pruzzo
- Department of Earth, Environmental and Life Sciences (DISTAV)University of GenoaGenoaCorso Europa 26, 16132Italy
| | - Laura Canesi
- Department of Earth, Environmental and Life Sciences (DISTAV)University of GenoaGenoaCorso Europa 26, 16132Italy
| | - Luigi Vezzulli
- Department of Earth, Environmental and Life Sciences (DISTAV)University of GenoaGenoaCorso Europa 26, 16132Italy
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12
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Yu L, Liu F, Li Y, Luo J, Jing R. DeepT3_4: A Hybrid Deep Neural Network Model for the Distinction Between Bacterial Type III and IV Secreted Effectors. Front Microbiol 2021; 12:605782. [PMID: 33552038 PMCID: PMC7858263 DOI: 10.3389/fmicb.2021.605782] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Accepted: 01/04/2021] [Indexed: 01/17/2023] Open
Abstract
Gram-negative bacteria can deliver secreted proteins (also known as secreted effectors) directly into host cells through type III secretion system (T3SS), type IV secretion system (T4SS), and type VI secretion system (T6SS) and cause various diseases. These secreted effectors are heavily involved in the interactions between bacteria and host cells, so their identification is crucial for the discovery and development of novel anti-bacterial drugs. It is currently challenging to accurately distinguish type III secreted effectors (T3SEs) and type IV secreted effectors (T4SEs) because neither T3SEs nor T4SEs contain N-terminal signal peptides, and some of these effectors have similar evolutionary conserved profiles and sequence motifs. To address this challenge, we develop a deep learning (DL) approach called DeepT3_4 to correctly classify T3SEs and T4SEs. We generate amino-acid character dictionary and sequence-based features extracted from effector proteins and subsequently implement these features into a hybrid model that integrates recurrent neural networks (RNNs) and deep neural networks (DNNs). After training the model, the hybrid neural network classifies secreted effectors into two different classes with an accuracy, F-value, and recall of over 80.0%. Our approach stands for the first DL approach for the classification of T3SEs and T4SEs, providing a promising supplementary tool for further secretome studies.
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Affiliation(s)
- Lezheng Yu
- School of Chemistry and Materials Science, Guizhou Education University, Guiyang, China
| | - Fengjuan Liu
- School of Geography and Resources, Guizhou Education University, Guiyang, China
| | - Yizhou Li
- College of Cybersecurity, Sichuan University, Chengdu, China
| | - Jiesi Luo
- Department of Pharmacology, School of Pharmacy, Southwest Medical University, Luzhou, China
| | - Runyu Jing
- College of Cybersecurity, Sichuan University, Chengdu, China
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13
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Spatiotemporal Regulation of Vibrio Exotoxins by HlyU and Other Transcriptional Regulators. Toxins (Basel) 2020; 12:toxins12090544. [PMID: 32842612 PMCID: PMC7551375 DOI: 10.3390/toxins12090544] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Revised: 08/17/2020] [Accepted: 08/19/2020] [Indexed: 02/06/2023] Open
Abstract
After invading a host, bacterial pathogens secrete diverse protein toxins to disrupt host defense systems. To ensure successful infection, however, pathogens must precisely regulate the expression of those exotoxins because uncontrolled toxin production squanders energy. Furthermore, inappropriate toxin secretion can trigger host immune responses that are detrimental to the invading pathogens. Therefore, bacterial pathogens use diverse transcriptional regulators to accurately regulate multiple exotoxin genes based on spatiotemporal conditions. This review covers three major exotoxins in pathogenic Vibrio species and their transcriptional regulation systems. When Vibrio encounters a host, genes encoding cytolysin/hemolysin, multifunctional-autoprocessing repeats-in-toxin (MARTX) toxin, and secreted phospholipases are coordinately regulated by the transcriptional regulator HlyU. At the same time, however, they are distinctly controlled by a variety of other transcriptional regulators. How this coordinated but distinct regulation of exotoxins makes Vibrio species successful pathogens? In addition, anti-virulence strategies that target the coordinating master regulator HlyU and related future research directions are discussed.
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Abstract
V. vulnificus is an opportunistic human pathogen that can cause life-threatening sepsis in immunocompromised patients via seafood poisoning or wound infection. Among the toxic substances produced by this pathogen, the MARTX toxin greatly contributes to disease progression by promoting the dysfunction and death of host cells, which allows the bacteria to disseminate and colonize the host. In response to this, host cells mount a counterattack against the invaders by upregulating various defense genes. In this study, the gene expression profiles of both host cells and V. vulnificus were analyzed by RNA sequencing to gain a comprehensive understanding of host-pathogen interactions. Our results suggest that V. vulnificus uses the MARTX toxin to subvert host cell immune responses as well as to oppose host counterattacks such as iron limitation. To understand toxin-stimulated host-pathogen interactions, we performed dual-transcriptome sequencing experiments using human epithelial (HT-29) and differentiated THP-1 (dTHP-1) immune cells infected with the sepsis-causing pathogen Vibrio vulnificus (either the wild-type [WT] pathogen or a multifunctional-autoprocessing repeats-in-toxin [MARTX] toxin-deficient strain). Gene set enrichment analyses revealed MARTX toxin-dependent responses, including negative regulation of extracellular related kinase 1 (ERK1) and ERK2 (ERK1/2) signaling and cell cycle regulation in HT-29 and dTHP-1 cells, respectively. Further analysis of the expression of immune-related genes suggested that the MARTX toxin dampens immune responses in gut epithelial cells but accelerates inflammation and nuclear factor κB (NF-κB) signaling in immune cells. With respect to the pathogen, siderophore biosynthesis genes were significantly more highly expressed in WT V. vulnificus than in the MARTX toxin-deficient mutant upon infection of dTHP-1 cells. Consistent with these results, iron homeostasis genes that limit iron levels for invading pathogens were overexpressed in WT V. vulnificus-infected dTHP-1 cells. Taken together, these results suggest that MARTX toxin regulates host inflammatory responses during V. vulnificus infection while also countering host defense mechanisms such as iron limitation. IMPORTANCEV. vulnificus is an opportunistic human pathogen that can cause life-threatening sepsis in immunocompromised patients via seafood poisoning or wound infection. Among the toxic substances produced by this pathogen, the MARTX toxin greatly contributes to disease progression by promoting the dysfunction and death of host cells, which allows the bacteria to disseminate and colonize the host. In response to this, host cells mount a counterattack against the invaders by upregulating various defense genes. In this study, the gene expression profiles of both host cells and V. vulnificus were analyzed by RNA sequencing to gain a comprehensive understanding of host-pathogen interactions. Our results suggest that V. vulnificus uses the MARTX toxin to subvert host cell immune responses as well as to oppose host counterattacks such as iron limitation.
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15
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Varela-Chavez C, Blondel A, Popoff MR. Bacterial intracellularly active toxins: Membrane localisation of the active domain. Cell Microbiol 2020; 22:e13213. [PMID: 32353188 DOI: 10.1111/cmi.13213] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 04/06/2020] [Accepted: 04/17/2020] [Indexed: 12/31/2022]
Abstract
Numerous bacterial toxins exert their activity by inactivating or modulating a specific intracellular host target. For this purpose, these toxins have developed efficient strategies to overcome the different host cell defences including specific binding to cell surface, internalisation, passage through the endosome or plasma membrane, exploiting intracellular trafficking and addressing to intracellular targets. Several intracellularly active toxins deliver an active domain into the cytosol that interacts with a target localised to the inner face of the plasma membrane. Thus, the large clostridial glucosylating toxins (LCGTs) target Rho/Ras-GTPases, certain virulence factors of Gram negative bacteria, Rho-GTPases, while Pasteurella multocida toxin (PMT) targets trimeric G-proteins. Others such as botulinum neurotoxins and tetanus neurotoxin have their substrate on synaptic vesicle membrane. LCGTs, PMT, and certain virulence factors from Vibrio sp. show a particular structure constituted of a four-helix bundle membrane (4HBM) protruding from the catalytic site that specifically binds to the membrane phospholipids and then trap the catalytic domain at the proximity of the membrane anchored substrate. Structural and functional analysis indicate that the 4HBM tip of the Clostridium sordellii lethal toxin (TcsL) from the LCGT family contain two loops forming a cavity that mediates the binding to phospholipids and more specifically to phosphatidylserine.
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Affiliation(s)
| | - Arnaud Blondel
- Unité de Bio-Informatique Structurale, Institut Pasteur, Paris, France
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16
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Woida PJ, Satchell KJF. The Vibrio cholerae MARTX toxin silences the inflammatory response to cytoskeletal damage before inducing actin cytoskeleton collapse. Sci Signal 2020; 13:13/614/eaaw9447. [PMID: 31937566 DOI: 10.1126/scisignal.aaw9447] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Multifunctional autoprocessing repeats-in-toxin (MARTX) toxins are pore-forming bacterial toxins that translocate multiple functionally independent effector domains into a target eukaryotic cell. Vibrio cholerae colonizes intestinal epithelial cells (IECs) and uses a MARTX toxin with three effector domains-an actin cross-linking domain (ACD), a Rho inactivation domain (RID), and an α/β hydrolase domain (ABH)-to suppress innate immunity and enhance colonization. We investigated whether these multiple catalytic enzymes delivered from a single toxin functioned in a coordinated manner to suppress intestinal innate immunity. Using cultured human IECs, we demonstrated that ACD-induced cytoskeletal collapse activated extracellular signal-regulated kinase, p38, and c-Jun amino-terminal kinase mitogen-activated protein kinase (MAPK) signaling to elicit a robust proinflammatory response characterized by the secretion of interleukin-8 (IL-8; also called CXCL8) and the expression of CXCL8, tumor necrosis factor (TNF), and other proinflammatory genes. However, RID and ABH, which are naturally delivered together with ACD, blocked MAPK activation through Rac1 and thus prevented ACD-induced inflammation. RID also abolished IL-8 secretion induced by heat-killed bacteria, TNF, or latrunculin A. Thus, MARTX toxins use enzymatic multifunctionality to silence the host response to bacterial factors and to the damage caused by the toxins. Furthermore, these data show how V. cholerae MARTX toxin suppresses intestinal inflammation and contributes to cholera being classically defined as a noninflammatory diarrheal disease.
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Affiliation(s)
- Patrick J Woida
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Karla J F Satchell
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
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Herrera A, Muroski J, Sengupta R, Nguyen HH, Agarwal S, Ogorzalek Loo RR, Mattoo S, Loo JA, Satchell KJF. N-terminal autoprocessing and acetylation of multifunctional-autoprocessing repeats-in-toxins (MARTX) Makes Caterpillars Floppy-like effector is stimulated by adenosine diphosphate (ADP)-Ribosylation Factor 1 in advance of Golgi fragmentation. Cell Microbiol 2019; 22:e13133. [PMID: 31658406 DOI: 10.1111/cmi.13133] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 09/26/2019] [Accepted: 10/11/2019] [Indexed: 12/17/2022]
Abstract
Studies have successfully elucidated the mechanism of action of several effector domains that comprise the multifunctional-autoprocessing repeats-in-toxins (MARTX) toxins of Vibrio vulnificus. However, the biochemical linkage between the cysteine proteolytic activity of Makes Caterpillars Floppy (MCF)-like effector and its cellular effects remains unknown. In this study, we identify the host cell factors that activate in vivo and in vitro MCF autoprocessing as adenosine diphosphate (ADP)-Ribosylation Factor 1 (ARF1) and ADP-Ribosylation Factor 3 (ARF3). Autoprocessing activity is enhanced when ARF1 is in its active [guanosine triphosphate (GTP)-bound] form compared to the inactive [guanosine diphosphate (GDP)-bound] form. Subsequent to auto-cleavage, MCF is acetylated on its exposed N-terminal glycine residue. Acetylation apparently does not dictate subcellular localization as MCF is found localized throughout the cell. However, the cleaved form of MCF gains the ability to bind to the specialized lipid phosphatidylinositol 5-phosphate enriched in Golgi and other membranes necessary for endocytic trafficking, suggesting that a fraction of MCF may be subcellularly localized. Traditional thin-section electron microscopy, high-resolution cryoAPEX localization, and fluorescent microscopy show that MCF causes Golgi dispersal resulting in extensive vesiculation. In addition, host mitochondria are disrupted and fragmented. Mass spectrometry analysis found no reproducible modifications of ARF1 suggesting that ARF1 is not post-translationally modified by MCF. Further, catalytically active MCF does not stably associate with ARF1. Our data indicate not only that ARF1 is a cross-kingdom activator of MCF, but also that MCF may mediate cytotoxicity by directly targeting another yet to be identified protein. This study begins to elucidate the biochemical activity of this important domain and gives insight into how it may promote disease progression.
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Affiliation(s)
- Alfa Herrera
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois
| | - John Muroski
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California
| | - Ranjan Sengupta
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana
| | - Hong Hanh Nguyen
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California
| | - Shivangi Agarwal
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois
| | - Rachel R Ogorzalek Loo
- Department of Biological Chemistry, David Geffen School of Medicine, UCLA Molecular Biology Institute, University of California-Los Angeles, Los Angeles, California.,UCLA/DOE Institute of Genomics and Proteomics, University of California-Los Angeles, Los Angeles, California
| | - Seema Mattoo
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana.,Purdue Institute for Inflammation, Immunology and Infectious Diseases, Purdue University, West Lafayette, Indiana
| | - Joseph A Loo
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California.,Department of Biological Chemistry, David Geffen School of Medicine, UCLA Molecular Biology Institute, University of California-Los Angeles, Los Angeles, California
| | - Karla J F Satchell
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois
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Guo RH, Im YJ, Shin SI, Jeong K, Rhee JH, Kim YR. Vibrio vulnificus RtxA1 cytotoxin targets filamin A to regulate PAK1- and MAPK-dependent cytoskeleton reorganization and cell death. Emerg Microbes Infect 2019; 8:934-945. [PMID: 31237474 PMCID: PMC6598492 DOI: 10.1080/22221751.2019.1632153] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cytoskeletal rearrangement and acute cytotoxicity occur in Vibrio vulnificus-infected host cells. RtxA1 toxin, a multifunctional autoprocessing repeats-in-toxin (MARTX), is essential for the pathogenesis of V. vulnificus and the programmed necrotic cell death. In this study, HeLa cells expressing RtxA1 amino acids 1491–1971 fused to GFP were observed to be rounded. Through yeast two-hybrid screening and subsequent immunoprecipitation validation assays, we confirmed the specific binding of a RtxA11491–1971 fragment with host-cell filamin A, an actin cross-linking scaffold protein. Downregulation of filamin A expression decreased the cytotoxicity of RtxA1 toward host cells. Furthermore, the phosphorylation of JNK and p38 MAPKs was induced by the RtxA1-filamin A interaction during the toxin-mediated cell death. However, the phosphorylation of these MAPKs was not observed during the RtxA1 intoxication of filamin A-deficient M2 cells. In addition, the depletion of pak1, which appeared to be activated by the RtxA1-filamin A interaction, inhibited RtxA1-induced phosphorylation of JNK and p38, and the cells treated with a pak1 inhibitor exhibited decreased RtxA1-mediated cytoskeletal rearrangement and cytotoxicity. Thus, the binding of filamin A by the RtxA11491–1971 domain appears to be a requisite to pak1-mediated MAPK activation, which contributes to the cytoskeletal reorganization and host cell death.
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Affiliation(s)
- Rui Hong Guo
- a College of Pharmacy and Research Institute of Drug Development , Chonnam National University , Gwangju , Republic of Korea
| | - Young Jun Im
- a College of Pharmacy and Research Institute of Drug Development , Chonnam National University , Gwangju , Republic of Korea
| | - Soo Im Shin
- c Department of Bioengineering and Biotechnology, College of Engineering , Chonnam National University , Gwangju , Republic of Korea
| | - Kwangjoon Jeong
- b Clinical Vaccine R&D Center and Department of Microbiology , Chonnam National University Medical School , Hwasun , Republic of Korea
| | - Joon Haeng Rhee
- b Clinical Vaccine R&D Center and Department of Microbiology , Chonnam National University Medical School , Hwasun , Republic of Korea
| | - Young Ran Kim
- a College of Pharmacy and Research Institute of Drug Development , Chonnam National University , Gwangju , Republic of Korea
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Makes caterpillars floppy-like effector-containing MARTX toxins require host ADP-ribosylation factor (ARF) proteins for systemic pathogenicity. Proc Natl Acad Sci U S A 2019; 116:18031-18040. [PMID: 31427506 PMCID: PMC6731672 DOI: 10.1073/pnas.1905095116] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
MARTX toxins present across multiple bacterial genera are primary virulence factors that facilitate initial colonization, dissemination, and lethality in a wide range of hosts, including humans. Upon entry into host cells, the toxins undergo a processing event to release their disease-related modularly structured effector domains. However, the mechanisms underlying processing and activation of diverse effector domains within the toxins remain unclear. Here, we use biochemical and structural biological approaches, in combination with cellular microbiological experiments, to demonstrate how Makes caterpillars floppy-like effector (MCF) or its homolog-containing MARTX toxins process effector modules and fully activate effectors. MCF-containing toxins target ADP-ribosylation factor proteins ubiquitously expressed in cells to activate and disseminate effectors across subcellular compartments simultaneously, eventually leading to systemic pathogenicity. Upon invading target cells, multifunctional autoprocessing repeats-in-toxin (MARTX) toxins secreted by bacterial pathogens release their disease-related modularly structured effector domains. However, it is unclear how a diverse repertoire of effector domains within these toxins are processed and activated. Here, we report that Makes caterpillars floppy-like effector (MCF)-containing MARTX toxins require ubiquitous ADP-ribosylation factor (ARF) proteins for processing and activation of intermediate effector modules, which localize in different subcellular compartments following limited processing of holo effector modules by the internal cysteine protease. Effector domains structured tandemly with MCF in intermediate modules become disengaged and fully activated by MCF, which aggressively interacts with ARF proteins present at the same location as intermediate modules and is converted allosterically into a catalytically competent protease. MCF-mediated effector processing leads ultimately to severe virulence in mice via an MCF-mediated ARF switching mechanism across subcellular compartments. This work provides insight into how bacteria take advantage of host systems to induce systemic pathogenicity.
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