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Martins D, Nerber HN, Roughton CG, Fasquelle A, Barwinska-Sendra A, Vollmer D, Gray J, Vollmer W, Sorg JA, Salgado PS, Henriques AO, Serrano M. Cleavage of an engulfment peptidoglycan hydrolase by a sporulation signature protease in Clostridioides difficile. Mol Microbiol 2024; 122:213-229. [PMID: 38922761 PMCID: PMC11309906 DOI: 10.1111/mmi.15291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Revised: 06/05/2024] [Accepted: 06/08/2024] [Indexed: 06/28/2024]
Abstract
In the model organism Bacillus subtilis, a signaling protease produced in the forespore, SpoIVB, is essential for the activation of the sigma factor σK, which is produced in the mother cell as an inactive pro-protein, pro-σK. SpoIVB has a second function essential to sporulation, most likely during cortex synthesis. The cortex is composed of peptidoglycan (PG) and is essential for the spore's heat resistance and dormancy. Surprisingly, the genome of the intestinal pathogen Clostridioides difficile, in which σK is produced without a pro-sequence, encodes two SpoIVB paralogs, SpoIVB1 and SpoIVB2. Here, we show that spoIVB1 is dispensable for sporulation, while a spoIVB2 in-frame deletion mutant fails to produce heat-resistant spores. The spoIVB2 mutant enters sporulation, undergoes asymmetric division, and completes engulfment of the forespore by the mother cell but fails to synthesize the spore cortex. We show that SpoIIP, a PG hydrolase and part of the engulfasome, the machinery essential for engulfment, is cleaved by SpoIVB2 into an inactive form. Within the engulfasome, the SpoIIP amidase activity generates the substrates for the SpoIID lytic transglycosylase. Thus, following engulfment completion, the cleavage and inactivation of SpoIIP by SpoIVB2 curtails the engulfasome hydrolytic activity, at a time when synthesis of the spore cortex peptidoglycan begins. SpoIVB2 is also required for normal late gene expression in the forespore by a currently unknown mechanism. Together, these observations suggest a role for SpoIVB2 in coordinating late morphological and gene expression events between the forespore and the mother cell.
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Affiliation(s)
- Diogo Martins
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República EAN, 2780-157 Oeiras, Portugal
| | - Hailee N. Nerber
- Texas A&M University, College Station, TX, Biology Department, Texas, USA
| | - Charlotte G. Roughton
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Amaury Fasquelle
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República EAN, 2780-157 Oeiras, Portugal
| | - Anna Barwinska-Sendra
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Daniela Vollmer
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
- Centre for Bacterial Cell Biology, Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Joe Gray
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Waldemar Vollmer
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
- Centre for Bacterial Cell Biology, Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, Brisbane, Australia
| | - Joseph A. Sorg
- Texas A&M University, College Station, TX, Biology Department, Texas, USA
| | - Paula S. Salgado
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
- Centre for Bacterial Cell Biology, Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Adriano O. Henriques
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República EAN, 2780-157 Oeiras, Portugal
| | - Mónica Serrano
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República EAN, 2780-157 Oeiras, Portugal
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Osborne MS, Brehm JN, Olivença C, Cochran AM, Serrano M, Henriques AO, Sorg JA. The impact of YabG mutations on C. difficile spore germination and processing of spore substrates. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.10.598338. [PMID: 38915615 PMCID: PMC11195116 DOI: 10.1101/2024.06.10.598338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/26/2024]
Abstract
YabG is a sporulation-specific protease that is conserved among sporulating bacteria. C. difficile YabG processes cortex destined proteins preproSleC into proSleC and CspBA to CspB and CspA. YabG also affects synthesis of spore coat/exosporium proteins CotA and CdeM. In prior work that identified CspA as the co-germinant receptor, mutations in yabG were found which altered the co-germinants required to initiate spore germination. To understand how these mutations in the yabG locus contribute to C. difficile spore germination, we introduced these mutations into an isogenic background. Spores derived from C. difficile yabG C207A (catalytically inactive), C. difficile yabG A46D, C. difficile yabG G37E, and C. difficile yabG P153L strains germinated in response to TA alone. Recombinantly expressed and purified preproSleC incubated with E. coli lysate expressing wild type YabG resulted in the removal of the pre sequence from preproSleC. Interestingly, only YabGA46D showed any activity towards purified preproSleC. Mutation of the YabG processing site in preproSleC (R119A) led to YabG shifting its processing to R115 or R112. Finally, changes in yabG expression under the mutant promoters were analyzed using a SNAP-tag and revealed expression differences at early and late stages of sporulation. Overall, our results support and expand upon the hypothesis that YabG is important for germination and spore assembly and, upon mutation of the processing site, can shift where it cleaves substrates.
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Affiliation(s)
- Morgan S. Osborne
- Department of Biology, Texas A&M University, College Station, TX 77845, USA
| | - Joshua N. Brehm
- Department of Biology, Texas A&M University, College Station, TX 77845, USA
| | - Carmen Olivença
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Alicia M. Cochran
- Department of Biology, Texas A&M University, College Station, TX 77845, USA
| | - Mónica Serrano
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Adriano O. Henriques
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Joseph A. Sorg
- Department of Biology, Texas A&M University, College Station, TX 77845, USA
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DiCandia MA, Edwards AN, Alcaraz YB, Monteiro MP, Lee CD, Vargas Cuebas G, Bagchi P, McBride SM. A conserved switch controls virulence, sporulation, and motility in C. difficile. PLoS Pathog 2024; 20:e1012224. [PMID: 38739653 PMCID: PMC11115286 DOI: 10.1371/journal.ppat.1012224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 05/23/2024] [Accepted: 04/25/2024] [Indexed: 05/16/2024] Open
Abstract
Spore formation is required for environmental survival and transmission of the human enteropathogenic Clostridioides difficile. In all bacterial spore formers, sporulation is regulated through activation of the master response regulator, Spo0A. However, the factors and mechanisms that directly regulate C. difficile Spo0A activity are not defined. In the well-studied Bacillus species, Spo0A is directly inactivated by Spo0E, a small phosphatase. To understand Spo0E function in C. difficile, we created a null mutation of the spo0E ortholog and assessed sporulation and physiology. The spo0E mutant produced significantly more spores, demonstrating Spo0E represses C. difficile sporulation. Unexpectedly, the spo0E mutant also exhibited increased motility and toxin production, and enhanced virulence in animal infections. We uncovered that Spo0E interacts with both Spo0A and the toxin and motility regulator, RstA. Direct interactions between Spo0A, Spo0E, and RstA constitute a previously unknown molecular switch that coordinates sporulation with motility and toxin production. Reinvestigation of Spo0E function in B. subtilis revealed that Spo0E induced motility, demonstrating Spo0E regulation of motility and sporulation among divergent species. Further, 3D structural analyses of Spo0E revealed specific and exclusive interactions between Spo0E and binding partners in C. difficile and B. subtilis that provide insight into the conservation of this regulatory mechanism among different species.
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Affiliation(s)
- Michael A. DiCandia
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, United States of America
| | - Adrianne N. Edwards
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, United States of America
| | - Ysabella B. Alcaraz
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, United States of America
| | - Marcos P. Monteiro
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, United States of America
| | - Cheyenne D. Lee
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, United States of America
| | - Germán Vargas Cuebas
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, United States of America
| | - Pritha Bagchi
- Emory Integrated Proteomics Core, Emory University, Atlanta, Georgia, United States of America
| | - Shonna M. McBride
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, United States of America
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Lee CD, Rizvi A, McBride SM. KipOTIA detoxifies 5-oxoproline and promotes the growth of Clostridioides difficile. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.01.592088. [PMID: 38746432 PMCID: PMC11092664 DOI: 10.1101/2024.05.01.592088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
Clostridioides difficile is an anaerobic enteric pathogen that disseminates in the environment as a dormant spore. For C. difficile and other sporulating bacteria, the initiation of sporulation is a regulated process that prevents spore formation under favorable growth conditions. In Bacillus subtilis , one such mechanism for preventing sporulation is the Kinase Inhibitory Protein, KipI, which impedes activation of the main sporulation kinase. In addition, KipI functions as part of a complex that detoxifies the intermediate metabolite, 5-oxoproline (OP), a harmful by-product of glutamic acid. In this study, we investigate the orthologous Kip proteins in C. difficile to determine their roles in the regulation of sporulation and metabolism. Using deletion mutants in kipIA and the full kipOTIA operon, we show that unlike in B. subtilis, the Kip proteins have no significant impact on sporulation. However, we found that the kip operon encodes a functional oxoprolinase that facilitates detoxification of OP. Further, our data demonstrate that KipOTIA not only detoxifies OP, but also allows OP to be used as a nutrient source that supports the robust growth of C. difficile , thereby facilitating the conversion of a toxic byproduct of metabolism into an effective energy source.
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Hu C, Garey KW. Microscopy methods for Clostridioides difficile. Anaerobe 2024; 86:102822. [PMID: 38341023 DOI: 10.1016/j.anaerobe.2024.102822] [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: 08/17/2023] [Revised: 01/25/2024] [Accepted: 01/29/2024] [Indexed: 02/12/2024]
Abstract
Microscopic technologies including light and fluorescent, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and cryo-electron microscopy have been widely utilized to visualize Clostridioides difficile at the molecular, cellular, community, and structural biology level. This comprehensive review summarizes the microscopy tools (fluorescent and reporter system) in their use to study different aspects of C. difficile life cycle and virulence (sporulation, germination) or applications (detection of C. difficile or use of antimicrobials). With these developing techniques, microscopy tools will be able to find broader applications and address more challenging questions to study C. difficile and C. difficile infection.
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Affiliation(s)
- Chenlin Hu
- University of Houston College of Pharmacy, Houston, TX, USA
| | - Kevin W Garey
- University of Houston College of Pharmacy, Houston, TX, USA.
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Pensinger DA, Dobrila HA, Stevenson DM, Hryckowian ND, Amador-Noguez D, Hryckowian AJ. Exogenous butyrate inhibits butyrogenic metabolism and alters virulence phenotypes in Clostridioides difficile. mBio 2024; 15:e0253523. [PMID: 38289141 PMCID: PMC10936429 DOI: 10.1128/mbio.02535-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Accepted: 12/20/2023] [Indexed: 02/13/2024] Open
Abstract
The gut microbiome engenders colonization resistance against the diarrheal pathogen Clostridioides difficile, but the molecular basis of this colonization resistance is incompletely understood. A prominent class of gut microbiome-produced metabolites important for colonization resistance against C. difficile is short-chain fatty acids (SCFAs). In particular, one SCFA (butyrate) decreases the fitness of C. difficile in vitro and is correlated with C. difficile-inhospitable gut environments, both in mice and in humans. Here, we demonstrate that butyrate-dependent growth inhibition in C. difficile occurs under conditions where C. difficile also produces butyrate as a metabolic end product. Furthermore, we show that exogenous butyrate is internalized into C. difficile cells and is incorporated into intracellular CoA pools where it is metabolized in a reverse (energetically unfavorable) direction to crotonyl-CoA and (S)-3-hydroxybutyryl-CoA and/or 4-hydroxybutyryl-CoA. This internalization of butyrate and reverse metabolic flow of a butyrogenic pathway(s) in C. difficile coincides with alterations in toxin release and sporulation. Together, this work highlights butyrate as a marker of a C. difficile-inhospitable environment to which C. difficile responds by releasing its diarrheagenic toxins and producing environmentally resistant spores necessary for transmission between hosts. These findings provide foundational data for understanding the molecular and genetic basis of how C. difficile growth is inhibited by butyrate and how butyrate alters C. difficile virulence in the face of a highly competitive and dynamic gut environment.IMPORTANCEThe gut microbiome engenders colonization resistance against the diarrheal pathogen Clostridioides difficile, but the molecular basis of this colonization resistance is incompletely understood, which hinders the development of novel therapeutic interventions for C. difficile infection (CDI). We investigated how C. difficile responds to butyrate, an end-product of gut microbiome community metabolism which inhibits C. difficile growth. We show that exogenously produced butyrate is internalized into C. difficile, which inhibits C. difficile growth by interfering with its own butyrate production. This growth inhibition coincides with increased toxin release from C. difficile cells and the production of environmentally resistant spores necessary for transmission between hosts. Future work to disentangle the molecular mechanisms underlying these growth and virulence phenotypes will likely lead to new strategies to restrict C. difficile growth in the gut and minimize its pathogenesis during CDI.
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Affiliation(s)
- Daniel A. Pensinger
- Department of Medicine, Division of Gastroenterology and Hepatology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
- Department of Medical Microbiology & Immunology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Horia A. Dobrila
- Department of Medicine, Division of Gastroenterology and Hepatology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
- Department of Medical Microbiology & Immunology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - David M. Stevenson
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Nicole D. Hryckowian
- Department of Medical Microbiology & Immunology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Daniel Amador-Noguez
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Andrew J. Hryckowian
- Department of Medicine, Division of Gastroenterology and Hepatology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
- Department of Medical Microbiology & Immunology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
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7
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Wetzel D, Carter ZA, Monteiro MP, Edwards AN, Scharer CD, McBride SM. The pH-responsive SmrR-SmrT system modulates C. difficile antimicrobial resistance, spore formation, and toxin production. Infect Immun 2024; 92:e0046123. [PMID: 38345371 PMCID: PMC10929453 DOI: 10.1128/iai.00461-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 01/23/2024] [Indexed: 02/27/2024] Open
Abstract
Clostridioides difficile is an anaerobic gastrointestinal pathogen that spreads through the environment as dormant spores. To survive, replicate, and sporulate in the host intestine, C. difficile must adapt to a variety of conditions in its environment, including changes in pH, the availability of metabolites, host immune factors, and a diverse array of other species. Prior studies showed that changes in intestinal conditions, such as pH, can affect C. difficile toxin production, spore formation, and cell survival. However, little is understood about the specific genes and pathways that facilitate environmental adaptation and lead to changes in C. difficile cell outcomes. In this study, we investigated two genes, CD2505 and CD2506, that are differentially regulated by pH to determine if they impact C. difficile growth and sporulation. Using deletion mutants, we examined the effects of both genes (herein smrR and smrT) on sporulation frequency, toxin production, and antimicrobial resistance. We determined that SmrR is a repressor of smrRT that responds to pH and suppresses sporulation and toxin production through regulation of the SmrT transporter. Further, we showed that SmrT confers resistance to erythromycin and lincomycin, establishing a connection between the regulation of sporulation and antimicrobial resistance.IMPORTANCEClostridioides difficile is a mammalian pathogen that colonizes the large intestine and produces toxins that lead to severe diarrheal disease. C. difficile is a major threat to public health due to its intrinsic resistance to antimicrobials and its ability to form dormant spores that are easily spread from host to host. In this study, we examined the contribution of two genes, smrR and smrT, on sporulation, toxin production, and antimicrobial resistance. Our results indicate that SmrR represses smrT expression, while production of SmrT increases spore and toxin production, as well as resistance to antibiotics.
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Affiliation(s)
- Daniela Wetzel
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, USA
| | - Zavier A. Carter
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, USA
| | - Marcos P. Monteiro
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, USA
| | - Adrianne N. Edwards
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, USA
| | - Christopher D. Scharer
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, USA
| | - Shonna M. McBride
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, USA
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Oludiran A, Malik A, Zourou AC, Wu Y, Gross SP, Siryapon A, Poudel A, Alleyne K, Adams S, Courson DS, Cotten ML, Purcell EB. Host-defense piscidin peptides as antibiotic adjuvants against Clostridioides difficile. PLoS One 2024; 19:e0295627. [PMID: 38252641 PMCID: PMC10802969 DOI: 10.1371/journal.pone.0295627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Accepted: 11/26/2023] [Indexed: 01/24/2024] Open
Abstract
The spore-forming intestinal pathogen Clostridioides difficile causes multidrug resistant infection with a high rate of recurrence after treatment. Piscidins 1 (p1) and 3 (p3), cationic host defense peptides with micromolar cytotoxicity against C. difficile, sensitize C. difficile to clinically relevant antibiotics tested at sublethal concentrations. Both peptides bind to Cu2+ using an amino terminal copper and nickel binding motif. Here, we investigate the two peptides in the apo and holo states as antibiotic adjuvants against an epidemic strain of C. difficile. We find that the presence of the peptides leads to lower doses of metronidazole, vancomycin, and fidaxomicin to kill C. difficile. The activity of metronidazole, which targets DNA, is enhanced by a factor of 32 when combined with p3, previously shown to bind and condense DNA. Conversely, the activity of vancomycin, which acts at bacterial cell walls, is enhanced 64-fold when combined with membrane-active p1-Cu2+. As shown through microscopy monitoring the permeabilization of membranes of C. difficile cells and vesicle mimics of their membranes, the adjuvant effect of p1 and p3 in the apo and holo states is consistent with a mechanism of action where the peptides enable greater antibiotic penetration through the cell membrane to increase their bioavailability. The variations in effects obtained with the different forms of the peptides reveal that while all piscidins generally sensitize C. difficile to antibiotics, co-treatments can be optimized in accordance with the underlying mechanism of action of the peptides and antibiotics. Overall, this study highlights the potential of antimicrobial peptides as antibiotic adjuvants to increase the lethality of currently approved antibiotic dosages, reducing the risk of incomplete treatments and ensuing drug resistance.
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Affiliation(s)
- Adenrele Oludiran
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia, United States of America
| | - Areej Malik
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia, United States of America
- Biomedical Sciences Program, Old Dominion University, Norfolk, Virginia, United States of America
| | - Andriana C. Zourou
- Department of Applied Science, William & Mary, Williamsburg, Virginia, United States of America
| | - Yonghan Wu
- Irvine Department of Physics and Astronomy, University of California, Los Angeles, California, United States of America
| | - Steven P. Gross
- Ivrine Department of Developmental and Cell Biology, University of California, Los Angeles, California, United States of America
| | - Albert Siryapon
- Irvine Department of Physics and Astronomy, University of California, Los Angeles, California, United States of America
| | - Asia Poudel
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia, United States of America
| | - Kwincy Alleyne
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia, United States of America
| | - Savion Adams
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia, United States of America
| | - David S. Courson
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia, United States of America
| | - Myriam L. Cotten
- Department of Applied Science, William & Mary, Williamsburg, Virginia, United States of America
| | - Erin B. Purcell
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia, United States of America
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Serrano M, Martins D, Henriques AO. Clostridioides difficile Sporulation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 1435:273-314. [PMID: 38175480 DOI: 10.1007/978-3-031-42108-2_13] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Some members of the Firmicutes phylum, including many members of the human gut microbiota, are able to differentiate a dormant and highly resistant cell type, the endospore (hereinafter spore for simplicity). Spore-formers can colonize virtually any habitat and, because of their resistance to a wide variety of physical and chemical insults, spores can remain viable in the environment for long periods of time. In the anaerobic enteric pathogen Clostridioides difficile the aetiologic agent is the oxygen-resistant spore, while the toxins produced by actively growing cells are the main cause of the disease symptoms. Here, we review the regulatory circuits that govern entry into sporulation. We also cover the role of spores in the infectious cycle of C. difficile in relation to spore structure and function and the main control points along spore morphogenesis.
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Affiliation(s)
- Mónica Serrano
- Instituto de Tecnologia Química e Biológica António Xavier, Oeiras, Portugal.
| | - Diogo Martins
- Instituto de Tecnologia Química e Biológica António Xavier, Oeiras, Portugal
| | - Adriano O Henriques
- Instituto de Tecnologia Química e Biológica António Xavier, Oeiras, Portugal
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10
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Shrestha S, Taib N, Gribaldo S, Shen A. Diversification of division mechanisms in endospore-forming bacteria revealed by analyses of peptidoglycan synthesis in Clostridioides difficile. Nat Commun 2023; 14:7975. [PMID: 38042849 PMCID: PMC10693644 DOI: 10.1038/s41467-023-43595-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 11/14/2023] [Indexed: 12/04/2023] Open
Abstract
The bacterial enzymes FtsW and FtsI, encoded in the highly conserved dcw gene cluster, are considered to be universally essential for the synthesis of septal peptidoglycan (PG) during cell division. Here, we show that the pathogen Clostridioides difficile lacks a canonical FtsW/FtsI pair, and its dcw-encoded PG synthases have undergone a specialization to fulfill sporulation-specific roles, including synthesizing septal PG during the sporulation-specific mode of cell division. Although these enzymes are directly regulated by canonical divisome components during this process, dcw-encoded PG synthases and their divisome regulators are dispensable for cell division during normal growth. Instead, C. difficile uses a bifunctional class A penicillin-binding protein as the core divisome PG synthase, revealing a previously unreported role for this class of enzymes. Our findings support that the emergence of endosporulation in the Firmicutes phylum facilitated the functional repurposing of cell division factors. Moreover, they indicate that C. difficile, and likely other clostridia, assemble a distinct divisome that therefore may represent a unique target for therapeutic interventions.
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Affiliation(s)
- Shailab Shrestha
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
- Program in Molecular Microbiology, Tufts University Graduate School of Biomedical Sciences, Boston, MA, USA
| | - Najwa Taib
- Institut Pasteur, Université Paris Cité, Evolutionary Biology of the Microbial Cell Unit, Paris, France
- Institut Pasteur, Université Paris Cité, Bioinformatics and Biostatistics Hub, F-75015, Paris, France
| | - Simonetta Gribaldo
- Institut Pasteur, Université Paris Cité, Evolutionary Biology of the Microbial Cell Unit, Paris, France
| | - Aimee Shen
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA.
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11
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Wetzel D, Carter ZA, Monteiro MP, Edwards AN, McBride SM. The pH-responsive SmrR-SmrT system modulates C. difficile antimicrobial resistance, spore formation, and toxin production. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.02.565354. [PMID: 37961610 PMCID: PMC10635087 DOI: 10.1101/2023.11.02.565354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Clostridioides difficile is an anaerobic gastrointestinal pathogen that spreads through the environment as dormant spores. To survive, replicate, and sporulate in the host intestine, C. difficile must adapt to a variety of conditions in its environment, including changes in pH, the availability of metabolites, host immune factors, and a diverse array of other species. Prior studies showed that changes in intestinal conditions, such as pH, can affect C. difficile toxin production, spore formation, and cell survival. However, little is understood about the specific genes and pathways that facilitate environmental adaptation and lead to changes in C. difficile cell outcomes. In this study, we investigated two genes, CD2505 and CD2506, that are differentially regulated by pH to determine if they impact C. difficile growth and sporulation. Using deletion mutants, we examined the effects of both genes (herein smrR and smrT ) on sporulation frequency, toxin production, and antimicrobial resistance. We determined that SmrR is a repressor of smrRT that responds to pH and suppresses sporulation and toxin production through regulation of the SmrT transporter. Further, we showed that SmrT confers resistance to erythromycin and lincomycin, establishing a connection between the regulation of sporulation and antimicrobial resistance. IMPORTANCE C. difficile is a mammalian pathogen that colonizes the large intestine and produces toxins that lead to severe diarrheal disease. C. difficile is a major threat to public health due to its intrinsic resistance to antimicrobials and its ability to form dormant spores that are easily spread from host to host. In this study, we examined the contribution of two genes, smrR and smrT on sporulation, toxin production, and antimicrobial resistance. Our results indicate that SmrR represses smrT expression, while production of SmrT increases spore and toxin production, as well as resistance to antibiotics.
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Marini E, Olivença C, Ramalhete S, Aguirre AM, Ingle P, Melo MN, Antunes W, Minton NP, Hernandez G, Cordeiro TN, Sorg JA, Serrano M, Henriques AO. A sporulation signature protease is required for assembly of the spore surface layers, germination and host colonization in Clostridioides difficile. PLoS Pathog 2023; 19:e1011741. [PMID: 37956166 PMCID: PMC10681294 DOI: 10.1371/journal.ppat.1011741] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 11/27/2023] [Accepted: 10/09/2023] [Indexed: 11/15/2023] Open
Abstract
A genomic signature for endosporulation includes a gene coding for a protease, YabG, which in the model organism Bacillus subtilis is involved in assembly of the spore coat. We show that in the human pathogen Clostridioidesm difficile, YabG is critical for the assembly of the coat and exosporium layers of spores. YabG is produced during sporulation under the control of the mother cell-specific regulators σE and σK and associates with the spore surface layers. YabG shows an N-terminal SH3-like domain and a C-terminal domain that resembles single domain response regulators, such as CheY, yet is atypical in that the conserved phosphoryl-acceptor residue is absent. Instead, the CheY-like domain carries residues required for activity, including Cys207 and His161, the homologues of which form a catalytic diad in the B. subtilis protein, and also Asp162. The substitution of any of these residues by Ala, eliminates an auto-proteolytic activity as well as interdomain processing of CspBA, a reaction that releases the CspB protease, required for proper spore germination. An in-frame deletion of yabG or an allele coding for an inactive protein, yabGC207A, both cause misassemby of the coat and exosporium and the formation of spores that are more permeable to lysozyme and impaired in germination and host colonization. Furthermore, we show that YabG is required for the expression of at least two σK-dependent genes, cotA, coding for a coat protein, and cdeM, coding for a key determinant of exosporium assembly. Thus, YabG also impinges upon the genetic program of the mother cell possibly by eliminating a transcriptional repressor. Although this activity has not been described for the B. subtilis protein and most of the YabG substrates vary among sporeformers, the general role of the protease in the assembly of the spore surface is likely to be conserved across evolutionary distance.
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Affiliation(s)
- Eleonora Marini
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República EAN, Oeiras, Portugal
| | - Carmen Olivença
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República EAN, Oeiras, Portugal
| | - Sara Ramalhete
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República EAN, Oeiras, Portugal
| | - Andrea Martinez Aguirre
- Texas A&M University, Department of Biology, College Station, Texas, United States of America
| | - Patrick Ingle
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Manuel N Melo
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República EAN, Oeiras, Portugal
| | - Wilson Antunes
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República EAN, Oeiras, Portugal
| | - Nigel P Minton
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Guillem Hernandez
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República EAN, Oeiras, Portugal
| | - Tiago N Cordeiro
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República EAN, Oeiras, Portugal
| | - Joseph A Sorg
- Texas A&M University, Department of Biology, College Station, Texas, United States of America
| | - Mónica Serrano
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República EAN, Oeiras, Portugal
| | - Adriano O Henriques
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República EAN, Oeiras, Portugal
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Rizvi A, Vargas-Cuebas G, Edwards AN, DiCandia MA, Carter ZA, Lee CD, Monteiro MP, McBride SM. Glycine fermentation by C. difficile promotes virulence and spore formation, and is induced by host cathelicidin. Infect Immun 2023; 91:e0031923. [PMID: 37754683 PMCID: PMC10580938 DOI: 10.1128/iai.00319-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Accepted: 08/14/2023] [Indexed: 09/28/2023] Open
Abstract
Clostridioides difficile is a leading cause of antibiotic-associated diarrheal disease. C. difficile colonization, growth, and toxin production in the intestine is strongly associated with its ability to use amino acids to generate energy, but little is known about the impact of specific amino acids on C. difficile pathogenesis. The amino acid glycine is enriched in the dysbiotic gut and is suspected to contribute to C. difficile infection. We hypothesized that the use of glycine as an energy source contributes to colonization of the intestine and pathogenesis of C. difficile. To test this hypothesis, we deleted the glycine reductase (GR) genes grdAB, rendering C. difficile unable to ferment glycine, and investigated the impact on growth and pathogenesis. Our data show that the grd pathway promotes growth, toxin production, and sporulation. Glycine fermentation also had a significant impact on toxin production and pathogenesis of C. difficile in the hamster model of disease. Furthermore, we determined that the grd locus is regulated by host cathelicidin (LL-37) and the cathelicidin-responsive regulator, ClnR, indicating that the host peptide signals to control glycine catabolism. The induction of glycine fermentation by LL-37 demonstrates a direct link between the host immune response and the bacterial reactions of toxin production and spore formation.
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Affiliation(s)
- Arshad Rizvi
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, USA
| | - Germán Vargas-Cuebas
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, USA
| | - Adrianne N. Edwards
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, USA
| | - Michael A. DiCandia
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, USA
| | - Zavier A. Carter
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, USA
| | - Cheyenne D. Lee
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, USA
| | - Marcos P. Monteiro
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, USA
| | - Shonna M. McBride
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, USA
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Edwards AN, McBride SM. The RgaS-RgaR two-component system promotes Clostridioides difficile sporulation through a small RNA and the Agr1 system. PLoS Genet 2023; 19:e1010841. [PMID: 37844084 PMCID: PMC10602386 DOI: 10.1371/journal.pgen.1010841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 10/26/2023] [Accepted: 10/02/2023] [Indexed: 10/18/2023] Open
Abstract
The ability to form a dormant spore is essential for the survival of the anaerobic pathogen, Clostridioides difficile, outside of the mammalian gastrointestinal tract. The initiation of sporulation is governed by the master regulator of sporulation, Spo0A, which is activated by phosphorylation. Multiple sporulation factors control Spo0A phosphorylation; however, this regulatory pathway is not well defined in C. difficile. We discovered that RgaS and RgaR, a conserved orphan histidine kinase and orphan response regulator, function together as a cognate two-component regulatory system to directly activate transcription of several genes. One of these targets, agrB1D1, encodes gene products that synthesize and export a small quorum-sensing peptide, AgrD1, which positively influences expression of early sporulation genes. Another target, a small regulatory RNA now known as SpoZ, impacts later stages of sporulation through a small hypothetical protein and an additional, unknown regulatory mechanism(s). Unlike Agr systems in many organisms, AgrD1 does not activate the RgaS-RgaR two-component system, and thus, is not responsible for autoregulating its own production. Altogether, we demonstrate that C. difficile utilizes a conserved two-component system that is uncoupled from quorum-sensing to promote sporulation through two distinct regulatory pathways.
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Affiliation(s)
- Adrianne N. Edwards
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, United States of America
| | - Shonna M. McBride
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, United States of America
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Marshall A, McGrath JW, Mitchell M, Fanning S, McMullan G. One size does not fit all - Trehalose metabolism by Clostridioides difficile is variable across the five phylogenetic lineages. Microb Genom 2023; 9:001110. [PMID: 37768179 PMCID: PMC10569727 DOI: 10.1099/mgen.0.001110] [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: 05/25/2023] [Accepted: 09/19/2023] [Indexed: 09/29/2023] Open
Abstract
Clostridioides difficile, the leading cause of antibiotic-associated diarrhoea worldwide, is a genetically diverse species which can metabolise a number of nutrient sources upon colonising a dysbiotic gut environment. Trehalose, a disaccharide sugar consisting of two glucose molecules bonded by an α 1,1-glycosidic bond, has been hypothesised to be involved in the emergence of C. difficile hypervirulence due to its increased utilisation by the RT027 and RT078 strains. Here, growth in trehalose as the sole carbon source was shown to be non-uniform across representative C. difficile strains, even though the genes for its metabolism were induced. Growth in trehalose reduced the expression of genes associated with toxin production and sporulation in the C. difficile R20291 (RT027) and M120 (RT078) strains in vitro, suggesting an inhibitory effect on virulence factors. Interestingly, the R20291 TreR transcriptional regulatory protein appeared to possess an activator function as its DNA-binding ability was increased in the presence of its effector, trehalose-6-phosphate. Using RNA-sequencing analysis, we report the identification of a putative trehalose metabolism pathway which is induced during growth in trehalose: this has not been previously described within the C. difficile species. These data demonstrate the metabolic diversity exhibited by C. difficile which warrants further investigation to elucidate the molecular basis of trehalose metabolism within this important gut pathogen.
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Affiliation(s)
- Andrew Marshall
- School of Biological Sciences, Queen’s University Belfast, 19 Chlorine Gardens, Belfast, BT9 5DL, UK
| | - John W. McGrath
- School of Biological Sciences, Queen’s University Belfast, 19 Chlorine Gardens, Belfast, BT9 5DL, UK
| | - Molly Mitchell
- University College Dublin-Centre for Food Safety University College Dublin, Dublin, Ireland
| | - Séamus Fanning
- University College Dublin-Centre for Food Safety University College Dublin, Dublin, Ireland
| | - Geoff McMullan
- School of Biological Sciences, Queen’s University Belfast, 19 Chlorine Gardens, Belfast, BT9 5DL, UK
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Shrestha S, Taib N, Gribaldo S, Shen A. Analyses of cell wall synthesis in Clostridioides difficile reveal a diversification in cell division mechanisms in endospore-forming bacteria. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.06.552200. [PMID: 37609260 PMCID: PMC10441361 DOI: 10.1101/2023.08.06.552200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
Current models of bacterial cell division assume that the core synthases of the multiprotein divisome complex, FtsW-FtsI, are the primary drivers of septal peptidoglycan (PG) synthesis. These enzymes are typically encoded in the highly conserved division and cell wall (dcw) cluster and are considered to be universally essential for cell division. Here, we combine bioinformatics analyses with functional characterization in the pathogen Clostridioides difficile to show that dcw-encoded PG synthases have undergone a surprising specialization in the sole endospore-forming phylum, Firmicutes, to fulfill sporulation-specific roles. We describe a novel role for these enzymes in synthesizing septal PG during the sporulation-specific mode of cell division in C. difficile. Although these enzymes are directly regulated by canonical divisome components during this process, dcw-encoded PG synthases and their divisome regulators are unexpectedly dispensable for cell division during normal growth. Instead, C. difficile uses its sole bifunctional class A penicillin-binding protein (aPBP) to drive cell division, revealing a previously unreported role for this class of PG synthases as the core divisome enzyme. Collectively, our findings reveal how the emergence of endosporulation in the Firmicutes phylum was a key driver for the functional repurposing of an otherwise universally conserved cellular process such as cell division. Moreover, they indicate that C. difficile, and likely other clostridia, assemble a divisome that differs markedly from previously studied bacteria, thus representing an attractive, unique target for therapeutic purposes.
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Affiliation(s)
- Shailab Shrestha
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
- Program in Molecular Microbiology, Tufts University Graduate School of Biomedical Sciences, Boston, MA, USA
| | - Najwa Taib
- Institut Pasteur, Université de Paris, Unit Evolutionary Biology of the Microbial Cell, Paris, France
- Institut Pasteur, Université Paris Cité, Bioinformatics and Biostatistics Hub, F-75015 Paris, France
| | - Simonetta Gribaldo
- Institut Pasteur, Université de Paris, Unit Evolutionary Biology of the Microbial Cell, Paris, France
| | - Aimee Shen
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
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17
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Wetzel D, Rizvi A, Edwards AN, McBride SM. The predicted acetoin dehydrogenase pathway represses sporulation of Clostridioides difficile. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.28.551048. [PMID: 37546766 PMCID: PMC10402147 DOI: 10.1101/2023.07.28.551048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
Clostridioides difficile is a major gastrointestinal pathogen that is transmitted as a dormant spore. As an intestinal pathogen, C. difficile must contend with variable environmental conditions, including fluctuations in pH and nutrient availability. Nutrition and pH both influence growth and spore formation, but how pH and nutrition jointly influence sporulation are not known. In this study, we investigated the dual impact of pH and pH-dependent metabolism on C. difficile sporulation. Specifically, we examined the impacts of pH and the metabolite acetoin on C. difficile growth and sporulation. We found that expression of the predicted acetoin dehydrogenase operon, acoRABCL , was pH-dependent and regulated by acetoin. Regulation of the C. difficile aco locus is distinct from other characterized systems and appears to involve a co-transcribed DeoR-family regulator rather than the sigma 54 -dependent activator. In addition, an acoA null mutant produced significantly more spores and initiated sporulation earlier than the parent strain. However, unlike other Firmicutes, growth and culture density of C. difficile was not increased by acetoin availability or disruption of the aco pathway. Together, these results indicate that acetoin, pH, and the aco pathway play important roles in nutritional repression of sporulation in C. difficile , but acetoin metabolism does not support cell growth as a stationary phase energy source. IMPORTANCE Clostridioides difficile, or C. diff , is an anaerobic bacterium that lives within the gut of many mammals and causes infectious diarrhea. C. difficile is able to survive outside of the gut and transmit to new hosts by forming dormant spores. It is known that the pH of the intestine and the nutrients available both affect the growth and sporulation of C. diffiicile, but the specific conditions that result in sporulation in the host are not clear. In this study, we investigated how pH and the metabolite acetoin affect the ability of C. difficile to grow, proliferate, and form spores. We found that a mutant lacking the predicted acetoin metabolism pathway form more spores, but their growth is not impacted. These results show that C. difficile uses acetoin differently than many other species and that acetoin has an important role as an environmental metabolite that influences spore formation.
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Edwards AN, McBride SM. The RgaS-RgaR two-component system promotes Clostridioides difficile sporulation through a small RNA and the Agr1 system. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.26.546640. [PMID: 37425791 PMCID: PMC10327067 DOI: 10.1101/2023.06.26.546640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
The ability to form a dormant spore is essential for the survival of the anaerobic, gastrointestinal pathogen Clostridioides difficile outside of the mammalian gastrointestinal tract. The initiation of sporulation is governed by the master regulator of sporulation, Spo0A, which is activated by phosphorylation. Multiple sporulation factors control Spo0A phosphorylation; however, this regulatory pathway is not well defined in C. difficile. We discovered that RgaS and RgaR, a conserved orphan histidine kinase and orphan response regulator, function together as a cognate two-component regulatory system to directly activate transcription of several genes. One of these targets, agrB1D1, encodes gene products that synthesize and export a small quorum-sensing peptide, AgrD1, which positively influences expression of early sporulation genes. Another target, a small regulatory RNA now known as SrsR, impacts later stages of sporulation through an unknown regulatory mechanism(s). Unlike Agr systems in many organisms, AgrD1 does not activate the RgaS-RgaR two-component system, and thus, is not responsible for autoregulating its own production. Altogether, we demonstrate that C. difficile utilizes a conserved two-component system that is uncoupled from quorum-sensing to promote sporulation through two distinct regulatory pathways.
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Affiliation(s)
- Adrianne N. Edwards
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Shonna M. McBride
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
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Fuchs M, Lamm-Schmidt V, Lenče T, Sulzer J, Bublitz A, Wackenreuter J, Gerovac M, Strowig T, Faber F. A network of small RNAs regulates sporulation initiation in Clostridioides difficile. EMBO J 2023:e112858. [PMID: 37140366 DOI: 10.15252/embj.2022112858] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 03/23/2023] [Accepted: 03/29/2023] [Indexed: 05/05/2023] Open
Abstract
The obligate anaerobic, enteric pathogen Clostridioides difficile persists in the intestinal tract by forming antibiotic-resistant endospores that contribute to relapsing and recurrent infections. Despite the importance of sporulation for C. difficile pathogenesis, environmental cues and molecular mechanisms that regulate sporulation initiation remain ill-defined. Here, by using RIL-seq to globally capture the Hfq-dependent RNA-RNA interactome, we discovered a network of small RNAs that bind to mRNAs encoding sporulation-related genes. We show that two of these small RNAs, SpoX and SpoY, regulate translation of the master regulator of sporulation, Spo0A, in an opposing manner, which ultimately leads to altered sporulation rates. Infection of antibiotic-treated mice with SpoX and SpoY deletion mutants revealed a global effect on gut colonization and intestinal sporulation. Our work uncovers an elaborate RNA-RNA interactome controlling the physiology and virulence of C. difficile and identifies a complex post-transcriptional layer in the regulation of spore formation in this important human pathogen.
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Affiliation(s)
- Manuela Fuchs
- Helmholtz Centre for Infection Research (HZI), Helmholtz Institute for RNA-based Infection Research (HIRI), Würzburg, Germany
- Faculty of Medicine, Institute for Molecular Infection Biology (IMIB), Julius-Maximilians-University of Würzburg (JMU), Würzburg, Germany
| | - Vanessa Lamm-Schmidt
- Helmholtz Centre for Infection Research (HZI), Helmholtz Institute for RNA-based Infection Research (HIRI), Würzburg, Germany
- Faculty of Medicine, Institute for Molecular Infection Biology (IMIB), Julius-Maximilians-University of Würzburg (JMU), Würzburg, Germany
| | - Tina Lenče
- Faculty of Medicine, Institute for Molecular Infection Biology (IMIB), Julius-Maximilians-University of Würzburg (JMU), Würzburg, Germany
| | - Johannes Sulzer
- Faculty of Medicine, Institute for Molecular Infection Biology (IMIB), Julius-Maximilians-University of Würzburg (JMU), Würzburg, Germany
| | - Arne Bublitz
- Helmholtz Centre for Infection Research (HZI), Braunschweig, Germany
| | - Janet Wackenreuter
- Helmholtz Centre for Infection Research (HZI), Helmholtz Institute for RNA-based Infection Research (HIRI), Würzburg, Germany
| | - Milan Gerovac
- Faculty of Medicine, Institute for Molecular Infection Biology (IMIB), Julius-Maximilians-University of Würzburg (JMU), Würzburg, Germany
| | - Till Strowig
- Helmholtz Centre for Infection Research (HZI), Braunschweig, Germany
- German Center for Infection Research (DZIF), Hannover-Braunschweig, Germany
| | - Franziska Faber
- Helmholtz Centre for Infection Research (HZI), Helmholtz Institute for RNA-based Infection Research (HIRI), Würzburg, Germany
- Faculty of Medicine, Institute for Molecular Infection Biology (IMIB), Julius-Maximilians-University of Würzburg (JMU), Würzburg, Germany
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DiCandia MA, Edwards AN, Lee CD, Monteiro MP, Cuebas GNV, Bagchi P, McBride SM. A Conserved Switch Controls Virulence, Sporulation, and Motility in C. difficile. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.28.534590. [PMID: 37034656 PMCID: PMC10081167 DOI: 10.1101/2023.03.28.534590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Spore formation is required for environmental survival and transmission of the human enteropathogenic Clostridioides difficile . In all bacterial spore formers, sporulation is regulated through activation of the master response regulator, Spo0A. However, the factors and mechanisms that directly regulate C. difficile Spo0A activity are not defined. In the well-studied Bacillus species, Spo0A is directly inactivated by Spo0E, a small phosphatase. To understand Spo0E function in C. difficile , we created a null mutation of the spo0E ortholog and assessed sporulation and physiology. The spo0E mutant produced significantly more spores, demonstrating Spo0E represses C. difficile sporulation. Unexpectedly, the spo0E mutant also exhibited increased motility and toxin production, and enhanced virulence in animal infections. We uncovered that Spo0E interacts with both Spo0A and the toxin and motility regulator, RstA. Direct interactions between Spo0A, Spo0E, and RstA constitute a previously unknown molecular switch that coordinates sporulation with motility and toxin production. Reinvestigation of Spo0E function in B. subtilis revealed that Spo0E induced motility, demonstrating Spo0E regulation of motility and sporulation among divergent species. Further, we found that Spo0E orthologs are widespread among prokaryotes, suggesting that Spo0E performs conserved regulatory functions in diverse bacteria.
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Zeng J, Wang H, Dong M, Tian GB. Clostridioides difficile spore: coat assembly and formation. Emerg Microbes Infect 2022; 11:2340-2349. [PMID: 36032037 PMCID: PMC9542656 DOI: 10.1080/22221751.2022.2119168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Clostridioides difficile (C. difficile) is a Gram-positive, spore-forming, toxin-producing, obligate anaerobic bacterium. C. difficile infection (CDI) is the leading cause of healthcare-associated infective diarrhoea. The infection is mediated by the spore, a metabolically inactive form of C. difficile. The spore coat acts as a physical barrier to defend against chemical insults from hosts and natural environments. The composition of spore coat has already been revealed; therefore, the interactive networks of spore coat proteins and the dynamic process of coat assembly are the keys to design strategies to control and cure CDI. This review gives a brief discussion of the signal processing and transcriptional regulation of C. difficile sporulation initiation. Following the discussion, the spore formation is also introduced. Finally, this review mainly focuses on the spore coat assembly, a poorly understood process in C. difficile, and important proteins that have been studied.
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Affiliation(s)
- Ji Zeng
- School of Biomedical and Pharmaceutical Sciences, Guangdong University of Technology, Guangzhou, Guangdong 510006, China
| | - Hao Wang
- School of Biomedical and Pharmaceutical Sciences, Guangdong University of Technology, Guangzhou, Guangdong 510006, China
| | - Min Dong
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
- Department of Urology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Guo-Bao Tian
- Department of Microbiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangdong 510080, China
- Advanced Medical Technology Center, The First Affiliated Hospital, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China
- School of Medicine, Xizang Minzu University, Xianyang, Shaanxi 712082, China
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Response Regulator CD1688 Is a Negative Modulator of Sporulation in Clostridioides difficile. J Bacteriol 2022; 204:e0013022. [PMID: 35852332 PMCID: PMC9380558 DOI: 10.1128/jb.00130-22] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Two-component signal transduction systems (TCSs), consisting of a sensor histidine kinase (HK) and a response regulator (RR), sense environmental stimuli and then modulate cellular responses, typically through changes in gene expression. Our previous work identified the DNA binding motif of CD1586, an RR implicated in Clostridioides difficile strain R20291 sporulation. To determine the role of this RR in the sporulation pathway in C. difficile, we generated a deletion strain of cd1688 in the historical 630 strain, the homolog of cd1586. The C. difficile Δcd1688 strain exhibited a hypersporulation phenotype, suggesting that CD1688 negatively regulates sporulation. Complementation of the C. difficile Δcd1688 strain restored sporulation. In contrast, a nonphosphorylatable copy of cd1688 did not restore sporulation to wild-type (WT) levels, indicating that CD1688 must be phosphorylated to properly modulate sporulation. Expression of the master regulator spo0A, the sporulation-specific sigma factors sigF, sigE, sigG, and sigK, and a signaling protein encoded by spoIIR was increased in the C. difficile Δcd1688 strain compared to WT. In line with the increased spoIIR expression, we detected an increase in mature SigE at an earlier time point, which arises from SpoIIR-mediated processing of pro-SigE. Taken together, our data suggest that CD1688 is a novel negative modulator of sporulation in C. difficile and contributes to mediating progression through the spore developmental pathway. These results add to our growing understanding of the complex regulatory events involved in C. difficile sporulation, insight that could be exploited for novel therapeutic development. IMPORTANCEClostridioides difficile causes severe gastrointestinal illness and is a leading cause of nosocomial infections in the United States. This pathogen produces metabolically dormant spores that are the major vehicle of transmission between hosts. The sporulation pathway involves an intricate regulatory network that controls a succession of morphological changes necessary to produce spores. The environmental signals inducing the sporulation pathway are not well understood in C. difficile. This work identified a response regulator, CD1688, that, when deleted, led to a hypersporulation phenotype, indicating that it typically acts to repress sporulation. Improving our understanding of the regulatory mechanisms modulating sporulation in C. difficile could provide novel strategies to eliminate or reduce spore production, thus decreasing transmission and disease relapse.
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Development of a Dual-Fluorescent-Reporter System in Clostridioides difficile Reveals a Division of Labor between Virulence and Transmission Gene Expression. mSphere 2022; 7:e0013222. [PMID: 35638354 PMCID: PMC9241537 DOI: 10.1128/msphere.00132-22] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The bacterial pathogen Clostridioides difficile causes gastroenteritis by producing toxins and transmits disease by making resistant spores. Toxin and spore production are energy-expensive processes that are regulated by multiple transcription factors in response to many environmental inputs. While toxin and sporulation genes are both induced in only a subset of C. difficile cells, the relationship between these two subpopulations remains unclear. To address whether C. difficile coordinates the generation of these subpopulations, we developed a dual-transcriptional-reporter system that allows toxin and sporulation gene expression to be simultaneously visualized at the single-cell level using chromosomally encoded mScarlet and mNeonGreen fluorescent transcriptional reporters. We then adapted an automated image analysis pipeline to quantify toxin and sporulation gene expression in thousands of individual cells under different medium conditions and in different genetic backgrounds. These analyses revealed that toxin and sporulation gene expression rarely overlap during growth on agar plates, whereas broth culture increases this overlap. Our results suggest that certain growth conditions promote a “division of labor” between transmission and virulence gene expression, highlighting how environmental inputs influence these subpopulations. Our data further suggest that the RstA transcriptional regulator skews the population to activate sporulation genes rather than toxin genes. Given that recent work has revealed population-wide heterogeneity for numerous cellular processes in C. difficile, we anticipate that our dual-reporter system will be broadly useful for determining the overlap between these subpopulations. IMPORTANCEClostridioides difficile is an important nosocomial pathogen that causes severe diarrhea by producing toxins and transmits disease by producing spores. While both processes are crucial for C. difficile disease, only a subset of cells express toxins and/or undergo sporulation. Whether C. difficile coordinates the subset of cells inducing these energy-expensive processes remains unknown. To address this question, we developed a dual-fluorescent-reporter system coupled with an automated image analysis pipeline to rapidly compare the expression of two genes of interest across thousands of cells. Using this system, we discovered that certain growth conditions, particularly growth on agar plates, induce a “division of labor” between toxin and sporulation gene expression. Since C. difficile exhibits phenotypic heterogeneity for numerous vital cellular processes, this novel dual-reporter system will enable future studies aimed at understanding how C. difficile coordinates various subpopulations throughout its infectious disease cycle.
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Conservation and Evolution of the Sporulation Gene Set in Diverse Members of the Firmicutes. J Bacteriol 2022; 204:e0007922. [PMID: 35638784 DOI: 10.1128/jb.00079-22] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The current classification of the phylum Firmicutes (new name, Bacillota) features eight distinct classes, six of which include known spore-forming bacteria. In Bacillus subtilis, sporulation involves up to 500 genes, many of which do not have orthologs in other bacilli and/or clostridia. Previous studies identified about 60 sporulation genes of B. subtilis that were shared by all spore-forming members of the Firmicutes. These genes are referred to as the sporulation core or signature, although many of these are also found in genomes of nonsporeformers. Using an expanded set of 180 firmicute genomes from 160 genera, including 76 spore-forming species, we investigated the conservation of the sporulation genes, in particular seeking to identify lineages that lack some of the genes from the conserved sporulation core. The results of this analysis confirmed that many small acid-soluble spore proteins (SASPs), spore coat proteins, and germination proteins, which were previously characterized in bacilli, are missing in spore-forming members of Clostridia and other classes of Firmicutes. A particularly dramatic loss of sporulation genes was observed in the spore-forming members of the families Planococcaceae and Erysipelotrichaceae. Fifteen species from diverse lineages were found to carry skin (sigK-interrupting) elements of different sizes that all encoded SpoIVCA-like recombinases but did not share any other genes. Phylogenetic trees built from concatenated alignments of sporulation proteins and ribosomal proteins showed similar topology, indicating an early origin and subsequent vertical inheritance of the sporulation genes. IMPORTANCE Many members of the phylum Firmicutes (Bacillota) are capable of producing endospores, which enhance the survival of important Gram-positive pathogens that cause such diseases as anthrax, botulism, colitis, gas gangrene, and tetanus. We show that the core set of sporulation genes, defined previously through genome comparisons of several bacilli and clostridia, is conserved in a wide variety of sporeformers from several distinct lineages of Firmicutes. We also detected widespread loss of sporulation genes in many organisms, particularly within the families Planococcaceae and Erysipelotrichaceae. Members of these families, such as Lysinibacillus sphaericus and Clostridium innocuum, could be excellent model organisms for studying sporulation mechanisms, such as engulfment, formation of the spore coat, and spore germination.
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DiCandia MA, Edwards AN, Jones JB, Swaim GL, Mills BD, McBride SM. Identification of functional Spo0A residues critical for sporulation in Clostridioides difficile. J Mol Biol 2022; 434:167641. [PMID: 35597553 DOI: 10.1016/j.jmb.2022.167641] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 04/26/2022] [Accepted: 05/15/2022] [Indexed: 10/18/2022]
Abstract
Clostridioides difficile is an anaerobic, Gram-positive pathogen that is responsible for C. difficile infection (CDI). To survive in the environment and spread to new hosts, C. difficile must form metabolically dormant spores. The formation of spores requires activation of the transcription factor Spo0A, which is the master regulator of sporulation in all endospore-forming bacteria. Though the sporulation initiation pathway has been delineated in the Bacilli, including the model spore-former Bacillus subtilis, the direct regulators of Spo0A in C. difficile remain undefined. C. difficile Spo0A shares highly conserved protein interaction regions with the B. subtilis sporulation proteins Spo0F and Spo0A, although many of the interacting factors present in B. subtilis are not encoded in C. difficile. To determine if comparable Spo0A residues are important for C. difficile sporulation initiation, site-directed mutagenesis was performed at conserved receiver domain residues and the effects on sporulation were examined. Mutation of residues important for homodimerization and interaction with positive and negative regulators of B. subtilis Spo0A and Spo0F impacted C. difficile Spo0A function. The data also demonstrated that mutation of many additional conserved residues altered C. difficile Spo0A activity, even when the corresponding Bacillus interacting proteins are not apparent in the C. difficile genome. Finally, the conserved aspartate residue at position 56 of C. difficile Spo0A was determined to be the phosphorylation site that is necessary for Spo0A activation. The finding that Spo0A interacting motifs maintain functionality suggests that C. difficile Spo0A interacts with yet unidentified proteins that regulate its activity and control spore formation.
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Affiliation(s)
- Michael A DiCandia
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Adrianne N Edwards
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Joshua B Jones
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Grace L Swaim
- Department of Neuroscience and Cell Biology, Yale University Graduate School of Arts and Sciences, New Haven, CT, USA
| | - Brooke D Mills
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Shonna M McBride
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA.
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Trzilova D, Warren MAH, Gadda NC, Williams CL, Tamayo R. Flagellum and toxin phase variation impacts intestinal colonization and disease development in a mouse model of Clostridioides difficile infection. Gut Microbes 2022; 14:2038854. [PMID: 35192433 PMCID: PMC8890394 DOI: 10.1080/19490976.2022.2038854] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Clostridioides difficile is a major nosocomial pathogen that can cause severe, toxin-mediated diarrhea and pseudomembranous colitis. Recent work has shown that C. difficile exhibits heterogeneity in swimming motility and toxin production in vitro through phase variation by site-specific DNA recombination. The recombinase RecV reversibly inverts the flagellar switch sequence upstream of the flgB operon, leading to the ON/OFF expression of flagellum and toxin genes. How this phenomenon impacts C. difficile virulence in vivo remains unknown. We identified mutations in the right inverted repeat that reduced or prevented flagellar switch inversion by RecV. We introduced these mutations into C. difficile R20291 to create strains with the flagellar switch "locked" in either the ON or OFF orientation. These mutants exhibited a loss of flagellum and toxin phase variation during growth in vitro, yielding precisely modified mutants suitable for assessing virulence in vivo. In a hamster model of acute C. difficile infection, the phase-locked ON mutant caused greater toxin accumulation than the phase-locked OFF mutant but did not differ significantly in the ability to cause acute disease symptoms. In contrast, in a mouse model, preventing flagellum and toxin phase variation affected the ability of C. difficile to colonize the intestinal tract and to elicit weight loss, which is attributable to differences in toxin production during infection. These results show that the ability of C. difficile to phase vary flagella and toxins influences colonization and disease development and suggest that the phenotypic variants generated by flagellar switch inversion have distinct capacities for causing disease.
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Affiliation(s)
- Dominika Trzilova
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA
| | - Mercedes A. H. Warren
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA
| | - Nicole C. Gadda
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA
| | - Caitlin L. Williams
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA
| | - Rita Tamayo
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA,CONTACT Rita Tamayo 125 Mason Farm Rd, CB #7290, Chapel Hill, NC27599-7290
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Abstract
The ability of the anaerobic gastrointestinal pathogen Clostridioides difficile to survive outside the host relies on the formation of dormant endospores. Spore formation is contingent on the activation of a conserved transcription factor, Spo0A, by phosphorylation. Multiple kinases and phosphatases regulate Spo0A activity in other spore-forming organisms; however, these factors are not well conserved in C. difficile. Previously, we discovered that deletion of a predicted histidine kinase, CD1492, increases sporulation, indicating that CD1492 inhibits C. difficile spore formation. In this study, we investigate the functions of additional predicted orphan histidine kinases CD2492, CD1579, and CD1949, which are hypothesized to regulate Spo0A phosphorylation. Disruption of CD2492 also increased sporulation frequency, similarly to the CD1492 mutant and in contrast to a previous study. A CD1492 CD2492 mutant phenocopied the sporulation and gene expression patterns of the single mutants, suggesting that these proteins function in the same genetic pathway to repress sporulation. Deletion of CD1579 variably increased sporulation frequency; however, knockdown of CD1949 expression did not influence sporulation. We provide evidence that CD1492, CD2492, and CD1579 function as phosphatases, as mutation of the conserved histidine residue for phosphate transfer abolished CD2492 function, and expression of the CD1492 or CD2492 histidine site-directed mutants or the wild-type CD1579 allele in a parent strain resulted in a dominant-negative hypersporulation phenotype. Altogether, at least three predicted histidine kinases, CD1492, CD2492, and CD1579 (herein, PtpA, PtpB and PtpC), repress C. difficile sporulation initiation by regulating activity of Spo0A. IMPORTANCE The formation of inactive spores is critical for the long-term survival of the gastrointestinal pathogen Clostridioides difficile. The onset of sporulation is controlled by the master regulator of sporulation, Spo0A, which is activated by phosphorylation. Multiple kinases and phosphatases control Spo0A phosphorylation; however, this regulatory pathway is not defined in C. difficile. We show that two predicted histidine kinase proteins, CD1492 (PtpA) and CD2492 (PtpB), function in the same regulatory pathway to repress sporulation by preventing Spo0A phosphorylation. We show that another predicted histidine kinase protein, CD1579 (PtpC), also represses sporulation and present evidence that a fourth predicted histidine kinase protein, CD1949, does not impact sporulation. These results support the idea that C. difficile inhibits sporulation initiation through multiple phosphatases.
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The Stickland Reaction Precursor trans-4-Hydroxy-l-Proline Differentially Impacts the Metabolism of Clostridioides difficile and Commensal Clostridia. mSphere 2022; 7:e0092621. [PMID: 35350846 PMCID: PMC9044972 DOI: 10.1128/msphere.00926-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
An intact gut microbiota confers colonization resistance against Clostridioides difficile through a variety of mechanisms, likely including competition for nutrients. Recently, proline was identified as an important environmental amino acid that C. difficile uses to support growth and cause significant disease. A posttranslationally modified form, trans-4-hydroxyproline, is highly abundant in collagen, which is degraded by host proteases in response to C. difficile toxin activity. The ability to dehydrate trans-4-hydroxyproline via the HypD glycyl radical enzyme is widespread among gut microbiota, including C. difficile and members of the commensal Clostridia, suggesting that this amino acid is an important nutrient in the host environment. Therefore, we constructed a C. difficile ΔhypD mutant and found that it was modestly impaired in fitness in a mouse model of infection, and was associated with an altered microbiota when compared to mice challenged with the wild-type strain. Changes in the microbiota between the two groups were largely driven by members of the Lachnospiraceae family and the Clostridium genus. We found that C. difficile and type strains of three commensal Clostridia had significant alterations to their metabolic gene expression in the presence of trans-4-hydroxyproline in vitro. The proline reductase (prd) genes were elevated in C. difficile, consistent with the hypothesis that trans-4-hydroxyproline is used by C. difficile to supply proline for energy metabolism. Similar transcripts were also elevated in some commensal Clostridia tested, although each strain responded differently. This suggests that the uptake and utilization of other nutrients by the commensal Clostridia may be affected by trans-4-hydroxyproline metabolism, highlighting how a common nutrient may be a signal to each organism to adapt to a unique niche. Further elucidation of the differences between them in the presence of hydroxyproline and other key nutrients will be important in determining their role in nutrient competition against C. difficile. IMPORTANCE Proline is an essential environmental amino acid that C. difficile uses to support growth and cause significant disease. A posttranslationally modified form, hydroxyproline, is highly abundant in collagen, which is degraded by host proteases in response to C. difficile toxin activity. The ability to dehydrate hydroxyproline via the HypD glycyl radical enzyme is widespread among gut microbiota, including C. difficile and members of the commensal Clostridia, suggesting that this amino acid is an important nutrient in the host environment. We found that C. difficile and three commensal Clostridia strains had significant, but different, alterations to their metabolic gene expression in the presence of hydroxyproline in vitro. This suggests that the uptake and utilization of other nutrients by the commensal Clostridia may be affected by hydroxyproline metabolism, highlighting how a common nutrient may be a signal to each organism to adapt to a unique niche. Further elucidation of the differences between them in the presence of hydroxyproline and other key nutrients will be important to determining their role in nutrient competition against C. difficile.
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Paredes-Sabja D, Cid-Rojas F, Pizarro-Guajardo M. Assembly of the exosporium layer in Clostridioides difficile spores. Curr Opin Microbiol 2022; 67:102137. [PMID: 35182899 DOI: 10.1016/j.mib.2022.01.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 01/14/2022] [Accepted: 01/20/2022] [Indexed: 02/07/2023]
Abstract
Clostridioides difficile is a Gram-positive, spore-forming obligate anaerobe and a major threat to the healthcare system world-wide. Because of its strict anaerobic requirements, the infectious and transmissible morphotype is the dormant spore. During infection, C. difficile produces spores that can persist in the host and are responsible for disease recurrence and transmission, especially between hospitalized patients. Although the C. difficile spore surface mediates critical interactions with host surfaces, this outermost layer, known as the exosporium, is poorly conserved when compared to members of the Bacillus genus. Notably, the exosporium has been shown to be important for the persistence of C. difficile in the host. In this review, the ultrastructural properties, composition, and morphogenesis of the exosporium will be discussed.
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Affiliation(s)
- Daniel Paredes-Sabja
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA; ANID - Millennium Science Initiative Program - Millennium Nucleus in the Biology of the Intestinal Microbiota, Santiago, Chile.
| | - Francisca Cid-Rojas
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA; ANID - Millennium Science Initiative Program - Millennium Nucleus in the Biology of the Intestinal Microbiota, Santiago, Chile
| | - Marjorie Pizarro-Guajardo
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA; ANID - Millennium Science Initiative Program - Millennium Nucleus in the Biology of the Intestinal Microbiota, Santiago, Chile
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Delerue T, Anantharaman V, Gilmore MC, Popham DL, Cava F, Aravind L, Ramamurthi KS. Bacterial developmental checkpoint that directly monitors cell surface morphogenesis. Dev Cell 2022; 57:344-360.e6. [PMID: 35065768 PMCID: PMC8991396 DOI: 10.1016/j.devcel.2021.12.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Revised: 11/15/2021] [Accepted: 12/20/2021] [Indexed: 01/05/2023]
Abstract
Bacillus subtilis spores are encased in two concentric shells: an outer proteinaceous "coat" and an inner peptidoglycan "cortex," separated by a membrane. Cortex assembly depends on coat assembly initiation, but how cells achieve this coordination across the membrane is unclear. Here, we report that the protein SpoVID monitors the polymerization state of the coat basement layer via an extension to a functional intracellular LysM domain that arrests sporulation when coat assembly is initiated improperly. Whereas extracellular LysM domains bind mature peptidoglycan, SpoVID LysM binds to the membrane-bound lipid II peptidoglycan precursor. We propose that improper coat assembly exposes the SpoVID LysM domain, which then sequesters lipid II and prevents cortex assembly. SpoVID defines a widespread group of firmicute proteins with a characteristic N-terminal domain and C-terminal peptidoglycan-binding domains that might combine coat and cortex assembly roles to mediate a developmental checkpoint linking the morphogenesis of two spatially separated supramolecular structures.
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Affiliation(s)
- Thomas Delerue
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Vivek Anantharaman
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20892, USA
| | - Michael C. Gilmore
- Laboratory for Molecular Infection Medicine Sweden (MIMS), Department of Molecular Biology, Umeå University, 90187 Umeå, Sweden
| | - David L. Popham
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA
| | - Felipe Cava
- Laboratory for Molecular Infection Medicine Sweden (MIMS), Department of Molecular Biology, Umeå University, 90187 Umeå, Sweden
| | - L. Aravind
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20892, USA
| | - Kumaran S. Ramamurthi
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA,Lead contact,Correspondence:
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Insights into the Structure and Protein Composition of Moorella thermoacetica Spores Formed at Different Temperatures. Int J Mol Sci 2022; 23:ijms23010550. [PMID: 35008975 PMCID: PMC8745062 DOI: 10.3390/ijms23010550] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 12/22/2021] [Accepted: 12/23/2021] [Indexed: 02/01/2023] Open
Abstract
The bacterium Moorella thermoacetica produces the most heat-resistant spores of any spoilage-causing microorganism known in the food industry. Previous work by our group revealed that the resistance of these spores to wet heat and biocides was lower when spores were produced at a lower temperature than the optimal temperature. Here, we used electron microcopy to characterize the ultrastructure of the coat of the spores formed at different sporulation temperatures; we found that spores produced at 55 °C mainly exhibited a lamellar inner coat tightly associated with a diffuse outer coat, while spores produced at 45 °C showed an inner and an outer coat separated by a less electron-dense zone. Moreover, misarranged coat structures were more frequently observed when spores were produced at the lower temperature. We then analyzed the proteome of the spores obtained at either 45 °C or 55 °C with respect to proteins putatively involved in the spore coat, exosporium, or in spore resistance. Some putative spore coat proteins, such as CotSA, were only identified in spores produced at 55 °C; other putative exosporium and coat proteins were significantly less abundant in spores produced at 45 °C. Altogether, our results suggest that sporulation temperature affects the structure and protein composition of M. thermoacetica spores.
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Romo JA, Kumamoto CA. Characterization of the Effects of Candida Gastrointestinal Colonization on Clostridioides difficile Infection in a Murine Model. Methods Mol Biol 2022; 2542:271-285. [PMID: 36008672 DOI: 10.1007/978-1-0716-2549-1_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The role of fungal colonizers of the gastrointestinal tract during disease states is not well understood. Antibiotic treatment renders patients highly susceptible to infection by the bacterial pathogen C. difficile while also leading to blooms in fungal commensals, setting the stage for trans-kingdom interactions. Here, we describe a murine model of Candida gastrointestinal colonization coupled to a C. difficile infection (CDI) model, the measurement of CFU of both organisms, and collection of cecum and colon contents for the purpose of quantifying C. difficile toxin production. Additionally, we describe how to induce and purify C. difficile spores.
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Affiliation(s)
- Jesús A Romo
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
| | - Carol A Kumamoto
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA.
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Edwards AN, Willams CL, Pareek N, McBride SM, Tamayo R. c-di-GMP Inhibits Early Sporulation in Clostridioides difficile. mSphere 2021; 6:e0091921. [PMID: 34878288 PMCID: PMC8653836 DOI: 10.1128/msphere.00919-21] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Accepted: 11/19/2021] [Indexed: 12/02/2022] Open
Abstract
The formation of dormant spores is essential for the anaerobic pathogen Clostridioides difficile to survive outside the host gastrointestinal tract. The regulatory pathways and environmental signals that initiate C. difficile spore formation within the host are not well understood. One second-messenger signaling molecule, cyclic diguanylate (c-di-GMP), modulates several physiological processes important for C. difficile pathogenesis and colonization, but the impact of c-di-GMP on sporulation is unknown. In this study, we investigated the contribution of c-di-GMP to C. difficile sporulation. The overexpression of a gene encoding a diguanylate cyclase, dccA, decreased the sporulation frequency and early sporulation gene transcription in both the epidemic R20291 and historical 630Δerm strains. The expression of a dccA allele encoding a catalytically inactive DccA that is unable to synthesize c-di-GMP no longer inhibited sporulation, indicating that the accumulation of intracellular c-di-GMP reduces C. difficile sporulation. A null mutation in dccA slightly increased sporulation in R20291 and slightly decreased sporulation in 630Δerm, suggesting that DccA contributes to the intracellular pool of c-di-GMP in a strain-dependent manner. However, these data were highly variable, underscoring the complex regulation involved in modulating intracellular c-di-GMP concentrations. Finally, the overexpression of dccA in known sporulation mutants revealed that c-di-GMP is likely signaling through an unidentified regulatory pathway to control early sporulation events in C. difficile. c-di-GMP-dependent regulation of C. difficile sporulation may represent an unexplored avenue of potential environmental and intracellular signaling that contributes to the complex regulation of sporulation initiation. IMPORTANCE Many bacterial organisms utilize the small signaling molecule cyclic diguanylate (c-di-GMP) to regulate important physiological processes, including motility, toxin production, biofilm formation, and colonization. c-di-GMP inhibits motility and toxin production and promotes biofilm formation and colonization in the anaerobic, gastrointestinal pathogen Clostridioides difficile. However, the impact of c-di-GMP on C. difficile spore formation, a critical step in this pathogen's life cycle, is unknown. Here, we demonstrate that c-di-GMP negatively impacts sporulation in two clinically relevant C. difficile strains, the epidemic strain R20291 and the historical strain 630Δerm. The pathway through which c-di-GMP controls sporulation was investigated, and our results suggest that c-di-GMP is likely signaling through an unidentified regulatory pathway to control C. difficile sporulation. This work implicates c-di-GMP metabolism as a mechanism to integrate environmental and intracellular cues through c-di-GMP levels to influence C. difficile sporulation.
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Affiliation(s)
- Adrianne N. Edwards
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, USA
| | - Caitlin L. Willams
- Department of Microbiology and Immunology, University of North Carolina—Chapel Hill, Chapel Hill, North Carolina, USA
| | - Nivedita Pareek
- Department of Microbiology and Immunology, University of North Carolina—Chapel Hill, Chapel Hill, North Carolina, USA
| | - Shonna M. McBride
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, USA
| | - Rita Tamayo
- Department of Microbiology and Immunology, University of North Carolina—Chapel Hill, Chapel Hill, North Carolina, USA
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Identification of ClpP Dual Isoform Disruption as an Anti-sporulation Strategy for Clostridioides difficile. J Bacteriol 2021; 204:e0041121. [PMID: 34807726 DOI: 10.1128/jb.00411-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Gram-positive bacterium Clostridioides difficile is a primary cause of hospital-acquired diarrhea, threatening both immunocompromised and healthy individuals. An important aspect of defining mechanisms that drive C. difficile persistence and virulence relies on developing a more complete understanding of sporulation. C. difficile sporulation is the single determinant of transmission and complicates treatment and prevention due to the chemical and physical resilience of spores. By extension, the identification of druggable targets that significantly attenuate sporulation would have a significant impact on thwarting C. difficile infection. Using a new CRISPR-Cas9 nickase genome editing methodology, stop codons were inserted early in the coding sequence for clpP1 and clpP2 to generate C. difficile mutants that no longer produced the corresponding isoforms of caseinolytic protease P (ClpP). The data show that genetic ablation of ClpP isoforms leads to altered sporulation phenotypes with the clpP1/clpP2 double mutant exhibiting asporogenic behavior. A small screen of known ClpP inhibitors in a fluorescence-based biochemical assay identified bortezomib as an inhibitor of C. difficile ClpP that produces dose-dependent inhibition of purified ClpP. Incubation of C. difficile cultures in the presence of bortezomib reveals anti-sporulation effects approaching that observed in the clpP1/clpP2 double mutant. This work identifies ClpP as a key contributor to C. difficile sporulation and provides compelling support for the pursuit of small molecule ClpP inhibitors as C. difficile anti-sporulating agents. IMPORTANCE Due to diverse roles of ClpP and the reliance of pathogens upon this system for infection, it has emerged as a target for antimicrobial development. Biology regulated by ClpP is organism-dependent and has not been defined in C. difficile. This work identifies ClpP as a key contributor to C. difficile sporulation and provides compelling support for the pursuit of small molecule ClpP inhibitors as anti-sporulating agents. The identification of new approaches and/or drug targets that reduce C. difficile sporulation would be transformative and are expected to find high utility in prophylaxis, transmission attenuation, and relapse prevention. Discovery of the ClpP system as a major driver to sporulation also provides a new avenue of inquiry for advancing the understanding of sporulation.
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Alves Feliciano C, Eckenroth BE, Diaz OR, Doublié S, Shen A. A lipoprotein allosterically activates the CwlD amidase during Clostridioides difficile spore formation. PLoS Genet 2021; 17:e1009791. [PMID: 34570752 PMCID: PMC8496864 DOI: 10.1371/journal.pgen.1009791] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 10/07/2021] [Accepted: 08/23/2021] [Indexed: 11/19/2022] Open
Abstract
Spore-forming pathogens like Clostridioides difficile depend on germination to initiate infection. During gemination, spores must degrade their cortex layer, which is a thick, protective layer of modified peptidoglycan. Cortex degradation depends on the presence of the spore-specific peptidoglycan modification, muramic-∂-lactam (MAL), which is specifically recognized by cortex lytic enzymes. In C. difficile, MAL production depends on the CwlD amidase and its binding partner, the GerS lipoprotein. To gain insight into how GerS regulates CwlD activity, we solved the crystal structure of the CwlD:GerS complex. In this structure, a GerS homodimer is bound to two CwlD monomers such that the CwlD active sites are exposed. Although CwlD structurally resembles amidase_3 family members, we found that CwlD does not bind Zn2+ stably on its own, unlike previously characterized amidase_3 enzymes. Instead, GerS binding to CwlD promotes CwlD binding to Zn2+, which is required for its catalytic mechanism. Thus, in determining the first structure of an amidase bound to its regulator, we reveal stabilization of Zn2+ co-factor binding as a novel mechanism for regulating bacterial amidase activity. Our results further suggest that allosteric regulation by binding partners may be a more widespread mode for regulating bacterial amidase activity than previously thought. Spore germination is essential for many spore-forming pathogens to initiate infection. In order for spores to germinate, they must degrade a thick, protective layer of cell wall known as the cortex. The enzymes that digest this layer selectively recognize the spore-specific cell wall modification, muramic-∂-lactam (MAL). MAL is made in part through the activity of the CwlD amidase, which is found in all spore-forming bacteria. While Bacillus subtilis CwlD appears to have amidase activity on its own, Clostridioides difficile CwlD activity depends on its binding partner, the GerS lipoprotein. To understand why C. difficile CwlD requires GerS, we determined the X-ray crystal structure of the CwlD:GerS complex and discovered that GerS binds to a site distant from CwlD’s active site. We also found that GerS stabilizes CwlD binding to its co-factor, Zn2+, indicating that GerS allosterically activates CwlD amidase. Notably, regulation at the level of Zn2+ binding has not previously been described for bacterial amidases, and GerS is the first protein to be shown to allosterically activate an amidase. Since binding partners of bacterial amidases were only first discovered 15 years ago, our results suggest that diverse mechanisms remain to be discovered for these critical enzymes.
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Affiliation(s)
- Carolina Alves Feliciano
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Brian E. Eckenroth
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
| | - Oscar R. Diaz
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Sylvie Doublié
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
| | - Aimee Shen
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- * E-mail:
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Shen A. Clostridioides difficile Spore Formation and Germination: New Insights and Opportunities for Intervention. Annu Rev Microbiol 2021; 74:545-566. [PMID: 32905755 DOI: 10.1146/annurev-micro-011320-011321] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Spore formation and germination are essential for the bacterial pathogen Clostridioides difficile to transmit infection. Despite the importance of these developmental processes to the infection cycle of C. difficile, the molecular mechanisms underlying how this obligate anaerobe forms infectious spores and how these spores germinate to initiate infection were largely unknown until recently. Work in the last decade has revealed that C. difficile uses a distinct mechanism for sensing and transducing germinant signals relative to previously characterized spore formers. The C. difficile spore assembly pathway also exhibits notable differences relative to Bacillus spp., where spore formation has been more extensively studied. For both these processes, factors that are conserved only in C. difficile or the related Peptostreptococcaceae family are employed, and even highly conserved spore proteins can have differential functions or requirements in C. difficile compared to other spore formers. This review summarizes our current understanding of the mechanisms controlling C. difficile spore formation and germination and describes strategies for inhibiting these processes to prevent C. difficile infection and disease recurrence.
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Affiliation(s)
- Aimee Shen
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA;
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Abstract
Clostridioides difficile is a leading cause of health care-associated infections worldwide. These infections are transmitted by C. difficile′s metabolically dormant, aerotolerant spore form. Functional spore formation depends on the assembly of two protective layers, a thick layer of modified peptidoglycan known as the cortex layer and a multilayered proteinaceous meshwork known as the coat. We previously identified two spore morphogenetic proteins, SpoIVA and SipL, that are essential for recruiting coat proteins to the developing forespore and making functional spores. While SpoIVA and SipL directly interact, the identities of the proteins they recruit to the forespore remained unknown. Here, we used mass spectrometry-based affinity proteomics to identify proteins that interact with the SpoIVA-SipL complex. These analyses identified the Peptostreptococcaceae family-specific, sporulation-induced bitopic membrane protein CD3457 (renamed SpoVQ) as a protein that interacts with SipL and SpoIVA. Loss of SpoVQ decreased heat-resistant spore formation by ∼5-fold and reduced cortex thickness ∼2-fold; the thinner cortex layer of ΔspoVQ spores correlated with higher levels of spontaneous germination (i.e., in the absence of germinant). Notably, loss of SpoVQ in either spoIVA or sipL mutants prevented cortex synthesis altogether and greatly impaired the localization of a SipL-mCherry fusion protein around the forespore. Thus, SpoVQ is a novel regulator of C. difficile cortex synthesis that appears to link cortex and coat formation. The identification of SpoVQ as a spore morphogenetic protein further highlights how Peptostreptococcaceae family-specific mechanisms control spore formation in C. difficile. IMPORTANCE The Centers for Disease Control has designated Clostridioides difficile as an urgent threat because of its intrinsic antibiotic resistance. C. difficile persists in the presence of antibiotics in part because it makes metabolically dormant spores. While recent work has shown that preventing the formation of infectious spores can reduce C. difficile disease recurrence, more selective antisporulation therapies are needed. The identification of spore morphogenetic factors specific to C. difficile would facilitate the development of such therapies. In this study, we identified SpoVQ (CD3457) as a spore morphogenetic protein specific to the Peptostreptococcaceae family that regulates the formation of C. difficile’s protective spore cortex layer. SpoVQ acts in concert with the known spore coat morphogenetic factors, SpoIVA and SipL, to link formation of the protective coat and cortex layers. These data reveal a novel pathway that could be targeted to prevent the formation of infectious C. difficile spores.
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Jones JB, Liu L, Rank LA, Wetzel D, Woods EC, Biok N, Anderson SE, Lee MR, Liu R, Huth S, Sandhu BK, Gellman SH, McBride SM. Cationic Homopolymers Inhibit Spore and Vegetative Cell Growth of Clostridioides difficile. ACS Infect Dis 2021; 7:1236-1247. [PMID: 33739823 PMCID: PMC8130196 DOI: 10.1021/acsinfecdis.0c00843] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
A wide range of synthetic polymers have been explored for antimicrobial activity. These materials usually contain both cationic and hydrophobic subunits because these two characteristics are prominent among host-defense peptides. Here, we describe a series of nylon-3 polymers containing only cationic subunits and their evaluation against the gastrointestinal, spore-forming pathogen Clostridioides difficile. Despite their highly hydrophilic nature, these homopolymers showed efficacy against both the vegetative and spore forms of the bacterium, including an impact on C. difficile spore germination. The polymer designated P34 demonstrated the greatest efficacy against C. difficile strains, along with low propensities to lyse human red blood cells or intestinal epithelial cells. To gain insight into the mechanism of P34 action, we evaluated several cell-surface mutant strains of C. difficile to determine the impacts on growth, viability, and cell morphology. The results suggest that P34 interacts with the cell wall, resulting in severe cell bending and death in a concentration-dependent manner. The unexpected finding that nylon-3 polymers composed entirely of cationic subunits display significant activities toward C. difficile should expand the range of other polymers considered for antibacterial applications.
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Affiliation(s)
- Joshua B. Jones
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Lei Liu
- Department of Chemistry and Department of Medicine, University of Wisconsin, Madison, WI, USA
| | | | - Daniela Wetzel
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Emily C. Woods
- Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA
| | - Naomi Biok
- Department of Chemistry and Department of Medicine, University of Wisconsin, Madison, WI, USA
| | | | - Myung-ryul Lee
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Runhui Liu
- State Key Laboratory of Bioreactor Engineering, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai, China
| | - Sean Huth
- Department of Chemistry, Princeton University, Princeton, NJ, USA
| | - Brindar K. Sandhu
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Samuel H. Gellman
- Department of Chemistry and Department of Medicine, University of Wisconsin, Madison, WI, USA
| | - Shonna M. McBride
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
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Martins D, DiCandia MA, Mendes AL, Wetzel D, McBride SM, Henriques AO, Serrano M. CD25890, a conserved protein that modulates sporulation initiation in Clostridioides difficile. Sci Rep 2021; 11:7887. [PMID: 33846410 PMCID: PMC8041843 DOI: 10.1038/s41598-021-86878-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 03/17/2021] [Indexed: 12/16/2022] Open
Abstract
Bacteria that reside in the gastrointestinal tract of healthy humans are essential for our health, sustenance and well-being. About 50-60% of those bacteria have the ability to produce resilient spores that are important for the life cycle in the gut and for host-to-host transmission. A genomic signature for sporulation in the human intestine was recently described, which spans both commensals and pathogens such as Clostridioides difficile and contains several genes of unknown function. We report on the characterization of a signature gene, CD25890, which, as we show is involved in the control of sporulation initiation in C. difficile under certain nutritional conditions. Spo0A is the main regulatory protein controlling entry into sporulation and we show that an in-frame deletion of CD25890 results in increased expression of spo0A per cell and increased sporulation. The effect of CD25890 on spo0A is likely indirect and mediated through repression of the sinRR´ operon. Deletion of the CD25890 gene, however, does not alter the expression of the genes coding for the cytotoxins or the genes involved in biofilm formation. Our results suggest that CD25890 acts to modulate sporulation in response to the nutrients present in the environment.
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Affiliation(s)
- Diogo Martins
- Instituto de Tecnologia Química E Biológica António Xavier, Avenida da República, 2780-157, Oeiras, Portugal
| | - Michael A DiCandia
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA, USA
| | - Aristides L Mendes
- Instituto de Tecnologia Química E Biológica António Xavier, Avenida da República, 2780-157, Oeiras, Portugal
| | - Daniela Wetzel
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA, USA
| | - Shonna M McBride
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA, USA
| | - Adriano O Henriques
- Instituto de Tecnologia Química E Biológica António Xavier, Avenida da República, 2780-157, Oeiras, Portugal
| | - Mónica Serrano
- Instituto de Tecnologia Química E Biológica António Xavier, Avenida da República, 2780-157, Oeiras, Portugal.
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Yi Z, Zhang T, Xie J, Zhu Z, Luo S, Zhou K, Zhou P, Chen W, Zhao X, Sun Y, Xia L, Ding X. iTRAQ analysis reveals the effect of gabD and sucA gene knockouts on lysine metabolism and crystal protein formation in Bacillus thuringiensis. Environ Microbiol 2021; 23:2230-2243. [PMID: 33331075 DOI: 10.1111/1462-2920.15359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Accepted: 12/08/2020] [Indexed: 11/27/2022]
Abstract
Lysine metabolism plays an important role in the formation of the insecticidal crystal proteins of Bacillus thuringiensis (Bt). The genes lam, gabD and sucA encode three key enzymes of the lysine metabolic pathway in Bt4.0718. The lam gene mainly affects the cell growth at stable period, negligibly affected sporulation and insecticidal crystal protein (ICP) production. While, the deletion mutant strains of the gabD and sucA genes showed that the growth, sporulation and crystal protein formation were inhibited, cells became slender, and insecticidal activity was significantly reduced. iTRAQ proteomics and qRT-PCR used to analyse the differentially expressed protein (DEP) between the two mutant strains and the wild type strain. The functions of DEPs were visualized and statistically classified, which affect bacterial growth and metabolism by regulating biological metabolism pathways: the major carbon metabolism pathways, amino acid metabolism, oxidative phosphorylation pathways, nucleic acid metabolism, fatty acid synthesis and peptidoglycan synthesis. The gabD and sucA genes in lysine metabolic pathway are closely related to the sporulation and crystal proteins formation. The effects of DEPs and functional genes on basic cellular metabolic pathways were studied to provide new strategies for the construction of highly virulent insecticidal strains, the targeted transformation of functional genes.
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Affiliation(s)
- Zixian Yi
- Hunan Provincial Key Laboratory for Microbial Molecular Biology, State Key Laboratory of Development Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Tong Zhang
- Hunan Provincial Key Laboratory for Microbial Molecular Biology, State Key Laboratory of Development Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Junyan Xie
- Hunan Provincial Key Laboratory for Microbial Molecular Biology, State Key Laboratory of Development Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Zirong Zhu
- Hunan Provincial Key Laboratory for Microbial Molecular Biology, State Key Laboratory of Development Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Sisi Luo
- Hunan Provincial Key Laboratory for Microbial Molecular Biology, State Key Laboratory of Development Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Kexuan Zhou
- Hunan Provincial Key Laboratory for Microbial Molecular Biology, State Key Laboratory of Development Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Pengji Zhou
- Hunan Provincial Key Laboratory for Microbial Molecular Biology, State Key Laboratory of Development Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Wenhui Chen
- Hunan Provincial Key Laboratory for Microbial Molecular Biology, State Key Laboratory of Development Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Xiaoli Zhao
- Hunan Provincial Key Laboratory for Microbial Molecular Biology, State Key Laboratory of Development Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Yunjun Sun
- Hunan Provincial Key Laboratory for Microbial Molecular Biology, State Key Laboratory of Development Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Liqiu Xia
- Hunan Provincial Key Laboratory for Microbial Molecular Biology, State Key Laboratory of Development Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Xuezhi Ding
- Hunan Provincial Key Laboratory for Microbial Molecular Biology, State Key Laboratory of Development Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
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Combined and Distinct Roles of Agr Proteins in Clostridioides difficile 630 Sporulation, Motility, and Toxin Production. mBio 2020; 11:mBio.03190-20. [PMID: 33443122 PMCID: PMC8534292 DOI: 10.1128/mbio.03190-20] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Clostridioides difficile accessory gene regulator 1 (agr1) locus consists of two genes, agrB1 and agrD1, that presumably constitute an autoinducing peptide (AIP) system. Typically, AIP systems function through the AgrB-mediated processing of AgrD to generate a processed form of the AIP that provides a concentration-dependent extracellular signal. Here, we show that the C. difficile 630 Agr1 system has multiple functions, not all of which depend on AgrB1. CRISPR-Cas9n deletion of agrB1, agrD1, or the entire locus resulted in changes in transcription of sporulation-related factors and an overall loss in spore formation. Sporulation was recovered in the mutants by providing supernatant from stationary-phase cultures of the parental strain. In contrast, C. difficile motility was reduced only when both AgrB1 and AgrD1 were disrupted. Finally, in the absence of AgrB1, the AgrD1 peptide accumulated within the cytoplasm and this correlated with increased expression of tcdR (15-fold), as well as tcdA (20-fold) and tcdB (5-fold), which encode the two major C. difficile toxins. The combined deletion of agrB1/agrD1 or deletion of only agrD1 did not significantly alter expression of tcdR or tcdB but did show a minor effect on tcdA expression. Overall, these data indicate that the Agr1-based system in C. difficile 630 carries out multiple functions, some of which are associated with prototypical AIP signaling and others of which involve previously undescribed mechanisms of action.IMPORTANCE C. difficile is a spore-forming, toxigenic, anaerobic bacterium that causes severe gastrointestinal illness. Understanding the ways in which C. difficile senses growth conditions to regulate toxin expression and sporulation is essential to advancing our understanding of this pathogen. The Agr1 system in C. difficile has been thought to function by generating an extracellular autoinducing peptide that accumulates and exogenously activates two-component signaling. The absence of the peptide or protease should, in theory, result in similar phenotypes. However, in contrast to longstanding assumptions about Agr, we found that mutants of individual agr1 genes exhibit distinct phenotypes in C. difficile These findings suggest that the Agr1 system may have other regulatory mechanisms independent of the typical Agr quorum sensing system. These data not only challenge models for Agr's mechanism of action in C. difficile but also may expand our conceptions of how this system works in other Gram-positive pathogens.
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Heise J, Witt P, Maneck C, Wichmann-Schauer H, Maurischat S. Prevalence and phylogenetic relationship of Clostridioides difficile strains in fresh poultry meat samples processed in different cutting plants. Int J Food Microbiol 2020; 339:109032. [PMID: 33388709 DOI: 10.1016/j.ijfoodmicro.2020.109032] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 12/11/2020] [Accepted: 12/15/2020] [Indexed: 01/07/2023]
Abstract
Clostridioides difficile is one of the most frequent causes of nosocomial infections in humans leading to (antibiotic-associated) diarrhea and severe pseudomembranous colitis. With an increasing frequency, C. difficile infections (CDI) are also observed independently of hospitalization and the age of the patients in an ambulant setting. One potential source of so-called community-acquired CDI is a zoonotic transmission to humans based on direct contact with animals or the consumption of food. To estimate the exposure of humans with C. difficile via food, we screened 364 different retail fresh poultry meat products purchased in Berlin and Brandenburg, Germany and further characterized the isolates. None of the 42 turkey or chicken meat samples without skin was contaminated. However, 51 (15.8%) of 322 tested fresh chicken meat samples with skin were C. difficile-positive. The vast majority (84.3%) of all isolates exhibited toxin genes tcdA and tcdB, whereas the binary toxin cdtA/B was absent. Most of the isolates (50/51) were susceptible to all six investigated antimicrobials. However, one non-toxigenic strain was multidrug resistant to the antimicrobials clindamycin and erythromycin. The isolates were mainly represented by PCR-ribotypes (RT) 001, RT002, RT005, and RT014, which were already associated with human CDI cases in Germany and were partially detected in poultry. The relatively high contamination rate of fresh retail chicken meat with skin purchased in Germany indicates chicken meat as a potential source of human infections. Moreover, we identified cutting plants with a higher rate of a C. difficile-contamination (21.4-32.8%). To compare the phylogenetic relationship of the isolated strains from certain cutting plants over several months in 2018 and 2019, we analyzed them using NGS followed by core genome MLST. Interestingly, highly related strains (0-3 alleles distance) of common clinical RT001 and RT002 isolates, as well as of the non-toxigenic RT205 isolates were detectable in same cutting plants over a period of three and 16 months, respectively.The continuous contamination with the same strain could be explained by the longterm persistence of this strain within the cutting plant (e.g., within the scalder), or with a recurring entry e.g. from the same fattening farm.
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Affiliation(s)
- Janine Heise
- German Federal Institute for Risk Assessment, Department Biological Safety, Unit Bacterial Toxins, Food Service, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany.
| | - Pascal Witt
- German Federal Institute for Risk Assessment, Department Biological Safety, Unit Bacterial Toxins, Food Service, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
| | - Corinna Maneck
- German Federal Institute for Risk Assessment, Department Biological Safety, Unit Bacterial Toxins, Food Service, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
| | - Heidi Wichmann-Schauer
- German Federal Institute for Risk Assessment, Department Biological Safety, Unit Bacterial Toxins, Food Service, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
| | - Sven Maurischat
- German Federal Institute for Risk Assessment, Department Biological Safety, Unit Bacterial Toxins, Food Service, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
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Role of SpoIVA ATPase Motifs during Clostridioides difficile Sporulation. J Bacteriol 2020; 202:JB.00387-20. [PMID: 32817091 PMCID: PMC7549369 DOI: 10.1128/jb.00387-20] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 08/04/2020] [Indexed: 01/04/2023] Open
Abstract
The major pathogen Clostridioides difficile depends on its spore form to transmit disease. However, the mechanism by which C. difficile assembles spores remains poorly characterized. We previously showed that binding between the spore morphogenetic proteins SpoIVA and SipL regulates assembly of the protective coat layer around the forespore. In this study, we determined that mutations in the C. difficile SpoIVA ATPase motifs result in relatively minor defects in spore formation, in contrast with Bacillus subtilis. Nevertheless, our data suggest that SipL preferentially recognizes the ATP-bound form of SpoIVA and identify a specific residue in the SipL C-terminal LysM domain that is critical for recognizing the ATP-bound form of SpoIVA. These findings advance our understanding of how SpoIVA-SipL interactions regulate C. difficile spore assembly. The nosocomial pathogen Clostridioides difficile is a spore-forming obligate anaerobe that depends on its aerotolerant spore form to transmit infections. Functional spore formation depends on the assembly of a proteinaceous layer known as the coat around the developing spore. In C. difficile, coat assembly depends on the conserved spore protein SpoIVA and the clostridial-organism-specific spore protein SipL, which directly interact. Mutations that disrupt their interaction cause the coat to mislocalize and impair spore formation. In Bacillus subtilis, SpoIVA is an ATPase that uses ATP hydrolysis to drive its polymerization around the forespore. Loss of SpoIVA ATPase activity impairs B. subtilis SpoIVA encasement of the forespore and activates a quality control mechanism that eliminates these defective cells. Since this mechanism is lacking in C. difficile, we tested whether mutations in the C. difficile SpoIVA ATPase motifs impact functional spore formation. Disrupting C. difficile SpoIVA ATPase motifs resulted in phenotypes that were typically >104-fold less severe than the equivalent mutations in B. subtilis. Interestingly, mutation of ATPase motif residues predicted to abrogate SpoIVA binding to ATP decreased the SpoIVA-SipL interaction, whereas mutation of ATPase motif residues predicted to disrupt ATP hydrolysis but maintain ATP binding enhanced the SpoIVA-SipL interaction. When a sipL mutation known to reduce binding to SpoIVA was combined with a spoIVA mutation predicted to prevent SpoIVA binding to ATP, spore formation was severely exacerbated. Since this phenotype is allele specific, our data imply that SipL recognizes the ATP-bound form of SpoIVA and highlight the importance of this interaction for functional C. difficile spore formation. IMPORTANCE The major pathogen Clostridioides difficile depends on its spore form to transmit disease. However, the mechanism by which C. difficile assembles spores remains poorly characterized. We previously showed that binding between the spore morphogenetic proteins SpoIVA and SipL regulates assembly of the protective coat layer around the forespore. In this study, we determined that mutations in the C. difficile SpoIVA ATPase motifs result in relatively minor defects in spore formation, in contrast with Bacillus subtilis. Nevertheless, our data suggest that SipL preferentially recognizes the ATP-bound form of SpoIVA and identify a specific residue in the SipL C-terminal LysM domain that is critical for recognizing the ATP-bound form of SpoIVA. These findings advance our understanding of how SpoIVA-SipL interactions regulate C. difficile spore assembly.
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Trzilova D, Anjuwon-Foster BR, Torres Rivera D, Tamayo R. Rho factor mediates flagellum and toxin phase variation and impacts virulence in Clostridioides difficile. PLoS Pathog 2020; 16:e1008708. [PMID: 32785266 PMCID: PMC7446863 DOI: 10.1371/journal.ppat.1008708] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 08/24/2020] [Accepted: 06/16/2020] [Indexed: 12/17/2022] Open
Abstract
The intestinal pathogen Clostridioides difficile exhibits heterogeneity in motility and toxin production. This phenotypic heterogeneity is achieved through phase variation by site-specific recombination via the DNA recombinase RecV, which reversibly inverts the "flagellar switch" upstream of the flgB operon. A recV mutation prevents flagellar switch inversion and results in phenotypically locked strains. The orientation of the flagellar switch influences expression of the flgB operon post-transcription initiation, but the specific molecular mechanism is unknown. Here, we report the isolation and characterization of spontaneous suppressor mutants in the non-motile, non-toxigenic recV flg OFF background that regained motility and toxin production. The restored phenotypes corresponded with increased expression of flagellum and toxin genes. The motile suppressor mutants contained single-nucleotide polymorphisms (SNPs) in rho, which encodes the bacterial transcription terminator Rho factor. Analyses using transcriptional reporters indicate that Rho contributes to heterogeneity in flagellar gene expression by preferentially terminating transcription of flg OFF mRNA within the 5' leader sequence. Additionally, Rho is important for initial colonization of the intestine in a mouse model of infection, which may in part be due to the sporulation and growth defects observed in the rho mutants. Together these data implicate Rho factor as a regulator of gene expression affecting phase variation of important virulence factors of C. difficile.
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Affiliation(s)
- Dominika Trzilova
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina, United States of America
| | - Brandon R. Anjuwon-Foster
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina, United States of America
| | - Dariana Torres Rivera
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina, United States of America
| | - Rita Tamayo
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina, United States of America
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Differential effects of 'resurrecting' Csp pseudoproteases during Clostridioides difficile spore germination. Biochem J 2020; 477:1459-1478. [PMID: 32242623 PMCID: PMC7200643 DOI: 10.1042/bcj20190875] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 03/31/2020] [Accepted: 04/03/2020] [Indexed: 01/02/2023]
Abstract
Clostridioides difficile is a spore-forming bacterial pathogen that is the leading cause of hospital-acquired gastroenteritis. C. difficile infections begin when its spore form germinates in the gut upon sensing bile acids. These germinants induce a proteolytic signaling cascade controlled by three members of the subtilisin-like serine protease family, CspA, CspB, and CspC. Notably, even though CspC and CspA are both pseudoproteases, they are nevertheless required to sense germinants and activate the protease, CspB. Thus, CspC and CspA are part of a growing list of pseudoenzymes that play important roles in regulating cellular processes. However, despite their importance, the structural properties of pseudoenzymes that allow them to function as regulators remain poorly understood. Our recently solved crystal structure of CspC revealed that its pseudoactive site residues align closely with the catalytic triad of CspB, suggesting that it might be possible to ‘resurrect' the ancestral protease activity of the CspC and CspA pseudoproteases. Here, we demonstrate that restoring the catalytic triad to these pseudoproteases fails to resurrect their protease activity. We further show that the pseudoactive site substitutions differentially affect the stability and function of the CspC and CspA pseudoproteases: the substitutions destabilized CspC and impaired spore germination without affecting CspA stability or function. Thus, our results surprisingly reveal that the presence of a catalytic triad does not necessarily predict protease activity. Since homologs of C. difficile CspA occasionally carry an intact catalytic triad, our results indicate that bioinformatic predictions of enzyme activity may underestimate pseudoenzymes in rare cases.
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Impact of deoxycholate on Clostridioides difficile growth, toxin production, and sporulation. Heliyon 2020; 6:e03717. [PMID: 32322715 PMCID: PMC7160582 DOI: 10.1016/j.heliyon.2020.e03717] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 01/27/2020] [Accepted: 03/30/2020] [Indexed: 12/15/2022] Open
Abstract
Purpose Bile acids play an important role in Clostridioides difficile life cycle. Deoxycholate (DCA), one of the most abundant secondary bile acids, is known to inhibit vegetative growth and toxin production. However, limited data are available on the role of DCA on C. difficile sporulation. Here, we investigated the phenotypic and genotypic impact of DCA on the growth, toxin production, and sporulation of C. difficile. Methodology Four genetically divergent C. difficile strains were cultured in nutrient-rich broth with and without DCA at various concentrations, and growth activity was evaluated for each strain. Cytotoxicity assays using culture supernatants from cells grown in nutrient-rich broth with and without 0.01% DCA were conducted. Sporulation efficiency was determined using sporulation media with and without 0.01% DCA. Transcript levels of tcdB and spo0A were analyzed using quantitative reverse-transcription polymerase chain reaction. Results We found that DCA led to growth reduction in a dose-depended manner and regulated toxin production by repressing tcdB expression during vegetative growth. To our knowledge, we have also provided the first evidence that DCA reduces C. difficile sporulation efficiency through the downregulation of spo0A expression during the sporulation stage. Conclusions DCA modulates C. difficile sporulation, vegetative growth, and toxin production.
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Taylor W, Camilleri E, Craft DL, Korza G, Granados MR, Peterson J, Szczpaniak R, Weller SK, Moeller R, Douki T, Mok WWK, Setlow P. DNA Damage Kills Bacterial Spores and Cells Exposed to 222-Nanometer UV Radiation. Appl Environ Microbiol 2020; 86:AEM.03039-19. [PMID: 32033948 PMCID: PMC7117916 DOI: 10.1128/aem.03039-19] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Accepted: 02/03/2020] [Indexed: 01/16/2023] Open
Abstract
This study examined the microbicidal activity of 222-nm UV radiation (UV222), which is potentially a safer alternative to the 254-nm UV radiation (UV254) that is often used for surface decontamination. Spores and/or growing and stationary-phase cells of Bacillus cereus, Bacillus subtilis, Bacillus thuringiensis, Staphylococcus aureus, and Clostridioides difficile and a herpesvirus were all killed or inactivated by UV222 and at lower fluences than with UV254B. subtilis spores and cells lacking the major DNA repair protein RecA were more sensitive to UV222, as were spores lacking their DNA-protective proteins, the α/β-type small, acid-soluble spore proteins. The spore cores' large amount of Ca2+-dipicolinic acid (∼25% of the core dry weight) also protected B. subtilis and C. difficile spores against UV222, while spores' proteinaceous coat may have given some slight protection against UV222 Survivors among B. subtilis spores treated with UV222 acquired a large number of mutations, and this radiation generated known mutagenic photoproducts in spore and cell DNA, primarily cyclobutane-type pyrimidine dimers in growing cells and an α-thyminyl-thymine adduct termed the spore photoproduct (SP) in spores. Notably, the loss of a key SP repair protein markedly decreased spore UV222 resistance. UV222-treated B. subtilis spores germinated relatively normally, and the generation of colonies from these germinated spores was not salt sensitive. The latter two findings suggest that UV222 does not kill spores by general protein damage, and thus, the new results are consistent with the notion that DNA damage is responsible for the killing of spores and cells by UV222IMPORTANCE Spores of a variety of bacteria are resistant to common decontamination agents, and many of them are major causes of food spoilage and some serious human diseases, including anthrax caused by spores of Bacillus anthracis Consequently, there is an ongoing need for efficient methods for spore eradication, in particular methods that have minimal deleterious effects on people or the environment. UV radiation at 254 nm (UV254) is sporicidal and commonly used for surface decontamination but can cause deleterious effects in humans. Recent work, however, suggests that 222-nm UV (UV222) may be less harmful to people than UV254 yet may still kill bacteria and at lower fluences than UV254 The present work has identified the damage by UV222 that leads to the killing of growing cells and spores of some bacteria, many of which are human pathogens, and UV222 also inactivates a herpesvirus.
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Affiliation(s)
- Willie Taylor
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, Connecticut, USA
| | - Emily Camilleri
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, Connecticut, USA
| | - D Levi Craft
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, Connecticut, USA
| | - George Korza
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, Connecticut, USA
| | - Maria Rocha Granados
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, Connecticut, USA
| | - Jaliyah Peterson
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, Connecticut, USA
| | - Renata Szczpaniak
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, Connecticut, USA
| | - Sandra K Weller
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, Connecticut, USA
| | - Ralf Moeller
- Space Microbiology Research Group, Radiation Biology Department, Institute for Aerospace Medicine, German Aerospace Center, Cologne, Germany
| | - Thierry Douki
- Universite Grenoble Alpes, CEA, CNRS, INAC-SYMMBEST, Grenoble, France
| | - Wendy W K Mok
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, Connecticut, USA
| | - Peter Setlow
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, Connecticut, USA
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Ramos-Silva P, Serrano M, Henriques AO. From Root to Tips: Sporulation Evolution and Specialization in Bacillus subtilis and the Intestinal Pathogen Clostridioides difficile. Mol Biol Evol 2020; 36:2714-2736. [PMID: 31350897 PMCID: PMC6878958 DOI: 10.1093/molbev/msz175] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Bacteria of the Firmicutes phylum are able to enter a developmental pathway that culminates with the formation of highly resistant, dormant endospores. Endospores allow environmental persistence, dissemination and for pathogens, are also infection vehicles. In both the model Bacillus subtilis, an aerobic organism, and in the intestinal pathogen Clostridioides difficile, an obligate anaerobe, sporulation mobilizes hundreds of genes. Their expression is coordinated between the forespore and the mother cell, the two cells that participate in the process, and is kept in close register with the course of morphogenesis. The evolutionary mechanisms by which sporulation emerged and evolved in these two species, and more broadly across Firmicutes, remain largely unknown. Here, we trace the origin and evolution of sporulation using the genes known to be involved in the process in B. subtilis and C. difficile, and estimating their gain-loss dynamics in a comprehensive bacterial macroevolutionary framework. We show that sporulation evolution was driven by two major gene gain events, the first at the base of the Firmicutes and the second at the base of the B. subtilis group and within the Peptostreptococcaceae family, which includes C. difficile. We also show that early and late sporulation regulons have been coevolving and that sporulation genes entail greater innovation in B. subtilis with many Bacilli lineage-restricted genes. In contrast, C. difficile more often recruits new sporulation genes by horizontal gene transfer, which reflects both its highly mobile genome, the complexity of the gut microbiota, and an adjustment of sporulation to the gut ecosystem.
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Affiliation(s)
- Paula Ramos-Silva
- Instituto Gulbenkian de Ciência, Oeiras, Portugal.,Marine Biodiversity Group, Naturalis Biodiversity Center, Leiden, The Netherlands
| | - Mónica Serrano
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Adriano O Henriques
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
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The Impact of pH on Clostridioides difficile Sporulation and Physiology. Appl Environ Microbiol 2020; 86:AEM.02706-19. [PMID: 31811041 DOI: 10.1128/aem.02706-19] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 12/03/2019] [Indexed: 12/18/2022] Open
Abstract
Clostridioides difficile is a pathogenic bacterium that infects the human colon to cause diarrheal disease. Growth of the bacterium is known to be dependent on certain bile acids, oxygen levels, and nutrient availability in the intestine, but how the environmental pH can influence C. difficile is mostly unknown. Previous studies indicated that C. difficile modulates the intestinal pH, and prospective cohort studies have found a strong association between a more alkaline fecal pH and C. difficile infection. Based on these data, we hypothesized that C. difficile physiology can be affected by various pH conditions. In this study, we investigated the impact of a range of pH conditions on C. difficile to assess potential effects on growth, sporulation, motility, and toxin production in the strains 630Δerm and R20291. We observed pH-dependent differences in sporulation rate, spore morphology, and viability. Sporulation frequency was lowest under acidic conditions, and differences in cell morphology were apparent at low pH. In alkaline environments, C. difficile sporulation was greater for strain 630Δerm, whereas R20291 produced relatively high levels of spores in a broad range of pH conditions. Rapid changes in pH during exponential growth impacted sporulation similarly among the strains. Furthermore, we observed an increase in C. difficile motility with increases in pH, and strain-dependent differences in toxin production under acidic conditions. The data demonstrate that pH is an important parameter that affects C. difficile physiology and may reveal relevant insights into the growth and dissemination of this pathogen.IMPORTANCE Clostridioides difficile is an anaerobic bacterium that causes gastrointestinal disease. C. difficile forms dormant spores which can survive harsh environmental conditions, allowing their spread to new hosts. In this study, we determine how intestinally relevant pH conditions impact C. difficile physiology in the two divergent strains, 630Δerm and R20291. Our data demonstrate that low pH conditions reduce C. difficile growth, sporulation, and motility. However, toxin production and spore morphology were differentially impacted in the two strains at low pH. In addition, we observed that alkaline environments reduce C. difficile growth, but increase cell motility. When pH was adjusted rapidly during growth, we observed similar impacts on both strains. This study provides new insights into the phenotypic diversity of C. difficile grown under diverse pH conditions present in the intestinal tract, and demonstrates similarities and differences in the pH responses of different C. difficile isolates.
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Strain-Dependent RstA Regulation of Clostridioides difficile Toxin Production and Sporulation. J Bacteriol 2020; 202:JB.00586-19. [PMID: 31659010 DOI: 10.1128/jb.00586-19] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Accepted: 10/21/2019] [Indexed: 02/04/2023] Open
Abstract
The anaerobic spore former Clostridioides difficile causes significant diarrheal disease in humans and other mammals. Infection begins with the ingestion of dormant spores, which subsequently germinate within the host gastrointestinal tract. There, the vegetative cells proliferate and secrete two exotoxins, TcdA and TcdB, which cause disease symptoms. Although spore formation and toxin production are critical for C. difficile pathogenesis, the regulatory links between these two physiological processes are not well understood and are strain dependent. Previously, we identified a conserved C. difficile regulator, RstA, that promotes sporulation initiation through an unknown mechanism and directly and indirectly represses toxin and motility gene transcription in the historical isolate 630Δerm To test whether perceived strain-dependent differences in toxin production and sporulation are mediated by RstA, we created an rstA mutant in the epidemic ribotype 027 strain R20291. RstA affected sporulation and toxin gene expression similarly but more robustly in R20291 than in 630Δerm In contrast, no effect on motility gene expression was observed in R20291. Reporter assays measuring transcriptional regulation of tcdR, the sigma factor gene essential for toxin gene expression, identified sequence-dependent effects influencing repression by RstA and CodY, a global nutritional sensor, in four diverse C. difficile strains. Finally, sequence- and strain-dependent differences were evident in RstA negative autoregulation of rstA transcription. Altogether, our data suggest that strain-dependent differences in RstA regulation contribute to the sporulation and toxin phenotypes observed in R20291. Our data establish RstA as an important regulator of C. difficile virulence traits.IMPORTANCE Two critical traits of Clostridioides difficile pathogenesis are toxin production, which causes disease symptoms, and spore formation, which permits survival outside the gastrointestinal tract. The multifunctional regulator RstA promotes sporulation and prevents toxin production in the historical strain 630Δerm Here, we show that RstA exhibits stronger effects on these phenotypes in an epidemic isolate, R20291, and additional strain-specific effects on toxin and rstA expression are evident. Our data demonstrate that sequence-specific differences within the promoter for the toxin regulator TcdR contribute to the regulation of toxin production by RstA and CodY. These sequence differences account for some of the variability in toxin production among isolates and may allow strains to differentially control toxin production in response to a variety of signals.
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