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Mookherjee A, Mitra M, Sason G, Jose PA, Martinenko M, Pietrokovski S, Jurkevitch E. Flagellar stator genes control a trophic shift from obligate to facultative predation and biofilm formation in a bacterial predator. mBio 2024; 15:e0071524. [PMID: 39037271 PMCID: PMC11323537 DOI: 10.1128/mbio.00715-24] [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: 03/07/2024] [Accepted: 06/13/2024] [Indexed: 07/23/2024] Open
Abstract
The bacterial predator Bdellovibrio bacteriovorus is considered to be obligatorily prey (host)-dependent (H-D), and thus unable to form biofilms. However, spontaneous host-independent (H-I) variants grow axenically and can form robust biofilms. A screen of 350 H-I mutants revealed that single mutations in stator genes fliL or motA were sufficient to generate flagellar motility-defective H-I strains able to adhere to surfaces but unable to develop biofilms. The variants showed large transcriptional shifts in genes related to flagella, prey-invasion, and cyclic-di-GMP (CdG), as well as large changes in CdG cellular concentration relative to the H-D parent. The introduction of the parental fliL allele resulted in a full reversion to the H-D phenotype, but we propose that specific interactions between stator proteins prevented functional complementation by fliL paralogs. In contrast, specific mutations in a pilus-associated protein (Bd0108) mutant background were necessary for biofilm formation, including secretion of extracellular DNA (eDNA), proteins, and polysaccharides matrix components. Remarkably, fliL disruption strongly reduced biofilm development. All H-I variants grew similarly without prey, showed a strain-specific reduction in predatory ability in prey suspensions, but maintained similar high efficiency in prey biofilms. Population-wide allele sequencing suggested additional routes to host independence. Thus, stator and invasion pole-dependent signaling control the H-D and the H-I biofilm-forming phenotypes, with single mutations overriding prey requirements, and enabling shifts from obligate to facultative predation, with potential consequences on community dynamics. Our findings on the facility and variety of changes leading to facultative predation also challenge the concept of Bdellovibrio and like organisms being obligate predators. IMPORTANCE The ability of bacteria to form biofilms is a central research theme in biology, medicine, and the environment. We show that cultures of the obligate (host-dependent) "solitary" predatory bacterium Bdellovibrio bacteriovorus, which cannot replicate without prey, can use various genetic routes to spontaneously yield host-independent (H-I) variants that grow axenically (as a single species, in the absence of prey) and exhibit various surface attachment phenotypes, including biofilm formation. These routes include single mutations in flagellar stator genes that affect biofilm formation, provoke motor instability and large motility defects, and disrupt cyclic-di-GMP intracellular signaling. H-I strains also exhibit reduced predatory efficiency in suspension but high efficiency in prey biofilms. These changes override the requirements for prey, enabling a shift from obligate to facultative predation, with potential consequences on community dynamics.
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Affiliation(s)
- Abhirup Mookherjee
- Department of Plant Pathology and Microbiology, Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Mohor Mitra
- Department of Plant Pathology and Microbiology, Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Gal Sason
- Department of Plant Pathology and Microbiology, Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Polpass Arul Jose
- Department of Plant Pathology and Microbiology, Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Maria Martinenko
- Department of Plant Pathology and Microbiology, Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Shmuel Pietrokovski
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Edouard Jurkevitch
- Department of Plant Pathology and Microbiology, Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
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2
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Partridge JD, Harshey RM. Flagellar protein FliL: A many-splendored thing. Mol Microbiol 2024. [PMID: 39096095 DOI: 10.1111/mmi.15301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Revised: 07/09/2024] [Accepted: 07/16/2024] [Indexed: 08/04/2024]
Abstract
FliL is a bacterial flagellar protein demonstrated to associate with, and regulate ion flow through, the stator complex in a diverse array of bacterial species. FliL is also implicated in additional functions such as stabilizing the flagellar rod, modulating rotor bias, sensing the surface, and regulating gene expression. How can one protein do so many things? Its location is paramount to understanding its numerous functions. This review will look at the evidence, attempt to resolve some conflicting findings, and offer new thoughts on FliL.
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Affiliation(s)
- Jonathan D Partridge
- Department of Molecular Biosciences and the LaMontagne Center for Infectious Diseases, The University of Texas at Austin, Austin, Texas, USA
| | - Rasika M Harshey
- Department of Molecular Biosciences and the LaMontagne Center for Infectious Diseases, The University of Texas at Austin, Austin, Texas, USA
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3
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Partridge JD, Dufour Y, Hwang Y, Harshey RM. Flagellar motor remodeling during swarming requires FliL. Mol Microbiol 2023; 120:670-683. [PMID: 37675594 PMCID: PMC10942728 DOI: 10.1111/mmi.15148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 08/18/2023] [Accepted: 08/20/2023] [Indexed: 09/08/2023]
Abstract
FliL is an essential component of the flagellar machinery in some bacteria, but a conditional one in others. The conditional role is for optimal swarming in some bacteria. During swarming, physical forces associated with movement on a surface are expected to exert a higher load on the flagellum, requiring more motor torque to move. FliL was reported to enhance motor output in several bacteria and observed to assemble as a ring around ion-conducting stators that power the motor. In this study we identify a common new function for FliL in diverse bacteria-Escherichia coli, Bacillus subtilis, and Proteus mirabilis. During swarming, all these bacteria show increased cell speed and a skewed motor bias that suppresses cell tumbling. We demonstrate that these altered motor parameters, or "motor remodeling," require FliL. Both swarming and motor remodeling can be restored in an E. coli fliL mutant by complementation with fliL genes from P. mirabilis and B. subtilis, showing conservation of a swarming-associated FliL function across phyla. In addition, we demonstrate that the strong interaction we reported earlier between FliL and the flagellar MS-ring protein FliF is confined to the RBM-3 domain of FliF that links the periplasmic rod to the cytoplasmic C-ring. This interaction may explain several phenotypes associated with the absence of FliL.
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Affiliation(s)
- Jonathan D. Partridge
- Department of Molecular Biosciences and the LaMontagne Center for Infectious Diseases, The University of Texas at Austin, Austin, Texas, USA
| | - Yann Dufour
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - YuneSahng Hwang
- Department of Molecular Biosciences and the LaMontagne Center for Infectious Diseases, The University of Texas at Austin, Austin, Texas, USA
| | - Rasika M. Harshey
- Department of Molecular Biosciences and the LaMontagne Center for Infectious Diseases, The University of Texas at Austin, Austin, Texas, USA
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4
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Khan F, Jeong GJ, Tabassum N, Kim YM. Functional diversity of c-di-GMP receptors in prokaryotic and eukaryotic systems. Cell Commun Signal 2023; 21:259. [PMID: 37749602 PMCID: PMC10519070 DOI: 10.1186/s12964-023-01263-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 08/09/2023] [Indexed: 09/27/2023] Open
Abstract
Cyclic bis-(3', 5')-dimeric guanosine monophosphate (c-di-GMP) is ubiquitous in many bacterial species, where it functions as a nucleotide-based secondary messenger and is a vital regulator of numerous biological processes. Due to its ubiquity, most bacterial species possess a wide range of downstream receptors that has a binding affinity to c-di-GMP and elicit output responses. In eukaryotes, several enzymes and riboswitches operate as receptors that interact with c-di-GMP and transduce cellular or environmental signals. This review examines the functional variety of receptors in prokaryotic and eukaryotic systems that exhibit distinct biological responses after interacting with c-di-GMP. Evolutionary relationships and similarities in distance among the c-di-GMP receptors in various bacterial species were evaluated to understand their specificities. Furthermore, residues of receptors involved in c-di-GMP binding are summarized. This review facilitates the understanding of how distinct receptors from different origins bind c-di-GMP equally well, yet fulfill diverse biological roles at the interspecies, intraspecies, and interkingdom levels. Furthermore, it also highlights c-di-GMP receptors as potential therapeutic targets, particularly those found in pathogenic microorganisms. Video Abstract.
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Affiliation(s)
- Fazlurrahman Khan
- Marine Integrated Biomedical Technology Center, The National Key Research Institutes in Universities, Pukyong National University, Busan, 48513, Republic of Korea.
- Research Center for Marine Integrated Bionics Technology, Pukyong National University, Busan, 48513, Republic of Korea.
| | - Geum-Jae Jeong
- Department of Food Science and Technology, Pukyong National University, Busan, 48513, Republic of Korea
| | - Nazia Tabassum
- Marine Integrated Biomedical Technology Center, The National Key Research Institutes in Universities, Pukyong National University, Busan, 48513, Republic of Korea
- Research Center for Marine Integrated Bionics Technology, Pukyong National University, Busan, 48513, Republic of Korea
| | - Young-Mog Kim
- Marine Integrated Biomedical Technology Center, The National Key Research Institutes in Universities, Pukyong National University, Busan, 48513, Republic of Korea.
- Research Center for Marine Integrated Bionics Technology, Pukyong National University, Busan, 48513, Republic of Korea.
- Department of Food Science and Technology, Pukyong National University, Busan, 48513, Republic of Korea.
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Partridge JD, Dufour Y, Hwang Y, Harshey RM. Flagellar motor remodeling during swarming requires FliL. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.14.549092. [PMID: 37503052 PMCID: PMC10370021 DOI: 10.1101/2023.07.14.549092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
FliL is an essential component of the flagellar machinery in some bacteria, but a conditional one in others. The conditional role is for optimal swarming in some bacteria. During swarming, physical forces associated with movement on a surface are expected to exert a higher load on the flagellum, requiring more motor torque to move. Bacterial physiology and morphology are also altered during swarming to cope with the challenges of surface navigation. FliL was reported to enhance motor output in several bacteria and observed to assemble as a ring around ion-conducting stators that power the motor. In this study we identify a common new function for FliL in diverse bacteria - Escherichia coli, Bacillus subtilis and Proteus mirabilis . During swarming, all these bacteria show increased cell speed and a skewed motor bias that suppresses cell tumbling. We demonstrate that these altered motor parameters, or 'motor remodeling', require FliL. Both swarming and motor remodeling can be restored in an E. coli fliL mutant by complementation with fliL genes from P. mirabilis and B. subtilis , showing conservation of swarming-associated FliL function across phyla. In addition, we demonstrate that the strong interaction we reported earlier between FliL and the flagellar MS-ring protein FliF is confined to the RBM-3 domain of FliF that links the periplasmic rod to the cytoplasmic C-ring. This interaction may explain several phenotypes associated with the absence of FliL.
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Affiliation(s)
- Jonathan D Partridge
- Department of Molecular Biosciences and the LaMontagne Center for Infectious Diseases The University of Texas at Austin, Austin, Texas, 78712, USA
| | - Yann Dufour
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - YuneSahng Hwang
- Department of Molecular Biosciences and the LaMontagne Center for Infectious Diseases The University of Texas at Austin, Austin, Texas, 78712, USA
| | - Rasika M Harshey
- Department of Molecular Biosciences and the LaMontagne Center for Infectious Diseases The University of Texas at Austin, Austin, Texas, 78712, USA
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Seidel M, Skotnicka D, Glatter T, Søgaard-Andersen L. During heat stress in Myxococcus xanthus, the CdbS PilZ domain protein, in concert with two PilZ-DnaK chaperones, perturbs chromosome organization and accelerates cell death. PLoS Genet 2023; 19:e1010819. [PMID: 37339150 DOI: 10.1371/journal.pgen.1010819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 06/07/2023] [Indexed: 06/22/2023] Open
Abstract
C-di-GMP is a bacterial second messenger that regulates diverse processes in response to environmental or cellular cues. The nucleoid-associated protein (NAP) CdbA in Myxococcus xanthus binds c-di-GMP and DNA in a mutually exclusive manner in vitro. CdbA is essential for viability, and CdbA depletion causes defects in chromosome organization, leading to a block in cell division and, ultimately, cell death. Most NAPs are not essential; therefore, to explore the paradoxical cdbA essentiality, we isolated suppressor mutations that restored cell viability without CdbA. Most mutations mapped to cdbS, which encodes a stand-alone c-di-GMP binding PilZ domain protein, and caused loss-of-function of cdbS. Cells lacking CdbA and CdbS or only CdbS were fully viable and had no defects in chromosome organization. CdbA depletion caused post-transcriptional upregulation of CdbS accumulation, and this CdbS over-accumulation was sufficient to disrupt chromosome organization and cause cell death. CdbA depletion also caused increased accumulation of CsdK1 and CsdK2, two unusual PilZ-DnaK chaperones. During CdbA depletion, CsdK1 and CsdK2, in turn, enabled the increased accumulation and toxicity of CdbS, likely by stabilizing CdbS. Moreover, we demonstrate that heat stress, possibly involving an increased cellular c-di-GMP concentration, induced the CdbA/CsdK1/CsdK2/CdbS system, causing a CsdK1- and CsdK2-dependent increase in CdbS accumulation. Thereby this system accelerates heat stress-induced chromosome mis-organization and cell death. Collectively, this work describes a unique system that contributes to regulated cell death in M. xanthus and suggests a link between c-di-GMP signaling and regulated cell death in bacteria.
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Affiliation(s)
- Michael Seidel
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Dorota Skotnicka
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Timo Glatter
- Core Facility for Mass Spectrometry & Proteomics, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Lotte Søgaard-Andersen
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
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McLaughlin M, Hershey DM, Reyes Ruiz LM, Fiebig A, Crosson S. A cryptic transcription factor regulates Caulobacter adhesin development. PLoS Genet 2022; 18:e1010481. [PMID: 36315598 PMCID: PMC9648850 DOI: 10.1371/journal.pgen.1010481] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 11/10/2022] [Accepted: 10/18/2022] [Indexed: 11/07/2022] Open
Abstract
Alphaproteobacteria commonly produce an adhesin that is anchored to the exterior of the envelope at one cell pole. In Caulobacter crescentus this adhesin, known as the holdfast, facilitates attachment to solid surfaces and cell partitioning to air-liquid interfaces. An ensemble of two-component signal transduction (TCS) proteins controls C. crescentus holdfast biogenesis by indirectly regulating expression of HfiA, a potent inhibitor of holdfast synthesis. We performed a genetic selection to discover direct hfiA regulators that function downstream of the adhesion TCS system and identified rtrC, a hypothetical gene. rtrC transcription is directly activated by the adhesion TCS regulator, SpdR. Though its primary structure bears no resemblance to any defined protein family, RtrC binds and regulates dozens of sites on the C. crescentus chromosome via a pseudo-palindromic sequence. Among these binding sites is the hfiA promoter, where RtrC functions to directly repress transcription and thereby activate holdfast development. Either RtrC or SpdR can directly activate transcription of a second hfiA repressor, rtrB. Thus, environmental regulation of hfiA transcription by the adhesion TCS system is subject to control by an OR-gated type I coherent feedforward loop; these regulatory motifs are known to buffer gene expression against fluctuations in regulating signals. We have further assessed the functional role of rtrC in holdfast-dependent processes, including surface adherence to a cellulosic substrate and formation of pellicle biofilms at air-liquid interfaces. Strains harboring insertional mutations in rtrC have a diminished adhesion profile in a competitive cheesecloth binding assay and a reduced capacity to colonize pellicle biofilms in select media conditions. Our results add to an emerging understanding of the regulatory topology and molecular components of a complex bacterial cell adhesion control system.
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Affiliation(s)
- Maeve McLaughlin
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America
| | - David M. Hershey
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Leila M. Reyes Ruiz
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Aretha Fiebig
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America
| | - Sean Crosson
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America
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8
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Lack of N-Terminal Segment of the Flagellin Protein Results in the Production of a Shortened Polar Flagellum in the Deep-Sea Sedimentary Bacterium Pseudoalteromonas sp. Strain SM9913. Appl Environ Microbiol 2021; 87:e0152721. [PMID: 34406825 DOI: 10.1128/aem.01527-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial polar flagella, comprised of flagellin, are essential for bacterial motility. Pseudoalteromonas sp. strain SM9913 is a bacterium isolated from deep-sea sediments. Unlike other Pseudoalteromonas strains that have a long polar flagellum, strain SM9913 has an abnormally short polar flagellum. Here, we investigated the underlying reason for the short flagellum and found that a single-base mutation was responsible for the altered flagellar assembly. This mutation leads to the fragmentation of the flagellin gene into two genes, PSM_A2281, encoding the core segment and the C-terminal segment, and PSM_A2282, encoding the N-terminal segment, and only gene PSM_A2281 is involved in the production of the short polar flagellum. When a chimeric gene of PSM_A2281 and PSM_A2282 encoding an intact flagellin, A2281::82, was expressed, a long polar flagellum was produced, indicating that the N-terminal segment of flagellin contributes to the production of a polar flagellum of a normal length. Analyses of the simulated structures of A2281 and A2281::82 and that of the flagellar filament assembled with A2281::82 indicate that due to the lack of two α-helices, the core of the flagellar filament assembled with A2281 is incomplete and is likely too weak to support the stability and movement of a long flagellum. This mutation in strain SM9913 had little effect on its growth and only a small effect on its swimming motility, implying that strain SM9913 can live well with this mutation in natural sedimentary environments. This study provides a better understanding of the assembly and production of bacterial flagella. IMPORTANCE Polar flagella, which are essential organelles for bacterial motility, are comprised of multiple flagellin subunits. A flagellin molecule contains an N-terminal segment, a core segment, and a C-terminal segment. The results of this investigation of the deep-sea sedimentary bacterium Pseudoalteromonas sp. strain SM9913 demonstrate that a single-base mutation in the flagellin gene leads to the production of an incomplete flagellin without the N-terminal segment and that the loss of the N-terminal segment of the flagellin protein results in the production of a shortened polar flagellar filament. Our results shed light on the important function of the N-terminal segment of flagellin in the assembly and stability of bacterial flagellar filament.
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Yan H, Chen W. The Promise and Challenges of Cyclic Dinucleotides as Molecular Adjuvants for Vaccine Development. Vaccines (Basel) 2021; 9:917. [PMID: 34452042 PMCID: PMC8402453 DOI: 10.3390/vaccines9080917] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 08/05/2021] [Accepted: 08/10/2021] [Indexed: 12/14/2022] Open
Abstract
Cyclic dinucleotides (CDNs), originally discovered as bacterial second messengers, play critical roles in bacterial signal transduction, cellular processes, biofilm formation, and virulence. The finding that CDNs can trigger the innate immune response in eukaryotic cells through the stimulator of interferon genes (STING) signalling pathway has prompted the extensive research and development of CDNs as potential immunostimulators and novel molecular adjuvants for induction of systemic and mucosal innate and adaptive immune responses. In this review, we summarize the chemical structure, biosynthesis regulation, and the role of CDNs in enhancing the crosstalk between host innate and adaptive immune responses. We also discuss the strategies to improve the efficient delivery of CDNs and the recent advance and future challenges in the development of CDNs as potential adjuvants in prophylactic vaccines against infectious diseases and in therapeutic vaccines against cancers.
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Affiliation(s)
- Hongbin Yan
- Department of Chemistry, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Wangxue Chen
- Human Health and Therapeutics Research Centre, National Research Council Canada, Ottawa, ON K1A 0R6, Canada
- Department of Biological Sciences, Brock University, St. Catharines, ON L2S 3A1, Canada
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10
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Abstract
Bacteria thrive both in liquids and attached to surfaces. The concentration of bacteria on surfaces is generally much higher than in the surrounding environment, offering bacteria ample opportunity for mutualistic, symbiotic, and pathogenic interactions. To efficiently populate surfaces, they have evolved mechanisms to sense mechanical or chemical cues upon contact with solid substrata. This is of particular importance for pathogens that interact with host tissue surfaces. In this review we discuss how bacteria are able to sense surfaces and how they use this information to adapt their physiology and behavior to this new environment. We first survey mechanosensing and chemosensing mechanisms and outline how specific macromolecular structures can inform bacteria about surfaces. We then discuss how mechanical cues are converted to biochemical signals to activate specific cellular processes in a defined chronological order and describe the role of two key second messengers, c-di-GMP and cAMP, in this process.
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Affiliation(s)
| | - Urs Jenal
- Biozentrum, University of Basel, CH-4056 Basel, Switzerland; ,
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11
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Krol E, Schäper S, Becker A. Cyclic di-GMP signaling controlling the free-living lifestyle of alpha-proteobacterial rhizobia. Biol Chem 2021; 401:1335-1348. [PMID: 32990642 DOI: 10.1515/hsz-2020-0232] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 09/14/2020] [Indexed: 12/12/2022]
Abstract
Cyclic-di-GMP (c-di-GMP) is a ubiquitous bacterial second messenger which has been associated with a motile to sessile lifestyle switch in many bacteria. Here, we review recent insights into c-di-GMP regulated processes related to environmental adaptations in alphaproteobacterial rhizobia, which are diazotrophic bacteria capable of fixing nitrogen in symbiosis with their leguminous host plants. The review centers on Sinorhizobium meliloti, which in the recent years was intensively studied for its c-di-GMP regulatory network.
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Affiliation(s)
- Elizaveta Krol
- Center for Synthetic Microbiology (SYNMIKRO), Philipps-Universität Marburg, D-35032 Marburg, Germany.,Department of Biology, Philipps-Universität Marburg, D-35032 Marburg, Germany
| | - Simon Schäper
- Center for Synthetic Microbiology (SYNMIKRO), Philipps-Universität Marburg, D-35032 Marburg, Germany
| | - Anke Becker
- Center for Synthetic Microbiology (SYNMIKRO), Philipps-Universität Marburg, D-35032 Marburg, Germany.,Department of Biology, Philipps-Universität Marburg, D-35032 Marburg, Germany
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12
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Three PilZ Domain Proteins, PlpA, PixA, and PixB, Have Distinct Functions in Regulation of Motility and Development in Myxococcus xanthus. J Bacteriol 2021; 203:e0012621. [PMID: 33875546 PMCID: PMC8316039 DOI: 10.1128/jb.00126-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
In bacteria, the nucleotide-based second messenger bis-(3'-5')-cyclic dimeric GMP (c-di-GMP) binds to effectors to generate outputs in response to changes in the environment. In Myxococcus xanthus, c-di-GMP regulates type IV pilus-dependent motility and the starvation-induced developmental program that results in formation of spore-filled fruiting bodies; however, little is known about the effectors that bind c-di-GMP. Here, we systematically inactivated all 24 genes encoding PilZ domain-containing proteins, which are among the most common c-di-GMP effectors. We confirm that the stand-alone PilZ domain protein PlpA is important for regulation of motility independently of the Frz chemosensory system and that Pkn1, which is composed of a Ser/Thr kinase domain and a PilZ domain, is specifically important for development. Moreover, we identify two PilZ domain proteins that have distinct functions in regulating motility and development. PixB, which is composed of two PilZ domains and an acetyltransferase domain, binds c-di-GMP in vitro and regulates type IV pilus-dependent and gliding motility in a Frz-dependent manner as well as development. The acetyltransferase domain is required and sufficient for function during growth, while all three domains and c-di-GMP binding are essential for PixB function during development. PixA is a response regulator composed of a PilZ domain and a receiver domain, binds c-di-GMP in vitro, and regulates motility independently of the Frz system, likely by setting up the polarity of the two motility systems. Our results support a model whereby PlpA, PixA, and PixB act in independent pathways and have distinct functions in regulation of motility. IMPORTANCE c-di-GMP signaling controls bacterial motility in many bacterial species by binding to downstream effector proteins. Here, we identify two PilZ domain-containing proteins in Myxococcus xanthus that bind c-di-GMP. We show that PixB, which contains two PilZ domains and an acetyltransferase domain, acts in a manner that depends on the Frz chemosensory system to regulate motility via the acetyltransferase domain, while the intact protein and c-di-GMP binding are essential for PixB to support development. In contrast, PixA acts in a Frz-independent manner to regulate motility. Taking our results together with previous observations, we conclude that PilZ domain proteins and c-di-GMP act in multiple independent pathways to regulate motility and development in M. xanthus.
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13
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Pecina A, Schwan M, Blagotinsek V, Rick T, Klüber P, Leonhard T, Bange G, Thormann KM. The Stand-Alone PilZ-Domain Protein MotL Specifically Regulates the Activity of the Secondary Lateral Flagellar System in Shewanella putrefaciens. Front Microbiol 2021; 12:668892. [PMID: 34140945 PMCID: PMC8203827 DOI: 10.3389/fmicb.2021.668892] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 04/19/2021] [Indexed: 11/13/2022] Open
Abstract
A number of bacterial species control the function of the flagellar motor in response to the levels of the secondary messenger c-di-GMP, which is often mediated by c-di-GMP-binding proteins that act as molecular brakes or clutches to slow the motor rotation. The gammaproteobacterium Shewanella putrefaciens possesses two distinct flagellar systems, the primary single polar flagellum and a secondary system with one to five lateral flagellar filaments. Here, we identified a protein, MotL, which specifically regulates the activity of the lateral, but not the polar, flagellar motors in response to the c-di-GMP levels. MotL only consists of a single PilZ domain binding c-di-GMP, which is crucial for its function. Deletion and overproduction analyses revealed that MotL slows down the lateral flagella at elevated levels of c-di-GMP, and may speed up the lateral flagellar-mediated movement at low c-di-GMP concentrations. In vitro interaction studies hint at an interaction of MotL with the C-ring of the lateral flagellar motors. This study shows a differential c-di-GMP-dependent regulation of the two flagellar systems in a single species, and implicates that PilZ domain-only proteins can also act as molecular regulators to control the flagella-mediated motility in bacteria.
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Affiliation(s)
- Anna Pecina
- Department of Microbiology and Molecular Biology, Justus-Liebig-Universität Gießen, Giessen, Germany
| | - Meike Schwan
- Department of Microbiology and Molecular Biology, Justus-Liebig-Universität Gießen, Giessen, Germany
| | - Vitan Blagotinsek
- Department of Chemistry, SYNMIKRO Research Center, Philipps-University Marburg, Marburg, Germany
| | - Tim Rick
- Department of Microbiology and Molecular Biology, Justus-Liebig-Universität Gießen, Giessen, Germany
| | - Patrick Klüber
- Department of Microbiology and Molecular Biology, Justus-Liebig-Universität Gießen, Giessen, Germany
| | - Tabea Leonhard
- Department of Microbiology and Molecular Biology, Justus-Liebig-Universität Gießen, Giessen, Germany
| | - Gert Bange
- Department of Chemistry, SYNMIKRO Research Center, Philipps-University Marburg, Marburg, Germany
| | - Kai M Thormann
- Department of Microbiology and Molecular Biology, Justus-Liebig-Universität Gießen, Giessen, Germany
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CRP-Like Transcriptional Regulator MrpC Curbs c-di-GMP and 3',3'-cGAMP Nucleotide Levels during Development in Myxococcus xanthus. mBio 2021; 13:e0004422. [PMID: 35164555 PMCID: PMC8844925 DOI: 10.1128/mbio.00044-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Myxococcus xanthus has a nutrient-regulated biphasic life cycle forming predatory swarms in the presence of nutrients and spore-filled fruiting bodies in the absence of nutrients. The second messenger 3'-5', 3'-5 cyclic di-GMP (c-di-GMP) is essential during both stages of the life cycle; however, different enzymes involved in c-di-GMP synthesis and degradation as well as several c-di-GMP receptors are important during distinct life cycle stages. To address this stage specificity, we determined transcript levels using transcriptome sequencing (RNA-seq) and transcription start sites using Cappable sequencing (Cappable-seq) during growth and development genome wide. All 70 genes encoding c-di-GMP-associated proteins were expressed, with 28 upregulated and 10 downregulated during development. Specifically, the three genes encoding enzymatically active proteins with a stage-specific function were expressed stage specifically. By combining operon mapping with published chromatin immunoprecipitation sequencing (ChIP-seq) data for MrpC (M. Robinson, B. Son, D. Kroos, L. Kroos, BMC Genomics 15:1123, 2014, http://dx.doi.org/10.1186/1471-2164-15-1123), the cAMP receptor protein (CRP)-like master regulator of development, we identified nine developmentally regulated genes as regulated by MrpC. In particular, MrpC directly represses the expression of dmxB, which encodes the diguanylate cyclase DmxB that is essential for development and responsible for the c-di-GMP increase during development. Moreover, MrpC directly activates the transcription of pmxA, which encodes a bifunctional phosphodiesterase that degrades c-di-GMP and 3',3'-cGAMP in vitro and is essential for development. Thereby, MrpC regulates and curbs the cellular pools of c-di-GMP and 3',3'-cGAMP during development. We conclude that temporal regulation of the synthesis of proteins involved in c-di-GMP metabolism contributes to c-di-GMP signaling specificity. MrpC is important for this regulation, thereby being a key regulator of developmental cyclic di-nucleotide metabolism in M. xanthus. IMPORTANCE The second messenger c-di-GMP is important during both stages of the nutrient-regulated biphasic life cycle of Myxococcus xanthus with the formation of predatory swarms in the presence of nutrients and spore-filled fruiting bodies in the absence of nutrients. However, different enzymes involved in c-di-GMP synthesis and degradation are important during distinct life cycle stages. Here, we show that the three genes encoding enzymatically active proteins with a stage-specific function are expressed stage specifically. Moreover, we find that the master transcriptional regulator of development MrpC directly regulates the expression of dmxB, which encodes the diguanylate cyclase DmxB that is essential for development, and of pmxA, which encodes a bifunctional phosphodiesterase that degrades c-di-GMP and 3',3'-cGAMP in vitro and is essential for development. We conclude that temporal regulation of the synthesis of proteins involved in c-di-GMP metabolism contributes to c-di-GMP signaling specificity and that MrpC plays an important role in this regulation.
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Yin W, Xu S, Wang Y, Zhang Y, Chou SH, Galperin MY, He J. Ways to control harmful biofilms: prevention, inhibition, and eradication. Crit Rev Microbiol 2020; 47:57-78. [PMID: 33356690 DOI: 10.1080/1040841x.2020.1842325] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Biofilms are complex microbial architectures that encase microbial cells in a matrix comprising self-produced extracellular polymeric substances. Microorganisms living in biofilms are much more resistant to hostile environments than their planktonic counterparts and exhibit enhanced resistance against the microbicides. From the human perspective, biofilms can be classified into beneficial, neutral, and harmful. Harmful biofilms impact food safety, cause plant and animal diseases, and threaten medical fields, making it urgent to develop effective and robust strategies to control harmful biofilms. In this review, we discuss various strategies to control biofilm formation on infected tissues, implants, and medical devices. We classify the current strategies into three main categories: (i) changing the properties of susceptible surfaces to prevent biofilm formation; (ii) regulating signalling pathways to inhibit biofilm formation; (iii) applying external forces to eradicate the biofilm. We hope this review would motivate the development of innovative and effective strategies for controlling harmful biofilms.
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Affiliation(s)
- Wen Yin
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, PR China
| | - Siyang Xu
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, PR China
| | - Yiting Wang
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, PR China
| | - Yuling Zhang
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, PR China
| | - Shan-Ho Chou
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, PR China
| | - Michael Y Galperin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
| | - Jin He
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, PR China
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Collins AJ, Smith TJ, Sondermann H, O'Toole GA. From Input to Output: The Lap/c-di-GMP Biofilm Regulatory Circuit. Annu Rev Microbiol 2020; 74:607-631. [PMID: 32689917 DOI: 10.1146/annurev-micro-011520-094214] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Biofilms are the dominant bacterial lifestyle. The regulation of the formation and dispersal of bacterial biofilms has been the subject of study in many organisms. Over the last two decades, the mechanisms of Pseudomonas fluorescens biofilm formation and regulation have emerged as among the best understood of any bacterial biofilm system. Biofilm formation by P. fluorescens occurs through the localization of an adhesin, LapA, to the outer membrane via a variant of the classical type I secretion system. The decision between biofilm formation and dispersal is mediated by LapD, a c-di-GMP receptor, and LapG, a periplasmic protease, which together control whether LapA is retained or released from the cell surface. LapA localization is also controlled by a complex network of c-di-GMP-metabolizing enzymes. This review describes the current understanding of LapA-mediated biofilm formation by P. fluorescens and discusses several emerging models for the regulation and function of this adhesin.
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Affiliation(s)
- Alan J Collins
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.,Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755, USA;
| | - T Jarrod Smith
- Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755, USA; .,Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, USA
| | | | - George A O'Toole
- Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755, USA;
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17
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Petchiappan A, Naik SY, Chatterji D. Tracking the homeostasis of second messenger cyclic-di-GMP in bacteria. Biophys Rev 2020; 12:719-730. [PMID: 32060735 PMCID: PMC7311556 DOI: 10.1007/s12551-020-00636-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Accepted: 02/05/2020] [Indexed: 01/09/2023] Open
Abstract
Cyclic-di-GMP (c-di-GMP) is an important second messenger in bacteria which regulates the bacterial transition from motile to sessile phase and also plays a major role in processes such as cell division, exopolysaccharide synthesis, and biofilm formation. Due to its crucial role in dictating the bacterial phenotype, the synthesis and hydrolysis of c-di-GMP is tightly regulated via multiple mechanisms. Perturbing the c-di-GMP homeostasis affects bacterial growth and survival, so it is necessary to understand the underlying mechanisms related to c-di-GMP metabolism. Most techniques used for estimating the c-di-GMP concentration lack single-cell resolution and do not provide information about any heterogeneous distribution of c-di-GMP inside cells. In this review, we briefly discuss how the activity of c-di-GMP metabolising enzymes, particularly bifunctional proteins, is modulated to maintain c-di-GMP homeostasis. We further highlight how fluorescence-based methods aid in understanding the spatiotemporal regulation of c-di-GMP signalling. Finally, we discuss the blind spots in our understanding of second messenger signalling and outline how they can be addressed in the future.
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Affiliation(s)
| | - Sujay Y Naik
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Dipankar Chatterji
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
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18
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Ma GL, Chandra H, Liang ZX. Taming the flagellar motor of pseudomonads with a nucleotide messenger. Environ Microbiol 2020; 22:2496-2513. [PMID: 32329141 DOI: 10.1111/1462-2920.15036] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 04/20/2020] [Accepted: 04/21/2020] [Indexed: 01/11/2023]
Abstract
Pseudomonads rely on the flagellar motor to rotate a polar flagellum for swimming and swarming, and to sense surfaces for initiating the motile-to-sessile transition to adopt a surface-dwelling lifestyle. Deciphering the function and regulation of the flagellar motor is of paramount importance for understanding the behaviours of environmental and pathogenic pseudomonads. Recent studies disclosed the preeminent role played by the messenger c-di-GMP in controlling the real-time performance of the flagellar motor in pseudomonads. The studies revealed that c-di-GMP controls the dynamic exchange of flagellar stator units to regulate motor torque/speed and modulates the frequency of flagellar motor switching via the chemosensory signalling pathways. Apart from being a rotary motor, the flagellar motor is emerging as a mechanosensor that transduces surface-induced mechanical signals into an increase of cellular c-di-GMP concentration to initiate the cellular programs required for long-term colonization. Collectively, the studies generate long-awaited mechanistic insights into how c-di-GMP regulates bacterial motility and the motile-to-sessile transition. The new findings also raise the fundamental questions of how cellular c-di-GMP concentrations are dynamically coupled to flagellar output and the proton-motive force, and how c-di-GMP signalling is coordinated spatiotemporally to fine-tune flagellar response and the behaviour of pseudomonads in solutions and on surfaces.
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Affiliation(s)
- Guang-Lei Ma
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, S637551, Singapore
| | - Hartono Chandra
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, S637551, Singapore
| | - Zhao-Xun Liang
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, S637551, Singapore.,Singapore Centre for Environmental Life Sciences Engineering (SCELSE), Nanyang Technological University, 60 Nanyang Drive, S637551, Singapore
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19
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Del Medico L, Cerletti D, Schächle P, Christen M, Christen B. The type IV pilin PilA couples surface attachment and cell-cycle initiation in Caulobacter crescentus. Proc Natl Acad Sci U S A 2020; 117:9546-9553. [PMID: 32295877 PMCID: PMC7196804 DOI: 10.1073/pnas.1920143117] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Understanding how bacteria colonize surfaces and regulate cell-cycle progression in response to cellular adhesion is of fundamental importance. Here, we use transposon sequencing in conjunction with fluorescence resonance energy transfer (FRET) microscopy to uncover the molecular mechanism for how surface sensing drives cell-cycle initiation in Caulobacter crescentus We identify the type IV pilin protein PilA as the primary signaling input that couples surface contact to cell-cycle initiation via the second messenger cyclic di-GMP (c-di-GMP). Upon retraction of pili filaments, the monomeric pilin reservoir in the inner membrane is sensed by the 17-amino acid transmembrane helix of PilA to activate the PleC-PleD two-component signaling system, increase cellular c-di-GMP levels, and signal the onset of the cell cycle. We termed the PilA signaling sequence CIP for "cell-cycle initiating pilin" peptide. Addition of the chemically synthesized CIP peptide initiates cell-cycle progression and simultaneously inhibits surface attachment. The broad conservation of the type IV pili and their importance in pathogens for host colonization suggests that CIP peptide mimetics offer strategies to inhibit surface sensing, prevent biofilm formation and control persistent infections.
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Affiliation(s)
- Luca Del Medico
- Institute of Molecular Systems Biology, Department of Biology, Eidgenössische Technische HochschuleZürich, Zürich 8093, Switzerland
| | - Dario Cerletti
- Institute of Molecular Systems Biology, Department of Biology, Eidgenössische Technische HochschuleZürich, Zürich 8093, Switzerland
| | - Philipp Schächle
- Institute of Molecular Systems Biology, Department of Biology, Eidgenössische Technische HochschuleZürich, Zürich 8093, Switzerland
| | - Matthias Christen
- Institute of Molecular Systems Biology, Department of Biology, Eidgenössische Technische HochschuleZürich, Zürich 8093, Switzerland
| | - Beat Christen
- Institute of Molecular Systems Biology, Department of Biology, Eidgenössische Technische HochschuleZürich, Zürich 8093, Switzerland
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20
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CdbA is a DNA-binding protein and c-di-GMP receptor important for nucleoid organization and segregation in Myxococcus xanthus. Nat Commun 2020; 11:1791. [PMID: 32286293 PMCID: PMC7156744 DOI: 10.1038/s41467-020-15628-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 03/19/2020] [Indexed: 01/04/2023] Open
Abstract
Cyclic di-GMP (c-di-GMP) is a second messenger that modulates multiple responses to environmental and cellular signals in bacteria. Here we identify CdbA, a DNA-binding protein of the ribbon-helix-helix family that binds c-di-GMP in Myxococcus xanthus. CdbA is essential for viability, and its depletion causes defects in chromosome organization and segregation leading to a block in cell division. The protein binds to the M. xanthus genome at multiple sites, with moderate sequence specificity; however, its depletion causes only modest changes in transcription. The interactions of CdbA with c-di-GMP and DNA appear to be mutually exclusive and residue substitutions in CdbA regions important for c-di-GMP binding abolish binding to both c-di-GMP and DNA, rendering these protein variants non-functional in vivo. We propose that CdbA acts as a nucleoid-associated protein that contributes to chromosome organization and is modulated by c-di-GMP, thus revealing a link between c-di-GMP signaling and chromosome biology. The second messenger c-di-GMP modulates multiple responses to environmental and cellular signals in bacteria. Here, Skotnicka et al. identify a protein that binds c-di-GMP and contributes to chromosome organization and segregation in Myxococcus xanthus, with DNA-binding activity regulated by c-di-GMP.
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21
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Cyclic di-GMP Signaling in Bacillus subtilis Is Governed by Direct Interactions of Diguanylate Cyclases and Cognate Receptors. mBio 2020; 11:mBio.03122-19. [PMID: 32156823 PMCID: PMC7064775 DOI: 10.1128/mbio.03122-19] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Second messengers are free to diffuse through the cells and to activate all responsive elements. Cyclic di-GMP (c-di-GMP) signaling plays an important role in the determination of the life style transition between motility and sessility/biofilm formation but involves numerous distinct synthetases (diguanylate cyclases [DGCs]) or receptor pathways that appear to act in an independent manner. Using Bacillus subtilis as a model organism, we show that for two c-di-GMP pathways, DGCs and receptor molecules operate via direct interactions, where a synthesized dinucleotide appears to be directly used for the protein-protein interaction. We show that very few DGC molecules exist within cells; in the case of exopolysaccharide (EPS) formation via membrane protein DgcK, the DGC molecules act at a single site, setting up a single signaling pool within the cell membrane. Using single-molecule tracking, we show that the soluble DGC DgcP arrests at the cell membrane, interacting with its receptor, DgrA, which slows down motility. DgrA also directly binds to DgcK, showing that divergent as well as convergent modules exist in B. subtilis. Thus, local-pool signal transduction operates extremely efficiently and specifically. Bacillus subtilis contains two known cyclic di-GMP (c-di-GMP)-dependent receptors, YdaK and DgrA, as well as three diguanylate cyclases (DGCs): soluble DgcP and membrane-integral DgcK and DgcW. DgrA regulates motility, while YdaK is responsible for the formation of a putative exopolysaccharide, dependent on the activity of DgcK. Using single-molecule tracking, we show that a majority of DgcK molecules are statically positioned in the cell membrane but significantly less so in the absence of YdaK but more so upon overproduction of YdaK. The soluble domains of DgcK and of YdaK show a direct interaction in vitro, which depends on an intact I-site within the degenerated GGDEF domain of YdaK. These experiments suggest a direct handover of a second messenger at a single subcellular site. Interestingly, all three DGC proteins contribute toward downregulation of motility via the PilZ protein DgrA. Deletion of dgrA also affects the mobility of DgcK within the membrane and also that of DgcP, which arrests less often at the membrane in the absence of DgrA. Both, DgcK and DgcP interact with DgrA in vitro, showing that divergent as well as convergent direct connections exist between cyclases and their effector proteins. Automated determination of molecule numbers in live cells revealed that DgcK and DgcP are present at very low copy numbers of 6 or 25 per cell, respectively, such that for DgcK, a part of the cell population does not contain any DgcK molecule, rendering signaling via c-di-GMP extremely efficient.
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22
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Structural Conservation and Diversity of PilZ-Related Domains. J Bacteriol 2020; 202:JB.00664-19. [PMID: 31740493 DOI: 10.1128/jb.00664-19] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 11/12/2019] [Indexed: 01/13/2023] Open
Abstract
The widespread bacterial second messenger cyclic diguanylate (c-di-GMP) regulates a variety of processes, including protein secretion, motility, cell development, and biofilm formation. c-di-GMP-dependent responses are often mediated by its binding to the cytoplasmic receptors that contain the PilZ domain. Here, we present comparative structural and sequence analysis of various PilZ-related domains and describe three principal types of them: (i) the canonical PilZ domain, whose structure includes a six-stranded beta-barrel and a C-terminal alpha helix, (ii) an atypical PilZ domain that contains two extra alpha helices and forms stable tetramers, and (iii) divergent PilZ-related domains, which include the eponymous PilZ protein and PilZN (YcgR_N) and PilZNR (YcgR_2) domains. We refine the second c-di-GMP binding motif of PilZ as [D/N]hSXXG and show that the hydrophobic residue h of this motif interacts with a cluster of conserved hydrophobic residues, helping maintain the PilZ domain fold. We describe several novel PilZN-type domains that are fused to the canonical PilZ domains in specific taxa, such as spirochetes, actinobacteria, aquificae, cellulose-degrading clostridia, and deltaproteobacteria. We propose that the evolution of the three major groups of PilZ domains included (i) fusion of pilZ with other genes, which produced Alg44, cellulose synthase, and other multidomain proteins; (ii) insertion of an ∼200-bp fragment, which resulted in the formation of tetramer-forming PilZ proteins; and (iii) tandem duplication of pilZ genes, which led to the formation of PilZ dimers and YcgR-like proteins.IMPORTANCE c-di-GMP is a ubiquitous bacterial second messenger that regulates motility, biofilm formation, and virulence of many bacterial pathogens. The PilZ domain is a widespread c-di-GMP receptor that binds c-di-GMP through its RXXXR and [D/N]hSXXG motifs; some PilZ domains lack these motifs and are unable to bind c-di-GMP. We used structural and sequence analysis to assess the diversity of PilZ-related domains and define their common features. We show that the hydrophobic residue h in the second position of the second motif is highly conserved; it may serve as a readout for c-di-GMP binding. We describe three principal classes of PilZ-related domains, canonical, tetramer-forming, and divergent PilZ domains, and propose the evolutionary pathways that led to the emergence of these PilZ types.
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Differences in protein structural regions that impact functional specificity in GT2 family β-glucan synthases. PLoS One 2019; 14:e0224442. [PMID: 31665152 PMCID: PMC6821405 DOI: 10.1371/journal.pone.0224442] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Accepted: 10/14/2019] [Indexed: 12/16/2022] Open
Abstract
Most cell wall and secreted β-glucans are synthesised by the CAZy Glycosyltransferase 2 family (www.cazy.org), with different members catalysing the formation of (1,4)-β-, (1,3)-β-, or both (1,4)- and (1,3)-β-glucosidic linkages. Given the distinct physicochemical properties of each of the resultant β-glucans (cellulose, curdlan, and mixed linkage glucan, respectively) are crucial to their biological and biotechnological functions, there is a desire to understand the molecular evolution of synthesis and how linkage specificity is determined. With structural studies hamstrung by the instability of these proteins to solubilisation, we have utilised in silico techniques and the crystal structure for a bacterial cellulose synthase to further understand how these enzymes have evolved distinct functions. Sequence and phylogenetic analyses were performed to determine amino acid conservation, both family-wide and within each sub-family. Further structural analysis centred on comparison of a bacterial curdlan synthase homology model with the bacterial cellulose synthase crystal structure, with molecular dynamics simulations performed with their respective β-glucan products bound in the trans-membrane channel. Key residues that differentially interact with the different β-glucan chains and have sub-family-specific conservation were found to reside at the entrance of the trans-membrane channel. The linkage-specific catalytic activity of these enzymes and hence the type of β-glucan chain built is thus likely determined by the different interactions between the proteins and the first few glucose residues in the channel, which in turn dictates the position of the acceptor glucose. The sequence-function relationships for the bacterial β-glucan synthases pave the way for extending this understanding to other kingdoms, such as plants.
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24
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Kuan N, Yeh K. Arginine within a specific motif near the N-terminal of FimY is critical for the maximal production of type 1 fimbriae in Salmonella enterica serovar Typhimurium. Microbiologyopen 2019; 8:e00846. [PMID: 30993839 PMCID: PMC6741139 DOI: 10.1002/mbo3.846] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2019] [Revised: 03/16/2019] [Accepted: 03/18/2019] [Indexed: 01/31/2023] Open
Abstract
An important Salmonella serovar for both human and animals Salmonella Typhimurium possesses 13 gene clusters that have the potential to produce fimbrial structure, among which the type 1 fimbriae with the binding specificity to mannose residue is the most commonly found type. Six structural genes and five regulatory genes comprise the fim gene cluster that is responsible for the production of type 1 fimbriae in S. Typhimurium. The fimY gene encodes a positive regulator for type 1 fimbrial expression since a deletion in fimY abolished the production of fimbriae. The N-terminal portion of FimY contains amino acid residues that exhibit some similarity as those found in the proteins possessing the PilZ domain, which is engaged in cyclic di-GMP binding. A fimY allele that had a change from arginine to alanine at position 7 (R7A) or 7 and 11 (R7/11A) generated by site-directed mutagenesis in a 6 RRERH11 R motif near N-terminal, when cloned in pACYC184 and transformed into a fimY-deleted strain, decreased the expression of fimA and fimZ. The number of type 1 fimbriae in these two transformants was also less than those of the other transformants that contained different fimY alleles in pACYC184 when observed in electron microscopy. However, changing from arginine to alanine at position 11 (R11A) remained the same as the wild-type fimY allele. It is likely that the arginine at the 7th position of FimY is critical for its maximal activating activity upon fimZ. Another motif 83 DI85 SLWIEK91 G motif did not affect the function of FimY. Although FimY has the two aforementioned motifs, which contain some amino acids that are present within those of the PilZ domain proteins, secondary structure prediction analysis did not reveal that FimY has a conformation commonly observed in PilZ-like proteins. Therefore, FimY and PilZ domain proteins are not homologs. Further investigation for a detailed analysis of FimY is thus warranted.
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Affiliation(s)
- Nan‐Ling Kuan
- Biology DivisionAnimal Health Research InstituteNew Taipei CityTaiwan
- Department of Veterinary Medicine, School of Veterinary Medicine, College of Bioresources and AgricultureNational Taiwan UniversityTaipeiTaiwan
| | - Kuang‐Sheng Yeh
- Department of Veterinary Medicine, School of Veterinary Medicine, College of Bioresources and AgricultureNational Taiwan UniversityTaipeiTaiwan
- National Taiwan University Veterinary HospitalTaipeiTaiwan
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25
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Ethanol Decreases Pseudomonas aeruginosa Flagellar Motility through the Regulation of Flagellar Stators. J Bacteriol 2019; 201:JB.00285-19. [PMID: 31109994 DOI: 10.1128/jb.00285-19] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Accepted: 05/17/2019] [Indexed: 12/16/2022] Open
Abstract
Pseudomonas aeruginosa frequently encounters microbes that produce ethanol. Low concentrations of ethanol reduced P. aeruginosa swim zone area by up to 45% in soft agar. The reduction of swimming by ethanol required the flagellar motor proteins MotAB and two PilZ domain proteins (FlgZ and PilZ). PilY1 and the type 4 pilus alignment complex (comprising PilMNOP) were previously implicated in MotAB regulation in surface-associated cells and were required for ethanol-dependent motility repression. As FlgZ requires the second messenger bis-(3'-5')-cyclic dimeric GMP (c-di-GMP) to represses motility, we screened mutants lacking genes involved in c-di-GMP metabolism and found that mutants lacking diguanylate cyclases SadC and GcbA were less responsive to ethanol. The double mutant was resistant to its effects. As published previously, ethanol also represses swarming motility, and the same genes required for ethanol effects on swimming motility were required for its regulation of swarming. Microscopic analysis of single cells in soft agar revealed that ethanol effects on swim zone area correlated with ethanol effects on the portion of cells that paused or stopped during the time interval analyzed. Ethanol increased c-di-GMP in planktonic wild-type cells but not in ΔmotAB or ΔsadC ΔgcbA mutants, suggesting c-di-GMP plays a role in the response to ethanol in planktonic cells. We propose that ethanol produced by other microbes induces a regulated decrease in P. aeruginosa motility, thereby promoting P. aeruginosa colocalization with ethanol-producing microbes. Furthermore, some of the same factors involved in the response to surface contact are involved in the response to ethanol.IMPORTANCE Ethanol is an important biologically active molecule produced by many bacteria and fungi. It has also been identified as a potential marker for disease state in cystic fibrosis. In line with previous data showing that ethanol promotes biofilm formation by Pseudomonas aeruginosa, here we report that ethanol reduces swimming motility using some of the same proteins involved in surface sensing. We propose that these data may provide insight into how microbes, via their metabolic byproducts, can influence P. aeruginosa colocalization in the context of infection and in other polymicrobial settings.
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26
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Illa MP, Khandelwal M, Sharma CS. Modulated Dehydration for Enhanced Anodic Performance of Bacterial Cellulose derived Carbon Nanofibers. ChemistrySelect 2019. [DOI: 10.1002/slct.201901359] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Mani Pujitha Illa
- Department of Materials Science and Metallurgical EngineeringIndian Institute of Technology, Hyderabad, Kandi- 502285 Telangana India
- Creative & Advanced Research Based On Nanomaterial (CARBON) LaboratoryDepartment of Chemical EngineeringIndian Institute of Technology, Hyderabad, Kandi- 502285 Telangana India
| | - Mudrika Khandelwal
- Department of Materials Science and Metallurgical EngineeringIndian Institute of Technology, Hyderabad, Kandi- 502285 Telangana India
| | - Chandra S. Sharma
- Creative & Advanced Research Based On Nanomaterial (CARBON) LaboratoryDepartment of Chemical EngineeringIndian Institute of Technology, Hyderabad, Kandi- 502285 Telangana India
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Sun Y, Xie Z, Sui F, Liu X, Cheng W. Identification of Cbp1, a c-di-GMP Binding Chemoreceptor in Azorhizobium caulinodans ORS571 Involved in Chemotaxis and Nodulation of the Host Plant. Front Microbiol 2019; 10:638. [PMID: 31001223 PMCID: PMC6454048 DOI: 10.3389/fmicb.2019.00638] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 03/13/2019] [Indexed: 01/10/2023] Open
Abstract
Cbp1, a chemoreceptor containing a PilZ domain was identified in Azorhizobium caulinodans ORS571, a nitrogen-fixing free-living soil bacterium that induces nodule formation in both the roots and stems of the host legume Sesbania rostrata. Chemoreceptors are responsible for sensing signals in the chemotaxis pathway, which guides motile bacteria to beneficial niches and plays an important role in the establishment of rhizobia-legume symbiosis. PilZ domain proteins are known to bind the second messenger c-di-GMP, an important regulator of motility, biofilm formation and virulence. Cbp1 was shown to bind c-di-GMP through the conserved RxxxR motif of its PilZ domain. A mutant strain carrying a cbp1 deletion was impaired in chemotaxis, a feature that could be restored by genetic complementation. Compared with the wild type strain, the Δcbp1 mutant displayed enhanced aggregation and biofilm formation. The Δcbp1 mutant induced functional nodules when inoculated individually. However, the Δcbp1 mutant was less competitive than the wild type in competitive root colonization and nodulation. These data are in agreement with the hypothesis that the c-di-GMP binding chemoreceptor Cbp1 in A. caulinodans is involved in chemotaxis and nodulation.
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Affiliation(s)
- Yu Sun
- Key Laboratory of Coastal Biology and Bioresource Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Zhihong Xie
- Key Laboratory of Coastal Biology and Bioresource Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, China.,Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
| | - Fu Sui
- Key Laboratory of Coastal Biology and Bioresource Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Xiaolin Liu
- Key Laboratory of Coastal Biology and Bioresource Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Wuzeng Cheng
- Shandong Huibang Bohai Agriculture Development Limited Company, Dongying, China
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The GGDEF Domain of the Phosphodiesterase PdeB in Shewanella putrefaciens Mediates Recruitment by the Polar Landmark Protein HubP. J Bacteriol 2019; 201:JB.00534-18. [PMID: 30670544 DOI: 10.1128/jb.00534-18] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 12/21/2018] [Indexed: 12/13/2022] Open
Abstract
Bacteria commonly exhibit a high degree of cellular organization and polarity which affect many vital processes such as replication, cell division, and motility. In Shewanella and other bacteria, HubP is a polar marker protein which is involved in proper chromosome segregation, placement of the chemotaxis system, and various aspects of pilus- and flagellum-mediated motility. Here, we show that HubP also recruits a transmembrane multidomain protein, PdeB, to the flagellated cell pole. PdeB is an active phosphodiesterase and degrades the second messenger c-di-GMP. In Shewanella putrefaciens, PdeB affects both the polar and the lateral flagellar systems at the level of function and/or transcription in response to environmental medium conditions. Mutant analysis on fluorescently labeled PdeB indicated that a diguanylate cyclase (GGDEF) domain in PdeB is strictly required for HubP-dependent localization. Bacterial two-hybrid and in vitro interaction studies on purified proteins strongly indicate that this GGDEF domain of PdeB directly interacts with the C-terminal FimV domain of HubP. Polar localization of PdeB occurs late during the cell cycle after cell division and separation and is not dependent on medium conditions. In vitro activity measurements did not reveal a difference in PdeB phosphodiesterase activities in the presence or absence of the HubP FimV domain. We hypothesize that recruitment of PdeB to the flagellated pole by HubP may create an asymmetry of c-di-GMP levels between mother and daughter cells and may assist in organization of c-di-GMP-dependent regulation within the cell.IMPORTANCE c-di-GMP-dependent signaling affects a range of processes in many bacterial species. Most bacteria harbor a plethora of proteins with domains which are potentially involved in synthesis and breakdown of c-di-GMP. A potential mechanism to elicit an appropriate c-di-GMP-dependent response is to organize the corresponding proteins in a spatiotemporal fashion. Here, we show that a major contributor to c-di-GMP levels and flagellum-mediated swimming in Shewanella, PdeB, is recruited to the flagellated cell pole by the polar marker protein HubP. Polar recruitment involves a direct interaction between HubP and a GGDEF domain in PdeB, demonstrating a novel mechanism of polar targeting by the widely conserved HubP/FimV polar marker.
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Moya-Beltrán A, Rojas-Villalobos C, Díaz M, Guiliani N, Quatrini R, Castro M. Nucleotide Second Messenger-Based Signaling in Extreme Acidophiles of the Acidithiobacillus Species Complex: Partition Between the Core and Variable Gene Complements. Front Microbiol 2019; 10:381. [PMID: 30899248 PMCID: PMC6416229 DOI: 10.3389/fmicb.2019.00381] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 02/13/2019] [Indexed: 12/24/2022] Open
Abstract
Cyclic and linear nucleotides are key elements of the signal transduction networks linking perception of the environment to specific cellular behavior of prokaryotes. These molecular mechanisms are particularly important in bacteria exposed to different, and frequently simultaneous, types of extreme conditions. This is the case in acidithiobacilli, a group of extremophilic bacteria thriving in highly acidic biotopes, that must also cope with significant variations in temperature, osmotic potentials and concentrations of various transition metals and metalloids. Environmental cues sensed by bacteria are transduced into differential levels of nucleotides acting as intracellular second messengers, promoting the activation or inhibition of target components and eliciting different output phenotypes. Cyclic (c) di-GMP, one of the most common bacterial second messengers, plays a key role in lifestyle changes in many bacteria, including acidithiobacilli. The presence of functional c-di-GMP-dependent signal transduction pathways in representative strains of the best-known linages of this species complex has been reported. However, a comprehensive panorama of the c-di-GMP modulated networks, the cognate input signals and output responses, are still missing for this group of extremophiles. Moreover, little fundamental understanding has been gathered for other nucleotides acting as second messengers. Taking advantage of the increasing number of sequenced genomes of the taxon, here we address the challenge of disentangling the nucleotide-driven signal transduction pathways in this group of polyextremophiles using comparative genomic tools and strategies. Results indicate that the acidithiobacilli possess all the genetic elements required to establish functional transduction pathways based in three different nucleotide-second messengers: (p)ppGpp, cyclic AMP (cAMP), and c-di-GMP. The elements related with the metabolism and transduction of (p)ppGpp and cAMP appear highly conserved, integrating signals related with nutrient starvation and polyphosphate metabolism, respectively. In contrast, c-di-GMP networks appear diverse and complex, differing both at the species and strain levels. Molecular elements of c-di-GMP metabolism and transduction were mostly found scattered along the flexible genome of the acidithiobacilli, allowing the identification of probable control modules that could be critical for substrate colonization, biofilm development and intercellular interactions. These may ultimately convey increased endurance to environmental stress and increased potential for gene sharing and adaptation to changing conditions.
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Affiliation(s)
- Ana Moya-Beltrán
- Microbial Ecophysiology Laboratory, Fundación Ciencia & Vida, Santiago, Chile.,Facultad de Ciencias de la Vida, Universidad Andrés Bello, Santiago, Chile.,Millennium Nucleus in the Biology of Intestinal Microbiota, Santiago, Chile
| | - Camila Rojas-Villalobos
- Microbial Ecophysiology Laboratory, Fundación Ciencia & Vida, Santiago, Chile.,Millennium Nucleus in the Biology of Intestinal Microbiota, Santiago, Chile
| | - Mauricio Díaz
- Laboratorio de Comunicación Bacteriana, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Nicolás Guiliani
- Laboratorio de Comunicación Bacteriana, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Raquel Quatrini
- Microbial Ecophysiology Laboratory, Fundación Ciencia & Vida, Santiago, Chile.,Millennium Nucleus in the Biology of Intestinal Microbiota, Santiago, Chile
| | - Matías Castro
- Microbial Ecophysiology Laboratory, Fundación Ciencia & Vida, Santiago, Chile.,Millennium Nucleus in the Biology of Intestinal Microbiota, Santiago, Chile
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Emerging paradigms for PilZ domain-mediated C-di-GMP signaling. Biochem Soc Trans 2019; 47:381-388. [PMID: 30710060 DOI: 10.1042/bst20180543] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 01/02/2019] [Accepted: 01/08/2019] [Indexed: 11/17/2022]
Abstract
PilZ domain-containing proteins constitute a large family of bacterial signaling proteins. As a widely distributed protein domain for the binding of the second messenger c-di-GMP, the canonical PilZ domain contains a set of motifs that define the binding site for c-di-GMP and an allosteric switch for propagating local conformational changes. Here, we summarize some new insights gathered from recent studies on the commonly occurring single-domain PilZ proteins, YcgR-like proteins and PilZ domain-containing cellulose synthases. The studies collectively illuminate how PilZ domains function as cis- or trans-regulatory domains that enable c-di-GMP to control the activity of its cellular targets. Overall, the review highlights the diverse protein structure, biological function and regulatory mechanism of PilZ domain-containing proteins, as well as the challenge of deciphering the function and mechanism of orphan PilZ proteins.
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Phosphodiesterase EdpX1 Promotes Xanthomonas oryzae pv. oryzae Virulence, Exopolysaccharide Production, and Biofilm Formation. Appl Environ Microbiol 2018; 84:AEM.01717-18. [PMID: 30217836 DOI: 10.1128/aem.01717-18] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 09/06/2018] [Indexed: 12/22/2022] Open
Abstract
In Xanthomonas oryzae pv. oryzae, the bacterial blight pathogen of rice, there are over 20 genes encoding GGDEF, EAL, and HD-GYP domains, which are potentially involved in the metabolism of second messenger c-di-GMP. In this study, we focused on the characterization of an EAL domain protein, EdpX1. Deletion of the edpX1 gene resulted in a 2-fold increase in the intracellular c-di-GMP levels, which were restored to the wild-type levels in the complemented ΔedpX1(pB-edpX1) strain, demonstrating that EdpX1 is an active phosphodiesterase (PDE) in X. oryzae pv. oryzae. In addition, colorimetric assays further confirmed the PDE activity of EdpX1 by showing that the E153A mutation at the EAL motif strongly reduced its activity. Virulence assays on the leaves of susceptible rice showed that the ΔedpX1 mutant was severely impaired in causing disease symptoms. In trans expression of wild-type edpX1, but not edpX1 E153A, was able to complement the weakened virulence phenotype. These results indicated that an active EAL domain is required for EdpX1 to regulate the virulence of X. oryzae pv. oryzae. We then demonstrated that the ΔedpX1 mutant was defective in secreting exopolysaccharide (EPS) and forming biofilms. The expression of edpX1 in the ΔedpX1 mutant, but not edpX1 E153A, restored the defective phenotypes to near-wild-type levels. In addition, we observed that EdpX1-green fluorescent protein (EdpX1-GFP) exhibited multiple subcellular localization foci, and this pattern was dependent on its transmembrane (TM) region, which did not seem to directly contribute to the regulatory function of EdpX1. Thus, we concluded that EdpX1 exhibits PDE activity to control c-di-GMP levels, and its EAL domain is necessary and sufficient for its regulation of virulence in X. oryzae pv. oryzae.IMPORTANCE Bacteria utilize c-di-GMP as a second messenger to regulate various biological functions. The synthesis and degradation of c-di-GMP are catalyzed by GGDEF domains and an EAL or HD-GYP domain, respectively. Multiple genes encoding these domains are often found in one bacterial strain. For example, in the genome of X. oryzae pv. oryzae PXO99A, 26 genes encoding proteins containing these domains were identified. Therefore, to fully appreciate the complexity and specificity of c-di-GMP signaling in X. oryzae pv. oryzae, the enzymatic activities and regulatory functions of each GGDEF, EAL, and HD-GYP domain protein need to be elucidated. In this study, we showed that the EAL domain protein EdpX1 is a major PDE to regulate diverse virulence phenotypes through the c-di-GMP signaling pathway.
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Foletti C, Kramer RA, Mauser H, Jenal U, Bleicher KH, Wennemers H. Functionalized Proline-Rich Peptides Bind the Bacterial Second Messenger c-di-GMP. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201801845] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Carlotta Foletti
- Laboratorium für Organische Chemie, D-CHAB; ETH Zürich; Vladimir-Prelog-Weg 3 8093 Zürich Switzerland
| | - Rolf A. Kramer
- Laboratorium für Organische Chemie, D-CHAB; ETH Zürich; Vladimir-Prelog-Weg 3 8093 Zürich Switzerland
| | - Harald Mauser
- Discovery Chemistry, PRCB; F. Hoffmann-La Roche AG; Grenzacherstr. 124 4070 Basel Switzerland
| | - Urs Jenal
- Biozentrum; University of Basel; Klingelbergstr, 50/70 4056 Basel Switzerland
| | - Konrad H. Bleicher
- Discovery Chemistry, PRCB; F. Hoffmann-La Roche AG; Grenzacherstr. 124 4070 Basel Switzerland
| | - Helma Wennemers
- Laboratorium für Organische Chemie, D-CHAB; ETH Zürich; Vladimir-Prelog-Weg 3 8093 Zürich Switzerland
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34
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Foletti C, Kramer RA, Mauser H, Jenal U, Bleicher KH, Wennemers H. Functionalized Proline-Rich Peptides Bind the Bacterial Second Messenger c-di-GMP. Angew Chem Int Ed Engl 2018. [PMID: 29521445 DOI: 10.1002/anie.201801845] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
c-di-GMP is an attractive target in the fight against bacterial infections since it is a near ubiquitous second messenger that regulates important cellular processes of pathogens, including biofilm formation and virulence. Screening of a combinatorial peptide library enabled the identification of the proline-rich tetrapeptide Gup-Gup-Nap-Arg, which binds c-di-GMP selectively over other nucleotides in water. Computational and CD spectroscopic studies provided a possible binding mode of the complex and enabled the design of a pentapeptide with even higher binding strength towards c-di-GMP. Biological studies showed that the tetrapeptide inhibits biofilm growth by the opportunistic pathogen P. aeruginosa.
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Affiliation(s)
- Carlotta Foletti
- Laboratorium für Organische Chemie, D-CHAB, ETH Zürich, Vladimir-Prelog-Weg 3, 8093, Zürich, Switzerland
| | - Rolf A Kramer
- Laboratorium für Organische Chemie, D-CHAB, ETH Zürich, Vladimir-Prelog-Weg 3, 8093, Zürich, Switzerland
| | - Harald Mauser
- Discovery Chemistry, PRCB, F. Hoffmann-La Roche AG, Grenzacherstr. 124, 4070, Basel, Switzerland
| | - Urs Jenal
- Biozentrum, University of Basel, Klingelbergstr, 50/70, 4056, Basel, Switzerland
| | - Konrad H Bleicher
- Discovery Chemistry, PRCB, F. Hoffmann-La Roche AG, Grenzacherstr. 124, 4070, Basel, Switzerland
| | - Helma Wennemers
- Laboratorium für Organische Chemie, D-CHAB, ETH Zürich, Vladimir-Prelog-Weg 3, 8093, Zürich, Switzerland
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35
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Opoku-Temeng C, Sintim HO. Targeting c-di-GMP Signaling, Biofilm Formation, and Bacterial Motility with Small Molecules. Methods Mol Biol 2018; 1657:419-430. [PMID: 28889311 DOI: 10.1007/978-1-4939-7240-1_31] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Bacteria possess several signaling molecules that regulate distinct phenotypes. Cyclic di-GMP (c-di-GMP) has emerged as a ubiquitous second messenger that regulates bacterial virulence, cell cycle, motility, and biofilm formation. The link between c-di-GMP signaling and biofilm formation affords novel strategies for treatment of biofilm-associated infections, which is a major public health problem. The complex c-di-GMP signaling pathway creates a hurdle in the development of small molecule modulators. Nonetheless, some progress has been made in this regard and inhibitors of c-di-GMP metabolizing enzymes that affect biofilm formation and motility have been documented. Herein we discuss the components of c-di-GMP signaling, their correlation with biofilm formation as well as motility and reported small molecule inhibitors of c-di-GMP signaling.
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Affiliation(s)
- Clement Opoku-Temeng
- Purdue Institute for Drug Discovery, Purdue University, 500 Oval Drive, West Lafayette, IN, 47907, USA.,Biochemistry Graduate Program, University of Maryland, College Park, MD, 20742, USA.,Department of Chemistry, Center for Drug Discovery, Purdue University, West Lafayette, IN, 47907, USA
| | - Herman O Sintim
- Purdue Institute for Drug Discovery, Purdue University, 500 Oval Drive, West Lafayette, IN, 47907, USA. .,Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA. .,Purdue Institute of Inflammation, Immunology and Infectious Disease, West Lafayette, IN, 47907, USA.
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36
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Tlr1612 is the major repressor of cell aggregation in the light-color-dependent c-di-GMP signaling network of Thermosynechococcus vulcanus. Sci Rep 2018; 8:5338. [PMID: 29593349 PMCID: PMC5871770 DOI: 10.1038/s41598-018-23628-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Accepted: 03/16/2018] [Indexed: 11/08/2022] Open
Abstract
Cyclic diguanylate (c-di-GMP) is a bacterial second messenger involved in sessile/motile lifestyle transitions. We previously reported that c-di-GMP is a crucial inducer of cell aggregation of the cyanobacterium Thermosynechococcus vulcanus. The three cooperating cyanobacteriochrome photoreceptors (SesA/B/C) regulate cell aggregation in a light color-dependent manner by synthesizing/degrading c-di-GMP. Although a variety of c-di-GMP signaling proteins are encoded in cyanobacterial genomes, how c-di-GMP signaling networks are organized remains elusive. Here we experimentally demonstrate that the cellulose synthase Tll0007, which is essential for cell aggregation, binds c-di-GMP although the affinity is low (Kd = 63.9 ± 5.1 µM). We also show that SesA-the main trigger of cell aggregation-is subject to strict product feedback inhibition (IC50 = 1.07 ± 0.13 µM). These results suggest that SesA-produced c-di-GMP may not directly bind to Tll0007. We therefore systematically analyzed all 10 of the genes encoding proteins containing a c-di-GMP synthesis/degradation domain. We identified Tlr1612, harboring both domains, as the major repressor of cell aggregation under the repressing teal-green light irradiation. tlr1612 acts downstream of sesA and is not regulated transcriptionally by light color, suggesting that Tlr1612 may be involved in c-di-GMP amplification in the signaling cascade. Post-transcriptional control is likely crucial for the light-regulated c-di-GMP signaling.
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Wang F, He Q, Su K, Gao F, Huang Y, Lin Z, Zhu D, Gu L. The PilZ domain of MrkH represents a novel DNA binding motif. Protein Cell 2018; 7:766-772. [PMID: 27650952 PMCID: PMC5055493 DOI: 10.1007/s13238-016-0317-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Affiliation(s)
- Feng Wang
- State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100, China
| | - Qing He
- State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100, China
| | - Kaixuan Su
- State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100, China
| | - Fei Gao
- State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100, China
| | - Yan Huang
- State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100, China
| | - Zong Lin
- Department of Biotechnology and Biomedicine, Yangtze Delta Region Institute of Tsinghua University, Jiaxing, 314006, China
| | - Deyu Zhu
- State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100, China.
| | - Lichuan Gu
- State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100, China.
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38
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Gründling A, Lee VT. Old concepts, new molecules and current approaches applied to the bacterial nucleotide signalling field. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0503. [PMID: 27672152 PMCID: PMC5052745 DOI: 10.1098/rstb.2015.0503] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/07/2016] [Indexed: 12/25/2022] Open
Abstract
Signalling nucleotides are key molecules that help bacteria to rapidly coordinate cellular pathways and adapt to changes in their environment. During the past 10 years, the nucleotide signalling field has seen much excitement, as several new signalling nucleotides have been discovered in both eukaryotic and bacterial cells. The fields have since advanced quickly, aided by the development of important tools such as the synthesis of modified nucleotides, which, combined with sensitive mass spectrometry methods, allowed for the rapid identification of specific receptor proteins along with other novel genome-wide screening methods. In this review, we describe the principle concepts of nucleotide signalling networks and summarize the recent work that led to the discovery of the novel signalling nucleotides. We also highlight current approaches applied to the research in the field as well as resources and methodological advances aiding in a rapid identification of nucleotide-specific receptor proteins. This article is part of the themed issue ‘The new bacteriology’.
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Affiliation(s)
- Angelika Gründling
- Section of Microbiology and MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London SW7 2AZ, UK
| | - Vincent T Lee
- Department of Cell Biology and Molecular Genetics, University of Maryland at College Park, College Park, MD 20742, USA
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Yan XF, Xin L, Yen JT, Zeng Y, Jin S, Cheang QW, Fong RACY, Chiam KH, Liang ZX, Gao YG. Structural analyses unravel the molecular mechanism of cyclic di-GMP regulation of bacterial chemotaxis via a PilZ adaptor protein. J Biol Chem 2017; 293:100-111. [PMID: 29146598 DOI: 10.1074/jbc.m117.815704] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 11/10/2017] [Indexed: 01/09/2023] Open
Abstract
The bacterial second messenger cyclic di-GMP (c-di-GMP) has emerged as a prominent mediator of bacterial physiology, motility, and pathogenicity. c-di-GMP often regulates the function of its protein targets through a unique mechanism that involves a discrete PilZ adaptor protein. However, the molecular mechanism for PilZ protein-mediated protein regulation is unclear. Here, we present the structure of the PilZ adaptor protein MapZ cocrystallized in complex with c-di-GMP and its protein target CheR1, a chemotaxis-regulating methyltransferase in Pseudomonas aeruginosa This cocrystal structure, together with the structure of free CheR1, revealed that the binding of c-di-GMP induces dramatic structural changes in MapZ that are crucial for CheR1 binding. Importantly, we found that restructuring and repositioning of two C-terminal helices enable MapZ to disrupt the CheR1 active site by dislodging a structural domain. The crystallographic observations are reinforced by protein-protein binding and single cell-based flagellar motor switching analyses. Our studies further suggest that the regulation of chemotaxis by c-di-GMP through MapZ orthologs/homologs is widespread in proteobacteria and that the use of allosterically regulated C-terminal motifs could be a common mechanism for PilZ adaptor proteins. Together, the findings provide detailed structural insights into how c-di-GMP controls the activity of an enzyme target indirectly through a PilZ adaptor protein.
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Affiliation(s)
- Xin-Fu Yan
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore; NTU Institute of Structural Biology, Nanyang Technological University, 59 Nanyang Drive, Singapore 639798, Singapore
| | - Lingyi Xin
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Jackie Tan Yen
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore; NTU Institute of Structural Biology, Nanyang Technological University, 59 Nanyang Drive, Singapore 639798, Singapore
| | - Yukai Zeng
- Bioinformatics Institute (A*STAR), 30 Biopolis Street, Number 07-01, S138671 Singapore, Singapore
| | - Shengyang Jin
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore; NTU Institute of Structural Biology, Nanyang Technological University, 59 Nanyang Drive, Singapore 639798, Singapore
| | - Qing Wei Cheang
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | | | - Keng-Hwee Chiam
- Bioinformatics Institute (A*STAR), 30 Biopolis Street, Number 07-01, S138671 Singapore, Singapore
| | - Zhao-Xun Liang
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
| | - Yong-Gui Gao
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore; NTU Institute of Structural Biology, Nanyang Technological University, 59 Nanyang Drive, Singapore 639798, Singapore; Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), 61 Biopolis Drive, Singapore 138673, Singapore.
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Nesper J, Hug I, Kato S, Hee CS, Habazettl JM, Manfredi P, Grzesiek S, Schirmer T, Emonet T, Jenal U. Cyclic di-GMP differentially tunes a bacterial flagellar motor through a novel class of CheY-like regulators. eLife 2017; 6:28842. [PMID: 29091032 PMCID: PMC5677366 DOI: 10.7554/elife.28842] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Accepted: 10/28/2017] [Indexed: 12/22/2022] Open
Abstract
The flagellar motor is a sophisticated rotary machine facilitating locomotion and signal transduction. Owing to its important role in bacterial behavior, its assembly and activity are tightly regulated. For example, chemotaxis relies on a sensory pathway coupling chemical information to rotational bias of the motor through phosphorylation of the motor switch protein CheY. Using a chemical proteomics approach, we identified a novel family of CheY-like (Cle) proteins in Caulobacter crescentus, which tune flagellar activity in response to binding of the second messenger c-di-GMP to a C-terminal extension. In their c-di-GMP bound conformation Cle proteins interact with the flagellar switch to control motor activity. We show that individual Cle proteins have adopted discrete cellular functions by interfering with chemotaxis and by promoting rapid surface attachment of motile cells. This study broadens the regulatory versatility of bacterial motors and unfolds mechanisms that tie motor activity to mechanical cues and bacterial surface adaptation.
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Affiliation(s)
- Jutta Nesper
- Focal Area of Infection Biology, Biozentrum of the University of Basel, Basel, Switzerland
| | - Isabelle Hug
- Focal Area of Infection Biology, Biozentrum of the University of Basel, Basel, Switzerland
| | - Setsu Kato
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, United States
| | - Chee-Seng Hee
- Focal Area of Structural Biology and Biophysics, Biozentrum of the University of Basel, Basel, Switzerland
| | - Judith Maria Habazettl
- Focal Area of Structural Biology and Biophysics, Biozentrum of the University of Basel, Basel, Switzerland
| | - Pablo Manfredi
- Focal Area of Infection Biology, Biozentrum of the University of Basel, Basel, Switzerland
| | - Stephan Grzesiek
- Focal Area of Structural Biology and Biophysics, Biozentrum of the University of Basel, Basel, Switzerland
| | - Tilman Schirmer
- Focal Area of Structural Biology and Biophysics, Biozentrum of the University of Basel, Basel, Switzerland
| | - Thierry Emonet
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, United States.,Department of Physics, Yale University, New Haven, United States
| | - Urs Jenal
- Focal Area of Infection Biology, Biozentrum of the University of Basel, Basel, Switzerland
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41
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Chiu BK, Kato S, McAllister SM, Field EK, Chan CS. Novel Pelagic Iron-Oxidizing Zetaproteobacteria from the Chesapeake Bay Oxic-Anoxic Transition Zone. Front Microbiol 2017; 8:1280. [PMID: 28769885 PMCID: PMC5513912 DOI: 10.3389/fmicb.2017.01280] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 06/26/2017] [Indexed: 01/11/2023] Open
Abstract
Chemolithotrophic iron-oxidizing bacteria (FeOB) could theoretically inhabit any environment where Fe(II) and O2 (or nitrate) coexist. Until recently, marine Fe-oxidizing Zetaproteobacteria had primarily been observed in benthic and subsurface settings, but not redox-stratified water columns. This may be due to the challenges that a pelagic lifestyle would pose for Zetaproteobacteria, given low Fe(II) concentrations in modern marine waters and the possibility that Fe oxyhydroxide biominerals could cause cells to sink. However, we recently cultivated Zetaproteobacteria from the Chesapeake Bay oxic–anoxic transition zone, suggesting that they can survive and contribute to biogeochemical cycling in a stratified estuary. Here we describe the isolation, characterization, and genomes of two new species, Mariprofundus aestuarium CP-5 and Mariprofundus ferrinatatus CP-8, which are the first Zetaproteobacteria isolates from a pelagic environment. We looked for adaptations enabling strains CP-5 and CP-8 to overcome the challenges of living in a low Fe redoxcline with frequent O2 fluctuations due to tidal mixing. We found that the CP strains produce distinctive dreadlock-like Fe oxyhydroxide structures that are easily shed, which would help cells maintain suspension in the water column. These oxides are by-products of Fe(II) oxidation, likely catalyzed by the putative Fe(II) oxidase encoded by the cyc2 gene, present in both CP-5 and CP-8 genomes; the consistent presence of cyc2 in all microaerophilic FeOB and other FeOB genomes supports its putative role in Fe(II) oxidation. The CP strains also have two gene clusters associated with biofilm formation (Wsp system and the Widespread Colonization Island) that are absent or rare in other Zetaproteobacteria. We propose that biofilm formation enables the CP strains to attach to FeS particles and form flocs, an advantageous strategy for scavenging Fe(II) and developing low [O2] microenvironments within more oxygenated waters. However, the CP strains appear to be adapted to somewhat higher concentrations of O2, as indicated by the presence of genes encoding aa3-type cytochrome c oxidases, but not the cbb3-type found in all other Zetaproteobacteria isolate genomes. Overall, our results reveal adaptations for life in a physically dynamic, low Fe(II) water column, suggesting that niche-specific strategies can enable Zetaproteobacteria to live in any environment with Fe(II).
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Affiliation(s)
- Beverly K Chiu
- Department of Geological Sciences, University of Delaware, NewarkDE, United States
| | - Shingo Kato
- Project Team for Development of New-Generation Research Protocol for Submarine Resources, Japan Agency for Marine-Earth Science and TechnologyKanagawa, Japan
| | - Sean M McAllister
- School of Marine Science and Policy, University of Delaware, NewarkDE, United States
| | - Erin K Field
- Department of Biology, East Carolina University, GreenvilleNC, United States
| | - Clara S Chan
- Department of Geological Sciences, University of Delaware, NewarkDE, United States.,School of Marine Science and Policy, University of Delaware, NewarkDE, United States
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42
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Abstract
Cyclic diguanylate (c-di-GMP) is a near universal signaling molecule produced by diguanylate cyclases that can direct a variety of bacterial behaviors. A major area of research over the last several years has been aimed at understanding how a cell with dozens of diguanylate cyclases can deploy a given subset of them to produce a desired phenotypic outcome without undesired cross talk between c-di-GMP-dependent systems. Several models have been put forward to address this question, including specificity of cyclase activation, tuned binding constants of effector proteins, and physical interaction between cyclases and effectors. Additionally, recent evidence has suggested that there may be a link between the catalytic state of a cyclase and its physical contact with an effector. This review highlights several key studies, examines the proposed global and local models of c-di-GMP signaling specificity in bacteria, and attempts to identify the most fruitful steps that can be taken to better understand how dynamic networks of sibling cyclases and effector proteins result in sensible outputs that govern cellular behavior.
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Affiliation(s)
- Kurt M Dahlstrom
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755;
| | - George A O'Toole
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755;
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43
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Velmourougane K, Prasanna R, Saxena AK. Agriculturally important microbial biofilms: Present status and future prospects. J Basic Microbiol 2017; 57:548-573. [PMID: 28407275 DOI: 10.1002/jobm.201700046] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 03/17/2017] [Accepted: 03/19/2017] [Indexed: 11/07/2022]
Abstract
Microbial biofilms are a fascinating subject, due to their significant roles in the environment, industry, and health. Advances in biochemical and molecular techniques have helped in enhancing our understanding of biofilm structure and development. In the past, research on biofilms primarily focussed on health and industrial sectors; however, lately, biofilms in agriculture are gaining attention due to their immense potential in crop production, protection, and improvement. Biofilms play an important role in colonization of surfaces - soil, roots, or shoots of plants and enable proliferation in the desired niche, besides enhancing soil fertility. Although reports are available on microbial biofilms in general; scanty information is published on biofilm formation by agriculturally important microorganisms (bacteria, fungi, bacterial-fungal) and their interactions in the ecosystem. Better understanding of agriculturally important bacterial-fungal communities and their interactions can have several implications on climate change, soil quality, plant nutrition, plant protection, bioremediation, etc. Understanding the factors and genes involved in biofilm formation will help to develop more effective strategies for sustainable and environment-friendly agriculture. The present review brings together fundamental aspects of biofilms, in relation to their formation, regulatory mechanisms, genes involved, and their application in different fields, with special emphasis on agriculturally important microbial biofilms.
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Affiliation(s)
| | - Radha Prasanna
- Division of Microbiology, ICAR-Indian Agricultural Research Institute, New Delhi, India
| | - Anil Kumar Saxena
- ICAR-National Bureau of Agriculturally Important Microorganisms (NBAIM), Mau Nath Bhanjan, Uttar Pradesh, India
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44
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Hallez R, Delaby M, Sanselicio S, Viollier PH. Hit the right spots: cell cycle control by phosphorylated guanosines in alphaproteobacteria. Nat Rev Microbiol 2017; 15:137-148. [PMID: 28138140 DOI: 10.1038/nrmicro.2016.183] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The class Alphaproteobacteria includes Gram-negative free-living, symbiotic and obligate intracellular bacteria, as well as important plant, animal and human pathogens. Recent work has established the key antagonistic roles that phosphorylated guanosines, cyclic-di-GMP (c-di-GMP) and the alarmones guanosine tetraphosphate and guanosine pentaphosphate (collectively referred to as (p)ppGpp), have in the regulation of the cell cycle in these bacteria. In this Review, we discuss the insights that have been gained into the regulation of the initiation of DNA replication and cytokinesis by these second messengers, with a particular focus on the cell cycle of Caulobacter crescentus. We explore how the fluctuating levels of c-di-GMP and (p)ppGpp during the progression of the cell cycle and under conditions of stress control the synthesis and proteolysis of key regulators of the cell cycle. As these signals also promote bacterial interactions with host cells, the enzymes that control (p)ppGpp and c-di-GMP are attractive antibacterial targets.
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Affiliation(s)
- Régis Hallez
- Bacterial Cell cycle and Development (BCcD), Unité de recherche en biologie des micro-organismes (URBM), University of Namur, 61 Rue de Bruxelles, Namur 5000, Belgium
| | - Marie Delaby
- Department of Microbiology and Molecular Medicine, Institute of Genetics &Genomics in Geneva (iGE3), Faculty of Medicine, University of Geneva, CH-1211 Geneva, Switzerland
| | - Stefano Sanselicio
- Department of Microbiology and Molecular Medicine, Institute of Genetics &Genomics in Geneva (iGE3), Faculty of Medicine, University of Geneva, CH-1211 Geneva, Switzerland.,Present address: Molecular Genetics Group, Groningen Biomolecular Sciences and Biotechnology Institute, Centre for Synthetic Biology, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Patrick H Viollier
- Department of Microbiology and Molecular Medicine, Institute of Genetics &Genomics in Geneva (iGE3), Faculty of Medicine, University of Geneva, CH-1211 Geneva, Switzerland
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45
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Mallory KL, Miller DP, Oliver LD, Freedman JC, Kostick-Dunn JL, Carlyon JA, Marion JD, Bell JK, Marconi RT. Cyclic-di-GMP binding induces structural rearrangements in the PlzA and PlzC proteins of the Lyme disease and relapsing fever spirochetes: a possible switch mechanism for c-di-GMP-mediated effector functions. Pathog Dis 2016; 74:ftw105. [PMID: 27852620 DOI: 10.1093/femspd/ftw105] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Revised: 08/17/2016] [Accepted: 10/18/2016] [Indexed: 12/14/2022] Open
Abstract
The c-di-GMP network of Borrelia burgdorferi, a causative agent of Lyme disease, consists of Rrp1, a diguanylate cyclase/response regulator; Hpk1, a histidine kinase; PdeA and PdeB, c-di-GMP phosphodiesterases; and PlzA, a PilZ domain c-di-GMP receptor. Borrelia hermsii, a causative agent of tick-borne relapsing fever, possesses a putative c-di-GMP regulatory network that is uncharacterized. While B. burgdorferi requires c-di-GMP to survive within ticks, the associated effector mechanisms are poorly defined. Using site-directed mutagenesis, size exclusion chromatography, isothermal titration calorimetry and fluorescence resonance energy transfer, we investigate the interaction of c-di-GMP with the Borrelia PilZ domain-containing Plz proteins: B. burgdorferi PlzA and B. hermsii PlzC. The Plz proteins were determined to be monomeric in their apo and holo forms and to bind c-di-GMP with high affinity with a 1:1 stoichiometry. C-di-GMP binding induced structural rearrangements in PlzA and PlzC. C-di-GMP binding proved to be dependent on positive charge at R145 of the PilZ domain motif, R145xxxR. Comparative sequence analyses led to the identification of Borrelia consensus sequences for the PilZ domain signature motifs. This study provides insight into c-di-GMP:Plz receptor interaction and identifies a possible switch mechanism that may regulate Plz protein effector functions.
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Affiliation(s)
- Katherine L Mallory
- Department of Microbiology and Immunology, Virginia Commonwealth University Medical Center, Richmond, VA 23298-0678, USA
| | - Daniel P Miller
- Department of Microbiology and Immunology, Virginia Commonwealth University Medical Center, Richmond, VA 23298-0678, USA
| | - Lee D Oliver
- Department of Microbiology and Immunology, Virginia Commonwealth University Medical Center, Richmond, VA 23298-0678, USA
| | - John C Freedman
- Department of Microbiology and Immunology, Virginia Commonwealth University Medical Center, Richmond, VA 23298-0678, USA
| | - Jessica L Kostick-Dunn
- Department of Microbiology and Immunology, Virginia Commonwealth University Medical Center, Richmond, VA 23298-0678, USA
| | - Jason A Carlyon
- Department of Microbiology and Immunology, Virginia Commonwealth University Medical Center, Richmond, VA 23298-0678, USA
| | - James D Marion
- Department of Chemistry and Biochemistry, University of California-San Diego, San Diego, CA 92110-8001, USA
| | - Jessica K Bell
- University of California-San Diego, San Diego, CA 92110-8001, USA
| | - Richard T Marconi
- Department of Microbiology and Immunology, Virginia Commonwealth University Medical Center, Richmond, VA 23298-0678, USA .,Center for Study of Biological Complexity, Virginia Commonwealth University Medical Center, Richmond, VA 23298-0678, USA
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46
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Xu L, Xin L, Zeng Y, Yam JKH, Ding Y, Venkataramani P, Cheang QW, Yang X, Tang X, Zhang LH, Chiam KH, Yang L, Liang ZX. A cyclic di-GMP-binding adaptor protein interacts with a chemotaxis methyltransferase to control flagellar motor switching. Sci Signal 2016; 9:ra102. [PMID: 27811183 DOI: 10.1126/scisignal.aaf7584] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The bacterial messenger cyclic diguanylate monophosphate (c-di-GMP) binds to various effectors, the most common of which are single-domain PilZ proteins. These c-di-GMP effectors control various cellular functions and multicellular behaviors at the transcriptional or posttranslational level. We found that MapZ (methyltransferase-associated PilZ; formerly known as PA4608), a single-domain PilZ protein from the opportunistic pathogen Pseudomonas aeruginosa, directly interacted with the methyltransferase CheR1 and that this interaction was enhanced by c-di-GMP. In vitro assays indicated that, in the presence of c-di-GMP, MapZ inhibited CheR1 from methylating the chemoreceptor PctA, which would be expected to increase its affinity for chemoattractants and promote chemotaxis. MapZ localized to the poles of P. aeruginosa cells, where the flagellar motor and other chemotactic proteins, including PctA and CheR1, are also located. P. aeruginosa cells exhibit a random walk behavior by frequently switching the direction of flagellar rotation in a uniform solution. We showed that binding of c-di-GMP to MapZ decreased the frequency of flagellar motor switching and that MapZ was essential for generating the heterogeneous motility typical of P. aeruginosa cell populations and for efficient surface attachment during biofilm formation. Collectively, the studies revealed that c-di-GMP affects flagellar motor output by regulating the methylation of chemoreceptors through a single-domain PilZ adaptor protein.
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Affiliation(s)
- Linghui Xu
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.,Guangdong Innovative and Entrepreneurial Research Team of Sociomicrobiology Basic Science and Frontier Technology, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou 510642, China
| | - Lingyi Xin
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Yukai Zeng
- Bioinformatics Institute, Agency for Science, Technology and Research (A*STAR), 30 Biopolis Street, #07-01, Singapore 138671, Singapore
| | - Joey Kuok Hoong Yam
- Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.,Interdisciplinary Graduate School, Nanyang Technological University, Singapore 637551, Singapore
| | - Yichen Ding
- Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.,Interdisciplinary Graduate School, Nanyang Technological University, Singapore 637551, Singapore
| | - Prabhadevi Venkataramani
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Qing Wei Cheang
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Xiaobei Yang
- Guangdong Innovative and Entrepreneurial Research Team of Sociomicrobiology Basic Science and Frontier Technology, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou 510642, China
| | - Xuhua Tang
- Institute of Molecular and Cell Biology, A*STAR, 61 Biopolis Drive, Singapore 138673, Singapore
| | - Lian-Hui Zhang
- Integrative Microbiology Research Centre, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou 510642, China
| | - Keng-Hwee Chiam
- Bioinformatics Institute, Agency for Science, Technology and Research (A*STAR), 30 Biopolis Street, #07-01, Singapore 138671, Singapore
| | - Liang Yang
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore. .,Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Zhao-Xun Liang
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
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47
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An intracellular compass spatially coordinates cell cycle modules in Caulobacter crescentus. Curr Opin Microbiol 2016; 33:131-139. [PMID: 27517351 DOI: 10.1016/j.mib.2016.06.007] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 06/24/2016] [Indexed: 12/27/2022]
Abstract
Cellular functions in Bacteria, such as chromosome segregation and cytokinesis, result from cascades of molecular events operating largely as self-contained modules. Regulated timing of these cellular modules stems from global genetic circuits that allow precise temporal activation with respect to cell cycle progression and cell differentiation. Critically, many of these functions occur at defined locations within the cell, and therefore regulators of each module must communicate to remain coordinated in space. In this perspective, we highlight recent discoveries in Caulobacter crescentus asymmetric cell division to illuminate diverse mechanisms by which a cellular compass, composed of scaffolding and signaling proteins, directs cell cycle modules to their exact cellular addresses.
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48
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Opoku-Temeng C, Zhou J, Zheng Y, Su J, Sintim HO. Cyclic dinucleotide (c-di-GMP, c-di-AMP, and cGAMP) signalings have come of age to be inhibited by small molecules. Chem Commun (Camb) 2016; 52:9327-42. [PMID: 27339003 DOI: 10.1039/c6cc03439j] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Bacteria utilize nucleotide-based second messengers to regulate a myriad of physiological processes. Cyclic dinucleotides have emerged as central regulators of bacterial physiology, controlling processes ranging from cell wall homeostasis to virulence production, and so far over thousands of manuscripts have provided biological insights into c-di-NMP signaling. The development of small molecule inhibitors of c-di-NMP signaling has significantly lagged behind. Recent developments in assays that allow for high-throughput screening of inhibitors suggest that the time is right for a concerted effort to identify inhibitors of these fascinating second messengers. Herein, we review c-di-NMP signaling and small molecules that have been developed to inhibit cyclic dinucleotide-related enzymes.
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Affiliation(s)
- Clement Opoku-Temeng
- Department of Chemistry, Center for Drug Discovery, Purdue University, West Lafayette, IN 47907, USA.
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49
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PilZ Domain Protein FlgZ Mediates Cyclic Di-GMP-Dependent Swarming Motility Control in Pseudomonas aeruginosa. J Bacteriol 2016; 198:1837-46. [PMID: 27114465 DOI: 10.1128/jb.00196-16] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 04/21/2016] [Indexed: 01/29/2023] Open
Abstract
UNLABELLED The second messenger cyclic diguanylate (c-di-GMP) is an important regulator of motility in many bacterial species. In Pseudomonas aeruginosa, elevated levels of c-di-GMP promote biofilm formation and repress flagellum-driven swarming motility. The rotation of P. aeruginosa's polar flagellum is controlled by two distinct stator complexes, MotAB, which cannot support swarming motility, and MotCD, which promotes swarming motility. Here we show that when c-di-GMP levels are elevated, swarming motility is repressed by the PilZ domain-containing protein FlgZ and by Pel polysaccharide production. We demonstrate that FlgZ interacts specifically with the motility-promoting stator protein MotC in a c-di-GMP-dependent manner and that a functional green fluorescent protein (GFP)-FlgZ fusion protein shows significantly reduced polar localization in a strain lacking the MotCD stator. Our results establish FlgZ as a c-di-GMP receptor affecting swarming motility by P. aeruginosa and support a model wherein c-di-GMP-bound FlgZ impedes motility via its interaction with the MotCD stator. IMPORTANCE The regulation of surface-associated motility plays an important role in bacterial surface colonization and biofilm formation. c-di-GMP signaling is a widespread means of controlling bacterial motility, and yet the mechanism whereby this signal controls surface-associated motility in P. aeruginosa remains poorly understood. Here we identify a PilZ domain-containing c-di-GMP effector protein that contributes to c-di-GMP-mediated repression of swarming motility by P. aeruginosa We provide evidence that this effector, FlgZ, impacts swarming motility via its interactions with flagellar stator protein MotC. Thus, we propose a new mechanism for c-di-GMP-mediated regulation of motility for a bacterium with two flagellar stator sets, increasing our understanding of surface-associated behaviors, a key prerequisite to identifying ways to control the formation of biofilm communities.
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50
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Skotnicka D, Smaldone GT, Petters T, Trampari E, Liang J, Kaever V, Malone JG, Singer M, Søgaard-Andersen L. A Minimal Threshold of c-di-GMP Is Essential for Fruiting Body Formation and Sporulation in Myxococcus xanthus. PLoS Genet 2016; 12:e1006080. [PMID: 27214040 PMCID: PMC4877007 DOI: 10.1371/journal.pgen.1006080] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 05/04/2016] [Indexed: 11/18/2022] Open
Abstract
Generally, the second messenger bis-(3'-5')-cyclic dimeric GMP (c-di-GMP) regulates the switch between motile and sessile lifestyles in bacteria. Here, we show that c-di-GMP is an essential regulator of multicellular development in the social bacterium Myxococcus xanthus. In response to starvation, M. xanthus initiates a developmental program that culminates in formation of spore-filled fruiting bodies. We show that c-di-GMP accumulates at elevated levels during development and that this increase is essential for completion of development whereas excess c-di-GMP does not interfere with development. MXAN3735 (renamed DmxB) is identified as a diguanylate cyclase that only functions during development and is responsible for this increased c-di-GMP accumulation. DmxB synthesis is induced in response to starvation, thereby restricting DmxB activity to development. DmxB is essential for development and functions downstream of the Dif chemosensory system to stimulate exopolysaccharide accumulation by inducing transcription of a subset of the genes encoding proteins involved in exopolysaccharide synthesis. The developmental defects in the dmxB mutant are non-cell autonomous and rescued by co-development with a strain proficient in exopolysaccharide synthesis, suggesting reduced exopolysaccharide accumulation as the causative defect in this mutant. The NtrC-like transcriptional regulator EpsI/Nla24, which is required for exopolysaccharide accumulation, is identified as a c-di-GMP receptor, and thus a putative target for DmxB generated c-di-GMP. Because DmxB can be-at least partially-functionally replaced by a heterologous diguanylate cyclase, these results altogether suggest a model in which a minimum threshold level of c-di-GMP is essential for the successful completion of multicellular development in M. xanthus.
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Affiliation(s)
- Dorota Skotnicka
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Gregory T. Smaldone
- Department of Microbiology and Molecular Genetics, University of California - Davis, Davis, California, United States of America
| | - Tobias Petters
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Eleftheria Trampari
- Molecular Microbiology Department, John Innes Centre, Norwich, United Kingdom
| | - Jennifer Liang
- Department of Microbiology and Molecular Genetics, University of California - Davis, Davis, California, United States of America
| | - Volkhard Kaever
- Research Core Unit Metabolomics, Hannover Medical School, Hannover, Germany
| | - Jacob G. Malone
- Molecular Microbiology Department, John Innes Centre, Norwich, United Kingdom
- School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
| | - Mitchell Singer
- Department of Microbiology and Molecular Genetics, University of California - Davis, Davis, California, United States of America
- * E-mail: (MS); (LSA)
| | - Lotte Søgaard-Andersen
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
- * E-mail: (MS); (LSA)
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