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Tani M, Wada H. How a Soft Rod Wraps around a Rotating Cylinder. PHYSICAL REVIEW LETTERS 2024; 132:058204. [PMID: 38364127 DOI: 10.1103/physrevlett.132.058204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 09/12/2023] [Accepted: 01/02/2024] [Indexed: 02/18/2024]
Abstract
The unique characteristics of helical coils are utilized in nature, manufacturing processes, and daily life. These coils are also pivotal in the development of soft machines, such as artificial muscles and soft grippers. The stability of these helical coils is generally dependent on the mechanical properties of the rods and geometry of the supporting objects. In this Letter, the shapes formed by a flexible, heavy rod wrapping around a slowly rotating rigid cylinder are investigated through a combination of experimental and theoretical approaches. Three distinct morphologies-tight coiling, helical wrapping, and no wrapping-are identified experimentally. These findings are rationalized by numerical simulations and a geometrically nonlinear Kirchhoff rod theory. Despite the frictional contact present, the local shape of the rod is explained by the interplay between bending elasticity, gravity, and the geometry of the system. Our Letter provides a comprehensive physical understanding of the ordered morphology of soft threads and rods. Implications of this understanding are significant for a wide range of phenomena, from the recently discovered wrapping motility mode of bacterial flagella to the design of an octopus-inspired soft gripper.
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Affiliation(s)
- Marie Tani
- Department of Physics, Tokyo Metropolitan University, Hachioji-City, Tokyo 192-0397, Japan
- Research Organization of Science and Technology, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan
| | - Hirofumi Wada
- Department of Physical Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan
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2
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Bondoc-Naumovitz KG, Laeverenz-Schlogelhofer H, Poon RN, Boggon AK, Bentley SA, Cortese D, Wan KY. Methods and Measures for Investigating Microscale Motility. Integr Comp Biol 2023; 63:1485-1508. [PMID: 37336589 PMCID: PMC10755196 DOI: 10.1093/icb/icad075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 05/31/2023] [Accepted: 06/06/2023] [Indexed: 06/21/2023] Open
Abstract
Motility is an essential factor for an organism's survival and diversification. With the advent of novel single-cell technologies, analytical frameworks, and theoretical methods, we can begin to probe the complex lives of microscopic motile organisms and answer the intertwining biological and physical questions of how these diverse lifeforms navigate their surroundings. Herein, we summarize the main mechanisms of microscale motility and give an overview of different experimental, analytical, and mathematical methods used to study them across different scales encompassing the molecular-, individual-, to population-level. We identify transferable techniques, pressing challenges, and future directions in the field. This review can serve as a starting point for researchers who are interested in exploring and quantifying the movements of organisms in the microscale world.
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Affiliation(s)
| | | | - Rebecca N Poon
- Living Systems Institute, University of Exeter, Stocker Road, EX4 4QD, Exeter, UK
| | - Alexander K Boggon
- Living Systems Institute, University of Exeter, Stocker Road, EX4 4QD, Exeter, UK
| | - Samuel A Bentley
- Living Systems Institute, University of Exeter, Stocker Road, EX4 4QD, Exeter, UK
| | - Dario Cortese
- Living Systems Institute, University of Exeter, Stocker Road, EX4 4QD, Exeter, UK
| | - Kirsty Y Wan
- Living Systems Institute, University of Exeter, Stocker Road, EX4 4QD, Exeter, UK
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3
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Ou J, Dong H, Luan X, Wang X, Liu Q, Chen H, Cao M, Xu Z, Liu Y, Zhao W. iTRAQ-based differential proteomic analysis of high- and low-virulence strains of Spiroplasma eriocheiris. Microb Pathog 2023; 184:106365. [PMID: 37741306 DOI: 10.1016/j.micpath.2023.106365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 09/17/2023] [Accepted: 09/18/2023] [Indexed: 09/25/2023]
Abstract
Spiroplasma eriocheiris is one of the major pathogenic bacteria in crustaceans, featuring high infectivity, rapid transmission, and an absence of effective control strategies, resulting in significant economic losses to the aquaculture industry. Research into virulence-related factors provides an important perspective to clarify how Spiroplasma eriocheiris is pathogenic to shrimps and crabs. Therefore, in this study, isobaric tags for relative and absolute quantitation (iTRAQ) technology was utilized to undertake a differential proteomic analysis of high- and low-virulence Spiroplasma eriocheiris strains at different growth phases. A total of 868 differentially expressed proteins (DEPs) were obtained, of which 31 novel proteins were identified by proteogenomic analysis. There were 62, 61, 175, and 235 DEPs between the log phase (YD) and non-log phase (YFD) of the high-virulence strain, between the log phase (CD) and non-log phase (CFD) of the low-virulence strain, between YD and CD, and between CFD and YFD, respectively. All the DEPs were compared with virulence protein databases (MvirDB and VFDB), and 68 virulence proteins of Spiroplasma eriocheiris were identified, of which 12 were involved in a total of 21 metabolic pathways, including motility, chemotaxis, growth, metabolism and virulence of the bacteria. The results of this study form the basis for further research into the molecular mechanism of virulence and physiological differences between high- and low-virulence strains of Spiroplasma eriocheiris, and provide a scientific basis for a detailed understanding of its pathogenesis.
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Affiliation(s)
- Jiangtao Ou
- Jiangsu Key Laboratory of Biochemistry and Biotechnology of Marine Wetland, School of Marine and Biological Engineering, Yancheng Institute of Technology, Yancheng, 224051, Province Jiangsu, China.
| | - Huizi Dong
- Jiangsu Key Laboratory of Biochemistry and Biotechnology of Marine Wetland, School of Marine and Biological Engineering, Yancheng Institute of Technology, Yancheng, 224051, Province Jiangsu, China
| | - Xiaoqi Luan
- Jiangsu Key Laboratory of Biochemistry and Biotechnology of Marine Wetland, School of Marine and Biological Engineering, Yancheng Institute of Technology, Yancheng, 224051, Province Jiangsu, China; Jiangsu Key Laboratory for Biodiversity & Biotechnology and Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China
| | - Xiang Wang
- Jiangsu Key Laboratory of Biochemistry and Biotechnology of Marine Wetland, School of Marine and Biological Engineering, Yancheng Institute of Technology, Yancheng, 224051, Province Jiangsu, China
| | - Qiao Liu
- Jiangsu Key Laboratory of Biochemistry and Biotechnology of Marine Wetland, School of Marine and Biological Engineering, Yancheng Institute of Technology, Yancheng, 224051, Province Jiangsu, China
| | - Hao Chen
- Jiangsu Key Laboratory of Biochemistry and Biotechnology of Marine Wetland, School of Marine and Biological Engineering, Yancheng Institute of Technology, Yancheng, 224051, Province Jiangsu, China
| | - Miao Cao
- Jiangsu Key Laboratory of Biochemistry and Biotechnology of Marine Wetland, School of Marine and Biological Engineering, Yancheng Institute of Technology, Yancheng, 224051, Province Jiangsu, China
| | - Zheqi Xu
- Jiangsu Key Laboratory of Biochemistry and Biotechnology of Marine Wetland, School of Marine and Biological Engineering, Yancheng Institute of Technology, Yancheng, 224051, Province Jiangsu, China
| | - Yang Liu
- Jiangsu Key Laboratory of Biochemistry and Biotechnology of Marine Wetland, School of Marine and Biological Engineering, Yancheng Institute of Technology, Yancheng, 224051, Province Jiangsu, China
| | - Weihong Zhao
- Jiangsu Key Laboratory of Biochemistry and Biotechnology of Marine Wetland, School of Marine and Biological Engineering, Yancheng Institute of Technology, Yancheng, 224051, Province Jiangsu, China
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4
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Ryan PM, Shaevitz JW, Wolgemuth CW. Bend or Twist? What Plectonemes Reveal about the Mysterious Motility of Spiroplasma. PHYSICAL REVIEW LETTERS 2023; 131:178401. [PMID: 37955476 DOI: 10.1103/physrevlett.131.178401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Accepted: 09/15/2023] [Indexed: 11/14/2023]
Abstract
Spiroplasma is a unique, helical bacterium that lacks a cell wall and swims using propagating helix hand inversions. These deformations are likely driven by a set of cytoskeletal filaments, but how remains perplexing. Here, we probe the underlying mechanism using a model where either twist or bend drive spiroplasma's chirality inversions. We show that Spiroplasma should wrap into plectonemes at different values of the length and external viscosity, depending on the mechanism. Then, by experimentally measuring the bending modulus of Spiroplasma and if and when plectonemes form, we show that Spiroplasma's helix hand inversions are likely driven by bending.
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Affiliation(s)
- Paul M Ryan
- Department of Physics, University of Arizona, Tucson, Arizona 85721, USA
| | - Joshua W Shaevitz
- Joseph Henry Laboratories of Physics and Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, USA
| | - Charles W Wolgemuth
- Department of Physics, University of Arizona, Tucson, Arizona 85721, USA
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721, USA
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5
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Nakane D. Rheotaxis in Mycoplasma gliding. Microbiol Immunol 2023; 67:389-395. [PMID: 37430383 DOI: 10.1111/1348-0421.13090] [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: 06/01/2023] [Revised: 06/22/2023] [Accepted: 06/23/2023] [Indexed: 07/12/2023]
Abstract
This review describes the upstream-directed movement in the small parasitic bacterium Mycoplasma. Many Mycoplasma species exhibit gliding motility, a form of biological motion over surfaces without the aid of general surface appendages such as flagella. The gliding motility is characterized by a constant unidirectional movement without changes in direction or backward motion. Unlike flagellated bacteria, Mycoplasma lacks the general chemotactic signaling system to control their moving direction. Therefore, the physiological role of directionless travel in Mycoplasma gliding remains unclear. Recently, high-precision measurements under an optical microscope have revealed that three species of Mycoplasma exhibited rheotaxis, that is, the direction of gliding motility is lead upstream by the water flow. This intriguing response appears to be optimized for the flow patterns encountered at host surfaces. This review provides a comprehensive overview of the morphology, behavior, and habitat of Mycoplasma gliding, and discusses the possibility that the rheotaxis is ubiquitous among them.
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Affiliation(s)
- Daisuke Nakane
- Department of Engineering Science, Graduate School of Informatics and Engineering, Tokyo, Japan
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6
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Swimming Motility Assays of Spiroplasma. Methods Mol Biol 2023; 2646:373-381. [PMID: 36842131 DOI: 10.1007/978-1-0716-3060-0_31] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/27/2023]
Abstract
Spiroplasma swim in liquids without the use of the bacterial flagella. This small helical bacterium propels itself by generating kinks that travel down the cell body. The kink translation is unidirectional, from the leading pole to the lagging pole, during cell swimming in viscous environments. This protocol describes a swimming motility assay of Spiroplasma eriocheiris for visualizing kink translations of the absolute handedness of the body helix with optical microscopy.
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Kiyama H, Kakizawa S, Sasajima Y, Tahara YO, Miyata M. Reconstitution of a minimal motility system based on Spiroplasma swimming by two bacterial actins in a synthetic minimal bacterium. SCIENCE ADVANCES 2022; 8:eabo7490. [PMID: 36449609 PMCID: PMC9710875 DOI: 10.1126/sciadv.abo7490] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Accepted: 10/14/2022] [Indexed: 05/24/2023]
Abstract
Motility is one of the most important features of life, but its evolutionary origin remains unknown. In this study, we focused on Spiroplasma, commensal, or parasitic bacteria. They swim by switching the helicity of a ribbon-like cytoskeleton that comprises six proteins, each of which evolved from a nucleosidase and bacterial actin called MreB. We expressed these proteins in a synthetic, nonmotile minimal bacterium, JCVI-syn3B, whose reduced genome was computer-designed and chemically synthesized. The synthetic bacterium exhibited swimming motility with features characteristic of Spiroplasma swimming. Moreover, combinations of Spiroplasma MreB4-MreB5 and MreB1-MreB5 produced a helical cell shape and swimming. These results suggest that the swimming originated from the differentiation and coupling of bacterial actins, and we obtained a minimal system for motility of the synthetic bacterium.
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Affiliation(s)
- Hana Kiyama
- Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
- Graduate School of Science, Osaka Metropolitan University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Shigeyuki Kakizawa
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
| | - Yuya Sasajima
- Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
- Graduate School of Science, Osaka Metropolitan University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Yuhei O. Tahara
- Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
- Graduate School of Science, Osaka Metropolitan University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
| | - Makoto Miyata
- Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
- Graduate School of Science, Osaka Metropolitan University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
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8
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Cytoskeletal components can turn wall-less spherical bacteria into kinking helices. Nat Commun 2022; 13:6930. [PMID: 36376306 PMCID: PMC9663586 DOI: 10.1038/s41467-022-34478-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 10/26/2022] [Indexed: 11/16/2022] Open
Abstract
Bacterial cell shape is generally determined through an interplay between the peptidoglycan cell wall and cytoplasmic filaments made of polymerized MreB. Indeed, some bacteria (e.g., Mycoplasma) that lack both a cell wall and mreB genes consist of non-motile cells that are spherical or pleomorphic. However, other members of the same class Mollicutes (e.g., Spiroplasma, also lacking a cell wall) display a helical cell shape and kink-based motility, which is thought to rely on the presence of five MreB isoforms and a specific fibril protein. Here, we show that heterologous expression of Spiroplasma fibril and MreB proteins confers helical shape and kinking ability to Mycoplasma capricolum cells. Isoform MreB5 is sufficient to confer helicity and kink propagation to mycoplasma cells. Cryoelectron microscopy confirms the association of cytoplasmic MreB filaments with the plasma membrane, suggesting a direct effect on membrane curvature. However, in our experiments, the heterologous expression of MreBs and fibril did not result in efficient motility in culture broth, indicating that additional, unknown Spiroplasma components are required for swimming.
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Liu P, Li Y, Ye Y, Chen J, Li R, Zhang Q, Li Y, Wang W, Meng Q, Ou J, Yang Z, Sun W, Gu W. The genome and antigen proteome analysis of Spiroplasma mirum. Front Microbiol 2022; 13:996938. [PMID: 36406404 PMCID: PMC9666726 DOI: 10.3389/fmicb.2022.996938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 10/10/2022] [Indexed: 06/16/2023] Open
Abstract
Spiroplasma mirum, small motile wall-less bacteria, was originally isolated from a rabbit tick and had the ability to infect newborn mice and caused cataracts. In this study, the whole genome and antigen proteins of S. mirum were comparative analyzed and investigated. Glycolysis, pentose phosphate pathway, arginine metabolism, nucleotide biosynthesis, and citrate fermentation were found in S. mirum, while trichloroacetic acid, fatty acids metabolism, phospholipid biosynthesis, terpenoid biosynthesis, lactose-specific PTS, and cofactors synthesis were completely absent. The Sec systems of S. mirum consist of SecA, SecE, SecDF, SecG, SecY, and YidC. Signal peptidase II was identified in S. mirum, but no signal peptidase I. The relative gene order in S. mirum is largely conserved. Genome analysis of available species in Mollicutes revealed that they shared only 84 proteins. S. mirum genome has 381 pseudogenes, accounting for 31.6% of total protein-coding genes. This is the evidence that spiroplasma genome is under an ongoing genome reduction. Immunoproteomics, a new scientific technique combining proteomics and immunological analytical methods, provided the direction of our research on S. mirum. We identified 49 proteins and 11 proteins (9 proteins in common) in S. mirum by anti-S. mirum serum and negative serum, respectively. Forty proteins in S. mirum were identified in relation to the virulence. All these proteins may play key roles in the pathogeny and can be used in the future for diagnoses and prevention.
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Affiliation(s)
- Peng Liu
- Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Basic Medical School, Hengyang Medical School, Institute of Pathogenic Biology, University of South China, Hengyang, China
| | - Yuxin Li
- Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Basic Medical School, Hengyang Medical School, Institute of Pathogenic Biology, University of South China, Hengyang, China
| | - Youyuan Ye
- Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Basic Medical School, Hengyang Medical School, Institute of Pathogenic Biology, University of South China, Hengyang, China
| | - Jiaxin Chen
- Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Basic Medical School, Hengyang Medical School, Institute of Pathogenic Biology, University of South China, Hengyang, China
| | - Rong Li
- Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Basic Medical School, Hengyang Medical School, Institute of Pathogenic Biology, University of South China, Hengyang, China
| | - Qinyi Zhang
- Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Basic Medical School, Hengyang Medical School, Institute of Pathogenic Biology, University of South China, Hengyang, China
| | - Yuan Li
- Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Basic Medical School, Hengyang Medical School, Institute of Pathogenic Biology, University of South China, Hengyang, China
| | - Wen Wang
- Key Laboratory for Aquatic Crustacean Diseases, College of Marine Science and Engineering, Nanjing Normal University, Nanjing, China
| | - Qingguo Meng
- Key Laboratory for Aquatic Crustacean Diseases, College of Marine Science and Engineering, Nanjing Normal University, Nanjing, China
| | - Jingyu Ou
- Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Basic Medical School, Hengyang Medical School, Institute of Pathogenic Biology, University of South China, Hengyang, China
| | - Zhujun Yang
- Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Basic Medical School, Hengyang Medical School, Institute of Pathogenic Biology, University of South China, Hengyang, China
| | - Wei Sun
- Jiangsu Provincial Center for Disease Control and Prevention, Nanjing, China
| | - Wei Gu
- Key Laboratory for Aquatic Crustacean Diseases, College of Marine Science and Engineering, Nanjing Normal University, Nanjing, China
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Harne S, Gayathri P. Characterization of heterologously expressed Fibril, a shape and motility determining cytoskeletal protein of the helical bacterium Spiroplasma. iScience 2022; 25:105055. [PMID: 36157586 PMCID: PMC9489929 DOI: 10.1016/j.isci.2022.105055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 06/20/2022] [Accepted: 08/29/2022] [Indexed: 11/30/2022] Open
Abstract
Fibril is a constitutive filament-forming cytoskeletal protein of unidentified fold, exclusive to members of genus Spiroplasma. It is hypothesized to undergo conformational changes necessary to bring about Spiroplasma motility through changes in cell helicity. However, the mechanism driving conformational changes in Fibril remains unknown. We expressed Fibril from S. citri in E. coli for its purification and characterization. Sodium dodecyl sulfate solubilized Fibril filaments and facilitated purification by affinity chromatography. An alternative protocol for obtaining enriched insoluble Fibril filaments was standardized using density gradient centrifugation. Electron microscopy of Fibril purified by these protocols revealed filament bundles. Probable domain boundaries of Fibril protein were identified based on mass spectrometric analysis of proteolytic fragments. Presence of α-helical and β-sheet signatures in FT-IR measurements suggests that Fibril filaments consist of an assembly of folded globular domains, and not a β-strand-based aggregation like amyloid fibrils.
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Affiliation(s)
- Shrikant Harne
- Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pashan, Pune 411008, India
| | - Pananghat Gayathri
- Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pashan, Pune 411008, India
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Sasajima Y, Kato T, Miyata T, Kawamoto A, Namba K, Miyata M. Isolation and structure of the fibril protein, a major component of the internal ribbon for Spiroplasma swimming. Front Microbiol 2022; 13:1004601. [PMID: 36274716 PMCID: PMC9582952 DOI: 10.3389/fmicb.2022.1004601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Accepted: 09/01/2022] [Indexed: 11/05/2022] Open
Abstract
Spiroplasma, which are known pathogens and commensals of arthropods and plants, are helical-shaped bacteria that lack a peptidoglycan layer. Spiroplasma swim by alternating between left- and right-handed helicity. Of note, this system is not related to flagellar motility, which is widespread in bacteria. A helical ribbon running along the inner side of the helical cell should be responsible for cell helicity and comprises the bacterial actin homolog, MreB, and a protein specific to Spiroplasma, fibril. Here, we isolated the ribbon and its major component, fibril filament, for electron microscopy (EM) analysis. Single-particle analysis of the fibril filaments using the negative-staining EM revealed a three-dimensional chain structure composed of rings with a size of 11 nm wide and 6 nm long, connected by a backbone cylinder with an 8.7 nm interval with a twist along the filament axis. This structure was verified through EM tomography of quick-freeze deep-etch replica sample, with a focus on its handedness. The handedness and pitch of the helix for the isolated ribbon and fibril filament agreed with those of the cell in the resting state. Structures corresponding to the alternative state were not identified. These results suggest that the helical cell structure is supported by fibril filaments; however, the helical switch is caused by the force generated by the MreB proteins. The isolation and structural outline of the fibril filaments provide crucial information for an in-depth clarification of the unique swimming mechanism of Spiroplasma.
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Affiliation(s)
- Yuya Sasajima
- Graduate School of Science, Osaka Metropolitan University, Osaka, Japan
| | - Takayuki Kato
- Institute for Protein Research, Osaka University, Suita, Osaka, Japan
| | - Tomoko Miyata
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
| | - Akihiro Kawamoto
- Institute for Protein Research, Osaka University, Suita, Osaka, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
- RIKEN Center for Biosystems Dynamics Research and Spring-8 Center, Suita, Osaka, Japan
- JEOL YOKOGUSHI Research Alliance Laboratories, Osaka University, Suita, Osaka, Japan
| | - Makoto Miyata
- Graduate School of Science, Osaka Metropolitan University, Osaka, Japan
- The OCU Advanced Research Institute for Natural Science and Technology (OCARINA), Osaka Metropolitan University, Osaka, Japan
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12
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Mechanical limitation of bacterial motility mediated by growing cell chains. Biophys J 2022; 121:2461-2473. [PMID: 35591787 DOI: 10.1016/j.bpj.2022.05.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 04/20/2022] [Accepted: 05/12/2022] [Indexed: 11/23/2022] Open
Abstract
Contrasting most known bacterial motility mechanisms, a bacterial sliding motility discovered in at least two Gram-positive bacterial families does not depend on designated motors. Instead, the cells maintain end-to-end connections following cell divisions to form long chains and exploit cell growth and division to push the cells forward. To investigate the dynamics of this motility mechanism, we constructed a mechanical model that depicts the interplay of the forces acting on and between the cells comprising the chain. Due to the exponential growth of individual cells, the tips of the chains can, in principle, accelerate to speeds faster than any known single-cell motility mechanism can achieve. However, analysis of the mechanical model shows that the exponential acceleration comes at the cost of an exponential buildup in mechanical stress in the chain, making overly long chains prone to breakage. Additionally, the mechanical model reveals that the dynamics of the chain expansion hinges on a single non-dimensional parameter. Perturbation analysis of the mechanical model further predicts the critical stress leading to chain breakage and its dependence on the non-dimensional parameter. Finally, we developed a simplistic population expansion model that uses the predicted breaking behavior to estimate the physical limit of chain-mediated population expansion. Predictions from the models provide critical insights into how this motility depends on key physical properties of the cell and the substrate. Overall, our models present a generically applicable theoretical framework for cell chain-mediated bacterial sliding motility and provide guidance for future experimental studies on such motility.
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