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The Coevolution of Biomolecules and Prebiotic Information Systems in the Origin of Life: A Visualization Model for Assembling the First Gene. Life (Basel) 2022; 12:life12060834. [PMID: 35743865 PMCID: PMC9225589 DOI: 10.3390/life12060834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 05/23/2022] [Accepted: 06/01/2022] [Indexed: 11/24/2022] Open
Abstract
Prebiotic information systems exist in three forms: analog, hybrid, and digital. The Analog Information System (AIS), manifested early in abiogenesis, was expressed in the chiral selection, nucleotide formation, self-assembly, polymerization, encapsulation of polymers, and division of protocells. It created noncoding RNAs by polymerizing nucleotides that gave rise to the Hybrid Information System (HIS). The HIS employed different species of noncoding RNAs, such as ribozymes, pre-tRNA and tRNA, ribosomes, and functional enzymes, including bridge peptides, pre-aaRS, and aaRS (aminoacyl-tRNA synthetase). Some of these hybrid components build the translation machinery step-by-step. The HIS ushered in the Digital Information System (DIS), where tRNA molecules become molecular architects for designing mRNAs step-by-step, employing their two distinct genetic codes. First, they created codons of mRNA by the base pair interaction (anticodon–codon mapping). Secondly, each charged tRNA transferred its amino acid information to the corresponding codon (codon–amino acid mapping), facilitated by an aaRS enzyme. With the advent of encoded mRNA molecules, the first genes emerged before DNA. With the genetic memory residing in the digital sequences of mRNA, a mapping mechanism was developed between each codon and its cognate amino acid. As more and more codons ‘remembered’ their respective amino acids, this mapping system developed the genetic code in their memory bank. We compared three kinds of biological information systems with similar types of human-made computer systems.
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Pelletier JF, Sun L, Wise KS, Assad-Garcia N, Karas BJ, Deerinck TJ, Ellisman MH, Mershin A, Gershenfeld N, Chuang RY, Glass JI, Strychalski EA. Genetic requirements for cell division in a genomically minimal cell. Cell 2021; 184:2430-2440.e16. [PMID: 33784496 DOI: 10.1016/j.cell.2021.03.008] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 01/27/2021] [Accepted: 03/03/2021] [Indexed: 12/15/2022]
Abstract
Genomically minimal cells, such as JCVI-syn3.0, offer a platform to clarify genes underlying core physiological processes. Although this minimal cell includes genes essential for population growth, the physiology of its single cells remained uncharacterized. To investigate striking morphological variation in JCVI-syn3.0 cells, we present an approach to characterize cell propagation and determine genes affecting cell morphology. Microfluidic chemostats allowed observation of intrinsic cell dynamics that result in irregular morphologies. A genome with 19 genes not retained in JCVI-syn3.0 generated JCVI-syn3A, which presents morphology similar to that of JCVI-syn1.0. We further identified seven of these 19 genes, including two known cell division genes, ftsZ and sepF, a hydrolase of unknown substrate, and four genes that encode membrane-associated proteins of unknown function, which are required together to restore a phenotype similar to that of JCVI-syn1.0. This result emphasizes the polygenic nature of cell division and morphology in a genomically minimal cell.
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Affiliation(s)
- James F Pelletier
- Center for Bits and Atoms, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - Lijie Sun
- J. Craig Venter Institute, La Jolla, CA 92037, USA
| | - Kim S Wise
- J. Craig Venter Institute, La Jolla, CA 92037, USA
| | | | - Bogumil J Karas
- Department of Biochemistry, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Thomas J Deerinck
- National Center for Microscopy and Imaging Research, University of California-San Diego, La Jolla, CA 92037, USA
| | - Mark H Ellisman
- National Center for Microscopy and Imaging Research, University of California-San Diego, La Jolla, CA 92037, USA
| | - Andreas Mershin
- Center for Bits and Atoms, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Neil Gershenfeld
- Center for Bits and Atoms, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | | | - John I Glass
- J. Craig Venter Institute, La Jolla, CA 92037, USA.
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Wu LJ, Lee S, Park S, Eland LE, Wipat A, Holden S, Errington J. Geometric principles underlying the proliferation of a model cell system. Nat Commun 2020; 11:4149. [PMID: 32811832 PMCID: PMC7434903 DOI: 10.1038/s41467-020-17988-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 07/24/2020] [Indexed: 02/07/2023] Open
Abstract
Many bacteria can form wall-deficient variants, or L-forms, that divide by a simple mechanism that does not require the FtsZ-based cell division machinery. Here, we use microfluidic systems to probe the growth, chromosome cycle and division mechanism of Bacillus subtilis L-forms. We find that forcing cells into a narrow linear configuration greatly improves the efficiency of cell growth and chromosome segregation. This reinforces the view that L-form division is driven by an excess accumulation of surface area over volume. Cell geometry also plays a dominant role in controlling the relative positions and movement of segregating chromosomes. Furthermore, the presence of the nucleoid appears to influence division both via a cell volume effect and by nucleoid occlusion, even in the absence of FtsZ. Our results emphasise the importance of geometric effects for a range of crucial cell functions, and are of relevance for efforts to develop artificial or minimal cell systems.
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Affiliation(s)
- Ling Juan Wu
- Centre for Bacterial Cell Biology, Biosciences Institute, Medical School, Newcastle University, Richardson Road, Newcastle upon Tyne, NE2 4AX, UK.
| | - Seoungjun Lee
- grid.1006.70000 0001 0462 7212Centre for Bacterial Cell Biology, Biosciences Institute, Medical School, Newcastle University, Richardson Road, Newcastle upon Tyne, NE2 4AX UK ,grid.13097.3c0000 0001 2322 6764Present Address: Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, SE5 9RX UK
| | - Sungshic Park
- grid.1006.70000 0001 0462 7212Centre for Bacterial Cell Biology, Biosciences Institute, Medical School, Newcastle University, Richardson Road, Newcastle upon Tyne, NE2 4AX UK ,grid.1006.70000 0001 0462 7212Interdisciplinary Computing and Complex BioSystems research group, School of Computing, Newcastle University, Newcastle upon Tyne, NE4 5TG UK
| | - Lucy E. Eland
- grid.1006.70000 0001 0462 7212Centre for Bacterial Cell Biology, Biosciences Institute, Medical School, Newcastle University, Richardson Road, Newcastle upon Tyne, NE2 4AX UK ,grid.1006.70000 0001 0462 7212Interdisciplinary Computing and Complex BioSystems research group, School of Computing, Newcastle University, Newcastle upon Tyne, NE4 5TG UK
| | - Anil Wipat
- grid.1006.70000 0001 0462 7212Centre for Bacterial Cell Biology, Biosciences Institute, Medical School, Newcastle University, Richardson Road, Newcastle upon Tyne, NE2 4AX UK ,grid.1006.70000 0001 0462 7212Interdisciplinary Computing and Complex BioSystems research group, School of Computing, Newcastle University, Newcastle upon Tyne, NE4 5TG UK
| | - Séamus Holden
- grid.1006.70000 0001 0462 7212Centre for Bacterial Cell Biology, Biosciences Institute, Medical School, Newcastle University, Richardson Road, Newcastle upon Tyne, NE2 4AX UK
| | - Jeff Errington
- Centre for Bacterial Cell Biology, Biosciences Institute, Medical School, Newcastle University, Richardson Road, Newcastle upon Tyne, NE2 4AX, UK.
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Chatterjee S. A symbiotic view of the origin of life at hydrothermal impact crater-lakes. Phys Chem Chem Phys 2018; 18:20033-46. [PMID: 27126878 DOI: 10.1039/c6cp00550k] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Submarine hydrothermal vents are generally considered as the likely habitats for the origin and evolution of early life on Earth. The theory suffers from the 'concentration problem' of cosmic and terrestrial biomolecules because of the vastness of the Eoarchean global ocean. An attractive alternative site would be highly sequestered, small, hydrothermal crater-lakes that might have cradled life on early Earth. A new symbiotic model for the origin of life at hydrothermal crater-lakes is proposed here. Meteoritic impacts on the Eoarchean crust at the tail end of the Heavy Bombardment period might have played important roles in the origin of life. Impacts and collisions that created hydrothermal crater lakes on the Eoarchean crust inadvertently became the perfect crucibles for prebiotic chemistry with building blocks of life, which ultimately led to the first organisms by prebiotic synthesis. In this scenario, life arose through four hierarchical stages of increasing molecular complexity in multiple niches of crater basins. In the cosmic stage (≥4.6 Ga), the building blocks of life had their beginnings in the interstellar space during the explosion of a nearby star. Both comets and carbonaceous chondrites delivered building blocks of life and ice to early Earth, which were accumulated in hydrothermal impact crater-lakes. In the geologic stage (∼4 Ga), crater basins contained an assortment of cosmic and terrestrial organic compounds, powered by hydrothermal, solar, tidal, and chemical energies, which drove the prebiotic synthesis. At the water surface, self-assembled primitive lipid membranes floated as a thick oil slick. Archean Greenstone belts in Greenland, Australia, and South Africa possibly represent the relics of these Archean craters, where the oldest fossils of thermophilic life (∼3.5 Ga) have been detected. In the chemical stage, monomers such as nucleotides and amino acids were selected from random assemblies of the prebiotic soup; they were polymerized at pores of mineral surfaces with the coevolution of RNA and protein molecules to form the 'RNA/protein world'. Lipid membranes randomly encapsulated these RNA and protein molecules to initiate a molecular symbiosis in a 'RNA/protein/lipid world' that led to hierarchical emergence of several cell components: plasma membranes, ribosomes, coding RNA and proteins, DNA, and finally protocells with a primitive genetic code. In the biological stage, the emergence of the first cells capable of reproduction, heredity, variation, and Darwinian evolution is the key breakthrough in the origin of life. RNA virus and prions may represent the evolutionary relics of the RNA/protein world that survived as parasites for billions of years. Although the proposed endosymbiotic model is speculative it has intrinsic heuristic value. Future experiments on encapsulated RNA virus and prions have the potential to create a synthetic cell that may confirm a coherent narrative of this hierarchical evolutionary sequence.
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Affiliation(s)
- Sankar Chatterjee
- Department of Geosciences, Museum of Texas Tech University, P. O. Box 43191, Lubbock, TX 79409, USA.
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Beltrán-Heredia E, Almendro-Vedia VG, Monroy F, Cao FJ. Modeling the Mechanics of Cell Division: Influence of Spontaneous Membrane Curvature, Surface Tension, and Osmotic Pressure. Front Physiol 2017; 8:312. [PMID: 28579960 PMCID: PMC5437162 DOI: 10.3389/fphys.2017.00312] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 04/30/2017] [Indexed: 11/13/2022] Open
Abstract
Many cell division processes have been conserved throughout evolution and are being revealed by studies on model organisms such as bacteria, yeasts, and protozoa. Cellular membrane constriction is one of these processes, observed almost universally during cell division. It happens similarly in all organisms through a mechanical pathway synchronized with the sequence of cytokinetic events in the cell interior. Arguably, such a mechanical process is mastered by the coordinated action of a constriction machinery fueled by biochemical energy in conjunction with the passive mechanics of the cellular membrane. Independently of the details of the constriction engine, the membrane component responds against deformation by minimizing the elastic energy at every constriction state following a pathway still unknown. In this paper, we address a theoretical study of the mechanics of membrane constriction in a simplified model that describes a homogeneous membrane vesicle in the regime where mechanical work due to osmotic pressure, surface tension, and bending energy are comparable. We develop a general method to find approximate analytical expressions for the main descriptors of a symmetrically constricted vesicle. Analytical solutions are obtained by combining a perturbative expansion for small deformations with a variational approach that was previously demonstrated valid at the reference state of an initially spherical vesicle at isotonic conditions. The analytic approximate results are compared with the exact solution obtained from numerical computations, getting a good agreement for all the computed quantities (energy, area, volume, constriction force). We analyze the effects of the spontaneous curvature, the surface tension and the osmotic pressure in these quantities, focusing especially on the constriction force. The more favorable conditions for vesicle constriction are determined, obtaining that smaller constriction forces are required for positive spontaneous curvatures, low or negative membrane tension and hypertonic media. Conditions for spontaneous constriction at a given constriction force are also determined. The implications of these results for biological cell division are discussed. This work contributes to a better quantitative understanding of the mechanical pathway of cellular division, and could assist the design of artificial divisomes in vesicle-based self-actuated microsystems obtained from synthetic biology approaches.
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Affiliation(s)
- Elena Beltrán-Heredia
- Departamento de Física Atómica, Molecular y Nuclear, Universidad Complutense de MadridMadrid, Spain.,Departamento de Química Física I, Universidad Complutense de MadridMadrid, Spain
| | - Víctor G Almendro-Vedia
- Departamento de Física Atómica, Molecular y Nuclear, Universidad Complutense de MadridMadrid, Spain.,Departamento de Química Física I, Universidad Complutense de MadridMadrid, Spain
| | - Francisco Monroy
- Departamento de Química Física I, Universidad Complutense de MadridMadrid, Spain.,Translational Biophysics, Instituto de Investigación Sanitaria Hospital 12 de Octubre (imas12)Madrid, Spain
| | - Francisco J Cao
- Departamento de Física Atómica, Molecular y Nuclear, Universidad Complutense de MadridMadrid, Spain
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Pernpeintner C, Frank JA, Urban P, Roeske CR, Pritzl SD, Trauner D, Lohmüller T. Light-Controlled Membrane Mechanics and Shape Transitions of Photoswitchable Lipid Vesicles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:4083-4089. [PMID: 28361538 DOI: 10.1021/acs.langmuir.7b01020] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Giant unilamellar vesicles (GUVs) represent a versatile model system to emulate the fundamental properties and functions associated with the plasma membrane of living cells. Deformability and shape transitions of lipid vesicles are closely linked to the mechanical properties of the bilayer membrane itself and are typically difficult to control under physiological conditions. Here, we developed a protocol to form cell-sized vesicles from an azobenzene-containing phosphatidylcholine (azo-PC), which undergoes photoisomerization on irradiation with UV-A and visible light. Photoswitching within the photolipid vesicles enabled rapid and precise control of the mechanical properties of the membrane. By varying the intensity and dynamics of the optical stimulus, controlled vesicle shape changes such as budding transitions, invagination, pearling, or the formation of membrane tubes were achieved. With this system, we could mimic the morphology changes normally seen in cells, in the absence of any molecular machines associated with the cytoskeleton. Furthermore, we devised a mechanism to utilize photoswitchable lipid membranes for storing mechanical energy and then releasing it on command as locally usable work.
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Affiliation(s)
- Carla Pernpeintner
- Photonics and Optoelectronics Group, Department of Physics and CeNS, Ludwig Maximilians University Munich , Amalienstraße 54, 80799 Munich, Germany
- Nanosystems Initiative Munich, Schellingstraße 4, 80799 Munich, Germany
| | - James A Frank
- Department of Chemistry and Center for Integrated Protein Science, Ludwig Maximilians University Munich , Butenandtstraße 5-13, 81377 Munich, Germany
| | - Patrick Urban
- Photonics and Optoelectronics Group, Department of Physics and CeNS, Ludwig Maximilians University Munich , Amalienstraße 54, 80799 Munich, Germany
| | - Christian R Roeske
- Photonics and Optoelectronics Group, Department of Physics and CeNS, Ludwig Maximilians University Munich , Amalienstraße 54, 80799 Munich, Germany
| | - Stefanie D Pritzl
- Photonics and Optoelectronics Group, Department of Physics and CeNS, Ludwig Maximilians University Munich , Amalienstraße 54, 80799 Munich, Germany
| | - Dirk Trauner
- Department of Chemistry and Center for Integrated Protein Science, Ludwig Maximilians University Munich , Butenandtstraße 5-13, 81377 Munich, Germany
- Nanosystems Initiative Munich, Schellingstraße 4, 80799 Munich, Germany
| | - Theobald Lohmüller
- Photonics and Optoelectronics Group, Department of Physics and CeNS, Ludwig Maximilians University Munich , Amalienstraße 54, 80799 Munich, Germany
- Nanosystems Initiative Munich, Schellingstraße 4, 80799 Munich, Germany
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8
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Scholey JM, Civelekoglu-Scholey G, Brust-Mascher I. Anaphase B. BIOLOGY 2016; 5:biology5040051. [PMID: 27941648 PMCID: PMC5192431 DOI: 10.3390/biology5040051] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 11/30/2016] [Accepted: 12/01/2016] [Indexed: 11/16/2022]
Abstract
Anaphase B spindle elongation is characterized by the sliding apart of overlapping antiparallel interpolar (ip) microtubules (MTs) as the two opposite spindle poles separate, pulling along disjoined sister chromatids, thereby contributing to chromosome segregation and the propagation of all cellular life. The major biochemical “modules” that cooperate to mediate pole–pole separation include: (i) midzone pushing or (ii) braking by MT crosslinkers, such as kinesin-5 motors, which facilitate or restrict the outward sliding of antiparallel interpolar MTs (ipMTs); (iii) cortical pulling by disassembling astral MTs (aMTs) and/or dynein motors that pull aMTs outwards; (iv) ipMT plus end dynamics, notably net polymerization; and (v) ipMT minus end depolymerization manifest as poleward flux. The differential combination of these modules in different cell types produces diversity in the anaphase B mechanism. Combinations of antagonist modules can create a force balance that maintains the dynamic pre-anaphase B spindle at constant length. Tipping such a force balance at anaphase B onset can initiate and control the rate of spindle elongation. The activities of the basic motor filament components of the anaphase B machinery are controlled by a network of non-motor MT-associated proteins (MAPs), for example the key MT cross-linker, Ase1p/PRC1, and various cell-cycle kinases, phosphatases, and proteases. This review focuses on the molecular mechanisms of anaphase B spindle elongation in eukaryotic cells and briefly mentions bacterial DNA segregation systems that operate by spindle elongation.
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Affiliation(s)
- Jonathan M Scholey
- Department of Molecular and Cell Biology, University of California, Davis, CA 95616, USA.
| | | | - Ingrid Brust-Mascher
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
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Divided we stand: splitting synthetic cells for their proliferation. SYSTEMS AND SYNTHETIC BIOLOGY 2014; 8:249-69. [PMID: 25136387 DOI: 10.1007/s11693-014-9145-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 03/29/2014] [Accepted: 04/01/2014] [Indexed: 01/22/2023]
Abstract
With the recent dawn of synthetic biology, the old idea of man-made artificial life has gained renewed interest. In the context of a bottom-up approach, this entails the de novo construction of synthetic cells that can autonomously sustain themselves and proliferate. Reproduction of a synthetic cell involves the synthesis of its inner content, replication of its information module, and growth and division of its shell. Theoretical and experimental analysis of natural cells shows that, whereas the core synthesis machinery of the information module is highly conserved, a wide range of solutions have been realized in order to accomplish division. It is therefore to be expected that there are multiple ways to engineer division of synthetic cells. Here we survey the field and review potential routes that can be explored to accomplish the division of bottom-up designed synthetic cells. We cover a range of complexities from simple abiotic mechanisms involving splitting of lipid-membrane-encapsulated vesicles due to physical or chemical principles, to potential division mechanisms of synthetic cells that are based on prokaryotic division machineries.
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Almendro-Vedia VG, Monroy F, Cao FJ. Mechanics of constriction during cell division: a variational approach. PLoS One 2013; 8:e69750. [PMID: 23990888 PMCID: PMC3749217 DOI: 10.1371/journal.pone.0069750] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2013] [Accepted: 06/12/2013] [Indexed: 11/19/2022] Open
Abstract
During symmetric division cells undergo large constriction deformations at a stable midcell site. Using a variational approach, we investigate the mechanical route for symmetric constriction by computing the bending energy of deformed vesicles with rotational symmetry. Forces required for constriction are explicitly computed at constant area and constant volume, and their values are found to be determined by cell size and bending modulus. For cell-sized vesicles, considering typical bending modulus of [Formula: see text], we calculate constriction forces in the range [Formula: see text]. The instability of symmetrical constriction is shown and quantified with a characteristic coefficient of the order of [Formula: see text], thus evidencing that cells need a robust mechanism to stabilize constriction at midcell.
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Affiliation(s)
- Victor G. Almendro-Vedia
- Departamento de Física Atómica, Molecular y Nuclear and Departamento de Química Física I, Universidad Complutense, Avenida Complutense s/n, Madrid, Spain
| | - Francisco Monroy
- Departamento de Química Física I, Universidad Complutense, Avenida Complutense s/n, Madrid, Spain
| | - Francisco J. Cao
- Departamento de Física Atómica, Molecular y Nuclear, Universidad Complutense, Avenida Complutense s/n, Madrid, Spain
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Mercier R, Kawai Y, Errington J. Excess membrane synthesis drives a primitive mode of cell proliferation. Cell 2013; 152:997-1007. [PMID: 23452849 DOI: 10.1016/j.cell.2013.01.043] [Citation(s) in RCA: 141] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2012] [Revised: 12/12/2012] [Accepted: 01/24/2013] [Indexed: 11/30/2022]
Abstract
The peptidoglycan cell wall is a hallmark of the bacterial subkingdom. Surprisingly, many modern bacteria retain the ability to switch into a wall-free state called the L-form. L-form proliferation is remarkable in being independent of the normally essential FtsZ-based division machinery and in occurring by membrane blebbing and tubulation. We show that mutations leading to excess membrane synthesis are sufficient to drive L-form division in Bacillus subtilis. Artificially increasing the cell surface area to volume ratio in wild-type protoplasts generates similar shape changes and cell division. Our findings show that simple biophysical processes could have supported efficient cell proliferation during the evolution of early cells and provide an extant biological model for studying this problem.
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Affiliation(s)
- Romain Mercier
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Medical School, Newcastle University, Richardson Road, Newcastle upon Tyne NE2 4AX, UK
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Murtas G. Early self-reproduction, the emergence of division mechanisms in protocells. MOLECULAR BIOSYSTEMS 2012; 9:195-204. [PMID: 23232904 DOI: 10.1039/c2mb25375e] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Synthetic Biology approaches are proposing model systems and providing experimental evidences that life can arise as spontaneous chemical self-assembly process where the ability to reproduce itself is an essential feature of the living system. The appearance of early cells has required an amphiphilic membrane compartment to confine molecular information against diffusion, and the ability to self-replicate the boundary layer and the genetic information. The initial spontaneous self-replication mechanisms based on thermodynamic instability would have evolved in a prebiotic and later biological catalysis. Early studies demonstrate that fatty acids spontaneously assemble into bilayer membranes, building vesicles able to grow by incorporation of free lipid molecules and divide. Early replication mechanisms may have seen inorganic molecules playing a role as the first catalysts. The emergence of a short ribozyme or short catalytic peptide may have initiated the first prebiotic membrane lipid synthesis required for vesicle growth. The evolution of early catalysts towards the simplest translation machine to deliver proteins from RNA sequences was likely to give early birth to one single enzyme controlling protocell membrane division. The cell replication process assisted by complex enzymes for lipid synthesis is the result of evolved pathways in early cells. Evolution from organic molecules to protocells and early cells, thus from chemistry to biology, may have occurred in and out of the boundary layer. Here we review recent experimental work describing membrane and vesicle division mechanisms based on chemico-physical spontaneous processes, inorganic early catalysis and enzyme based mechanisms controlling early protocell division and finally the feedback from minimal genome studies.
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Affiliation(s)
- Giovanni Murtas
- Istituto di Farmacologia Traslazionale, CNR, via fosso del Cavaliere 100, 00133, Roma, Italy.
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Briers Y, Walde P, Schuppler M, Loessner MJ. How did bacterial ancestors reproduce? Lessons from L-form cells and giant lipid vesicles. Bioessays 2012; 34:1078-84. [DOI: 10.1002/bies.201200080] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Intracellular vesicles as reproduction elements in cell wall-deficient L-form bacteria. PLoS One 2012; 7:e38514. [PMID: 22701656 PMCID: PMC3368840 DOI: 10.1371/journal.pone.0038514] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 05/07/2012] [Indexed: 11/19/2022] Open
Abstract
Cell wall-deficient bacteria, or L-forms, represent an extreme example of bacterial plasticity. Stable L-forms can multiply and propagate indefinitely in the absence of a cell wall. Data presented here are consistent with the model that intracellular vesicles in Listeria monocytogenes L-form cells represent the actual viable reproductive elements. First, small intracellular vesicles are formed along the mother cell cytoplasmic membrane, originating from local phospholipid accumulation. During growth, daughter vesicles incorporate a small volume of the cellular cytoplasm, and accumulate within volume-expanding mother cells. Confocal Raman microspectroscopy demonstrated the presence of nucleic acids and proteins in all intracellular vesicles, but only a fraction of which reveals metabolic activity. Following collapse of the mother cell and release of the daughter vesicles, they can establish their own membrane potential required for respiratory and metabolic processes. Premature depolarization of the surrounding membrane promotes activation of daughter cell metabolism prior to release. Based on genome resequencing of L-forms and comparison to the parental strain, we found no evidence for predisposing mutations that might be required for L-form transition. Further investigations revealed that propagation by intracellular budding not only occurs in Listeria species, but also in L-form cells generated from different Enterococcus species. From a more general viewpoint, this type of multiplication mechanism seems reminiscent of the physicochemical self-reproducing properties of abiotic lipid vesicles used to study the primordial reproduction pathways of putative prokaryotic precursor cells.
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Abstract
Self-assembled vesicles are essential components of primitive cells. We review the importance of vesicles during the origins of life, fundamental thermodynamics and kinetics of self-assembly, and experimental models of simple vesicles, focusing on prebiotically plausible fatty acids and their derivatives. We review recent work on interactions of simple vesicles with RNA and other studies of the transition from vesicles to protocells. Finally we discuss current challenges in understanding the biophysics of protocells, as well as conceptual questions in information transmission and self-replication.
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Affiliation(s)
- Irene A Chen
- FAS Center for Systems Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
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