Biology subjects

Gozen, I.

Publications and source records attributed to Gozen, I..

9 recordsLinked to original sources

bioRxiv2025

Protocell formation on micrometeorites

We report on the formation of membranous protocells by self-assembly of lipids on micrometeorites, the extraterrestrial particles that have been continuously reaching the surface of the Earth ever since its formation. Synergistic interactions of lipid compartments with pristine extraterrestrial surfaces are entirely unexplored, but constitute a possible scenario for early evolution of primitive cells by a surface energy-driven transformation mechanism. Lipids utilize the surface energy of the particles to adhere to them and autonomously transform into spherical compartments, typically through formation of lipid nanotubes. Natural sand particles of similar composition and shape were simultaneously investigated for reference, showing that certain lipid compositions prefer micrometeorite surfaces. The elemental composition of the particles, their surface texture and cleanness altogether may be contributing to the differences observed in lipid behavior. Lipid nanotubes on- and extending out of- the micrometeorites were observed to carry lipid particles and connect to other objects in the surrounding environment.

biophysics↗

bioRxiv2021

Colony-like Protocell Superstructures

We report the formation, growth, and dynamics of model protocell superstructures on solid surfaces, resembling single cell colonies. These structures, consisting of several layers of lipidic compartments enveloped in a dome-shaped outer lipid bilayer, emerged as a result of spontaneous shape transformation of lipid agglomerates deposited on thin film aluminum surfaces. Collective protocell structures were observed to be mechanically more stable compared to isolated spherical compartments. We show that the model colonies encapsulate DNA and accommodate non-enzymatic, strand displacement DNA reactions. The membrane envelope is able to disassemble and expose individual daughter protocells, which can migrate and attach via nano-tethers to distant surface locations, while maintaining their encapsulated contents. Some colonies feature exo-compartments, which spontaneously extend out of the enveloping bilayer, internalize DNA, and merge again with the superstructure. A continuum elastohydrodynamic theory that we developed reveals that the subcompartment formation must be governed by attractive van der Waals (vdW) interactions between the membrane and surface. The balance between membrane bending and vdW interactions yields a critical length scale of 273 nm, above which the membrane invaginations can form subcompartments. The findings support our hypotheses that in extension of the lipid world hypothesis, protocells may have existed in the form of colonies, potentially benefiting from the increased mechanical stability provided by a superstructure.

biophysics↗

bioRxiv2021

Transport among protocells via tunneling nanotubes

We employ model protocell networks for evaluation of molecular transport through lipid nanotubes as potential means of communication among primitive cells on the early Earth. Network formation is initiated by deposition of multilamellar lipid reservoirs onto a silicon oxide surface in an aqueous environment. These reservoirs autonomously develop into surface-adhered protocells interconnected via lipid nanotubes, and encapsulate solutes from the ambient buffer in the process. We prepare networks in the presence of DNA and RNA and observe encapsulation of these molecules, and their diffusive transport between the lipid compartments via the interconnecting nanotubes. By means of an analytical model we determine key physical parameters affecting the transport, such as nanotube diameter and compartment size. We conclude that nanotube-mediated transport in self-organized nanotube-vesicle networks could have been a possible pathway of chemical communication between primitive, self-assembled protocells under early earth conditions, circumventing the necessity for crossing the membrane barrier. We suggest this transport within a closed protocell network as a feasible means of RNA and DNA exchange under primitive prebiotic conditions, possibly facilitating early replication.

biophysics↗

bioRxiv2021

Spontaneous formation of prebiotic compartment colonies on Hadean Earth and pre-Noachian Mars

The primitive cells that emerged at the origin of life are commonly viewed as spherical biosurfactant shells, freely suspended in aqueous media1-3. This model explains initial, but not subsequent events in the development process towards structured protocells. Taking into consideration the involvement of naturally occurring surfaces, which were abundant on the early Earth4, we report feasible and productive pathways for the development of primitive cells. Surfaces intrinsically possess energy, easily utilized by the interfacing amphiphiles, such as lipids, to attain self-organization and spontaneous transformations5-7. We show that the physical interaction of phospholipid pools with 20 Hadean Earth analogue materials as well as a Martian meteorite composed of fused regolith representing the ancient crust of Mars, consistently lead to the shape transformation and autonomous formation of surfactant compartment assemblies. Dense, colony-like protocell populations grow from these lipid deposits, predominantly at the grain boundaries or cleavages of the investigated natural surfaces, and remain there for several days. The model protocells in our study are able to autonomously develop, transform and pseudo-divide, and encapsulate RNA as well as DNA. We also demonstrate that they can accommodate non-enzymatic, DNA strand displacement reactions. Our findings suggest a feasible route towards the transformation from nonliving to living entities, and provide fresh support for the Lipid World hypothesis8.

biophysics↗

bioRxiv2021

Mixed fatty acid-phospholipid protocell networks

Self-assembled membranes composed of both fatty acids and phospholipids are both permeable for solutes and structurally stable, which was likely an advantageous combination for the development of primitive cells on the early Earth. Here we report on the solid surface-assisted formation of primitive mixed-surfactant membrane compartments, i.e. model protocells, from multilamellar lipid reservoirs composed of different ratios of fatty acids and phospholipids. Similar to the previously discovered enhancement of model protocell formation on solid substrates, we achieve spontaneous multi-step self-transformation of mixed surfactant reservoirs into closed surfactant containers, interconnected via nanotube networks. Some of the fatty acid containing compartments in the networks exhibit colony-like growth. We demonstrate that the compartments generated from fatty acid-containing phospholipid membranes feature increased permeability coefficients for molecules in the ambient solution, for fluorescein up to 7*10-6 cm/s and for RNA up to 3.5*10-6 cm/s. Our findings indicate that surface-assisted autonomous protocell formation and development, starting from mixed amphiphiles, is a plausible scenario for the early stages of the emergence of primitive cells.

biophysics↗

bioRxiv2020

Subcompartmentalization and pseudo-division of model protocells

Membrane enclosed intracellular compartments have been exclusively associated with the eukaryotes, represented by the highly compartmentalized last eukaryotic common ancestor. Recent evidence showing the presence of membranous compartments with specific functions in archaea and bacteria makes it conceivable that the last universal common ancestor and its hypothetical precursor, the protocell, could have exhibited compartmentalization. To our knowledge, there are no experimental studies yet that have tested this hypothesis. We report on an autonomous subcompartmentalization mechanism for protocells which results in the transformation of initial subcompartments to daughter protocells. The process is solely determined by the fundamental materials properties and interfacial events, and do not require biological machinery or chemical energy supply. In the light of our findings, we propose that similar events could have taken place under early Earth conditions, leading to the development of compartmentalized cells and potentially, primitive division.

biophysics↗

bioRxiv2020

Rapid growth and fusion of protocells in surface-adhered membrane networks

Elevated temperatures might have promoted the nucleation, growth and replication of protocells on the early Earth. Recent reports have shown evidence that moderately high temperatures not only permit protocell assembly at the origin of life, but could have actively supported it. Here we show the fast nucleation and growth of vesicular compartments from autonomously formed lipid networks on solid surfaces, induced by a moderate increase in temperature. Branches of the networks, initially consisting of self-assembled interconnected nanotubes, rapidly swell into microcompartments which can spontaneously encapsulate RNA fragments. The increase in temperature further causes fusion of adjacent network-connected compartments, resulting in the redistribution of the RNA. The experimental observations and the mathematical model indicate that the presence of nanotubular interconnections between protocells facilitates the fusion process.

biophysics↗

bioRxiv2018

A cellular automaton for modeling non-trivial biomembrane ruptures

A novel cellular automaton (CA) for simulating biological membrane rupture is proposed. Constructed via simple rules governing deformation, tension, and fracture, the CA incorporates ideas from standard percolation models and bond-based fracture methods. The model is demonstrated by comparing simulations with experimental results of a double bilayer lipid membrane expanding on a solid substrate. Results indicate that the CA can capture non-trivial rupture morphologies such as floral patterns and the saltatory dynamics of fractal avalanches observed in experiments. Moreover, the CA provides insight into the poorly understood role of inter-layer adhesion, supporting the hypothesis that the density of adhesion sites governs rupture morphology.

bioengineering↗

bioRxiv2018

A nanotube-mediated path to protocell formation

Cellular compartments are membrane-enclosed, spatially distinct microenvironments which confine and protect biochemical reactions in the biological cell. On the early Earth, the autonomous formation of compartments is thought to have led to the encapsulation of nucleotides, thereby satisfying a starting condition for the emergence of life. Recently, surfaces have come into focus as potential platforms for the self-assembly of prebiotic compartments, as significantly enhanced vesicle formation was reported in the presence of solid interfaces. The detailed mechanism of such formation at the mesoscale is still under discussion. We report here on the spontaneous transformation of solid surface-adhered lipid deposits to unilamellar membrane compartments through a straightforward sequence of topological changes, proceeding via a network of interconnected lipid nanotubes. We show that this transformation is entirely driven by surface-free energy minimization and does not require hydrolysis of organic molecules, or external stimuli such as electrical currents or mechanical agitation. The vesicular structures take up and encapsulate their external environment during formation, and can subsequently separate and migrate upon exposure to hydrodynamic flow. This may link, for the first time, the self-directed transition from weakly organized bioamphiphile assemblies on solid surfaces to protocells with secluded internal contents.\n\nSignificanceThe nature of the physical and chemical mechanisms behind the formation, growth and division of the earliest protocells is among the key questions concerning the origin of life. Establishing a simple pathway for the assembly of protocell structures from the primordial soup is a particular challenge. Emerging evidence supporting the assumption that solid surfaces have a governing role in protocell formation has recently expanded the scope, and created new inspiration for investigation. By presenting a physical path from self-assembled amphiphile-based membranes on solid surfaces to spherical single-membrane compartments via a consistent sequence of transformations, solely driven by the materials properties of the interfaces, a direct link between the presence of functional biomolecules and the development of protocells can be established.

biophysics↗