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Early Life Could Have Originated Without Membranes

3D illustration of human cells with visible nuclei, representing biological cell structure.
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A team of researchers at Ludwig-Maximilians-Universität (LMU) has demonstrated that metabolic reactions can take place in the absence of a cell membrane, within water-filled pores exposed to heat flow. This experimental setup simulates conditions thought to be common on early Earth and suggests a plausible setting for the emergence of life.


The study, published in Nature Physics, explores how thin rock pores, containing small volumes of water and exposed to a temperature gradient, can concentrate diverse molecular components and trigger reactions. These confined environments lack any physical boundaries akin to modern cell membranes but can still promote interactions between biological building blocks.

A physical setting for protometabolism

The researchers used custom chambers to replicate water-filled pores, sandwiching a sheet of water between transparent plates and applying a temperature gradient across it. They observed that the thermal difference causes diluted molecules to accumulate toward the colder side, leading to sufficient concentrations to initiate biochemical reactions.


Polymerase

A polymerase is an enzyme that synthesizes long chains of nucleic acids. It is critical in processes like DNA replication and RNA transcription in living organisms.

Thermal gradient

A thermal gradient refers to a difference in temperature across a physical space. It can drive the movement and accumulation of molecules and is thought to have played a role in early biochemical reactions.


In these experiments, more than 100 molecular components were introduced, including amino acids, nucleotides, ribosomes and polymerases. These are the essential ingredients for protein and RNA synthesis. When left diluted, the mixture could not initiate protein production. However, under the applied heat flow, the components concentrated and successfully synthesized a marker protein known as superfolder green fluorescent protein (sfGFP).


Superfolder green fluorescent protein (sfGFP)

sfGFP is a stable and highly fluorescent variant of green fluorescent protein. It is often used in molecular biology as a marker to track gene expression or protein production.

Challenging the role of membranes in early life

The findings challenge the assumption that cell membranes are a prerequisite for organized biochemical activity. Instead, the thermal gradient in confined pores can mimic some of the functions of membranes, such as compartmentalization and concentration of reactants, without forming a physical boundary.

“Our investigations show that this simple physical mechanism, which would have been very common on early Earth, can perform many functions that would normally require a cell membrane.”



Dr. Dieter Braun.

This insight offers a potential solution to the longstanding question of how cellular life could begin in the absence of fully formed membranes or established metabolic cycles. It supports the idea that life may have originated in geothermally active environments where heated rock and water interacted in microstructured spaces.

Applications for synthetic biology

Beyond its implications for the origin of life, the study also opens new possibilities for synthetic biology. Creating artificial cells that sustain themselves and divide has been limited by the need for membrane structures that permit nutrient exchange. This research suggests that non-membranous systems based on thermal gradients could serve as a platform for building simpler synthetic life forms.


Reference: Floroni A, Yeh Martín N, Matreux T, et al. Membraneless protocell confined by a heat flow. Nat Phys. 2025. doi: 10.1038/s41567-025-02935-4


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