When the pressure builds, archaea go multicellular

Archaea are tiny, single-celled organisms often confused with bacteria. They live everywhere – from inside salty lakes to down our own guts – and yet, they rarely get the attention they deserve.

Although they are unicellular and might look like bacteria on the outside, archaea are genetically closer to plants and animals.

And now, new research shows they’re capable of something that was long thought to be exclusive to more complex life forms.

Scientists have uncovered a surprising trait in archaea: under certain physical conditions, these microscopic organisms can behave like multicellular beings.

This finding may change the way we think about life’s earliest building blocks and the evolution of biological complexity.

What makes archaea so unique?

Archaea don’t have the rigid cell walls that many bacteria do. Instead, they’re wrapped in a flexible protein surface. That detail sparked curiosity.

“The absence of a covalent-bound cell wall suggests a more dynamic, but less rigid structure, leading to the hypothesis that archaea might be ‘squishy’ and sensitive to mechanical stimuli,” explained Alex Bisson from Brandeis University.

This initial hunch led the research team to examine what happens when these “squishy” cells are put under pressure.

The result? A completely unexpected display of complex behavior.

From simplicity to multicellular structure

The team studied Haloferax volcanii, an archaeon known for surviving in extreme environments like salt flats.

When the cells of this species were placed under mechanical pressure, something extraordinary occurred. They didn’t divide the way that single-celled organisms normally do.

Instead, they got bigger and started forming organized structures that resembled tissues. These clusters even contained multiple copies of genetic material.

“It was Theopi Rados, the first author leading the project, who first observed and described this remarkable behavior,” said Bisson.

“As Olivia Leland, co-first author, aptly put it – it’s as if the cells were squished down and then encouraged to grow wider and taller, more like a rising sourdough loaf than traditional cell division.”

This physical transformation suggests that archaea have a hidden potential for structural organization, despite their very ancient origins.

“That such behavior can be triggered by a simple physical constraint and involves cytoskeletal remodeling, and coordinated cellularization suggests that the capacity for structural organization runs deeper in biology than previously thought,” remarked Rados.

A universal thread of complexity?

This study doesn’t just shed light on the archaea – it challenges assumptions about all forms of life.

“Our work shows that the emergence of complexity in life isn’t limited to a few special branches on the tree of life – it’s a deeper property, present even in lineages we’ve long overlooked,” noted Vikram Alva of the Max Planck Institute for Biology in Tübingen.

“This work also underscores the power of combining comparative genomics with observable traits to uncover genes behind novel behaviors – an approach that has long driven discoveries in plants and animals,” Pedro Escudeiro, a postdoctoral researcher in the Alva group, added.

The research emphasizes that mechanical pressure alone can coax a basic single-celled organism into displaying a complex, multicellular-like response.

“The fact that archaea can orchestrate complex from tissue-like structures suggests that nature can emerge complex traits from seemingly unsophisticated raw materials,” remarked Bisson.

A new direction in cell biology

The findings may not only be applicable to archaea.

“We found that mechanical compression induces multicellularity, a surprising finding, to say the least!” said Tanmay Bharat from the MRC Laboratory of Molecular Biology in Cambridge.

This suggests other single-celled organisms might also have the hidden ability to form multicellular structures – if exposed to the right conditions.

It’s long been understood that archaea don’t do well in confined spaces, likely due to their flexible outer layers. But now, that same flexibility appears to be key to their ability to adapt and organize.

This raises an important question for future research: Could multicellularity be a more common and accessible state than previously believed?

This study encourages scientists to revisit the origins of complex life – not just by examining genetics, but by paying attention to the physical forces that shape biology from the outside in.

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Researchers from Brandeis University, the MRC Laboratory of Molecular Biology in Cambridge, and the Max Planck Institute for Biology in Tübingen participated in this study.

The full study was published in the journal Science.

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