Microbial cells have a fascinating and unexpected communication system

It’s not every day that humble microbial cells make a splash, but recent research indicates that these tiny life forms have an unexpected capacity to exchange electrical signals and coordinate motions.

They might look simple on the outside, yet new findings suggest their internal teamwork is more complex than we once thought. 

The research reveals that colonies of a single-celled organism called Salpingoeca rosetta actively synchronize their shape and movement through voltage-gated calcium signals. 

This activity appears to happen at the edge of multicellularity, offering curious hints about how animals may have gained their early nerve and muscle systems.

Signaling in microbial cell colonies

Biologists have known for years that these marine microorganisms can form small, ball-shaped clusters, yet only now are researchers uncovering the communication channels they use to coordinate their shape changes. 

The study at the center of this buzz was spearheaded by first author Jeffrey Colgren and last author Pawel Burkhardt, from the Burkhardt group at the Michael Sars Centre, University of Bergen. 

They found that, when these microbes link up into rosette-shaped colonies, they pull off synchronized stunts involving cell contraction and simultaneous flagellar “pauses.”

The group observed that these moves can be switched on and off by altering the levels of calcium outside the cells.

Origin of multicellularity in microbes

“We found communication among the cells of the colonies, which regulates shape and ciliary beating across the rosette,” explained Colgren.

He observed that each individual cell within the cluster uses its own voltage-gated calcium channels. That same type of channel is present in the muscles and nerves of animals. 

At a glance, it might sound fancy for a microbe, but it highlights the possibility that simpler creatures already had the building blocks for complex body structures.

The ability to start or stop movement on a dime allows each cell to respond to environmental changes with surprising speed.

Parallels in microbial cell signaling

One intriguing parallel can be seen in certain sponges that also rely on active tissues to draw water through their bodies, even though they are without nerves or muscles.

A sponge can briefly halt the beating of its collar cells after sensing undesirable particles in the water. S. rosetta, for its part, demonstrates a small-scale version of this process by using coordinated pulses of calcium to stop ciliary beating. 

Observers notice that this phenomenon can happen in unison across the entire colony, which is quite a feat for an organism that doesn’t even crack the millimeter mark.

Multicellularity in action

“S. rosetta is a powerful model for investigating the emergence of multicellularity,” says Burkhardt. The dividing line between single-celled and multicellular life can be fuzzy, and organisms like S. rosetta flip back and forth between being solitary and grouping up. 

The fact that these microbes can share signals within a colony suggests that they possess at least some basic wiring for collaboration. That coordination might be especially useful in crowded or changing conditions. 

Scientists suspect that if cells can pass electrical messages around the circle, then the whole cluster acts as a better-fed, more unified version of itself.

Importance for early nervous systems

“This evidence of how information flows between cells in choanoflagellate colonies demonstrates cell-cell signaling at the cusp of multicellularity,” stressed Colgren.

The big takeaway is that a group of cells – still lacking real nerve fibers – can synchronize movements using communication patterns similar to those used in animal neurons. 

This discovery runs alongside the idea that ancient organisms may have started with basic electrical networks, eventually paving the way for today’s complex brains.

It also raises the question whether other, simple life forms also have hidden communication systems that have not yet been detected.

Feeding and coordination

By forming a rosette, these cells place their feeding structures on the outside surface.

This arrangement can help them capture bacterial prey with extra efficiency, especially if every cell coordinates its efforts. Prior analyses hint that improved feeding was a key perk of early multicellularity. 

Researchers saw that when S. rosetta’s cilia pause, food particles sometimes get jostled loose, suggesting that minor “resets” keep the filter mechanism going at its best.

Colonies might even share information about local bacterial levels, so everyone benefits from the best mealtime strategies.

Future of microbial cell signaling research

“The tools developed and findings from this study open up a lot of new and interesting questions,” stated Colgren. There is now an eagerness to investigate how, exactly, the signals hop from one cell to the next. 

A line of inquiry also involves whether these mini-contractions might influence swimming direction, colony spacing, or survival in shifting environments.

The researchers aim to see if other choanoflagellate species carry the same equipment or use different methods for cellular harmony. 

As the team refines their imaging and genetic approaches, the hope is that future experiments will keep revealing bigger clues about the earliest sparks of nerve and muscle function.

Glancing back, looking ahead

The excitement around these discoveries reflects how little we know about the fine details of life’s transition from single celled organisms to multicellular animals and plants.

What looks basic or primitive can teach us a lot about how real bodies coordinate movement, sense surroundings, and evolve new types of organization. 

Tiny though they may be, these rosette-forming microbes remind us that even the smallest corners of biology hold plenty of intrigue for those willing to take a closer peek.

The study is published in Science Advances.

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