New research suggests that colonies ofbacteria can organize themselves into ring-like patterns which are similar to embryo development and were thought to be unique to plants and animals.
A growing reputation for acting strangely like multicellular organisms has led to the emergence of colonies ofbacteria called biofilms. The sticky plaque that builds up on our teeth can be found almost anywhere, from boat hull to crops.
As we have come to learn, biofilms can form sophisticated patterns that look like how plants and animals grow, as this new research shows.
"We are seeing that biofilms are much more sophisticated than we thought, and that they share a collective memory similar to neurons in the brain," says Grol Sel of the University of California San Diego, whose previous research suggested biofilms share a collective memory similar to neurons in
It's been shown that biofilms can use long-range electrical signals to recruit other species to join their communities.
Sel and colleagues have observed ring-like structures in the lab that are reminiscent of developmental'stripes' seen in plants and animals.
In multicellular organisms, this cellular patterning known as segmentation gives rise to different types of tissues and complex body forms, whereas the most primitive structures of single-cell bacterium are thought to be the most primitive.
The researchers write that their discovery shows that the developmental patterning mechanism is exclusive to plant systems.
In the lab, the team grew a rod-shaped bacterium that is found in soil and humans.
The growing biofilms formed clear circular bands when they were deprived of nitrogen. The video shows a colony growing over two days.
The researchers think that this patterning is caused by a genetic circuitry in the cells that responds to stress when there is a shortage of nitrogen.
The modelling and experiments showed that as the biofilms grew, a 'wave' of nutrient depletion moved across the bacterial cells, essentially 'freezing' each cell in place with the stress-mitigating genes they were using at the time.
The researchers found that the stress response created repeating segments of different cell types in the circular biofilm, which is consistent with a 'clock and waveform' mechanism, which has only been seen in highly evolved organisms before this.
"In an expanding biofilm, replicating cells at the leading edge might naturally occur during development, leaving behind daughter cells that become embedded within the biofilm and thus have less nutrient access," the researchers wrote.
Sel and colleagues speculate that this patterning mechanism might be another way that biofilms cope with unpredictable conditions, as not all spores are formed at the same time and the same region of the biofilm.
The researchers note that this is not the first time that scientists have spied communities mimicking multicellular organisms, and there are obvious differences between the two.
In 2020, scientists showed how the growth of a colony is similar to the development of an embryo.
The first life was multicellular, and not a single-celled, according to a geneticist from the Catholic University of Croatia.
Sel and colleagues point out that there are no clear-cut boundaries between cell types in the same way that embryos have no clear-cut boundaries between cell layers.
The recent observations are reigniting some big questions about what constitutes a multicellular organisms when simple single-celled organisms appear to be far more advanced than we first thought.
The debate will be renewed by this latest study, according to Tanmay Bharat. It would be interesting to study where the differences are.
The study was published in a journal.
