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'Simple' microorganisms have been discovered to organize themselves in complex patterns.

Gürol Süel's group at the University of California San Diego has discovered a number of amazing characteristics displayed by clusters of bacteria that dwell together in communities known as biofilms over the last several years.

Biofilms can be found in a variety of places in the living world, including sewer pipes, kitchen worktops, and even the surfaces of our teeth. A prior study found that these biofilms use sophisticated mechanisms to communicate with one another, while another found that biofilms had a strong memory capacity.

Süel's lab, in collaboration with Stanford University and the Universitat Pompeu Fabra in Spain, has discovered a biofilm trait that reveals these communities to be significantly more evolved than previously thought. Biofilm cells are arranged in elaborate patterns, a feature previously solely associated with higher-level organisms such as plants and animals, according to Biological Sciences graduate student Kwang-Tao Chou, former Biological Sciences graduate student Daisy Lee, Süel, and his colleagues. The findings, which are the result of eight years of research, were published in the journal Cell on January 6th.

Süel, a UC San Diego professor in the Division of Biological Sciences' Section of Molecular Biology with affiliations in the San Diego Center for Systems Biology, BioCircuits Institute, and Center for Microbiome Innovation, said, "We are seeing that biofilms are much more sophisticated than we thought." "From a scientific standpoint, our findings show that cell patterning throughout development is far older than previously understood. The ability of cells to segment themselves in space and time appears to have evolved over a billion years, not just in plants and vertebrates."

Biofilm communities are made up of a variety of cells. Previously, scientists did not believe that these diverse cells could be ordered into intricate, regulated patterns. The researchers created experiments and a mathematical model to uncover the genetic foundation for a "clock and wavefront" process, which had previously only been seen in highly evolved creatures such as plants, fruit flies, and humans. As the biofilm grows and consumes nutrients, a "wave" of nutrient depletion sweeps across the bacterial community, freezing a molecular clock inside each cell at a specific time and location, resulting in a complex composite pattern of repeated segments of different cell types.

The ability to uncover the genetic circuit underpinning the biofilm's ability to form community-wide concentric rings of gene expression patterns was a milestone for the researchers. The researchers were then able to develop predictions that showed biofilms could create numerous segments on their own.

The authors of the Cell publication write, "Our study indicates that bacterial biofilms exploit a developmental patterning mechanism previously thought to be specific to vertebrates and plant systems."

The findings of the study have ramifications in a variety of fields of study. Biofilms are of interest in applications ranging from medical to the food industry, and even the military, due to their pervasiveness in our lives. Biofilms, as platforms capable of testing how simple cell systems may organise themselves into complex patterns, could be beneficial in developmental biology, for example, to explore specific features of the clock and waveform mechanism in vertebrates.

"We can see that bacterial communities are not just globs of cells," said Süel, who sees bacteria as new paradigms for investigating developmental patterns as a result of research collaborations. "Having a bacterial system helps us to supply some answers that are harder to achieve in vertebrate and plant systems since bacteria are more experimentally accessible systems that may bring new insights for the study of development," says the researcher.

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