‘Simple’ bacteria found to organize surprisingly elaborate patterns

UCSD researchers found that Bacillus subtilis, a soil bacterium, creates concentric rings reminiscent of developmental “lines” created by the tick clock. The researchers discovered that bacterial biofilms use a clock-wave interface process to form a cell similar to that of plants and animals. Credit: Kwang Tao Chu

She found the genetic mechanism that enables bacterial cell communities to organize into surprisingly complex parts, revealing similarities with how plants and animals evolved.

Over the past several years, research from the lab of biologist Gurul Sol at the University of California San Diego has revealed a series of fascinating features exhibited by groups of bacteria that live together in communities known as biofilms.

Biofilms permeate the living world, inhabiting sewer pipes, kitchen counters, and even the surface of our teeth. A previous research study showed that these biofilms use sophisticated systems to communicate with each other, while another study demonstrated that biofilms have a strong memory capacity.

Sowell’s lab, along with researchers at Stanford University and Pompeu Fabra University in Spain, has discovered a biofilm feature that reveals that these communities are much more advanced than previously thought. Kwang Tao Chu, a biosciences graduate student, and former biosciences graduate student Daisy Li, Sewell and their colleagues discovered that biofilm cells are organized in elaborate patterns, a feature previously associated with higher-order organisms such as plants and animals. The results, which describe the culmination of eight years of research, were published January 6, 2022 in the journal. cell.

Clock and Wavefront

Artistic depiction of cells in the wave-clock-front process, an evolutionarily advanced growth mechanism associated with multicellular organisms. Communities of single-celled organisms were thought to be devoid of such a complex pattern. Credit: Nicholas Wilson

“We see that biofilms are more complex than we thought,” said Sowell, a UCSD professor in the Department of Biological Sciences’ Molecular Biology, with affiliations at the San Diego Center for Systems Biology and the BioCircuits Institute and Center. To innovate the microbiome. “From a biological perspective, our results indicate that the concept of cell modeling during evolution is much older than previously thought. Apparently, the ability of cells to divide themselves in space and time not only appeared with plants and vertebrates, but may be more than a billion years old.”

Bacterial biofilms form segments (green) as they grow, similar to vertebrates during evolution. Time-lapse film (left) and extremity projection (right) of Bacillus subtilis biofilm. Green indicates the nitrogen stress response as reported by PnasA-yfp. Fluorescence images were overlaid on the corresponding bright field images. Scale bar, 1 mm. Credit: Kwang Tao Chu

Biofilm communities consist of cells of different types. Scientists had not previously thought that these disparate cells could be organized into complex, organized patterns. For the new study, the scientists developed experiments and a mathematical model that revealed the genetic basis of the “clock and wave front” mechanism, which was previously only seen in highly evolved organisms ranging from plants to fruit flies to humans. As the biofilm expands and nutrients are consumed, a ‘wave’ of nutrient depletion travels through cells within the bacterial community and freezes a molecular clock within each cell at a specific time and place, creating a complex complex pattern of repeating segments of distinct cell types.

The researchers’ breakthrough was the ability to identify the genetic circuit underlying the ability of biofilms to generate community-wide concentric rings of gene expression patterns. The researchers were then able to make predictions showing that biofilms can inherently generate many passages.

The authors note in cell paper.

Biofilm transmission

The image depicts a thin biofilm that transitions between stressed cells (green) and cells differentiated into dormant spores (purple). Credit: Kwang Tao Chu

The study findings offer implications for several areas of research. As biofilms are pervasive in our lives, they are of importance in applications ranging from medicine to the food industry and even the military. Biofilms as systems with the ability to test how simple cellular systems can organize themselves into complex patterns can be useful in evolutionary biology to investigate specific aspects of the waveform and clock mechanism operating in vertebrates, as one example.

“We can see that bacterial communities are not just balls of cells,” said Sowell, who envisions a research collaboration that presents bacteria as new models for studying growth patterns. “Having a bacterial system allows us to provide some answers that are hard to get in vertebrate and plant systems because bacteria provide experimentally accessible systems that can provide new development insights.”

Reference: “Cellular Differentiation of Fragmentation Clock Patterns in a Bacterial Biofilm” By Quang Tao Zhou, Dong Yun De Lee, Jian Jing Qiu, Leticia Galera Laporta, San Li, Jordi Garcia Ogalvo and Gurull M. Soil, January 6, 2022, cell.
DOI: 10.1016 / j.cell.2021.12.001

Co-authors of the paper include: Quang Tao Chu (graduate student at UCSD), Dong Yun Lee (former graduate student at UCSD, now a postdoctoral researcher at Stanford University), and Jian Jing Chiu (post-doctoral researcher at UCSD), Leticia Galera Laporta (post-doctoral researcher at UCSD), San Lee (former UCSD researcher), Jordi Garcia Ogalvo (professor at Pompeu Fabra University) and Gurul Soil (Professor, University of California, San Diego).

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