Biological complexity: geometry of biofilms (Introduction)

by David Turell , Wednesday, July 10, 2024, 19:19 (136 days ago) @ David Turell

Present since the start of life:

https://phys.org/news/2024-07-geometry-life-physicists-biofilm-growth.html

"The paper, "The biophysical basis of bacterial colony growth," was published in Nature Physics this week, and it shows that the fitness of a biofilm—its ability to grow, expand, and absorb nutrients from the medium or the substrate—is largely impacted by the contact angle that the biofilm's edge makes with the substrate. The study also found that this geometry has a bigger influence on fitness than anything else, including the rate at which the cells can reproduce.

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"Understanding how biofilms grow—and what factors contribute to their growth rate—could lead to critical insights on controlling them, with applications for human health, like slowing the spread of infection or creating cleaner surfaces.

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"While biofilms are ubiquitous in nature, studying them has proven difficult. Because these "cities of microorganisms" are comprised of tiny individuals, scientists have struggled to image them successfully.

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"Leveraging interferometry, the team began conducting new biofilm experiments, investigating how colonies' shapes changed over time. Co-first author Gabi Steinbach, formerly a postdoctoral scholar in Yunker's lab and now a scientific research coordinator at the University of Maryland, noticed that every colony had a specific shape when it was small: a spherical cap, like a slice from the top of a sphere, or a droplet of water. It's a shape that shows up often in physics, and that sparked the team's interest.

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"Finally, Thomas Day, a former graduate student in Yunker's lab, now a postdoctoral fellow at the University of Southern California, and one of the authors of the paper, suggested a quirky problem of geometry called the napkin ring problem.

"'As soon as we started to think about the napkin ring problem, we were able to start developing a mathematical toolkit," Yunker says, though the solution wasn't effortless. "We couldn't find anyone who had ever looked at a spherical cap napkin ring before, because the application is very rare."

"Pokhrel, alongside two co-authors, was responsible for working out the geometry. He discovered that the cells grew exponentially at the edge of the shape, expanding further onto the medium, while the cells in the middle grew upward, creating a shape not unlike an egg in a frying pan—if the egg white was expanding outwards, while the yolk was only growing taller.

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"After incorporating their findings into a mathematical model, the team found that the contact angle was the most important factor: the angle that the very edge of the biofilm made when it touched the surface it was growing on. That single geometric quality is even more important to a biofilm's growth than the rate at which it can reproduce cells.

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"'Biology is complex," Yunker says. In nature, the surface a biofilm is growing on may not be as consistent as a laboratory surface, and colonies may have different mutations or may consist of more than one species. "But we first needed to understand what happens when temperature and nutrient availability are steady."

"And while the model is based on how biofilms behave in a controlled lab environment, it's a critical first step in understanding how they may behave in nature."

Comment: from 3.5+ billion years ago Australian stromatolites to modern biofilms, bacteria started life and are still here playing an important role in Earth's ecosystems. Usually evolution supplants entire families of organisms. Not bacteria which have a vital role in supporting the structure of life itself. A huge component of allies, with a few bad actors.