The biochemistry of cell communication:biofilm perculation (Introduction)

by David Turell , Saturday, August 04, 2018, 22:03 (2302 days ago) @ David Turell

Biofilm has communication signals across the mass of cells:

https://www.sciencedaily.com/releases/2018/07/180726085914.htm

"A concept known as 'percolation' is helping microbiologists explain how communities of bacteria can effectively relay signals across long distances. Once regarded as a simple cluster of microorganisms, communities of bacteria have been found to employ a strategy we use to brew coffee and extract oil from the sea. Percolation helps the microscopic community thrive and survive threats, such as chemical attacks from antibiotics.

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"Cells at the edge of these communities tend to grow more robustly than their interior counterparts because they have access to more nutrients. To keep this edge growth in check and ensure the entire community is fit and balanced, the "hungry" members of the biofilm interior send electrochemical signals to members at the exterior. These signals halt consumption at the edge, allowing nutrients to pass through to the interior cells to avoid starvation.

"'This keeps the interior fed well enough and if a chemical attack comes and takes out some of the exterior cells, then the protected interior is able to continue and the whole population can survive," said Larkin, a UC San Diego Biological Sciences postdoctoral scholar. "It is essential that the electrochemical signal be consistently transmitted all the way to the biofilm edge because that is the place where the growth must be stopped for the community to reap the most benefit from signaling."

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"In a community of bacteria, signals pass from cell to cell in a connected path over a distance of hundreds of cells. Using fluorescence microscopes, the researchers were able to track individual cells that were "firing" (transmitting a signal). The scientists found that the fraction of firing cells and their distribution in space precisely matched theoretical predictions of the onset of percolation. In other words, the bacterial community had a fraction of firing cells that was precisely at the tipping point between having no connectivity and full connectivity among cells, also known as a critical phase transition point.

"'We're all familiar with how we make coffee through percolation and it's an interesting twist that bacteria appear to use the same concept to accomplish the very complicated task of efficiently relaying an electrochemical signal over very long distances from cell to cell," said Süel.

"'It's interesting that these bacteria, which are so-called simple, single-cell organisms, are using a fairly sophisticated strategy to solve this community-level problem," said Larkin. "It's sophisticated enough that we humans are using it to extract oil, for example.'"

Comment: Most likely an automatic electrochemical series of reactions from interior to exterior, passed from contiguous cell to contiguous cell.