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The Baffling Intelligence of a Single Cell
Hraness wrote this summary from a saved copy of the source. Quotations are taken word for word from the source.
gist
James Somers and Edwin Morris tell the story of E. coli chemotaxis, the way a brainless bacterium forages for nutrients, as a deep slice of biology in place of a textbook’s parade of names. With interactive simulations, animations and diagrams, they follow the system from run-and-tumble swimming through membrane receptors, the CheA–CheY phosphorylation signal, methylation as a chemical memory, and the switching, self-assembling flagellar motor, then survey the experiments and computer models that revealed it.
ideas
- Run and tumble. A cell swims straight, then tumbles to a random new heading, tumbling less often when things are improving; even this simple rule finds food more often than not.
- A nose of proteins. Attractant-specific receptors in the membrane change shape when molecules bind, and the arrayed receptors integrate their signals, a prototype of senses like smell and sight.
- Signal by phosphorylation. Receptors regulate the kinase CheA, which phosphorylates CheY; CheY-P diffuses to the flagellar motors and makes them switch rotation, triggering tumbles.
- Methylation as memory. Slow methylation of receptors resets their sensitivity, so the cell treats its current concentration as normal and responds across five orders of magnitude.
- Nanomachines and individuality. The motor is self-assembled, spins about 1,500 times a second at close to 100% efficiency, and its filaments bundle; cells differ through signaling dynamics, not just genes.
quotes
“It was too much about the names of things.”
“The cell learns to treat whatever concentration it stumbles into as the new normal”
“The flagellar motor operates with close to 100% energy efficiency.”
“And the craziest part is that like all molecular nanomachines it is entirely self-assembled.”