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What's bacterial chemotaxis?
Bacterial locomotion
The enteric bacteria like Escherichia coli can locomote in the medium using flagella.
They have two modes of flagellar rotation, clockwise and counterclockwise. Clockwise rotation generates run (smooth swim) and Counterclockwise rotation generates tumble (changing direction).
If some kinds of nutirition (amino acids, sugar, etc.) go higher concentration, the signal is transmitted from chemoreceptors to flagellar motor and give bias to the random walk. Fraction of time spent in run get longer if this signal is transmitted, resulting in nearer position to the nutrition rich environment.
This is a phenomena called chemotaxis.
Signaling pathway
this figure is taken from ref.[1].
| Protein | Function |
|---|---|
| MCP | Methyl accepting proteins (Tar, Trg, Tsr, Aer, Tap) |
| CheA | Autokinase; Phosphodonor for CheY/CheB |
| CheB | Methylesterase that removes methyl groups from the receptor |
| CheR | Methyltransferase that adds methyl groups to the receptor |
| CheW | Scaffolding protein required for stably coupling receptors and CheA |
| CheY | Cytosolic response regulator that carries the signal to flagellar motor |
| CheZ | Enzyme that facilitates dephosphorylation of CheY protein |
Stimulus response
When a bacterium are exposed to ...
Adaptation
It will be gradually...
Perfect adaptation
A characterictics in this adaptation
Robustness
robustness
References
[1]Bray, D., Bourret, R.B. and Simon, M.I., Computer simulation of the phosphorylation cascade controlling bacterial chemotaxis. Mol. Biol. Cell (1993) 4:469-482.
