Training Bacteria To Deliver Drugs? 29
Hugh Pickens writes "While it may seem unlikely that single-celled organisms could be trained to salivate like Pavlov's dog at the sound of a bell, researchers say that bacteria can 'learn' to associate one stimulus with another by employing molecular circuits. This raises the possibility that bioengineers could teach bacteria to act as sentinels for the human body, ready to spot and respond to signs of danger. As with Pavlov's dog, the bacteria in the model learn to build stronger associations between the two stimuli the more they occur together. Now called Hebbian learning, it's often expressed as a situation in which 'neurons that fire together wire together.'" (More below.)
"Bacteria, of course, don't have synapses or nerve cells, but Eva Jablonka, who just published a paper on conditioning in single-celled organisms (PDF), says it seems 'quite possible at the theoretical level, and I don't see great obvious hurdles for the construction of the suggested vectors.' The trick will be to train bacteria to recognize chemical processes in the body that are associated with danger like an adverse and dangerous reaction to a drug, or to the presence of tumor cells."
Not Hebb (Score:5, Informative)
They're called Hebbian cellular assemblies because many cells work together. This is an entirely different concept than a single celled organism alone adapting physiologically to stimuli. That effect is well known. It has been examined in terms of altering DNA to change the organism's reactions with that altered DNA being transfered to others, as well as in chemical/mRNA learning and communication as outlined by James McConnell (Worm Runner's Digest) and many others. The only thing nearly unique in TFA is the specific task proposed. If it's worth publication, so is every other potential result of this well established effect. There was no reason to bring up Hebb. TFA would have been better (though not necessarily much good) had he been left out.
Oh yeah (Score:3, Informative)
I forgot: Training them to deliver drugs is comparatively trivial compared to the other training necessary -- making them able to avoid detection by the immune system and not to react with hostility when it does. A bacterium that usually doesn't trigger the body's defenses can trigger it after being altered. Altered bug == not the same bug.
Re:Except.. (Score:3, Informative)
Bacteria can sense chemical gradients. This is particularly useful being able to determine whether a long-term food supply is nearby and to continue reproducing or to just slow down and stick together with other bacteria. Then you get all sorts of amazing patterns forming [tau.ac.il].