|MadSci Network: Microbiology|
I am curious if pathogenic enterics can alter normal behavior. Furthermore, if they can, is it a neurological pathway or a metabolic by-product that is inducing the changes. I know that bacteria proliferate in response to catecholamines, which is a neurological link. On the other hand, bacteria produce products which enter the system and influence the other flora. This question stems from the fact that at any given time the outbred population of humans is affected by a subclinical asymptomatic infection. I believe our behavior is influenced by nontypical gut flora.
I am not aware of any bacteria that is known to have an effect on normal behaviour outside of making people feel ill and physically tired and thus physically depressed. I am not aware of any bacteria that cause a mental change in the behaviour of an individual outside of this generally feeling of illness that I am sure you are familiar with.
But to answer your question, could an enteric bacteria alter your behaviour. It is theoretically possible that a bacteria could produce a substance, hormone, or waste by product, or toxin that could have an effect on you mental behaviour. Some of the most potent toxins known to man specifically target your nervous system. It is important to understand that we have only isolated and identiefied aproximately 4000 species of bacteria. Some have estimated that this reperesents only 1% of bacterial species on the Earth. Also, it is important to apreciate the complexity of the niche a human body provides. In one very exhaustive study it was determined that there are over 200 species of bacteria in a persons mouth. I would be incrediblely surprised if a significant amoun of research had been done on even half of those species, and I can garantee that exhaustive research has been done on none of those species. There are literally thousands of people studying Escherichia coli today, and there are still many genes for which there is absolutely no know function.
Given the complexity of life, anything you can imagine within reason is possible, and maybe even probable. But you will never know, life is just to complex, and the answers are too hard to come by.
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