Naked Science Forum
Life Sciences => Cells, Microbes & Viruses => Topic started by: jmode on 03/10/2008 22:04:46
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Jeremy Mode asked the Naked Scientists:
What are the antimicrobials (soaps and sanitizers) doing to the evolution of the human immune system?
If we are killing off all the bacteria and viruses that would normally stimulate our immune system, what is stimulating the evolution of the immune system, in this supper sanitized society? How deficient has the immune system become over the last 50 years and are we breeding superbugs using antimicrobials?
Is there any parallels to the misuse of the Antibiotics.
This is in response to the show on 9/22/2008 (http://www.thenakedscientists.com/HTML/podcasts/show/2008.09.21/)
What do you think?
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Well, it is important to understand that evolution does not occur with in a single individual but in populations over many generations. So there isn't really any worry about something pushing the evolution of the human immune system. Additionally, most of these bacteria are on the exterior of the human and so don't stimulate the immune system anyway (of course, the chance of them getting in is why we wash the hands anyway, so obviously it can happen). In general the immune system is either working or depressed. You can't really supercharge it or boost it in any way.
That said, the generations of bacteria are MUCH shorter, so the use of antimicrobials does indeed create a new environment that a bacteria that better fits the niche will out perform other bacteria that are hurt by the environment. So the potential is there for these antimicrobials to help "breed a super bug."
My guess though, with no factual data that I know of to back me up, is that the change in the environment on our hands is pretty minor overall. You touch on what I do think is a problem though... the misuse of antibiotics.
The issue isn't necessarily evolutionary (though that is there), but simply environmental. If you use a broad spectrum antibiotic it kills any suseptible bacteria and those that are less suseptible live to repopulate the now free niche that you created by killing off their competition. So, the need to use the antibiotic has to outweight the potential for harm it creates (really the rule of thumb for ANY medicine).
Sean Mahoney
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Actually, evolution does occur with a single individual. It's just that it's only when the mutation in that individual confers an advantage over the other individuals and gets propagated through the species that we recognise that evolution has occurred.
Parallel evolution, where the same advantageous random mutation occurs in many individuals at the same time isn't actually impossible but the probability of it happening is so low that it approaches the impossible i.e. the odds of it occurring approaches 1:infinity.