As living organisms, bacteria are encoded by DNA, and DNA occasionally mutates. Sometimes genetic mutations render a bacterium immune to an antibiotic’s chemical tactics. The few cells that might escape antibiotic pressure then have a sudden advantage: with their counterparts wiped out, resources abound, and the remaining antibiotic-resistant bacteria proliferate. It’s a problem not only for the host—you or me when we are treated with an antibiotic and develop a resistant strain—but also for anyone with whom we happen to share our resistant bacteria, say, on a door handle or keyboard. In fact, most resistant bacteria develop not in people but in livestock fed antibiotics to promote growth; these resistant bacteria infect people through contaminated animal products. This is how even antibiotic “naive” people come to be infected with resistant strains of bacteria.

I see this all the time as a family doctor. A woman has a urinary tract infection. I tell her that her bacteria are resistant to this or that antibiotic, and she says, “But I’ve never taken any of those.” Welcome to the global human soup.

  • CeeBee@lemmy.world
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    8 months ago

    Yes, genetic drift is evolution

    Not “genetic drift”. Although I did forget a critical word. I meant to say “allele frequency drift” which is distinctly different than genetic drift.

    Allele frequency drift simply describes a shift in how common a genetic trait exists, or is expressed, within a population group. The overall genetics of the group are the same. Even if there were no changes to the collective genetics of a population over millions of years (no evolution) you can still have allele frequency drift.

    This is what I mean by “allele frequency drift isn’t evolution”. It’s a mathematical expression of the ratio a gene is expressed within a population group. It doesn’t describe any genomic changes or mutations.

    The first generation can have frequency 1.0 of a trait, gen 2 can have 1.5, gen 3 can have 2.0, and then back down again over the next few generations. But generation 10 can have an (nearly) identical genome to generation 1.