1.4.3. Life will not be Eradicated

Summary: This text describes an experiment where bacteria evolve resistance to antibiotics in a large petri dish with varying concentrations of the drug. The bacteria initially spread in areas without antibiotics, then mutants appear that can survive higher concentrations. This process repeats until the bacteria can survive in extremely high concentrations of antibiotics.

So this paper came out in a journal called Science and just fascinating video. So a few minutes, just watch it. So what we ended up building was basically a petri dish, except that it's 2 feet by 4 feet. And the way we set it up is that there are nine bands and at the base of each of these bands, we put a normal petri dish thick agger with different amounts of antibiotic. On the outside, there's no antibiotic. Just in from that, there's barely more than the coli can survive. Inside of that, there's 10 times as much, 100 times, and then finally the middle band has 1,000 times as much antibiotic. And then across the top of it, pour some thin agar that bacteria can move around in. The background is black because there's ink in it and the bacteria appear as white. First, you see they spread in the area where there's no antibiotic up until the point they can no longer survive. Then a mutant appears on the right. It's resistant to the antibiotic. It spreads until it starts to compete with other mutants around it. When these mutants hit the next boundary, they too have to pause and develop new mutations to make it into 10 times as much antibiotic. And then you see the different mutants repeat this at 100. And after about 11 days, they finally make it into 1,000 times as much antibiotic as the wild type can survive. And so we can see by this process of accumulating successive mutations that bacteria which are normally sensitive to an antibiotic can evolve resistance to extremely high concentrations a short period of time