No End to this (Fascinating) War


There’s this BBC podcast called The Infinite Monkey Cage that had an episode on the immune system. I found these aspects fascinating:
-          The body produces cells with receptors that “protrude out” of the cell. These receptors can lock onto specific cells of the intruder the way a jig saw piece fits into only one other piece. If they find a fit, they know it’s an intruder and go into attack mode;
-          Ok, but don’t the intruders/germs mutate over time? How does the body create new receptor shapes for the mutants? Aha, the body shuffles around the genes thereby creating random shaped receptors on a continuous basis. And the rest is luck: the hope that one of those randomly shaped receptor would lock into the mutated germ!
-          That’s impressive, but couldn’t such randomly shaped receptors accidentally turn out to be a match for a body part? Would the immune system then end up attacking the body itself? Great question, and the answer is that the body has a “sieve” that filters out the receptors that match parts of the body before the rest are released.

Ok, so that’s how the body fights. But we humans also use antibiotics to fight. And until recently, that war was going in cycles, writes Ed Yong:
“We thrust; they parry.”
But now, we seem to be losing the war. That certainly aligns with all the talk about “superbugs” and antibiotic resistant bacteria.

Enter Houra Merrikh. She and her team think they might have found a bacterial evolvability factor, “a molecule these microbes need to rapidly evolve into drug-resistant strains”. Most importantly, that’s a molecule that’s shared across lots of bacteria and serves the same function everywhere.

Merrikh’s approach is to turn off this evolvability molecule. In other words, she won’t try to kill the bacteria (that’s left to the antibiotics). Rather, her approach is to prevent/slow down the evolution of the bacteria so they don’t become resistant to the antibioitics. Put glamorously, she’s building the “anti-evolution drug”.

Other such attempts in the past have tried to disable the aptly named “SOS system” of bacteria. Since those ideas hit all defences of the bacteria against everything, not just antibiotics, they make the bacteria very vulnerable. That, in turn, increases the evolutionary pressure on the bacteria to find a counter-measure. Not so with Merrikh’s approach, which doesn’t change anything about the bacteria, except slowing its rate of change in the future.

Will Merrikh’s approach win the war on bacteria for good? Almost certainly not, since evolution always finds new ways. But just because that’s true, it won’t stop us (and bacteria) from fighting the battle in new ways…

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