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I'm a complete layperson to the topic, but wouldn't having more attack avenues that must be evolved against also result in more resources dedicated to survival

I'm a complete layperson to the topic, but wouldn't having more attack avenues that must be evolved against also result in more resources dedicated to survival and eventually compromise the dangerous impact bacteria could have in the first place? i.e. if it's spending energy building anti-anti-bacterial mechanisms, it's not spending as much energy replicating or producing a toxin or whatever.

rcar 9y ago
That's not really how antibiotic resistance develops: it happens at a population-level rather than an individual bacterium level. If, for example, you've got an antibiotic that messes with normal cell wall formation in a particular species, but some in the population randomly have some mutation that still allows the cell wall to function normally, those bacteria will survive the antibiotic. If the infection isn't then controlled by other means, the resistant bacteria will make up a larger percentage of the infecting bacterial population in the next generation. That's why taking full courses of antibiotics is important so that your immune system can focus on the resistant bacteria that the antibiotic can't touch.
Declanomous 9y ago
You have part of the idea right. However you have to consider that evolutionary pressure works with regards to competition for resources. So yes a drug-resistant bacteria might be outcompeted for limited resources in a normal environment by bacteria without that adaptation. However, if there is an antibiotic introduced into the environment, the drug-resistant bacteria will probably have proportionally more resources than the non-adapted bacteria did before the drug was introduced, due to a complete elimination of their competition. This is assuming that the adaptations bacteria have that enables them to be drug resistant harm their fitness in a drug-free environment in the first place. It is entirely possible that the drug was targeting a trait that actually required more resources to produce, but that wasn't selected against because it was basically vestigial. I think it's a pretty big misconception that the force of natural selection is directed towards absolute efficiency. I'd classify the process of natural selection as a 'good enough' mechanism.
deleted 9y ago
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btilly 9y ago
It definitely takes resources for the bacteria to defend against the attack. However not enough to limit its ability to make us sick. (In fact bacteria already have a significant evolutionary incentive to not make us too sick - a dead person doesn't scatter germs as well as a merely uncomfortable person.) But if you completely remove the antibiotic from the environment, the resources required to maintain the defense offer a small selective disadvantage. Resistant strains of bacteria do not remain resistant indefinitely. Repeated exposure to the antibiotic is needed to maintain resistance. But even very low exposure levels will suffice for that.
emiliobumachar 9y ago
It could go either way, but intuitively I think it's much more common that the anti-anti-bacterial mechanisms have negligible costs. Just like software doesn't usually face sudden new performance issues when vulnerabilities are patched. Sure, openSSL is technically slower once they patched heartbleed, but not much slower. Certainly not enough to be a factor in anyone's decision of whether to use it. I'm also a complete layperson to the topic, as you may have guessed already.

rcar 9y ago

That's not really how antibiotic resistance develops: it happens at a population-level rather than an individual bacterium level. If, for example, you've got an antibiotic that messes with normal cell wall formation in a particular species, but some in the population randomly have some mutation that still allows the cell wall to function normally, those bacteria will survive the antibiotic. If the infection isn't then controlled by other means, the resistant bacteria will make up a larger percentage of the infecting bacterial population in the next generation. That's why taking full courses of antibiotics is important so that your immune system can focus on the resistant bacteria that the antibiotic can't touch.

Declanomous 9y ago

You have part of the idea right. However you have to consider that evolutionary pressure works with regards to competition for resources. So yes a drug-resistant bacteria might be outcompeted for limited resources in a normal environment by bacteria without that adaptation. However, if there is an antibiotic introduced into the environment, the drug-resistant bacteria will probably have proportionally more resources than the non-adapted bacteria did before the drug was introduced, due to a complete elimination of their competition. This is assuming that the adaptations bacteria have that enables them to be drug resistant harm their fitness in a drug-free environment in the first place. It is entirely possible that the drug was targeting a trait that actually required more resources to produce, but that wasn't selected against because it was basically vestigial. I think it's a pretty big misconception that the force of natural selection is directed towards absolute efficiency. I'd classify the process of natural selection as a 'good enough' mechanism.

deleted 9y ago

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btilly 9y ago

It definitely takes resources for the bacteria to defend against the attack. However not enough to limit its ability to make us sick. (In fact bacteria already have a significant evolutionary incentive to not make us too sick - a dead person doesn't scatter germs as well as a merely uncomfortable person.) But if you completely remove the antibiotic from the environment, the resources required to maintain the defense offer a small selective disadvantage. Resistant strains of bacteria do not remain resistant indefinitely. Repeated exposure to the antibiotic is needed to maintain resistance. But even very low exposure levels will suffice for that.

emiliobumachar 9y ago

It could go either way, but intuitively I think it's much more common that the anti-anti-bacterial mechanisms have negligible costs. Just like software doesn't usually face sudden new performance issues when vulnerabilities are patched. Sure, openSSL is technically slower once they patched heartbleed, but not much slower. Certainly not enough to be a factor in anyone's decision of whether to use it. I'm also a complete layperson to the topic, as you may have guessed already.