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It is a known fact that bacteria develop immunity to antibiotics. Why then did not all bacteria develop immunity to natural antibiotics like penicillin in the fungi?

It is for sure that fungi did not care to continue killing all bacteria so that them won't be able to develop immunity (as we're adviced today to use antibiotics carefully, in order not to develop a superinfection)..

Looking at all the time span that bacteria and fungi exist, it seems unlikely that there'd be any bacteria left not yet immune to penicillin at all. However, that's not the case, the antibiotic is still a rather successful one.

noncom
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    As far as my limited genetics background allows me to assess this question, it is population genetics. Let's not close this well-researched question based on a philosophical community question.. – AliceD Nov 03 '15 at 13:25
  • @AliceD hi! I am sorry, I think I don't get your second sentence... could you please say it differently? :) – noncom Nov 03 '15 at 18:30
  • @noncom - that second sentence was addressed to the community at large. Don't worry about it. – AliceD Nov 03 '15 at 23:01
  • @AliceD however well researched question might be, if it is a case of the CW post, then there is no point repeating the same stuff again and again. Newton's law does not change if you replace a "ball" with a "car". Why did all bacteria not evolve antibiotic resistance is clearly an example of the CW question. Just replace "organism" with "bacteria" and "trait" with "antibiotic resistance". Can you explain why this post is different? Also, that post is not philosophical. We created the post such that all possible relevant scientific points are cited to address the evolution problem. – WYSIWYG Nov 04 '15 at 05:38
  • @noncom many bacteria previously sensitive to the antibiotics are becoming resistant. – WYSIWYG Nov 04 '15 at 05:42
  • @WYSIWYG So, basically, you have marked the question as a duplicate of a question on general trait acquisition/persistance and together with that you give a broader answer in the comments that there actually are bacteria that become resistant, but do not mention if you mean natural or engineered antibiotics. Turns out that you have attributed half of the question as a duplicate of another, but marking the whole question as duplicate, and the other half was simply ignored at first and then briefly touched in the comments. Thus, the question was first broken down, and then its parts mistreated – noncom Nov 05 '15 at 13:08
  • @WYSIWYG Technically, you are right, the "why" of my question is probably answered in the referred duplicate, but there's more to it, and that "more" is being lost. – noncom Nov 05 '15 at 13:11
  • @noncom Okay. You can edit your question to focus on the "more" part; add more details so that it is no more yet another example of the CW question. We can have this reopened then. – WYSIWYG Nov 06 '15 at 05:35

1 Answers1

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For a natural immunity to evolve, two things have to happen:

  • The immunity has to actually occur. That means all the necessary mutations will need to be there to grant this bacterium resistance to penicillin. For penicillin, for example, bacteria that evolved such a resistance evolved to produce the enzyme beta-lactamase.

  • The immunity has to grant an advantage. Penicillin is produced by Penicillium, which is a mold found in environments with lots of oxygen. Lots of bacterial species have never encountered penicillin and the vast majority (for example anaerobic bacteria that don't infect humans) never will. In the absence of this pressure, a resistance to penicillin, even if it evolves, will likely deteriorate within a few generations because the individuals with the resistance do not have an advantage in survival. Producing an enzyme such as beta-lactamase is not without its costs (protein synthesis).

While bacteria van exchange genetic material in the form of plasmids between different species, so not all species would need to evolve beta-lactamase de novo, this is also only "helpful" if the bacteria a) come in contact with resistant bacteria species, and b) if this resistance confers an advantage for the receiving species.

Origins and Evolution of Antibiotic Resistance

Mechanisms of Bacterial Resistance to Antibiotics

YviDe
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