According to the theory of natural selection, selected clone of bacteria are capable of tolerating specific stress factors. But when does this selection happen? Does it happen before the exposure to particular factor? Or is it a consequence of exposure to a particular factor? Is the specific clone of bacteria inherently resistant to that specific stress factor or does it acquire resistance following exposure to that particular factor?
Hello Dr. Artur.
Antibiotic resistance is explained in terms of natural selection. The nature selects a specific clone of bacteria which possess the ability to tolerate antibiotics. My question was, does this selection occur even before the exposure to antibiotics or after exposure to antibiotics? I think I made my question clear.
Hello Dr. Artur!!
Thank you for your answer. I just wanted to know whether the bacteria possess the ability to resist an antibiotics even before exposure to that antibiotic. And according to your response, the bacteria possess this ability to resist even before exposure to specific antibiotic.
By saying, 'nature selects....' I meant to say that a particular clone among the whole bacterial population are bestowed with this ability to resist an antibiotic. Exactly I was referring to Darwin's theory of natural selection. Am I right if I say that a specific clone of bacteria is randomly enabled by the nature to a specific antibiotic even before exposure to that particular antibiotic?
Oops!! I'm terribly sorry Dr. Artur!! I got my answer. I just thought of making it sound complementary to theory of 'natural selection'! Out of curiosity, i would like to know why the theory is actually called the 'theory of natural selection'??!!!
Thank you Dr. Ali!
Am I right if I say that a few bacteria are inherently resistant to the action of a few antibiotics but a few other bacteria, after exposure to antibiotics develop mechanisms to resist the action of antibiotics?
There seems to be confusion between two differing mechanisms of selection, analog or digital. In analog selection, organisms gradually adapt and adjust to antibiotics. In digital selection, organisms are either susceptible to antibiotics, and die off, or they are not susceptible. The simplest explanation seems to be the digital one, whereby over time resistant variants displace the susceptibles.
Dear Dr. Artur,
Thanks for your answer.
I did do a bit of literature search. But I found it really confusing. Many have expressed different opinions which should be clearly evident if you go through all the answers for this question. However, I will make sure that I will acquaint myself with necessary insights.
Thank you once again.
"A single point mutation may be is not enough in a cell to confer antibiotic resistance and it has to happen in several generations selected in right time and right place when they would skip toxicity of higher dosage."
I am no expert here, but I do not see why it may be thought that it is new rather than old mutations that lead to antibiotic resistance. Some years ago it was found that a very small number of patients were resistant to AIDS, but was that not because they already had a rare genome before they got infected with HIV?
"Individual cells surviving the toxicity of an antibiotic through one or accumulation of several mutations demonstrate natural evolution or adaptation and could propagate successfully in presence of specific antibiotic."
I am still confused about this. Are you saying
- After exposure to an antibiotic, an individual cell then adapts to this attack OR
- Antibiotics kill off the previously susceptible cells
Am sorry a novice in this topic but i like to ask . . . " does the presence of a stressor increase in an environment increase the rate of mutation in which case the chance of acquiring a favorable trait is increased"
" does the presence of a stressor increase in an environment increase the rate of mutation in which case the chance of acquiring a favorable trait is increased" : this is said about mobile genetic elements which could increase genome rearrangements at some time due to some stressing conditions in the environment ; this has been proposed to explain some aspects of plant domestication
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