Is antibiotic resistance proof of evolution?

Answer 1

You have a population of bacteria that are all variant, morphologically and, rather redundantly, genetically. The antibiotic is applied and some of these bacteria are resistant ( this is simplistic, but valid ) and survive to reproduce. They have been naturally selected and their alleles, which conferred their resistance, are represented in the next generation of bacteria. This is evolution; the change in allele frequency over time in a population of organisms.

Answer 2

When a population of bacteria is bombarded with antibiotics, the 'weak' ones will die. The ones with some resistance built in will survive, and divide to form a new population of copies of themselves, or a resistant population. This in itself is survival of the fittest in a very pure form.

Answer 3

Evolution is the change in allele frequency over time in a population of organisms.

So, the bacterial variants that are resistant to the antibiotic used will clone the next generation of bacteria who are also resistant to the particular antibiotic that was used in the first place. This resistance is genetically based, alleles, so this shifts the frequency of these alleles, nonresistant alleles become much rarer and resistant alleles become much greater, and evolution happens.

Answer 4

Antibiotic ResistanceSay you have a subject with a bacterial infection and you want to treat him with an antibiotic. Initially, lets say 99.9% of those bacteria have no resistance to the antibiotic. After treatment, 99.9% of those bacteria have been killed. The next generation of bacteria in this individual (the 0.1% left), although not great in number, will be entirely antibiotic resistant as will subsequent generations.

From before treatment to after treatment, you can see how the frequency of the resistance gene has increased dramatically to the changing environment. The very few bacteria that did have the resistance were more fit in the antibiotic environment and the gene was preserved and proliferated in future generations.

This same case could occur with 100% of the bacteria being not resistant. Although bacteria don't necessarily make more mistakes in protein synthesis and DNA replication than eukaryotes, bacteria will certainly divide mitotically at a quicker pace. The more divisions a cell makes, the more likely it will make a mistake. These mistakes in the context of evolution would be called "mutations," which may or may not be beneficial. So even if every bacterium in the subject initially is not resistant to the antibiotic, an auspicious (or inauspicious for the individual) mutation will introduce the resistance gene.

Overusing antibiotics is a problem for this very reason; antibiotic resistant bacterial strains are more likely to develop. Often times in corporate farms, livestock are fed antibiotics to fatten them. Unfortunately, bacteria on the farms are becoming increasingly resistant to even the most powerful antibiotics, a risk to the consumer.

Answer 5

Any sort of nucleotide switches exist in the realm of evolution, and can lead to 'micro' and then 'macro' evolution.