Let's say penicillin can kill the bacteria. After using it for 10 years, the bacteria developed resistance to penicillin, so no one is using penicillin anymore because it has no effect. After 15 years, reports have found that most of the bacteria loss the penicillin resistant trait.
If the doctors start prescribing penicillin to fight the bacteria again, would you expect penicillin resistant to evolve faster, about the same time, or slower than the first time they developed resistance, which was 15 years?
***I thought it would be faster for those bacteria in the population that used to develop resistance in the past and about the same time for those bacteria that are never treated with penicillin before. This is just my instinct, correlating that to how the human immune system is operating.
faster. There probably were several genes involved in the resistance, and when it lost the resistance, chances are that most are still present.
Your instinct is partially correct. When it comes to the evolution of resistance, it is important to understand that it is based on natural selection and genetic adaptation. However, there are a few key factors that may affect how quickly resistance evolves in a population.
In the scenario you mentioned, where bacteria developed resistance to penicillin over a period of 10 years and then lost that resistance over 15 years, we can consider a few possibilities for how resistance might evolve if penicillin is reintroduced.
1. Bacteria that previously developed resistance: It is possible that some bacteria in the population still retain the genetic mechanisms for resistance. If penicillin is reintroduced, these bacteria may have a higher chance of evolving resistance faster than the first time since they have previously demonstrated the ability to adapt. This is due to the fact that they already possess a genetic basis for resistance, and with exposure to the antibiotic again, they could potentially utilize and enhance those mechanisms more rapidly.
2. Bacteria that never developed resistance: Bacteria that were not previously exposed to penicillin or never developed resistance in the first place may not have the same initial advantage as the previously resistant bacteria. However, since the genes for resistance can be transferred between bacteria through horizontal gene transfer, they may still acquire resistance genes from the populations that previously developed resistance. This means that over time, they could catch up and develop resistance at a similar pace.
It's important to note that the actual pace at which resistance evolves can be influenced by various factors such as the rate of mutation, the population size, the genetic diversity within the population, and the selective pressure exerted by the antibiotic. Different bacteria species and strains may also have varying capacities to evolve resistance.
In summary, the bacteria that previously developed resistance might have a head start in evolving resistance again if penicillin is reintroduced, but other bacteria may still acquire resistance through gene transfer. The actual rate at which resistance evolves can be influenced by multiple factors and can vary between different bacterial populations.