So here's a question for you. Have you ever had strep throat? Not all sore throats are strep, but strep throat is caused by bacteria. And if you have had it before, it typically really hurts.
And chances are, if you have had it, you've taken a course of antibiotics. Antibiotics are specifically designed to terminate. Prokaryote cells, which in your body would be bacteria, instead of your own cells which are eukaryote cells.
We have another video all about bacteria and antibiotics, but this video is going to mention a concern we all have right now about antibiotic resistance that can happen in bacteria. It's also the perfect opportunity to illustrate a process that usually takes a very long time to see, natural selection. Now let's explain a basic example of natural selection. Consider these frogs sitting on logs in their habitat.
Now let's assume that these are the same species of frogs so they can breed with each other and they pass down their DNA to their offspring. Naturally there is variety in these frogs. Some of these frogs are darker green, maybe almost a brown, and some of them are lighter green.
There's a variety of traits even in the same species. just like in people. So back to the log.
You know what else is in this habitat? Predators. And the predators are finding here that the lighter frogs are much easier to see in this habitat than the darker frogs.
So in this particular environment, the darker frogs are having an easier time surviving and potentially more fitness if they can breed. Fitness in the biological sense is determined by not how long they live, But by how many offspring they have, these darker frogs pass down their DNA to their offspring so that the new baby frogs will have the DNA from their parents. The lighter frogs are being selected against, since they're easier to see in this habitat.
Over a long period of time, you could expect to see a higher frequency of darker frogs. If it continues for a very long time, it could even result in all the frogs in this area being darker. Evolution, which is change over time, could take place because natural selection has occurred.
Natural selection is a mechanism of evolution. And one thing to point out, it doesn't necessarily mean that the allele for lighter color is gone completely. The allele could be recessive and carried within the population.
And because of processes like crossing over and mutations, there are opportunities for variety. But... And if this habitat and predators do not change, then the darker frogs will continue to have more fitness. Now, we want to point out that variations and mutations are not things that an organism can will itself to have. Frogs can't just think, you know, it's better for me to be darker, so I'm just going to have some variation to be darker.
Because if that was true, well, let's just say I might be a bit different. Mutations and variations, they are random. possible they might not have any effect on an organism's fitness. So in that case the genes are to be passed down if the organism happens to be able to reproduce. Or variations and mutations can be negative.
If they are negative and negatively affect the organism's fitness, meaning no babies, well then that trait will not be passed down. But if they have a positive effect on the fitness then that frog may have more babies than average because that trait is helping them survive and reproduce. It's an adaptation, and over time there will be more babies with those genes, and over time that trait that is an advantage will be more frequent in the population.
So what does this have to do with natural selection in bacteria that occurs from antibiotics? Well, keep in mind there is variation in bacteria as well. For example, Some of them might have an enhanced cell wall that makes it hard for an antibiotic to enter. Or they could contain enzymes that could assist in breaking down an antibiotic.
Now remember, the bacteria didn't will themselves to have those traits. Like our frog example, they are random variations. However, when you take antibiotics, the environment is being altered.
The bacteria that have traits that allow them to survive that particular antibiotic will have higher fitness and can reproduce. Bacteria that do not have traits to help them with the antibiotics do not have very much fitness because they're dying. And they can't have fitness if they're dead.
Selection has taken place and the resistant bacteria are the survivors. And once all their competition is killed off, these survivors can reproduce easily with few competition. And every cell that comes from them will inherit that gene that allows them to be resistant to that specific type of antibiotic. Bacteria also have this amazing ability to transfer genes to other bacteria, so they could potentially share that resistant gene with other bacteria. It is possible for this specific type of antibiotic to maybe not be as effective for this person in the future.
Hospitals especially have this challenge because they are treating multiple patients with bacterial infections in a closed environment. So healthcare workers must have good hygiene practices so... that they do not spread resistant bacterial infections from one infected person to another. So this example of natural selection was observable in a shorter amount of time, which can result in evolution in bacteria.
But what can be done about this resistance issue? Well scientists are often in the process of developing new antibiotics. We do have many types of antibiotics available, so scientists hope to stay one step ahead of bacteria.
But there are still bacterial strains out there that have developed a resistance to commonly used antibiotics, making them very difficult to treat. So it's important to only take antibiotics for bacterial infections. Antibiotics don't work against viruses, and you don't want to be introducing antibiotics in your body when you don't need them.
That will just further select for bacteria that have some form of resistance. It's also important to mention that many vaccines like the DTaP vaccine can protect you from serious, potentially deadly bacterial infections such as diphtheria, tetanus, and pertussis. Well, that's it for the Amoeba Sisters, and we remind you to stay curious.