John Tyndall's Experiment

in this video, we're going to begin our lesson on john Tindall's experiment. Now before we get into the details of john Tindall's experiment, Its first helpful to point out that one of the drawbacks from louis pastures results were that not every scientist could replicate them when they tried to replicate his experiment. In fact, some scientists that tried to replicate louis Pasteur's experiment would still discover some microbial growth in the swan neck flask even after sterilizing with heat. Now notice that we have sterilizing here in quotes. And that's because these scientists that tried to replicate louis Pasteur's experiment thought that they were sterilizing the flask with heat when in fact they were not sterilizing. But really it wasn't until john Tyndall came around that people started to realize this fact here. And so John Tyndall was a physicist from the 1800s that showed and explained why sometimes Louis Pasteur's experiment could not always be replicated. And so John Tyndall found that some types of Broth could not be sterilized even after extremely long boiling times, john Tyndall realized that depending on the type of broth that broth could contain different types of microbes. And he grouped these microbes into two groups. The first group were the heat sensitive microbes which are microbes that are sensitive to heat, meaning that these microbes would die when exposed to high enough heat. And then the second group of microbes that john Tyndall identified were heat resistant microbes, or microbes that are resistant to heat, meaning that they can tolerate and survive and high levels of heat. And so if we take a look at this image down below, we can get a better understanding of john Tindall's experiment and how he showed why some scientists could not replicate louis pastures results and how he further validated biogenesis. And so notice over here, on the left hand side, we have an image of John Tyndall who lived from 1822, and conducted this experiment in 1881. And so notice that here, what we have is one of the swan neck flask uh that was used in louis pastures experiment. And so what john Tyndall realized was that depending on the type of broth, the broth could either contain heat sensitive microbes, which is what we focus on the top here, or the broth could contain heat resistant microbes. And so even after really long boiling times, uh the heat sensitive microbes of course are going to end up as dead cells as you see here because they are sensitive to eat, they will die and that will lead to sterilization. However, the broths that contain heat resistant microbes, uh those microbes like it hot like this guy right here because they like it hot. That means that they are going to be resistant and be able to grow and survive because they can tolerate high amounts of heat. And so some of the scientists tried to replicate louis Pasteur's experiment. We're using Bross that contained heat resistant microbes. And so that's why there was microbial growth in the broth when they thought they were sterilizing when in fact they were not. And so some of the main conclusions of john Tindall's experiment was that the microbes can exist in two forms. The first form are going to be the heat sensitive microbes which are going to be the microbes that die upon exposure to high amounts of heat. But then the second type of microbes are the heat resistant microbes. And these heat resistant microbes can tolerate and survive high amounts of heat. And so different types sterilization techniques will vary for different types of microbes. And so in order to sterilize the broth that contains heat resistant microbes, they'll have to use a different type of sterilization techniques. Now, later in our course, we'll talk all about different types of sterilization techniques. But for now, what we can point out here Is that in the same year, so in 1881, the scientists Ferdinand Cohen actually discovered what are known as endo spores and endo spores. Are these heat resistant forms that some bacteria can take on and we'll talk a lot more about endo spores later in our course. But notice that in our image we're showing you these endo spores and these endo spores are heat resistant. And so that's that's just an example of some heat resistant microbes. And so again, the scientists that contained uh had endospore contaminants in their broth, they would not be able to replicate louis pastures results. And so john Tyndall was the one that pointed this fact out. And so this helped to support louis pastures uh results, and it helped to further validate biogenesis. And so this here concludes our brief introduction to john Tindall's experiment and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.

Louis Pasteur and John Tyndall worked together to:

• A. Develop antiseptic surgery.
• B. Disprove that microorganisms could arise from non-living matter.
• C. Discover the cause of French wine spoilage.
• D. Develop a cholera vaccine.
• E. Develop methods for isolating bacteria in pure culture.