In this video, we're going to begin our lesson on molecular Koch's postulates. It's important to note that in 1988, Stanley Falkow, a scientist, proposed a revised set of Koch's postulates, which are known today as molecular Koch's postulates. Molecular Koch's postulates, as the name implies, are used to identify the molecular cause of a pathogen's virulence factors. Recall that virulence factors are the specific traits of an organism that allow it to cause disease, that allow it to be pathogenic. Therefore, molecular Koch's postulates can be used to explain why some microbial strains are pathogenic based on their virulence factors while other microbial strains are not pathogenic. If we take a look at our image down below, notice that we're showing you molecular Koch's postulates, and specifically, we're showing you Stanley Falkow over here, and he's saying that these postulates use molecular techniques and so he'll call them Molecular Koch's postulates. Again, they can be used to identify the specific virulence factors that allow a microbial strain to cause disease. We'll get to talk more details about the specific, molecular Koch's postulates in our next lesson video, so I'll see you all there.
Molecular Koch's Postulates - Online Tutor, Practice Problems & Exam Prep
Intro to Molecular Koch's Postulates
Video transcript
The 3 Molecular Koch's Postulates
Video transcript
So there are actually 3 Molecular Koch's postulates that are used to identify the virulence factors in a pathogenic microbe. And so down below, we're going to take a look at the 3 Molecular Koch's postulates in this image. And so the first of the postulates states that the suspected virulence factor gene or the gene's product must be found in every pathogenic strain of the microbe and then it must be absent in the nonpathogenic strains of the microbe. And so if we take a look at our image down below, notice on the left-hand side we're showing you the pathogenic strain of a specific bacteria and this pathogenic strain of the bacteria notice contains the virulence factor gene or the suspected virulence factor gene, and therefore, it's going to have the suspected virulence factor gene's product as well on its surface, these surface proteins are these little, reddish triangles here, and so this one because it is the pathogenic strain of the bacteria, it is going to be able to cause the disease. Now notice on the right we're showing you the nonpathogenic strain of the bacteria which is lacking the virulence factor gene or the suspected virulence factor gene and it is lacking the suspected virulence factor gene's product.
Now the second of the molecular Koch's postulate states that mutating the suspected virulence factor gene must either remove or reduce the pathogen's virulence. Or in other words, mutating the suspected virulence factor gene must remove or reduce the pathogen's ability to cause disease. And so notice that we're taking the pathogenic strain of the bacteria, and here we have the suspected virulence factor gene, and we are going to mutate that suspected virulence factor gene. And so you can see the mutation over here on the right-hand side. And so now we have a mutated version. And so this mutation must, again, either remove or reduce the pathogen's virulence to create a nonpathogenic strain of the bacteria, which is what we're showing you here. And so that would be a good sign that this gene right here is indeed a virulence factor.
Now the third of the molecular Koch's postulate states that reversing that same exact mutation must restore or increase the pathogen's virulence. And so if we start with the mutated nonpathogenic strain of the bacteria, if we take this mutation and we reverse the mutation so that it goes back to its original form, then, it must again create the pathogenic strain of the bacteria. And so if all 3 of these molecular Koch's postulates are stated, then the suspected virulence factor, we would conclude that it is indeed a virulence factor that contributes to the pathogen's ability to cause disease. And so this here concludes our brief lesson on the 3 molecular Koch's postulates, and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.
Which of the following answers is not a reason why Dr. Falkow developed molecular Koch's postulates?
Virulence factors include which of the following answers?
Which of the following answers describes virulence factors of a pathogen?
