 My name is Ishaad Hussain. I'm a professor of Microbiology. This course has been named Microbiology and has been specifically designed for MS biotechnology students. Today we are talking about microbes and their classification. The learning objective for this talk include what are microbes? Why do we classify them? What are the basis for that classification? And what type of organisms we encounter in our lives? And how organisms are named scientifically? So what are microbes? Microbes, they also are called germs and microorganisms. As the name indicates, these are very small objects that cannot be seen with the naked eye. So we need some amplification process like a microscope to see them, to study them. And the studying of microbes is what we call microbiology, although microbiology has many branches. But overall the study that involves microbes or any aspect of microbes is called microbiology. There are many branches we would talk about those branches in the Duke course. We would learn more about them. Microbes are very simple in their structure. If you compare a microbe with an animal or a human, we see that animals and humans are multicellular. And those cells are arranged into tissues and then the tissues are arranged into organs. But because microbes are simple and mostly they're unicellular, they're not organized like multicellular, typical multicellular organisms like humans or animals. So they're very simple. But they have various kinds in them. There's a lot of diversity. And because of that diversity, classifying them is really a challenge for the microbiologists. Generally, all microbes could be grouped either into prokaryotes or into eukaryotes. Prokaryotes, they don't have a defined nucleus. On the other hand, eukaryotes have a distinct nucleus. As could be seen in this picture, large cell belongs to a eukaryote whereas the smaller one is a prokaryotic cell. As you can see, the nucleus is very well defined in the eukaryotic cell but there is no such division in the prokaryotic cell. Now, why do we classify organisms? As you can see that studying anything randomly, it does not make much sense. So if we have a lot of things and that needs to be arranged, we would have to develop some scheme, some plan, maybe based on their shape, maybe on their size or maybe on their uses. Similarly, microorganisms, they're classified because classifying them makes life easier. And the benefits that we get include that we can study them conveniently as a group. They're easy to identify when we classify, when we put them into different groups, it is easy to identify them. Similarly, their interrelationships between these various groups could be established and similarly evolutionary relationships among various organisms could be studied as well. Now, what are the bases for classification of microorganisms? They are classified based on the similarities that they share with each other. It could be a shape or physical structure, what we call morphology. It could be biochemical similarities, could be generic similarities like DNA sequences or RNA sequences that they share with each other or even evolutionary relationships. It could be used for classifying them.