Important Concepts and Terms — Introduction to Microbiology

by Vincent Racaniello, PhD

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    00:02 Hello and welcome to Introduction to Microbiology. My learning goals for you include, you will be able to define a microbe, you'll understand the differences among archaeal, bacterial and eukaryotic microbes, you will appreciate that microbes are everywhere and outnumber all other living things, you'll know why microbes are essential for life and you'll appreciate how microbes shape the earth. Let's begin with the definition of a microbe. The word microbe has 'micro' in it, and that comes from 'microscope' and that's because what these are small organisms visible only under the microscope. The study of microbes is called microbiology.

    00:51 There are a number of different kinds of microbes that we're going to be talking about, and the first group is called the bacteria. Here is an electron micrograph, a high magnification image of a common bacteria that's in your intestine, E. coli, you can see that they're rod shaped, they are individual cells and they have a number of properties that we're going to be discussing, this is magnified about 100,000 times.

    01:18 Bacteria have a number of properties that distinguish them from the cells that are in you and I. For example, they don't have nuclei as do ourselves and they don't have membrane-bound organelles like mitochondria or chloroplasts which are found in plants. There are a lot of different shapes of bacteria, they include rods, spheres and spirals and a few others.

    01:47 There are many, many bacteria on earth; our estimate is about 5×10 to the 30th, that's a huge number, actually bigger than we can really comprehend. You may be used to about a billion which is a giga of something, well 10 to the 30th is a lot more than that.

    02:07 The bacteria can be found in every environment on earth, wherever you look, whether it be in soil, in the oceans, in rocks even, you can find bacteria.

    02:20 Another group of microbes that I'd like to tell you about are the archaea. When the archaea were first discovered, they looked like bacteria, they can occur as spheres or rods, and so scientists thought these must be bacteria, so they were classified along with them. These archaea lack nuclei and they also lack membrane-bound organelles like mitochondria and chloroplast and so it was thought these must be bacteria, but it turned out that we were wrong.

    02:53 The archaea are evolutionarily closer to eukaryotes, the cells within us, in you and I, these are eukaryotic cells, archaea resemble them more than they resemble bacteria. Archaea are often found in extreme environments and we like to call them extremophiles, because they love those extreme environments and here's one of them, this is a hot spring in Yellowstone National Park in the US where the waters are over 90°C, some of the archaea love to grow in these environments, it is truly amazing. One of the archaea that grows in such extreme environment is called pyrococcus furiosus, and I love this particular archaea. You can see it's an oval shaped cell with lots of what we call flagella at one end, and this is how these cells move around. But they are not always present in just extreme environments, some of the archaea live more normally, like we do, you can find them in soils, you can find them in oceans, you can find them in other wet areas like marshlands and they are also in us, in you and I, we contain archaea. You can find them in your colon, your large intestine, they are in your mouth and they are also found on your skin.

    About the Lecture

    The lecture Important Concepts and Terms — Introduction to Microbiology by Vincent Racaniello, PhD is from the course Microbiology: Introduction.

    Included Quiz Questions

    1. both have a cell membrane
    2. They both have membrane bound organelles such as mitochondria.
    3. They both have a prominent nucleus with a well established nuclear membrane.
    4. Both bacteria and human cells contain chloroplasts to provide essential nutrients.
    5. Both bacteria and human cells are exclusively rod shaped.
    1. Lungs
    2. Skin
    3. Colon
    4. Mouth
    5. GI tract
    1. They both lack nuclei and membrane bound organelles
    2. They are evolutionarily similar
    3. They colonize different environments
    4. They have symbiotic relationships with humans
    5. They lack a cell wall

    Author of lecture Important Concepts and Terms — Introduction to Microbiology

     Vincent Racaniello, PhD

    Vincent Racaniello, PhD

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    excellent lectures
    By Fadia W. on 18. September 2018 for Important Concepts and Terms — Introduction to Microbiology

    Assalam-o-Alikum! Sir your lectures are very informative and its my humble request kindly give us access to download these lectures because lots of time taken by lecture due to internet problem plz try to understand and give us access of downloading

    By Alexander W. on 04. August 2017 for Important Concepts and Terms — Introduction to Microbiology

    He is a great professor. He takes all his time to explain the topics.