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The Concept of Microorganisms – Introduction to Microbiology

by Vincent Racaniello, PhD
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    00:00 Now microbiology, the study of microbes is a relatively recent science. Humans didn't always think there were very small things in the world that could be only seen with a microscope.

    00:11 We thought everything that we could see was all that there was. It took a Dutch lens maker Antonie Van Leeuwenhoek to actually see the first microbe. He made the first microscope which is shown here and he took pond water, he took his own fluids and he looked at them under this microscope. And he was amazed to see that there were tiny organisms swimming around. About 100 years later, Louis Pasteur working in France, made a science out of microbiology.

    00:45 He showed that microbes, like bacteria, could grow in a liquid broth, but that they were not spontaneously generated. One of the prevalent thoughts at this time was that life arose spontaneously; Louis Pasteur put an end to that theory. He also found that microbes were responsible for the processes that gave us wine and cheese and bread. And finally Robert Koch, working in Germany, showed that some microbes could cause animal and human diseases.

    01:22 So these were the origins of microbiology and you can see that it's a relatively recent science.

    01:31 Now why do we care about microbes? There are lots of reasons that they're very important.

    01:36 To quote John Ingraham, “They are our progenitors, our inventors and our keepers”. We evolved from microbes and today without them, we couldn't survive. They are everywhere in us and on us, not just humans, but in animals as well, they're all over the earth, you can find them in soil, you can find them in hot springs, they're at the bottom of the ocean, they're on mountaintops, they're in the air, they're even inside of rocks and you can find them kilometers below the surface of the earth. Only microbes can take nitrogen gas from the air and convert it into a chemical that can be used by other lifeforms to grow, that's called fixing nitrogen and many plants have bacteria growing in their roots so that they can acquire the nitrogen that they need to grow. Only bacteria can degrade cellulose, which is a big component of plants. And by degrading the cellulose, they release carbon that other living things can use. If it weren't for the bacteria, the plants would just die and lie on the floor of the forest and never be recycled, so bacteria are very important for recycling nutrients in our ecosystems. Now bacteria live all over us as well as within us as well. They're in our intestines, they're in our stomachs, they're everywhere, they're on our skin and this diagram shows you all the different kinds of bacteria that are located in different parts of our skin alone. And the different colors on the pie charts show you the different colonies or communities of bacteria that are found, from your eyes, to your hands, to your feet. All of these bacteria have a function, they're beneficial for us, we call this our microbiom. And in fact the number of bacteria in us outnumber the number of human cells in us. It's safe to say that without microbes, other organisms on earth would not exist.


    About the Lecture

    The lecture The Concept of Microorganisms – Introduction to Microbiology by Vincent Racaniello, PhD is from the course Microbiology: Introduction.


    Included Quiz Questions

    1. Fix nitrogen
    2. Asexually reproduce
    3. Break down fructose
    4. Convert carbon dioxide to a usable chemical in the soil
    5. Stop the degradation of our ecosystem

    Author of lecture The Concept of Microorganisms – Introduction to Microbiology

     Vincent Racaniello, PhD

    Vincent Racaniello, PhD


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