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Why do we Care About Microbes? – Introduction to Microbiology

by Vincent Racaniello, PhD
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    00:01 There are other reasons why we care about microbes of course and that is because some of them make us sick, and there are diseases caused by bacteria like Staphylococci and Pseudomonas, some of which are shown here. There are protozoan parasitic diseases caused by Entamoeba, Giardia and Plasmodium. There are fungal diseases caused by Histoplasma and Candid. And of course all of these microbes that we've talked about have their viruses.

    00:35 And there are also viruses that infect humans that cause disease such as HIV, poliovirus and influenza. But it turns out that the organisms that cause disease are a small fraction of all those that are out there, most of them are in fact beneficial. Many microbes live in a close relationship with another organism. We call that a symbiotic relationship, and when both the microbe and the other organism benefits, we call it a mutualistic symbiotic relationship. An example is the bacteria in our intestines, we provide those trillions of bacteria with a place to live and some nutrients and in turn they give us nutrients in exchange, they help our immune system develop, and they provide countless other benefits as well. We can take this mutualism a step further. Some organisms, in some organisms the bacteria not just live in them, but they actually live inside of their cells and this is called Endosymbiosis. It's very common in insects, and this picture shows an insect cell that's full of vesicles of bacteria growing in them. This is not at all harmful; in fact it's beneficial for the insect. I'll give you an example of an endosymbiosis and this takes place in the aphid, a common insect that lives off of plants. The aphid drinks the sap of plants in order to live and that's all that the aphid drinks, however, sap is made largely of sugars and animals cannot live on sugars alone. Within the aphid, and in fact within the cells of the aphid, is a bacteria called buchnera aphidicola and that bacteria takes the sugars that the aphid eats and converts them to other compounds like amino acids, so the aphid can grow. So the bacteria gets a place to live and gets sugars and in turn the aphid gets to grow.

    02:45 So I hope that you have learned today that you'll be able to define a microbe. I hope you'll understand the differences among archaea, bacterial and eukaryotic microbes. I hope you'll appreciate that microbes are everywhere on earth and that they outnumber every other living thing on our planet. I hope you'll know why microbes are essential for life and I hope you'll appreciate how microbes have shaped the earth.


    About the Lecture

    The lecture Why do we Care About Microbes? – Introduction to Microbiology by Vincent Racaniello, PhD is from the course Microbiology: Introduction.


    Included Quiz Questions

    1. Buchnera aphidicola
    2. Histoplasma
    3. Pseudomonas
    4. Giardia
    5. Staphylococci
    1. Microbes are classified into two main types: positive contributors and negative contributors.
    2. Microbes help to shape various parts of the physical Earth.
    3. Microbes live all over and within the human body.
    4. Microbes are exceptionally good at surviving extreme pH and temperature.
    5. Microbes outnumber every other living thing on the planet.

    Author of lecture Why do we Care About Microbes? – Introduction to Microbiology

     Vincent Racaniello, PhD

    Vincent Racaniello, PhD


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