by Vincent Racaniello, PhD

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      Foliensatz 03 Viruses MicrobiologyBasic.pdf
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    Hello and welcome to the world of viruses. After listening to this lecture today, I hope you'll be able to know when and how viruses were discovered. I hope you'll understand the defining features of viruses. You should appreciate that viruses are everywhere and outnumber cellular life. You will know that there are good viruses, as well as bad viruses. And finally, you'll be able to answer the question: Are viruses alive? We live and prosper in a cloud of viruses. Viruses infect all living things on the planet. We regularly eat, touch and breathe billions of virus particles on a daily basis. As I sit here today, I'm probably inhaling some viruses and depending on what you're doing, if you're eating something, you're probably eating viruses as well. We simply can't escape them. More amazingly perhaps, is that we carry viral genomes as part of our genetic material. That's right, I'm about 8% viral and so are you. The number of viruses on the planet is staggering. Let's just consider the number of viruses that infect bacteria, these are called bacteriophages. In the waters of the world, it's estimated that there are over 10 to the 30th bacteriophages; this is a huge number, bigger than Avogadro's number. So let's try and put this into a form that maybe it's easier to understand. A phage particle weighs about 10 to the -15 grams, that's a femtogram. So if we multiply that by the 10th to the 30th total bacteriophage particles on earth, we get a number that is staggering. That biomass exceeds the weight of elephants by over a thousand fold. So this is a virus that you can't even see, but there are so many of them on the planet that they weigh a 1000 times more than elephants....

    About the Lecture

    The lecture Viruses by Vincent Racaniello, PhD is from the course Microbiology: Introduction. It contains the following chapters:

    • Virus Overview
    • How 'Infected' Are We?
    • Good Viruses
    • Are Viruses Alive?
    • Viruses Are Very Small
    • Viruses Are Not as Small as We Once Thought!
    • How Old Are Viruses?
    • Virus Discovery
    • We Continue to Discover New Viruses

    Included Quiz Questions

    1. LTR retrotransposons
    2. Introns
    3. SINES
    4. LINES
    1. Our immune system is effective at limiting viral disease.
    2. These viruses do not replicate well.
    3. None of the given answers are correct.
    4. The viruses interfere with each other.
    1. A virus is an obligate, infectious intracellular parasite.
    2. Viruses reproduce by binary fission.
    3. A cellular host is needed for viruses to reproduce.
    4. The viral genome can be DNA or RNA.
    5. Viral particles are formed by de novo assembly of newly synthesized components
    1. By transmitting a disease to tobacco plants using a cell-free filtrate of diseased leaves.
    2. Pasteur showed that viruses could replicate in a sterile medium.
    3. Leeuwenhoek saw viruses in his microscope.
    4. Robert Koch showed that viruses grown in broth could cause disease.

    Author of lecture Viruses

     Vincent Racaniello, PhD

    Vincent Racaniello, PhD

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